Hybrids Based on Layered Silicates

Hyb ids based on laye ed Silica es Disse a ion zu E langung des akademischen G ades eines Dok o s de Na u wissenscha en (D . e . na .) im P omo ionsp og amm Polyme Science an de Bay eu he G aduie enschule ü Ma hema ik und Na u wissenscha en (BayNAT) de Uni e si ä Bay eu h Vo geleg on S ephan Weiß gebo en in Cobu g Bay eu h, 2013 Die o liegende A bei wu de in de Zei on Janua 2009 bis Feb ua 2013 in Bay- eu h am Leh s uhl Mak omolekula e Chemie II un e Be euung on He n P o . D . Axel H. E. Mülle ange e ig . Volls ändige Abd uck de on de G aduie enschule BayNAT de Uni e si ä Bay- eu h genehmig en Disse a ion zu E langung des akademischen G ades eines Dok- o s de Na u wissenscha en (D . e . na .). P omo ionsgesuch einge eich am: 02.05.2013 Zulassung du ch das Lei ungsg emium: 07.05.2013 Wissenscha liches Kolloquium: 11.06.2013 Am ie ende Di ek o : P o . D . F.X. Schmid P ü ungsausschuß: P o . D . Axel. H. E. Mülle (E s gu ach e ) P o . D . Ad eas Fe y (Zwei gu ach e ) P o . D . Raine Schobe (Vo si z) P o . D . Jose B eu Fü meine wunde olle Familie. »Nich s schockie mich. Ich bin Wissenscha le .« Indiana Jones »Wha su p ises me mos o all in mankind, is ha man will lose hei heal h in o - de o ge money and hen hey lose ha money in o de o eco e hei heal h. A he same ime while wo ying abou he u u e, hey o ge o li e he p esen , his way hey end up li ing in nei he he p esen no he u u e. They li e as i hey a e ne e going o die and hey die as i hey ha e ne e li ed.« Buddha Table o Con en s Table o Con en s SUMMARY .............................................................................................................................. 1 GLOSSARY .............................................................................................................................. 5 1 CHAPTER 1: INTRODUCTION ......................................................................... 7 1.1 Laye ed silica es ........................................................................................................................ 7 1.1.1 Na u al mon mo illoni e ....................................................................................................... 9 1.1.2 Syn he ic hec o i e (Na- luo ohec o i e) ............................................................................. 10 1.1.3 Na u al kaolini e .................................................................................................................. 11 1.2 O ganic/ino ganic hyb id nanopa icles .................................................................................. 12 1.2.1 Clay based hyb id nanopa icles .......................................................................................... 13 1.2.2 Pa chy nanopa icles ........................................................................................................... 14 1.2.3 Janus nanopa icles ............................................................................................................. 14 1.3 (Clay ein o ced) nanocomposi es .......................................................................................... 16 1.3.1 Nanocomposi es based on homopolyme s ......................................................................... 17 1.3.2 Nanocomposi es based on polyme blends ........................................................................ 17 1.4 Mo i a ion and objec i e o his hesis ................................................................................... 18 2 CHAPTER 2: EXPERIMENTAL PART AND METHODS ............................................ 20 2.1 Ma e ials ................................................................................................................................ 20 2.2 Ins umen a ion ...................................................................................................................... 21 2.2.1 Nuclea magne ic esonance spec oscopy (NMR) ............................................................. 21 2.2.2 Size exclusion ch oma og aphie (SEC) ................................................................................. 22 2.2.3 T ansmission elec on mic oscopy (TEM) ........................................................................... 22 2.2.4 Scanning elec on mic oscope (SEM) .................................................................................. 22 2.2.5 The mog a ime ic analysis (TGA) ...................................................................................... 22 2.2.6 Dynamic ligh sca e ing ...................................................................................................... 22 2.2.7 S abili y measu emen s (LUMiFuge®) ................................................................................. 23 2.2.8 Cha ge i a ion s abili y analysis (S abisize ®) ................................................................... 23 2.2.9 Dynamic-mechanical analysis (DMA) and ensile es s ....................................................... 23 2.2.10 Powde X- ay di ac ion (PXRD) ..................................................................................... 24 2.2.11 Fou ie - ans o m in a ed spec oscopy (FT-IR) ............................................................ 24 2.2.12 Speci ic su ace a ea measu emen s .............................................................................. 24 Table o Con en s 2.3 Tailo ing o s acks heigh and s i ness o luo ohec o i e ....................................................... 24 2.4 Syn hesis o he copolyme s o su ace modi ica ion ............................................................ 25 2.4.1 Syn hesis o he ca echol-modi ied PMMA copolyme (PCM) ............................................ 25 2.4.2 Syn hesis o poly(2-(2-b omoisobu y yloxy)e hyl me hac yla e)-s a -(2- dime hyl(amino)e hyl me hac yla e) (MI) ia Re e sible Addi ion-F agmen a ion Chain T ans e (RAFT) polyme iza ion ....................................................................................................................... 26 2.4.3 Syn hesis o poly(2-(dime hylamino)e hyl me hac yla e) (PDMAEMA) based diblocks ia RAFT ............................................................................................................................................. 27 2.5 Clay su ace modi ica ion ........................................................................................................ 28 2.5.1 Su ace modi ica ion o K- luo ohec o i e and su ace-ini ia ed A om T ans e Radical Polyme iza ion (si-ATRP) o me hyl me hac yla e (MMA) ................................................................ 28 2.5.2 Su ace modi ica ion o mon mo illoni e (MMT) ................................................................ 29 2.5.3 Su ace modi ica ion o kaolini e ........................................................................................ 30 2.6 P epa a ion o clay/polyme nanocomposi es ........................................................................ 31 2.6.1 Embedding o K- luo ohec o i e/PMMA hyb id pa icles (hyb id-hec ) in o a PMMA Ma ix o ensile es ing ............................................................................................................................... 31 2.6.2 P epa a ion o hyb id-clay/polys y ene (PS)/PMMA nanocomposi e samples o TEM analysis ............................................................................................................................................. 31 2.6.3 P epa a ion o hyb id-MMT/PS/PMMA nanocomposi e samples o DMA ........................ 32 3 CHAPTER 3: HYBRID MICA-LIKE PARTICLES BASED ON HIGH ASPECT RATIO FLUOROHECTORITE ............................................................................................................. 33 3.1 P epa a ion o ailo ed mica-like K- luo ohec o i e/PMMA hyb id pa icles .......................... 33 3.1.1 Tailo ing o a high aspec a io mica-like nano ille ............................................................ 33 3.1.2 Selec i e su ace modi ica ion o he mica-like nano ille .................................................. 34 3.1.3 Su ace-ini ia ed ATRP o MMA ........................................................................................... 38 3.2 Mechanical p ope ies o he clay/PMMA nanocomposi es .................................................... 44 3.3 Conclusion .............................................................................................................................. 46 4 CHAPTER 4: PATCHY HYBRID PARTICLES BASED ON POLYMER GRAFTED MONTMORILLONITE (MMT) ............................................................................................. 47 4.1 P epa a ion o pa chy hyb id pa icles based on MMT ........................................................... 47 4.1.1 Syn hesis o DMAEMA based diblock copolyme s ia sequen ial RAFT polyme iza ion ..... 48 4.1.2 Solu ion beha iou o he diblock copolyme s .................................................................... 52 4.1.3 Modi ica ion o he basal planes ......................................................................................... 54 Table o Con en s 4.2 Mechanical p ope ies o he clay/PMMA/PS nanocomposi es .............................................. 57 4.2.1 P epa a ion o clay/PS/PMMA blends ................................................................................. 57 4.2.2 DMA o he blends ............................................................................................................... 60 4.3 Conclusion .............................................................................................................................. 61 5 CHAPTER 5: HYBRID JANUS PARTICLES BASED ON POLYMER MODIFIED KAOLINITE ............................................................................................................................. 62 5.1 P epa a ion o hyb id janus pa icles based on kaolini e ........................................................ 62 5.1.1 Syn hesis o he copolyme s PCM and D16-b-S115 ................................................................ 64 5.1.2 Modi ica ion o he kaolini e basal planes .......................................................................... 66 5.2 TEM Analysis o he mo phology o he hyb id-kaolini e / PMMA/ PS nanocomposi es ......... 72 5.3 Conclusion .............................................................................................................................. 75 6 CHAPTER 6: REFERENCES ......................................................................................... 76 ACKNOWLEDGEMENTS .................................................................................................. 82 Chap e 1 7 1 Chap e 1: In oduc ion 1.1 Laye ed silica es In mankind's ea ly his o y, he u iliza ion o new ma e ials lead o majo echnological p og ess, om he s one- o e he b onze- o he coppe -age, he new ma e ials enabled be e ools, be e hygiene and be e p o ec ion and also o en decided he a e o ci iliza ions. Mode n socie y in con as needs highly specialized ma e ials, o en ailo ed o a single ask, o ace he challenges o i s apidly ad ancing echnological sec o s like au omo i e, ae ospace, hygiene, ene gy and enginee ing. Li ing in he age o polyme s, he e is al eady a la ge supply o basic and ad anced ma e ials o choose om, bu he in oduc ion o nano echnology, and wi h i nanopa icles, opened up a as ange o possibili ies o be e and no el ma e ials, whe e e en he cheapes basic polyme s, which make up mos o he daily-use i ems a ound he wo ld, can be mixed wi h a small amoun o nanosized objec s o enhance and al e hei p ope ies signi ican ly1. Clay mine als ha e been used since housands o yea s by cul u es wo ldwide as ce amics, bu due o hei mani old o he p ope ies, e.g. high wa e adso p ion, capaci y o ca ion exchange, non-New onian luid beha io hey ound hei way in o mode n applica ions, like il a ion, pu i ica ion, encapsula ion o was es, d illing and ga dening. A ecen ly ad anced opic and one o g owing in e es is hei use in polyme ic ma e ials as cheap and e sa ile nano ille s o enhance hei oughness, lame e a dency and gas ba ie p ope ies. All o hese p ope ies a e a di ec esul om hei unique laye ed shee -like s uc u e a e which hey a e named and classi ied. Ga y W. Beall and Clois E. Powell ask as an in oduc o y ques ion o hei book2: „Can one imagine he u ili y o a dispe sed-phase ein o cemen o polyme s ha has a hickness o 1 nm, a pla e-like mo phology wi h minimal dimensions o 150 o 200 nm, obus wi h a modulus o 180 GPa, non- oxic [...], a su ace a ea in excess o 750 m²/g, a cha ge sui able o al e ing i s hyd ophilic balance a will, and a e ac i e index simila o polyme so ha he nanopa icle will appea anspa en in he In oduc ion 8 polyme composi e? How di icul would i be o p epa e such a pa icle?” As he au ho s a e discussing na u ally occu ing laye ed silica es, his he o ical ques ion ampli ies he po en ial which lies in hese clay mine als ound all o e he wo ld in sedimen a y ocks like ben oni es o kaoline. Laye s a e held oge he by an-de -Waals o ces, hyd ogen bonds and elec os a ic in e ac ions o ming la ge s acks ( ac oids) in he d y s a e. Each laye is oughly 1 nm in heigh and is made up om wo di e en basic building blocks3, namely [TO4]- e ahed a and [M(O,OH)6]-oc ahed a. Mos commonly e ahed al ca ions a e Si4+, Al3+ and Fe3+, while oc ahed a ea u e Al3+, Fe3+, Mg2+, Fe2+ o Li+. Each co ne o one polyhed on is occupied by O2-, OH- o F- anions. Te ahed a a e connec ed ia h ee sha ed co ne s and o m a wo-dimensional hexagonal la ice s uc u e (Figu e 1.1). The ou h apical co ne ac s as connec ion o he oc ahed al laye . Oc ahed a a e connec ed o each o he by sha ed edges and he uppe and lowe iangula sides o all e ahed a lie in plane espec i ely. Figu e 1.1 Schema ic ep esen a ion o a 2:1 laye ed Silica e. T= Te ahed on, O=oc ahed on. Rep in ed wi h pe mission om e e ence [4]. The e a e wo impo an ypes o laye ed silica es, in bo h cases each lamella consis s o one oc ahed al laye connec ed ei he on one side o a e ahed al laye (named 1:1 laye ed silica e, e.g. kaolini e, chap e 1.1.3) o sandwich-like on bo h sides (called 2:1 laye ed silica e, e.g. mon mo illoni e o hec o i e, chap e 1.1.1 and Chap e 1 9 1.1.2). This has a majo in luence on he way how each silica e compensa es i s laye cha ge esul ing om isomo phous subs i u ion. Any ca ion in he e ahed al o oc ahed al laye which is eplaced by a ca ion o lowe alency will con ibu e o a pe manen ne laye cha ge, ζ, which is compensa ed by coun e -ions close o he laye . The amoun o (exchangeable) coun e -ions is deno ed as ca ion exchange capaci y (CEC). In he case o 2:1 silica es he ca ions eside on he ex e nal basal planes and in he in e laye spaces. The in e laye dis ance a ies wi h he ca ion species and i s deg ee o hyd a ion be ween 9.1 Å and 18.0 Å. A 1:1 silica e does no ha e any ca ions in i s in e laye space and compensa es i s cha ge only a he ex e nal e ahed al laye . In he case whe e he open spaces o all oc ahed ons a e illed wi h ca ions he laye is called ioc ahed al o b uci ic (e.g. hec o i e, see chap e 1.1.2), while an occupa ion o only 2/3 is named dioc ahed al o gibbsi ic (e.g. mon mo illoni e and kaolini e, chap e 1.1.1 and 1.1.3) (Figu e B7c). As a esul ca ions o highe alency (Al3+ s. Mg2+) a e inco po a ed in o dioc ahed al s uc u es o compensa e o he laye cha ge. Wi h na u al silica es a ying deg ees o isomo phous subs i u ion occu in each laye , depending on he condi ions unde which hey we e o med. 1.1.1 Na u al mon mo illoni e Mon mo illoni e (MMT) is a na u al 2:1 laye ed silica e om he smec i e g oup wi h he dioc ahed al s uc u e (Na, Ca)0.3(Al, Mg)2(Si4O10)(OH)2·nH2O. I is ound all o e he wo ld5. I is an al e a ion p oduc o olcanic u and ash, o ming ben oni e beds, and o wall ocks bo de ing hyd o he mal mine al deposi s. I o ms unde alkaline condi ions o poo d ainage, wi h Mg, Ca, Na, and K emaining in he soil. As i is a na u al p oduc i con ains impu i ies, mos commonly eldspa , qua z, mica, ca bona e and hyd oxyca bona e, which ha e o be emo ed p io o comme cial applica ion. Fu he mo e, all o i s p ope ies depend on he condi ions i was o med unde , a ying wi h i s o igin. E.g. he CEC eaches om 90 up o 150 meq/100g as he nega i e cha ge is dis ibu ed inhomogenously inside each laye and be ween laye s, esul ing in inhomogeneous su ace co e age wi h coun e ions, In oduc ion 10 some imes esul ing in clus e s o ming a ound spo s wi h high densi y o isomo phous subs i u ion6, 7. Coun e ions usually a e hyd a ed sodium o calcium ca ions, and inc easing hyd a ion os e s desagg ega ion o ac oids and pa ial ex olia ion. Delamina ion in o singula laye s o 1 nm heigh is only obse ed a e ion exchange wi h Li and emo al o amo phous binde s. Combined wi h a la e al dimension o up o o e 300 nm, hey can each aspec a ios, α, o up o 300 in heo y. Though, hese single shee s lose hei in insic s i ness and s a o cu l and b eak unde shea (e.g. du ing mixing), hei p ac ical aspec a io a e p ocessing is usually no highe han 1008. Ne e heless, due o i s easy mining and p ocessing MMT apidly became he comme cially mos a ac i e clay as an addi i e o polyme ic ma ices in he las decades and he e is a ange o companies, supplying MMT wi h di e en g ades o pu i y, dimensions and CEC. In i s p is ine o m i is only miscible wi h hyd ophilic polyme s, such as poly(e hylene oxide) and poly( inyl alcohol)9, 10. To ende MMT miscible wi h hyd ophobic polyme s, alkali coun e ions classically a e exchanged wi h ca ionic-o ganic su ac an s, such as alkylammonium sal s11, 12. 1.1.2 Syn he ic hec o i e (Na- luo ohec o i e) Hec o i e is a 2:1 laye ed silica e commonly o he s uc u e Na0.3(Mg,Li)3Si4O10(OH, F)2. Na u al hec o i e belongs o he smec i e g oup as well and is ela ed o mon mo illoni e, bu has a ioc ahed al s uc u e. I s na u al a ian su e s om he same impu i ies and inhomogeni ies desc ibed in 1.1.1. To omi hose disad an ages, classical solid-s a e eac ions and mel syn hesis ha e been used o p oduce a i icial hec o i e. High empe a u es lead o s a is ical dis ibu ion o isomo phous subs i u ion, gene a ing a homogeneous laye cha ge. Un il ecen ly his p ocedu e has been e y expensi e and indus ially inapplicable. De elopmen o a new syn he ic ou e in powe ul high equency u naces by Hussein Kalo a he depa men o Ino ganic Chemis y I o Uni e si y o Bay eu h unde supe ision o P o . B eu allows o p oduc ion quan i ies o kilog ams wi h a p ice o 18 €/kg. Bu p ice is no he only bene i ; by syn hesis i is possible o c ea e much la ge pla ele s, leading o huge p ac ical aspec a ios α o up o 20000 in case Chap e 1 11 o Li- luo ohec o i e o annealed Na- luo ohec o i e (hec o i e whe e pa o he oc ahed al O-a oms ha e been eplaced by F-a oms is called luo ohec o i e). Wi h homogenei y in su ace cha ge and a less impu i ies han na u al clay13 i is possible o con ol al e na ion be ween a highly hyd a ed ‘shea -labile’ s a e and a nonhyd a ed ’shea -s i ’, mica-like s a e by simple ca ion exchange. This ansi ion be ween hyd a ion s a es canno be obse ed o na u al MMT due o he e ogenei y o cha ge densi y and lowe laye cha ge. Ca ion exchange owa d Mg- luo ohec o i e gi es a highly hyd a ed and he e o e ‘shea -labile’ s a e, enabling ex olia ion by applica ion o shea o ces in a s i ed media mill14. A subsequen ca ion exchange wi h K+ ions yielded a collapsed non-swollen, ‘shea -s i ´, mica-like ma e ial. Powde x- ay di ac ion (PXRD) measu emen s showed ha collapsed s acks will no exchange in e laye ca ions and hus eac i i y is es ic ed o ex e nal basal planes. This p e en s he cu a u e obse ed in delamina ed single shee s and should subs an ially inc ease po en ial ein o cemen e ec s15. These unique p ope ies ha e led o a enewed academic in e es o de elop hyb id ma e ials based on syn he ic hec o i e o indus ial applica ions. 1.1.3 Na u al kaolini e Kaolini e is a 1:1 silica e, wi h he o mula uni o Al2Si2O5(OH)4. Tac oid heigh anges om 70 nm o 100 nm and la e al ex ension a ies be ween 500 nm and 15 µm, depending s ongly on i s o igin. Kaolini e has se e al ea u es no ound in 2:1 silica es. Single lamellae in ac oids a e no held oge he by an-de -Waals o ces bu by s ong hyd ogen bonds be ween µ-hyd oxide-g oups o he oc ahed al laye and he silicon ne wo k o he e ahed a (Figu e 1.2)16, esul ing in much smalle in e lamella dis ances o 7.2 Å. This makes in e cala ion di icul and es ic s i o only a small ange o neu al molecules wi h high dipola momen s like Dime hyl sul oxide (DMSO)17 and N-Me hyl o mamide (NMF)18. In oduc ion 12 Figu e 1.2 Schema ic ep esan a ion o 1:1 laye ed silica e (kaolini e). OS= Oc ahed al su ace, TS= e ahed al su ace. Rep in ed wi h pe mission om e e ence [14]. The mos in e es ing ea u e in he pa icle a chi ec u e is he p ese a ion o i s pola lamella s uc u e h oughou he ac oid, which means each pa icle has wo chemically dis inc su aces, which can also be selec i ely a ge ed o modi ica ion o c ea e Janus s uc u es (see chap e 1.2.3). A combina ion o bo h ea u es (no in e cala ion and chemically dis inc ex e nal su aces) leads o he in e es ing ac ha he nega i e cha ge gene a ed by isomo phous subs i u ion o Si4+ agains Al3+ in he e ahed al laye can only be compensa ed by coun e ions a he e ahed al su ace (abb e ia ed TS), which means he ou e mos e ahed al laye o a ac oid19, 20. Na u al coun e ions a e sodium and calcium, which a e easily eplaced by o he ions espec i e o hei compa a i ely low CEC, which lies a ~2.6 meq/100g. Recen s udies show ha he oc ahed al laye can be selec i ely add essed by molecules bea ing a ca echol moie y21. Those g oups mos likely will unde go a condensa ion eac ion and bind co alen ly o he µ-hyd oxide g oups o he oc ahed al su ace (called OS), simila o wha was obse ed wi h alcohols and s uc u ally ela ed aluminum oxide su aces22, 23. 1.2 O ganic/ino ganic hyb id nanopa icles Nanoma e ials ha e, by de ini ion, a leas one dimension in he nanome e scale (<100 nm) and show no el p ope ies s ongly in luenced by he la ge su ace o Chap e 1 13 olume a io. The syn hesis, cha ac e iza ion, and applica ions o nanopa icles a e among he mos impo an sec ions o he wide ange o nano echnology. In ecen yea s, nanopa icles ha e gained emendous a en ion as he ansi ion om mic opa icles o nanopa icles was seen o lead o immense changes in he physical and chemical p ope ies o a ma e ial. Due o he as inc ease in su ace a ea o olume a io gained om his s ep down in leng h scale, su ace a oms and hei e ec s now play a dominan ole o e bulk a oms. Especially when in oduced in o composi es, he huge speci ic in e phase a ea al e s he p ope ies o he ma ix conside ably. Resea ch s a ed in he 1980s wi h nanopa icles made om one ma e ial24-26, bu i was quickly disco e ed, ha adding a shell a ound he co e pa icle gi es ise o new ma e ials only possible by combina ion o bo h p ope ies27-29. The name “co e/shell” pa icles was adop ed o ma e ials consis ing o a ino ganic/o ganic co e o di e en shapes and an ino ganic o o ganic shell. Applica ions a e mani old30 and ad ances in su ace modi ica ion echniques allow o e e new combina ions o co e p ope ies and shell p ope ies. A ecen example o he mul i unc ionali y o ino ganic co e/ polyme ic shell hyb ids a e supe pa amagne ic and luo escen CdSe(ZnS) nanopa icles coa ed wi h p o ec i e silica and bea ing a polyme ic he mo- esponsi e poly(N-isop opylac ylamide) shell31. 1.2.1 Clay based hyb id nanopa icles Clay pa icles a e well sui ed ino ganic co es o he c ea ion o hyb id pa icles. E en he symme ical 2:1 s uc u e o smec i es al eady p o ides wo chemically di e en eac i e si es o a aching a shell: basal su aces and edges. The p e iously desc ibed inhe en nega i e laye cha ge o laye ed silica es enables acile modi ica ion o he basal su ace and in e laye spaces wi h o ganic molecules bea ing a posi i ely cha ged g oup by simple ca ion exchange. Modi ica ion o edge loca ed silanol g oups wi h silicon halides, acid halides o silazanes leads o s onge co alen bonds. Bo h si es can be accessed o go beyond simple alkyl ammonium su ac an modi ica ion by a aching polyme s wi h ailo ed p ope ies ia con olled polyme iza ion o sui able monome s and chain leng h. Classically smec i e-based In oduc ion 14 hyb id nanopa icles a e implemen ed in o polyme ic ma e ials o enhance oughness, lame e a dancy and gas ba ie p ope ies. 1.2.2 Pa chy nanopa icles Fo mix u es o polyme species o di e en pola i y i is ene ge ically a ou able o seg ega e and o m domains o hei single polyme species, espec i ely. I bound o an in lexible co e, comple e phase seg ega ion becomes inhe en ly di icul and o ma ion o compa men alized (pa chy) shells can be obse ed. The e has been a ecen b eak h ough in c ea ion o mul icompa men micelles by hie a chical sel -assembly o ABC iblock e polyme s32 and pa chy wo mlike c ys alline co e micelles made om ABC iblocks wi h c ys allisable co e33. These g oups epo on he po en ial o pa chy pa icles o hie a chical s ep-g ow h polyme iza ion o mul icompa men micelles in o “mic on-scaled segmen ed sup acolloid polyme s”32 and hei use as supe su ac an s close o pu e Janus colloids in su ace ac i i y, while usually being less complica ed o p oduce. On he co e/shell pa icle side he e a e ew examples u ilizing he p omising po en ial o a pa chy shell. Fu he mo e, mos o he p oduced pa chy pa icles a e sphe ical in na u e34. As shown by Schmelz e al. pa chy pa icles made om iblock e polyme s wi h c ys allized middle block ac as gian su ac an s in mix u es o immiscible luids, educing he su ace ension wi h an e ec compa able o ha o Janus cylinde s35. In his hesis we use disc-like mon mo illoni e 2:1 laye ed silica es as co e o in es iga e he in luence o a pa chy shell on i s in e acial beha io in an immiscible polyme blend. 1.2.3 Janus nanopa icles Pa icles which embed exac ly wo dis inc sides o su aces o di e en chemical p ope y and/o pola i y in o one s uc u e a e called Janus pa icles, named a e he Roman god Janus wi h wo aces and whose name is used symbolically o en i ies showing cha ac e o beha io o wo incompa ible sides. This non- cen osymme ic appea ance leads o a unique se o cha ac e is ics ega ding Chap e 1 15 ma e ial p ope ies and sel -assembly beha io 36. A whole spec um o di e en Janus pa icle a chi ec u es is known. Janus pa icles can be ca ego ized acco ding o hei dimensions. The e a e h ee-dimensional sphe ical pa icles, wo e sions o wo-dimensional disc-like s uc u es and wo di e en one-dimensional cylinde s. While hei o e all geome y can be simple and symme ic, he lack o chemical cen osymme y p o ed o be he bigges challenge in hei p epa a ion. The pionee s in he ield o Janus pa icles we e Casag ande and Veyssié. They embedded hal o a mesoscopic glass bead in o a subs a e and hen silyla ed he o he hal . As he amoun o pa icles p oducible by hose syn heses was e y limi ed, all hei me hods had he majo d awback ha hey we e no applicable on a la ge scales37, 38. Recen ly he applica ion o pho opolyme iza ion and pho oli hog aphic polyme iza ion o mic o luidic de ices enabled an e en highe deg ee o con ol and s uc u al a ie y. The mic o luidic de ice sends a wo-phase s eam in o a channel. The e i is cu in o d ople s by an aqueous c oss low, con aining su ac an s o s abilize he esul an pa icles. Then a pho opolyme iza ion locks he shape o he biphasic pa icles. Un o una ely his me hod is no able o c ea e pa icles wi h submic on dimensions ye 39. Ano he in e es ing app oach was de eloped by Mülle and cowo ke s36 , using he sel - assembly beha io o iblock e polyme s. T iblock polyme s wi h phase-sepa a ing ou e blocks will unde go sel -assembly upon ilm cas ing and o m nanome e - scaled bulk s uc u es, which can be locked by c osslinking he inne pa (in his case polybu adiene). Upon dissolu ion o he polyme , he c osslinked pa will p ese e i s bulk shape and hus will yield non-cen osymme ic pa icles. By de ined enginee ing o he e polyme composi ion he bulk s uc u e and hus he esul ing pa icle shape and size can be con olled. All hese app oaches ha e in common, ha hey s a wi h symme ical sys ems and b eak hose apa in o non-symme ical pa icles o complica edly syn hesize non symme ical building blocks o s a wi h ins ead o applying in insically pola pa icles like kaolini e. As desc ibed in chap e 1.1.3 i is possible o add ess each side indi idually in solu ion, acili a ing he c ea ion o disc-like Janus pa icles based on a laye ed silica e, e en in la ge quan i ies. In oduc ion 16 Se e al ields o applica ion esul om he unique s uc u al p ope ies o Janus pa icles. They ha e e oked g ea academic in e es , as hey ep esen a class o pa icles wi h ex ao dina y sel -assembly beha io . Fundamen al unde s anding o sel -assembly p ocesses is a ibu ed wi h he possibili y o c ea e new unc ionali ies no p esen in he indi idual building blocks by assembling hem in o hie a chical supe s uc u es. Thei eno mous su ace ac i i y pu s hem in o he ocus o indus ial applica ions as supe -su ac an s and s uc u ing agen s in polyme blends. Fu he mo e he aniso opic cha ac e o single Janus pa icles is used o op ical and analy ical p obes in con ined space 40, 41, medical senso s o cell a ge ing42 and swi chable elec o-op ical de ices39. . 1.3 (Clay ein o ced) nanocomposi es The comme cial b eak h ough o clay ein o ced nanocomposi es happened in he ea ly 1990´s when Toyo a esea che s published hei wo k on nylon-6-clay he moplas ic nanocomposi e echnology43, 44. The key aspec was a undamen al imp o emen o p ope ies a minimal loading. A only 4.2 w % clay he modulus doubled, s eng h inc eased by 50 % and he hea dis o ion empe a u e (HDT) inc eased by 80 °C compa ed o nea polyme . Toyo a s ill holds a b oad ange o pa en s in his echnological ield. Ne e heless academic and indus ial in e es is s ill s ong and esea ch and de elopmen o clay ein o ced nanocomposi es is g owing. Fo mos applica ions i is necessa y o o ganophilize he clay su ace o inc ease he compa ibili y wi h he ma ix and enable a good dispe sabili y. A well known comme cial b and o o ganophilized MMT is he Cloisi e p oduc amily by Rockwood Addi i es, which has been op imized o applica ion in alipha ic polyme ma ices. On hei p oduc webpage i is claimed ha hei clay based p oduc s can ac as a new lame e a dan app oach, inc ease modulus and ensile s eng h, imp o e ba ie p ope ies, inc ease dimensional s abili y, a e he moplas ic ecyclable, imp o e cla i y, inc ease HDT, ein o ce and lowe densi y45, while a a much lowe loading (3-5 w %) compa ed o con en ional ille s (20-60%). Howe e , as mos o Chap e 2 23 2.2.7 S abili y measu emen s (LUMiFuge®) The s abili y measu emen s we e pe o med in a LUMiFuge® 114 (LUM) wi h a a iable o a ion equency o 300, 600, 900 pm ( ounds pe minu e) and di e en ime in e als o 200 s, 300 s, and 900 s, espec i ely. Kaolini e suspensions (0.25 w %) in THF and wa e we e placed in ubes in ho izon al posi ions on he disc o he LUMiFuge®. Du ing he ho izon al o a ion o his disc he anspa encies o he suspensions we e measu ed in he a ea be ween he menisci and he sedimen . The mean anspa ency o he whole a ea was de e mined. The anspa ency was measu ed in ime in e als o 10 s while inc easing o a ion speed s epwise. High u bidi y, e en a e applying cen i ugal o ces indica es a s able suspension. 2.2.8 Cha ge i a ion s abili y analysis (S abisize ®) De e mina ion o poin o ze o cha ge o he clay pla ele s was done using a S abisize ® (Pa icle Me ix GmbH). The e o e he mic oionic clouds o localized pa icles a e displaced by low induced ia a pis on. The gene a ed po en ial is measu ed and used o moni o ing i a ion wi h mono- and polyca ionic species. A e comple e eplacemen o displaceable sodium ions by immobile ca ions he poin o ze o cha ge is eached. Fou sepa a e solu ions con aining he polyca ionic MI solu ion (1 g/l) in deionized wa e (DI) we e p epa ed wi h di e en pH alues using ace ic acid (100 %) in o de o p o onize he amine unc ions. The poin o ze o cha ge o he clay basal su ace was measu ed using a cha ge i a ion s abili y analyze . 2.2.9 Dynamic-mechanical analysis (DMA) and ensile es s Dynamic-mechanical analysis (DMA) expe imen s a e ca ied ou in he ension mode a a cons an o ce o 5 N and a empe a u e ange om 30 o 140 °C using a Me le Toledo DMA/STDA 861e. The hea ing a e is 5 °C/min and he es specimens is app oxima ely 25 mm in leng h, 6 mm in wid h and 1 mm in hickness. Tensile modulus, ensile s eng h and elonga ion a b eak we e measu ed using a Uni e sal Tensile Tes e acco ding o ISO 527 applying a s ain a e o 1 mm/min. Fo Expe imen al Pa and Me hods 24 each ma e ial a leas 8 samples we e es ed. The elonga ion a b eak was de e mined by a mac o-displacemen - ansduce . 2.2.10 Powde X- ay di ac ion (PXRD) The powde X- ay di ac ion (PXRD) pa e ns we e eco ded in e lec ion mode using nickel il e ed Cu-Kα adia ion λ =1.54187 Å on a B agg-B en ano-geome y di ac ome e (PANaly ical Xpe -P o) equipped wi h an X′Cele a o Scien i ic RTMS de ec o . 2.2.11 Fou ie - ans o m in a ed spec oscopy (FT-IR) The pa icles powde s o un ea ed and ea ed clay we e cha ac e ized wi h a Nicole FTIR 460 (The mo Nicole Co p.). The ansmi ance abso p ion spec a we e scanned 64 imes a 4 cm-1 spec al esolu ion a oom empe a u e. 2.2.12 Speci ic su ace a ea measu emen s The speci ic su ace a ea o a eeze-d ied K-hec sample was calcula ed om he N2 adso p ion/deso p ion iso he ms using he B unaue -Emme -Telle (BET) equa ion. Measu emen s we e ca ied ou on a Quan ach ome No a 2000e analyze . 2.3 Tailo ing o s acks heigh and s i ness o luo ohec o i e The aqueous dispe sion o syn he ic Na-hec was ans e ed o a highly hyd a ed ‘shea -labile’ s a e by exchanging he in e laye Na+ wi h Mg2+ ca ions (Mg-hec ). The aqueous dispe sion o Mg-hec was p ocessed in a s i ed media mill (LabS a LS1) o 60 minu es in o de o ex olia e he ac oid s acks by applying shea o ces. The deg ee o ex olia ion was con olled by he numbe o milling passages14. Subsequen ly, he clay was ans e ed in o a collapsed and non-swollen ‘shea -s i ’ mica-like ma e ial (K-hec ) wi h no in ac ys alline eac i i y by exchanging Mg2+ wi h K+ ca ions56. All exchanging p ocedu es we e ollowed by washing se e al imes wi h wa e o emo e chlo ine ions. Chap e 2 25 2.4 Syn hesis o he copolyme s o su ace modi ica ion 2.4.1 Syn hesis o he ca echol-modi ied PMMA copolyme (PCM) 3,4-Dibenzoxybenzoic acid 1 and 3-hyd oxyp opylbenzoa e 2 we e p epa ed ollowing li e a u e p ocedu es (scheme 5.1).57 3-Me hac yloyloxyp opyl-3,4-dibenzoxybenzoa e 3 Compound 2 (2.11 g, 5.38 mmol) was dissol ed in d y DCM (20 ml) and cooled in an ice ba h. E 3N (1.12 ml, 8.07 mmol) and me hac yloyl chlo ide (626 µl, 6.47 mmol) we e added and he eac ion mix u e was s i ed a oom empe a u e o 3 h. A e washing wi h wa e he aqueous phase was ex ac ed wi h DCM and he combined o ganic phases we e d ied o e Na2SO4, il e ed and concen a ed in acuum. The esidue was pu i ied by column ch oma og aphy (silica gel 60, e hyl ace a e/n- hexane 1:2, / ). Yield: 1.64 g (3.57 mmol, 67%); colo less oil; R = 0.63 (e hyl ace a e/n-hexane 1:2); νmax (ATR)/cm-1: 3032, 2963, 1711, 1636, 1599, 1510, 1454, 1427, 1380, 1321, 1266, 1204, 1163, 1130, 1104, 1038, 1006, 944, 815, 761, 734, 695; 1H NMR (300 MHz, CDCl3):  1.92 (3 H, s), 2.0-2.2 (2 H, m), 4.28 (2 H, , 3J 6.3 Hz), 4.36 (2 H, , 3J 6.3 Hz), 5.18 (2 H, s), 5.21 (2 H, s), 5.5-5.6 (1 H, m), 6.0-6.1 (1 H, m), 6.91 (1 H, d, 3J 9.0 Hz), 7.3-7.5 (10 H, m), 7.6-7.7 (2 H, m); 13C NMR (75.5 MHz, CDCl3):  18.3, 28.2, 61.3, 61.4, 70.8, 71.2, 113.2, 115.6, 123.0, 124.0, 125.6, 127.1, 127.4, 127.9, 128.0, 128.5, 128.6, 128.9, 136.2, 136.5, 136.8, 148.3, 153.0, 166.1, 167.3; m/z (%) 461 (13) [M+], 460 (47) [M+], 369 (6), 317 (8), 225 (17), 181 (27), 127 (12), 91 (100). Copolyme PCBM 4 Me hyl me hac yla e (650 mg, 6.52 mmol), compound 3 (100 mg, 0.22 mmol) and dodecane hiol (26 mg, 0.13 mmol) we e dissol ed in d y THF (3 ml) unde a gon a mosphe e and AIBN (10 mg) was added o he eac ion mix u e, which was s i ed unde e lux o 5 h. The solu ion was pou ed in o cyclohexane (100 ml) and he appea ing colo less p ecipi a e was collec ed and p ecipi a ed once mo e om an ace one/cyclohexane mix u e. Yield: 710 mg; colo less solid; νmax (ATR)/cm-1: 2996, Expe imen al Pa and Me hods 26 2952, 1722, 1601, 1484, 1448, 1432, 1385, 1363, 1268, 1241, 1189, 1144, 989, 965, 911, 842, 761, 748, 698; 1H NMR (300 MHz, ace one-d6):  0.8-1.0 (33 H, m), 1.8-2.0 (24 H, m), 3.61 (30 H, s), 4.1-4.2 (2 H, m), 4.3-4.4 (2 H, m), 5.2-5.3 (4 H, m), 7.1-7.7 (13 H, m). Copolyme PCM 5 Compound 4 (580 mg) was dissol ed in dioxane/me hanol (40 ml, 1:1), lushed wi h a gon and 10% Pd/C (80 mg) was added. The a gon a mosphe e was eplaced by hyd ogen gas and he eac ion mix u e was s i ed a oom empe a u e o 5 h. The suspension was il e ed o e celi e and he il a e was concen a ed in acuum. The oily esidue was i u a ed wi h n-hexane and d ied in acuum. Yield: 500 mg; o - whi e solid; νmax (ATR)/cm-1: 3392, 2996, 2950, 1725, 1605, 1480, 1444, 1386, 1270, 1239, 1191, 1146, 1121, 988, 965, 889, 873, 842, 765, 750; 1H NMR (300 MHz, DMSO-d6):  0.5-0.9 (33 H, m), 1.6-2.0 (24 H, m), 3.55 (30 H, s), 4.0-4.1 (2 H, m), 4.2- 4.3 (2 H, m), 6.81 (1 H, d, 3J 7.9 Hz), 7.2-7.4 (2 H, m), 9.32 (1 H, s), 9.81 (1 H, s); 13C NMR (75.5 MHz, DMSO-d6):  16.1, 18.4, 27.5, 43.9, 51.6, 53.7, 60.8, 115.2, 116.3, 120.5, 121.8, 145.0, 150.4, 165.5, 176.2, 176.9, 177.3. 2.4.2 Syn hesis o poly(2-(2-b omoisobu y yloxy)e hyl me hac yla e)-s a - (2-dime hyl(amino)e hyl me hac yla e) (MI) ia Re e sible Addi ion- F agmen a ion Chain T ans e (RAFT) polyme iza ion To a 100 ml ound bo om lask, equipped wi h ubbe sep um, 1.7 g (6.1 mmol) o BIEM, 6.7 g (42.8 mmol) o DMAEMA, 270 mg (1.2 mmol) o 2-cyano-2-p opyl benzodi hioa e (CPBT), 100 mg (0.6 mmol) o AIBN, 40 ml o DMSO as sol en and 2 ml o anisole as in e nal s anda d we e added. A e h ee eeze-pump- haw cycles he eac ion was placed in o an oil ba h a 70 °C o 4 h o each a con e sion o 54% as de e mined by 1H NMR spec oscopy. The esul ing polyme solu ion was cooled down, exposed o ai and dialysed agains dioxane un il no monome ela ed peaks a 5.8-6.4 ppm we e de ec ed by NMR spec oscopy. Mn = 9000 g/mol and Mw = 16000 g/mol was de e mined ia SEC wi h DMAc as eluen and a DMAEMA calib a ion. The inal polyme is om he e on e e ed o as maco-ini ia o (MI). 1H Chap e 2 27 NMR (300 MHz, CDCl3, δ in ppm): 4.4 – 4.1 (R-C(-CH3)-COO-CH2-CH2-OOC-C(CH3)2-B ), 4.0 (R-C(-CH3)-COO-CH2-CH2-N-(CH3)2), 2.6 (R-C(-CH3)-COO-CH2-CH2-N-(CH3)2), 2.2 (R- C(-CH3)-COO-CH2-CH2-N-(CH3)2), 1.9 (R-C(-CH3)-COO-CH2-CH2-OOC-C(CH3)2-B ), 1.8 (R- C(-CH3)-COO-CH2-CH2-N-(CH3)2). 2.4.3 Syn hesis o poly(2-(dime hylamino)e hyl me hac yla e) (PDMAEMA) based diblocks ia RAFT All polyme iza ions we e ca ied ou a 80°C in sep um sealed lasks. De ailed amoun s o eac an s a e lis ed in Table 1. In each case DMAEMA p ecu so s we e p epa ed by placing 1,4-dioxane, DMAEMA, AIBN, he chain ans e agen (CTA), 2- cyano-2-p opyl benzodi hioa e, and 1,3,5- ioxane in he eac ion lask. Ni ogen low was es ablished o 20 min a oom empe a u e and hen he polyme iza ion was ini ia ed by hea ing he lask in an oil-ba h. The p ecu so solu ion was ans e ed o a degassed and hea ed solu ion o 1,4-dioxane, second monome and 1,3,5- ioxane a e 4h a a ypical con e sion o DMAEMA o abo e 90 %. The eac ion was e mina ed by cooling in an ice ba h and exposu e o a mosphe ic oxygen. The polyme s we e pu i ied by p ecipi a ion in o a non-sol en (isop opanol o PS con aining diblocks and cyclohexane o PMMA con aining diblocks) and eeze-d ied om 1,4-dioxane. Final polyme s a e abb e ia ed D17-b-M300 in he case o poly(2-(dime hylamino)e hyl me hac yla e)17-block-poly(me hyl me hac yla e)300 and D17-b-S360 in he case o poly(2-(dime hylamino)e hyl me hac yla e)17-block- polys y ene300. Table 1 Applied amoun s o chemicals in he p epa a ion o he PDMAEMA-mac o-CTA and he diblock-copolyme s in 1,4-dioxane . Fo mula a DMAEMA / mg, mmol CTA / mg, mmol AIBN / mg, mmol Monome / g, mmol Sol en / ml D17-b-M300 380; 2.5 54; 0.25 15; 0.09 12.0; 120 30 D16-b-S360 1083; 6.9 149; 0.67 38; 0.24 35.2; 338 30 D16-b-S115 1402; 9.1 100; 0.45 26; 0.18 18.8; 181 30 a epea ing uni s o DMAEMA calcula ed by sub ac ing he molecula weigh o CPBDT (221.00 g/mol) and di iding by he molecula weigh o DMAEMA (157.21 g/mol), epea ing uni s o he second block Expe imen al Pa and Me hods 28 we e calcula ed by sub ac ing he molecula weigh o DMAEMA block, ac onyms: D: DMAEMA, , S: s y ene, M: MMA Figu e 3.1 a) Syn hesis o he s a is ical copolyme (PDB) and cha ac e iza ion ia b) 1H-NMR spec um and c) SEC ace wi h DMAc as an eluen . 2.5 Clay su ace modi ica ion 2.5.1 Su ace modi ica ion o K- luo ohec o i e and su ace-ini ia ed A om T ans e Radical Polyme iza ion (si-ATRP) o me hyl me hac yla e (MMA) The ex e nal su ace o K-hec (10 g) was modi ied wi h he MI (320 mg) in DI wa e a pH=6.8. Subsequen ly, he loccula ed hyd ophobic nanopla ele s (O-hec ) we e cen i uged and edispe sed in THF. The g a ing o MMA was ini ia ed om O-hec ia a coppe media ed ATRP in he p esence o EBiB as a ee sac i icial ini ia o . All expe imen s we e pe o med unde ine a mosphe e in a con en ional un p ocedu e58, 59; A dispe sion o he O-hec (10 g; calcula ed 390 µmol o ini ia ing 4 3 2 1 0 chemical shi [ppm] 20 22 24 26 28 30 32 34 elu ion olume [ml] b) c) a) Chap e 2 29 si es) in 400 ml THF, MMA (164.5 g; 1.462 mol) and EBiB (19 mg; 97.5 µmol) we e added o a lask and sealed wi h a ubbe sep um. The eac ion mix u e was degassed h ee imes by eeze-pump- haw cycles and illed wi h a gon. In a sepa a e lask a s ock solu ion o PMDETA, Cu(I)Cl and Cu(II)Cl2 (338 mg; 975 µmol, 115.8 mg; 1.17 mmol and 39.2 mg; 292.5 µmol) in 20 ml anisole was degassed o 30 min unde a gon. Finally, 10ml o he s ock solu ion was in oduced o he eac ion lask by a sy inge. The eac ion lask was imme sed in an oil ba h a 80 °C. Samples we e wi hd awn a a ious imes o moni o he eac ion kine ics and i was s opped a e 300 min by cooling and exposing o ai . The inal hyb ids o K-hec wi h a polyme ic shell o PMMA chains wi h an a e age DP o 380 (hyb id-hec (DP 380)) we e cen i uged and washed se e al imes wi h THF. As a e e ence a nano ille wi h a comme cial su ac an , dodecylamine, was used a e p o ona ion using one equi alen o HCl (0.1 mol). S anda d p ocedu es we e used o exchange he K+ ca ions wi h he o ganic ca ion (C12 ammonium chlo ide)60. A e ion exchange, he modi ied nanopla ele s (C12-hec ) we e cen i uged and washed se e al imes wi h DI wa e , e hanol, and THF. 2.5.2 Su ace modi ica ion o mon mo illoni e (MMT) The diblock copolyme solu ions o D17-b-M300 and D17-b-S360 o su ace modi ica ion o MMT we e p epa ed in wo di e en ways: 1. Solu ions wi h p e- o med micelles o D17-b-M300 and D17-b-S360 we e p epa ed by dissol ing he polyme in THF and adding wa e (pH=6.5) d opwise un il u bidi y occu ed. 2. Molecula ly dispe sed solu ions we e p epa ed by adding he eeze d ied polyme in o THF and s i ing un il no solids we e isible anymo e and he anspa en solu ion had a sligh ly pink colou . The polyme solu ions (30 mg, 1 mg/mL) we e added o a dispe sion o MMT in wa e (100 mg, 5 mg/mL, pH=6.5) using a cannula and s i ed o e nigh . Final MMT/PS/PMMA hyb id pa icles (hyb id-MMT) we e pu i ied by emo ing non- ancho ed polyme ia cen i uga ion a 4000 pm, decan a ion o he supe na an and edispe sion in wa e (1x) and THF (3x) using ul asonica ion. Expe imen al Pa and Me hods 30 2.5.3 Su ace modi ica ion o kaolini e I is possible o modi y each side, he e ahed al su ace and he oc ahed al su ace (TS and OS), o he kaolini e speci ically and indi idually wi hou in luencing he o he side as shown in a p e ious publica ion21. The o de o modi ica ion chosen, s a ing wi h D16-b-S115 has a pu ely p ac ical pu pose, as he DMAEMA block o he D16-b-S115 is cha ged a pH 6 and hus kaolini e can be modi ied in aqueous suspension whe e i is dispe sed bes . A e ca ion exchange he unila e ally modi ied kaolini e can be dispe sed in THF mo e easily han unmodi ied kaolini e, as seen in Fig. 5.4 (s abili y measu emen s). PCM is soluble in THF, bu no in wa e . Ne e heless p is ine kaolini e can be modi ied by PCM as i s s ep as well, bu o ha kaolini e has o be dispe sed in THF by igo ous s i ing i s . Modi ica ion o TS 100 mg D16-b-S115 we e dissol ed in 30 ml THF. 400 mg o he kaolini e was suspended in 30 ml o wa e (pH~ 5.5, deg ee o p o ona ion o he DMAEMA block ~80 %61). A e 20 min o s i ing a comple e loccula ion o he kaolini e was achie ed and he suspension was washed en imes wi h THF o emo e he excess o D16-b-S115. The hyb id was dispe sed and s o ed in THF o p e en d ying. Modi ica ion o OS 100 mg o PCM was dissol ed in 20 ml d y THF unde a gon a mosphe e in a Schlenk lask. 400 mg kaolini e (p is ine o al eady unila e ally modi ied hyb id) was dispe sed in he PCM THF solu ion by igo ous s i ing o e nigh a 60 °C. A e he eac ion he kaolini e was washed en imes wi h THF o emo e he excess o PCM and hen dispe sed in THF o gi e hyb id-kaolini e. Chap e 2 31 2.6 P epa a ion o clay/polyme nanocomposi es 2.6.1 Embedding o K- luo ohec o i e/PMMA hyb id pa icles (hyb id-hec ) in o a PMMA Ma ix o ensile es ing Two di e en K- luo ohec o i e/PMMA hyb id nanopa icles we e e alua ed as nano ille s in a PMMA ma ix: hyb id-hec (DP 380) and C12-hec we e mixed wi h a solu ion o PMMA in THF (5 w . -% clay loading), espec i ely. To ensu e good dis ibu ion o he clay in he polyme ma ix bo h dispe sions we e placed in an o e head shake o e nigh . Bo h dispe sions we e ilm cas ed and d ied in a acuum o en i s a 90 °C o 14 h ollowed by d ying a 140 °C o ano he 18 h. Nea PMMA was ea ed in a simila way be o e mel compounding. The d ied nanocomposi e ma e ials we e mel -compounded in a discon inuous coun e - o a ing win-sc ew mic ocompounde (DSM Xplo e, 15 ml mic ocompounde ) a a empe a u e o 190 °C, a mixing speed o 210 pm and a mixing ime o 3 min. The ma e ial was added s epwise o he unning mic ocompounde and du ing each cycle a ba ch o 7.5 g was p ocessed. A e ex usion, he mel was injec ion-moulded wi h a mic oinjec o (DSM Xplo e 12 ml injec ion moulding machine; mel empe a u e: 190 °C; mould empe a u e: 40 °C; injec ion p essu e: 8 ba ) in o dumbbell specimens (75 mm × 5 mm × 2 mm) o ensile es ing. 2.6.2 P epa a ion o hyb id-clay/polys y ene (PS)/PMMA nanocomposi e samples o TEM analysis PS and PMMA in he a io o 1:2 we e dissol ed in THF. The polyme con en o he solu ions was 10 w %. 50 mg o hyb id-clay (hyb id-MMT o hyb id-kaolini e) was suspended in 10 ml o he PS/PMMA solu ions by 15 minu es o s ong shea ing (Heidolph Silen C ushe , 16.000 pm) a 30 °C, esul ing in 5 w % hyb id-clay in he inal, d y blend. A ilm was cas by le ing he sol en e apo a e slowly om he mix u e in a glass ial. The esul ing d y ilm was cu wi h an ul amic o ome and examined ia TEM. Expe imen al Pa and Me hods 32 2.6.3 P epa a ion o hyb id-MMT/PS/PMMA nanocomposi e samples o DMA The PS/PMMA ma ix con aining he hyb ids is cas in o glass pe i dishes and d ied in a acuum o en. The polyme is c ushed and mel p essed in o DMA mould samples using ho pla es om P/O/Webe co. (Ge many). The samples a e mel ed a 200 °C wi hou p essu e o abou 6 minu es, emo ing las aces o THF, hen hea p essed o 5 minu es using 70-75 kN and inally cold p essed o 3 minu es using 30- 40 kN. Chap e 3 39 clay su ace. The ATRP echnique allows o p epa a ion o polyme s wi h na ow molecula weigh dis ibu ions and p ecise con ol o e he a chi ec u e. Table 3.1 gi es he numbe and weigh a e age molecula weigh s Mn and Mw, espec i ely, o he ee PMMA g own in solu ion de e mined by SEC as a unc ion o eac ion ime. The di e ences be ween heo e ical and expe imen al alues can be a ibu ed o an ini ia ion e iciency o less han 100%. Table 3.1 Molecula weigh s o he ee PMMA chains as a unc ion o polyme iza ion ime in THF [MMA] : [PMDETA] : [EBiB/MI] : [Cu(I)Cl] : [Cu(II)Cl2] (3000 : 2 : 0.2/0.8 : 1.2 : 0.3) Reac ion ime (min) Con .a (%) DP a Mn a (kg/mol) DP b Mn b (kg/mol) Mw b (kg/mol) PDI b 10 1 36 3.5 84 8.4 10.0 1.2 20 2 72 7.2 100 10.0 13.0 1.3 30 4 120 12.0 150 15.0 17.0 1.1 60 5 143 14.3 190 19.0 23.0 1.2 120 7 203 20.3 310 31.0 36.0 1.2 300 9 263 26.3 380 38.0 50.0 1.3 a de e mined by 1H NMR spec oscopy. b de e mined by SEC wi h THF as eluen and PMMA s anda d calib a ion. The eac ion shows a con olled cha ac e wi h a e y good polydispe si y index. Fig. 3.6 (le ) shows i s -o de kine ic o ln[M0]/[M] as a unc ion o ime, whe eas, polyme iza ion a e slowed down a e 120 min. This indica es ha he numbe o he ini ia ing species emained app oxima ely cons an up o 120 min eac ion ime and hen s a ed o dec ease. Fu he mo e, by plo ing he molecula weigh e sus con e sion as in Fig. 3.6 ( igh ), a linea inc ease asce ained he con olled beha iou o he eac ion. Based on a su ace a ea o 68 m²/g o K-hec we can calcula e a g a ing densi y o 0.08 chains pe nm² using he ollowing o mula: Hyb id mica-like pa icles 40 Whe e 𝜌 is he g a ing densi y (chains pe nm2), MP is he mola amoun o PMMA chains wi h a DP o 380, NA is he A ogad o cons an and SA is he su ace a ea in m2/g. Figu e 3.6 (▲) Fi s -o de kine ic plo o he polyme iza ion o PMMA. (■) E olu ion o he molecula weigh wi h con e sion o PMMA. Fo a quali a i e analysis o he g a ed polyme hyb id, FT-IR spec a o nea PMMA and hyb id nano ille wi h g a ed PMMA chains a e compa ed in Fig. 3.7. Cha ac e is ic CH ib a ions (2800-3000 cm-1), C=O ib a ion (1727 cm-1) and C-O ib a ion (1263 cm-1) con i m he p esence o PMMA on he su ace e en a e ex ensi e washing wi h THF. Chap e 3 41 Figu e 3.7 FT-IR spec a o nea PMMA (black), su ace modi ied O-hec ( ed) and hyb id nano ille (blue). The amoun o su ace g a ed PMMA was examined by TGA (Fig. 3.8). As expec ed, nanocomposi es wi h longe polyme chains showed a highe weigh loss o o ganic ma e ial. O-hec was ound o ha e 3.1 % loss o ola ile ma e ials a e hea ing up o 400 °C ( he weigh loss p io o 100 °C is neglec ed due o he aces o sol en ). The g a ed hyb ids showed a weigh loss o 15.2 % and 32.4 % o g a ed PMMA chains wi h a DP o 150 and 380, espec i ely. Hyb id mica-like pa icles 42 100 200 300 400 500 600 700 0 20 40 60 80 100 hyb id (DP 150) nea PMMA hyb id (DP 380) weigh (%) empe a u e (°C) O-hec Figu e 3.8 TGA measu emen s showing weigh loss e sus empe a u e o O-hec ( ed), hyb id wi h PMMA DP 150 (blue), hyb id wi h PMMA DP 380 (g een) and nea PMMA (black). Powde X- ay di ac ion (PXRD) was used o ack any changes in he in e lamella spacing du ing p epa a ion o he hyb id nano ille . The PXRD pa e ns o ex olia ed K-hec and he hyb id nano ille a e shown in Fig. 3.9. Chap e 3 43 5 6 7 8 9 10 in ensi y (a.u.) 2 (°) d (001): 1 nm Figu e 3.9 PXRD pa e ns o he (001) peak o K-hec (─), C12-hec (∙∙∙) and o hyb id nano ille (DP 380) (---). The eco ded PXRD pa e ns showed no shi ing o he cha ac e is ic (001) sha p e lec ion a d001= 9.9 Å which is ypical o non-hyd a ed mica-like clay. This obse a ion assu es ha all ea men s including su ace g a ing do no ha e any in luence on he in e lamella s uc u e. The mo phological changes o he clay’s ex e nal su ace we e analyzed using scanning elec on mic oscopy (SEM). In Fig. 3.10 a) a high aspec a io o K-hec can be seen a e ex olia ion, ha ing a la ge la e al ex ension and smoo h su ace. In compa ison o O-hec (Fig. 3.10 b), he su ace g a ed hyb id nano ille has a oughe and coa se su ace (Fig. 3.10 c). The pa e n is ypical o collapsed PMMA chains in a d ied s a e o ming mush oom-like s uc u es, as expec ed o he achie ed g a ing densi y. Hyb id mica-like pa icles 44 Figu e 3.10 SEM images o a) ex olia ed K-hec , b) su ace mo phology p io o O-hec c) Su ace o hyb id nano ille co e ed wi h collapsed polyme chains abo e en anglemen leng h. *(A ows indica e clay agmen s om milling ea men , ac ual polyme s a e he smalle s uc u es on he su ace). 3.2 Mechanical p ope ies o he clay/PMMA nanocomposi es The mechanical p ope ies o nea PMMA and PMMA/clay nanocomposi es de e mined by ensile e alua ion es s a a 5 w % clay loading a e p esen ed in Fig.6. Wi h inco po a ion o hyb id clay pa icles he ensile modulus o PMMA/clay nanocomposi es showed a signi ican enhancemen compa ed o nea PMMA. The imp o emen o C12-hec is al eady 45 % and hyb id-hec (DP 380) almos doubled he ensile modulus wi h an imp o emen o 84 %. The addi ion o he nanopla ele s has no signi ican in luence on he ensile s eng h. The elonga ion a b eak is educed by 35% in case o C12-hec and on he con a y shows an inc ease o 18% o he hyb id-hec (DP 380). Chap e 3 45 Figu e 3.9 Young’s modulus (o ange, s iped), ensile s eng h (g ey) and elonga ion a b eak (blue) o nea PMMA and wo di e en clay/PMMA nanocomposi es. The inco po a ion o high aspec a io nanopla ele s in o a PMMA ma ix al eady leads o a signi ican ein o cemen e ec compa ed o nea PMMA as demons a ed by Fische e al. in 201269. The op imiza ion o he p epa a ion me hod h ough solu ion blending elimina es any agglome a es o med in a no mal mel blending p ocess, which usually a e he cause o a signi ican educ ion in he ensile s eng h70. The absence o such agglome a es educes any local s ess concen a ion in he ma ix and hus he ensile s eng h o he composi e is no a ec ed by he addi ion o he nano ille . Signi ican shi s in he elonga ion a b eak beha iou we e obse ed depending on he ype o nano ille . Usually, he addi ion o igid nano ille s o a b i le ma ix leads o an inc ease in modulus a he expense o s eng h, s ain and oughness as emb i lemen akes place71. This beha iou was obse ed o he inco po a ion o C12-hec , which inc eased he modulus by 45 %, bu educed he elonga ion a b eak by 35 %. The clay ac s as a ba ie and hus es ic s he sliding o polyme chains among each o he . On he con a y a signi ican inc ease in modulus and elonga ion a b eak was obse ed o Hyb id mica-like pa icles 46 he no el hyb id nano ille , which emphasizes he impo ance o he addi ion o polyme ic chains ma ching he pola i y o he ma ix on o he hyb id’s su ace. This leads o a be e adhesion o he nano ille o he ma ix, which gene a es an e ec i e s ess ans e om he ma ix o he nano ille while s ill pa icipa ing in he sliding o polyme chains among each o he and consequen ly leads o a signi ican inc ease in bo h, he modulus and elonga ion a b eak wi hou sac i icing ensile s eng h. 3.3 Conclusion Su ace-ini ia ed ATRP was success ully employed o g a PMMA chains om he ex e nal basal planes o a shea -s i , mica-like K-hec o c ea e no el hyb id nano ille . The employed syn he ic luo ohec o i e was cha ac e ized by a high aspec a io and homogenei y o laye cha ge, while he mul iple ancho ing g oups o he syn hesized mac oini ia o enabled a s ong adhesion o he clay’s su ace. The kine ic s udy o si-ATRP o PMMA con i med a con olled polyme iza ion in a linea a ia ion. Fu he mo e, g a ed polyme chains allow o s able dispe sions o he hyb ids in a ious o ganic sol en s. The ob ained hyb id nano ille shows a s ong ein o cing e ec a e being compounded in o a PMMA ma ix due o he syne gis ic e ec o inhe en shea s i ness and huge la e al ex ension o he clay i sel and he op imized in e ace be ween he hyb id nano ille and he ma ix h ough addi ion o a ailo ed polyme ic shell. Chap e 4 47 4 Chap e 4: Pa chy hyb id pa icles based on poly- me g a ed mon mo illoni e (MMT) 4.1 P epa a ion o pa chy hyb id pa icles based on MMT To compa ibilize an immiscible bina y polyme blend, a hyb id clay pa icle wi h homogeneous shell as used in he las chap e is no pe ec . Based on he assump ion, ha a pa icle wi h a bina y polyme shell should be d awn owa ds he in e ace i placed in o a mix u e o wo immiscible componen s (polyme s in a blend o liquids o di e en pola i y) by he Picke ing e ec , we c ea ed disc-like pa icles wi h compa men alized su ace, bea ing pa ches o polyme , each ma ching one o he componen s o an immiscible blend (Figu e 4.1). We hypo hesize, ha he ac ion o polyme chains wi h un a ou able in e ac ions would collapse and s ay close o he solid su ace o he hyb id disc, whe eas polyme chains wi h a ou able in e ac ion would p o ude in o he ma ix. Fig. 4.1 Gene al app oach o pa chy hyb id nanodiscs ia g a ing o diblock copolyme s on o clay su ace and selec i e collapse o chains a an in e ace. Pa chy Hyb id Pa icles 48 4.1.1 Syn hesis o DMAEMA based diblock copolyme s ia sequen ial RAFT polyme iza ion Fig. 4.2 RAFT-polyme iza ion o DMAEMA using 2-cyano-2-p opyl benzodi hioa e (CPBDT) as chain ans e agen As shown in chap e 3 and in li e a u e, posi i ely cha ged poly(2- (dime hylamino)e hyl me hac yla e) (PDMAEMA) can i mly a ach o nega i ely cha ged su aces, like hose o laye ed silica es o colloidal silica64, 72. In his chap e , p o ona ed PDMAEMA is inco po a ed in o a diblock copolyme and, as i can be cha ged posi i ely depending on he pH o pe manen ly by qua e niza ion, is used as a lexible ca ionic ancho ing g oup o equip clay pa icles wi h a polyme ic shell. The polyme o DMAEMA is easily accessible ia RAFT polyme iza ion and can unde go copolyme iza ion wi h a ange o di e en monome s g ea ly con ibu ing o he lexibili y o modi ying clay su aces wi h polyme s o di e en pola i ies, esponsi eness and sensi i i ies. I se ed as an ancho o he MMT ex e nal planes ia ca ion exchange. The block-leng h was kep sho and s ayed in he ange o 14 o 20 epea ing uni s o all diblock-copolyme s, as wi h inc easing leng h o chain i becomes mo e likely o c osslink se e al pla ele s by he same ancho ing block. Con olled adical polyme iza ion by he RAFT-p ocess gua an ees low polydispe si ies o he ob ained polyme s which is a p econdi ion o gene a e well de ined mic ophase-sepe a ed solu ions and hus con ol o e pa ch size. Also RAFT polyme iza ion is applicable o a ious monome s and he syn hesis o block- copolyme s is acile. Chap e 4 55 Fig. 4.8 SEM images o hyb ids based on hec o i e (le ) and MMT ( igh ) modi ied wi h a 1:1 (mola ) mix u e o D17-b-M300 and D16-b-S360 in THF By his app oach i was possible o modi y se e al ypes o clay ( o kaolini e see chap e 5): The small pa icle ( ac oid) size and agglome a ion in o band-like s uc u es o sel -suppo ing clay ilms upon d ying makes i di icul o isualize he success ul g a ing and i s pa chiness in gene al on he su ace o MMT. Since no indi idual pla ele s a e isible, bu a he agglome a es o se e al µm in diame e , i is impossible o dis inguish polyme om pla ele s. As a p oo o p inciple la ge and s i e syn he ic clay was used. The same shea -s i K- luo ohec o i e om chap e 3 was modi ied ia “g a ing on o”. Quali a i e analysis o SEM images showed less g a ing densi y and mo e inhomogeneous su ace co e age (Fig. 4.8) as compa ed o expe imen s wi h polyme ic shells a ached ia a “g a ing om” echnique (Fig. 3.10). While SEM analysis o he syn he ic clays deli e ed e idence o success ul g a ing o polyme on o he clay su ace, i was no possible o p o e g a ing o bo h polyme species in his way. 1H-NMR analysis was used o de e mine whe he p e e en ial adso p ion o ei he o he polyme s occu ed. Ra ios be ween peaks o he 5 a oma ic p o ons in he PS block (δ=6.4-7.2 ppm) and he 3 p o ons o he CH3- O- es e g oup o he PMMA block (δ=3.6 ppm) whe e compa ed, be ween he solu ion used o modi y he clay and he supe na an a e cen i uga ion o he i s Pa chy Hyb id Pa icles 56 ime. Bo h a ios o PS o PMMA we e oughly he same be o e and a e modi ica ion (de ia ion o less han 10%), which leads o he assump ion ha adso p ion is p ima ily con olled by he PDMAEMA block, which is o compa able leng h in all cases, and he e is no signi ican p e e en ial adso p ion depending on he species o he second block wi h he gi en species. -100 0 100 200 300 400 500 600 700 800 80 85 90 95 100 Weigh [%] Tempe a u e [°c] Fig. 4.9 TGA esul s showing he empe a u e dependen weigh s o di e en hyb id pa icles: unmodi ied MMT (solid g ay), D16-b-S360 modi ied MMT (solid black), D17-b- M300 modi ied MMT (s iped g ay), pa chy hyb id MMT modi ied wi h bo h a o emen ioned diblock copolyme s (solid ed) To quan i y he amoun o su ace-bound polyme a he mog a ime ic analysis (TGA) was pe o med (Fig. 4.9): unmodi ied MMT showed a o al mass loss o 2 %, while all hyb ids showed a mass loss o a ound 12-15 % in he mos ele an egion (200-500 °C), which gi es a calcula ed g a ing densi y o 0.5 uni s o DMAEMA pe nm² o comple ely ex olia ed MMT using he ollowing o mula: Whe e; ρ is he g a ing densi y (ini ia o pe nm2), MD is he a e age mola amoun o DMAEMA uni s pe g o hyb id, NA is he A ogad o cons an and SA is he su ace Chap e 4 57 a ea o 68 m2/g. The calcula ed alue is a ound hal o he ca ion exchange capaci y (CEC) alue p o ided by he company o he employed MMT (PGV) in a heo e ical delamina ed s a e and. The disc epancy can be explained by incomple e ex olia ion. 4.2 Mechanical p ope ies o he clay/PMMA/PS nanocomposi es 4.2.1 P epa a ion o clay/PS/PMMA blends Dually modi ied PS/PMMA-pa chy hyb id pa icles, wi h he polyme pa ches on each side should be able o selec i ely collapse o ex end o ma ch he su ace ension o he polyme phase hey eside in, we e es ed as compa ibilize s in ilms o PS/PMMA blends cas om THF, a good sol en o bo h polyme s and a good dispe san o he hyb ids. Loca ed a an in e ace, each side should collapse he incompa ible polyme chains and ex end he compa ible ones in o he ma ix, o ming a Janus-like s uc u e. Fo compa ison and o be able o es ima e he e ec o he pa chy cha ac e addi ional blends wi h homogeneously modi ied clay (ei he PS o PMMA as shell) and blends wi h unmodi ied MMT we e p epa ed by sol en cas ing unde he same condi ions. A PS/PMMA a io o 1:2 (w /w ) was chosen. The Flo y-Huggins pa ame e o a blend o his molecula weigh is χSM = 0.041 a 20 °C74 indica ing i s incompa ibili y. The samples o ansmission elec on mic oscopy (TEM) we e p epa ed by cas ing he polyme solu ion wi h dispe sed clay in o a glass ial ollowed by slow d ying and mic o ome cu ing. The di e ence be ween PS and PMMA is clea ly isible in he TEM images (Fig. 4.9) e en wi hou selec i e s aining. Da k g ey a eas esul om s onge elec on con as o PS and ligh g ey a eas om PMMA, which is mo e easily damaged by he elec on beam. The clay pa icles appea e en da ke , almos black, and hei p o ile shapes a e clea ly isible due o hei s ong con as , he comple ely whi e egions a e holes in he ilm in oduced du ing ul a mic o ome cu ing. Pa chy Hyb id Pa icles 58 We a e awa e o he ac ha sol en e apo a ion will ap he sys em in a me as able s a e and such p epa ed ilms can only show a quali a i e aspec o compa ibiliza ion achie ed by ou hyb id pa icles. Fo pu e PS/PMMA blend ilms o compa able molecula weigh wi hou compa ibilize , i is known, ha la ge (se e al µm in diame e ) sphe ical domains o he mino i y phase inside a ma ix o med by he majo i y phase esul om phase seg ega ion51. F om li e a u e on classical o ganoclays (e.g. Cloisi e 20A), i is known, ha modi ica ion wi h simple alkyl chains will lead o dispe sion only in he PMMA phase o a PS/PMMA blend and o ma ion o clus e s in PS homopolyme blends.75 Analysis o blends mixed wi h PS-g a ed MMT (modi ied wi h D16-b-S360) showed ha he hyb ids wi hou excep ion s ay in he PS phase o assemble a he in e ace, hough no s ong endency o in e acial in e ac ion is obse ed (Fig. 4.10 a). Simila esul s a e ob ained o hyb ids based on PMMA-g a ed MMT (modi ied wi h D17-b-M300). Bo h hyb ids s ay in he phase o he polyme hei su ace is modi ied wi h. Though being he mino i y phase, we can ind p ominen ly huge domains o PMMA, illed wi h andomly o ien ed hyb id pla ele s (Fig. 4.10 b). The obse ed polygonal shape o polyme domains can be a ibu ed o inc eased iscosi y o he ille - ich phase a he han in e acial ac i i y, as he e a e only a ew pla ele s di ec ly assembled a he in e ace. Fig. 4.10 TEM images o 2:1 (w /w ) PS/PMMA blend ilms a) showing D16-b-S360 modi ied hyb ids in he PS phase only, b) D17-b-M300 modi ied hyb ids in PMMA phase. The ac ion o he added hyb id is 5 w % and he scale ba ep esen s 1 µm. b ) a ) Chap e 4 59 Blends compa ibilized wi h pa chy hyb id pa icles (shell based on modi ica ion wi h a 1:1 (mola ) mix u e o D16-b-S360 and D17-b-M300) show a comple ely di e en s uc u e. Hyb ids a e andomly o ien ed and dis ibu ed o e he whole blend in bo h phases and he in e ace (Fig. 4.11 a). The domain size is educed compa ed o blends compa ibilized wi h unmodi ied and single-polyme -species modi ied clay. Domain shapes a e comple ely i egula (Fig. 4.11 b), ollowing he shape o pla ele s whe e hey eside in he in e ace. As no all o he in e acial a ea is co e ed, he hyb ids ac as a physical ba ie and inc ease iscosi y, p e en ing he o ma ion o la ge sphe ical domains (Fig. 4.11 b). Rega ding he s uc u e o he polyme ic shell o he pa chy hyb ids, we expec h ee di e en cases: a hyb id esiding in he PS phase will ha e i s PMMA chains collapsed nea he clay su ace, sc eened by ex ended PS chains, in e ac ing wi h he ma ix. Hyb ids in he PMMA phase will show opposi e beha iou , whe e PMMA chains a e ex ended and PS chains a e collapsed. In an in e ace, a hyb id would show bo h a o emen ioned beha iou s a once, acco ding o he polyme phase he espec i e side is acing. Fig. 4.11 TEM images o 2:1 (w /w ) PS/PMMA blend ilms a) showing pa chy hyb ids wi h PMMA and PS shell in he PS phase, he PMMA phase and he in e ace, b) close up. The ac ion o he added pa chy hyb ids is 5 w % and he scale ba ep esen s 1 µm. As he blend mo phology is c ea ed unde in luence o THF as a sol en and is ixa ed only a e slow e apo a ion o he sol en , he shell o each hyb id has enough ime a ) b ) Pa chy Hyb id Pa icles 60 and is lexible enough o ex end and collapse i s polyme chains o ma ch he in e acial ension / su ace ene gy o he polyme phase i esides in. Compa ed o a pu e Janus o Picke ing pa icle i can ind i s ene ge ic minimum no only a an in e ace, bu inside one o he phases as well. 4.2.2 DMA o he blends F om he a ie y o DMA da a, he s o age modulus, E', is plo ed in dependence o he hea ing empe a u e, T. (Fig. 4.12). 20 40 60 80 100 120 140 160 -0,5 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 S o age Modulus E' [GPa] Tempe a u e [°C] Fig. 4.12 DMA esul s showing he empe a u e dependend s o age moduli o 2:1 PS:PMMA blends: uncompa ibilized pu e blend (solid black), blend compa ibilized wi h 5 w % alkylammonium-modi ied PGV (do ed g ay) and compa ibilized wi h pa chy hyb ids o PGV (solid ed). The s o age modulus o a pu e, uncompa ibilized 2:1 PS/PMMA blend is 3.2 ±0.1 GPa a 35 °C, compa ibiliza ion wi h a C12-alkylammonium modi ied MMT esul ed in a s o age modulus inc ease o ~7 % o 3.4 ±0.1 GPa, while compa ibiliza ion by a pa chy hyb id esul ed in an inc ease o 17 % o 3.9 ± 0.1 GPa (Fig. 4.12). Thus, a signi ican ly highe deg ee o ein o cemen is obse ed by compa ibilizing he blend wi h pa chy hyb ids han wi h simple o ganoclay. Chap e 4 61 4.3 Conclusion The expe imen al da a p esen ed con i m he success ul g a ing o di e en pa ches o wo diblock copolyme species on o he su ace o clays om he smec i e g oup, c ea ing no el pa chy hyb id pa icles. We used a e sa ile and simple app oach o syn hesize unc ional diblock copolyme s which consis o a sho ancho ing block o a ach o he clay su ace and a longe block adding he desi ed pola i y o unc ionali y. A combina ion o wo o mo e o di e en diblock copolyme s g a ed on o clay can lead o a dynamic shell which is able o adap o en i onmen s o di e en pola i y and e en show in e acial ac i i y in immiscible polyme blends. The dispe sion in bo h phases and he in e ace o an immiscible polyme blend indica es he ele ance o he heo e ical concep o selec i e polyme chain collapse and ex ension in he polyme ic shell o he pa icles and leads o a ein o cing e ec , shown in an inc ease o up o 17 % in Young’s-modulus. While he p esen ed me hod did no lead o Janus- ype beha iou , cha ac e ized by p e e able p esence in he in e ace, he me hod should allow u he in e es ing combina ions o di e en diblock copolyme s o unc ionalize he pa chy shell o he hyb id pa icles, opening up new ields un eachable wi h homogeneously modi ied pa icles. Hyb id Janus Pa icles 62 5 Chap e 5: Hyb id Janus pa icles based on polyme modi ied kaolini e This chap e is he esul o he coope a ion wi h Dunja Hi seman and majo pa s o his chap e we e published in Polyme 2013, 54, 1388-1396 unde he i le: “Hyb id Janus pa icles based on polyme -modi ied kaolini e” by S ephan Weiss, Dunja Hi semann, Be nha d Bie sack, Mazen Ziadeh, Axel H.E. Mülle , Jose B eu, Tex and espec i e igu es a e adap ed and ep in ed wi h pe mission. Copy igh 2013 Else ie 5.1 P epa a ion o hyb id janus pa icles based on kaolini e The in es iga ions o andomly compa men alized, pa chy hyb id pa icles based on MMT showed in e acial ac i i y oo low o a ach o he in e phase be ween PS and PMMA in an immiscible blend o bo h. One o he easons we ound was he lexibili y o he pa icle shell, wi h immiscible pa ches collapsing and miscible pa ches ex ending in o he ma ix, hus keeping he hyb id pa icle lexible enough o adap o i s su oundings, independen o whe e i was loca ed. The nex logical s ep was o c ea e disc-like Janus hyb id pa icles, wi h a shell comp ised o exac ly wo chemically dis inc , opposi ely loca ed compa men s, inc easing in insic pola i y o he hyb id and a ge ing he in e phase o he blend as he ene ge ically mos a ou able loca ion. 2:1 Smec i es, like hec o i e and mon mo illoni e a e no well sui ed o c ea e Janus pa icles, as i is e y edious o selec i ely add ess each o hei ex e nal basal planes indi idually. Howe e , due o i s pola c ys al s uc u e, he wo opposing ex e nal basal planes o kaolini e, TS and OS a e unca ed by dis inc unc ional g oups and may selec i ely be modi ied by simple ca ion exchange and co alen g a ing ia ca echol g oups, espec i ely, making i he pe ec base o a disc-like hyb id Janus pa icle. As an example we chose poly((2- dime hylamino)e hyl me hac yla e)-block-polys y ene (D16-b-S115) and poly(3-(2,3- dihyd oxy-benzoyloxy)p opyl me hac yla e)-s a -(me hyl me hac yla e)) (PCM). Chap e 5 63 HO OH O O OO *3 O N O20 O O * 90 s a block * 115 H (H2C)3 Fig. 5.1 S uc u e o poly(3-(2,3-dihyd oxybenzoyloxy)p opyl me hac yla e)-s a -(me hyl me hac yla e) (PCM) ( op) and poly(2-(dime hylamino)e hyl me hac yla e)-block- polys y ene (D16-b-S115) ca ions (bo om). PCM is a s a is ical copolyme , while D16-b-S115 is a block copolyme (Fig. 5.1). Consequen ly, bo h modi ie s in e ac wi h he kaolini e basal planes in a di e en manne (Fig. 5.2). PCM will likely be close o he OS, o ming sho loops o lying la . In con as , he polys y ene block migh a ange b ush-like on he TS o he kaolini e. The esul ing Janus pa icles a e ailo ed o compa ibilizing PS-PMMA o indus ially mo e ele an PPE–SAN (poly(2,6-dime hyl-1,4-phenylene e he ) (PPE), poly(s y ene- co-ac yloni ile) (SAN)) blends50, 51. Hyb id Janus Pa icles 64 Fig. 5.2 Schema ic pic u e o a) p is ine kaolini e, b) modi ied wi h D16-b-S115 on he e ahed al su ace (TS), c) u he modi ied wi h PCM on he opposi e oc ahed al su ace (OS) and d) embedding o he inal hyb id pa icle a he in e ace in a PS- PMMA blend. 5.1.1 Syn hesis o he copolyme s PCM and D16-b-S115 Syn hesis o he ca echol-modi ied poly(me hyl me hac yla e) copolyme (PCM) Ini ially, a sui able ca echol modi ied me hac yla e monome was p epa ed o copolyme iza ion wi h me hyl me hac yla e (MMA). 3,4-Dibenzoxy-(3- hyd oxyp opyl)benzoa e 2 was ob ained om 3,4-dibenzoxybenzoic acid 1.57 Reac ion o 2 wi h me hac yloyl chlo ide ga e he mixed dies e 3 (Scheme 5.1). OBn OBn CO2H OBn OBn O O OH OBn OBn O O O O 12 3 (i) (ii) Scheme 5.1 Syn hesis o he ca echol monome . Reagen s and condi ions: (i) SOCl2, CH2(CH2OH)2, E 3N, THF / DCM, . ., 5 h, 51%; (ii) CH2C(CH3)COCl, E 3N, DCM, . ., 3 h, 67%. Monome 3 was copolyme ized wi h a 30- old excess o MMA by ee adical polyme iza ion using AIBN as ini ia o and dodecane hiol as ans e agen o gain con ol and educe molecula weigh , gi ing copolyme 4. 1H NMR spec oscopy and Chap e 5 71 he s a is ical copolyme PCM s ays compa a i ely close o he su ace. Mo eo e , he hyd a ed ino ganic ca ions esiding a unmodi ied TS con ibu e o an e icien elec os a ic s abiliza ion o PCM-kaolini e in wa e . Al e na i ely, he s abili y o PCM-kaolini e migh be explained by he o ma ion o sandwich s uc u es as depic ed in Fig. 6a (blue amed inse ). Fo such sandwich s uc u es only he hyd ophilic TS a e exposed o he aqueous media. Such polyme -b idged sandwich s uc u es would no be expec ed o D16-b-S115-kaolini e because he long PS- b ushes will hampe dime - o ma ion s e ically. In THF (Fig. 5.6b) bo h, he PCM-kaolini e (Fig. 5.6b, blue) as well as he D16-b-S115- kaolini e (Fig. 5.6b, ed), showed good s abili y which in u n is compa able o ha o he dually modi ied D16-b-S115/PCM-kaolini e (Fig. 5.6b, black). This sugges s ha e en he sho PCM loops a he OS we e able o assu e a good s abili y in THF and expec edly he longe chains pe o m as well. Mo eo e , i would be expec ed ha sandwich s uc u es o D16-b-S115- and PCM-kaolini e a e o med (Fig. 5.6b, ed and blue squa es). Fig. 5.6 In eg a ed anspa ency o 0.25 w % suspensions in a) wa e and b) THF o p is ine kaolini e (pink), PCM-kaolini e (blue), D16-b-S115-kaolini e ( ed) and D16-b-S115/PCM- kaolini e (black) unde ime dependen cen i ugal o ces o 300 pm, 600 pm, and 900 pm. In summa y, he s abili ies in wa e - and THF-suspensions obse ed o he di e en kaolini e samples a e in line wi h a speci ic modi ica ion o TS and OS by D16-b-S115 and PCM, espec i ely, and s ongly suppo he Janus cha ac e o D16-b-S115/PCM- kaolini e. Hyb id Janus Pa icles 72 5.2 TEM Analysis o he mo phology o he hyb id-kaolini e / PMMA/ PS nanocomposi es Dually modi ied D16-b-S115/PCM-kaolini e, whe e he su ace ensions o he opposing basal su aces a e ine- uned o ma ch PS and PMMA, espec i ely, was es ed as compa ibilize in ilms o incompa ible PS-PMMA blends cas om THF, simila o he p ocess used in chap e 4.3.4. Fo compa ison and o be able o es ima e he e ec o he Janus cha ac e in excess o he pu e Picke ing e ec addi ional blends wi h unila e ally modi ied and blends wi h unmodi ied kaolini e we e p epa ed by sol en cas ing unde he same condi ions. A PS/PMMA a io o 1:2 (w /w ) was chosen. The samples o ansmission elec on mic oscopy (TEM) we e p epa ed by cas ing he polyme solu ion wi h dispe sed clay in o a glass ial ollowed by slow d ying and mic o ome cu ing. All images a e uns ained. Da k g ey a eas esul om s onge elec on con as o PS and ligh g ey a eas om PMMA. The kaolini e pa icles appea e en da ke , almos black, and hei shapes a e clea ly isible due o hei s ong con as , he comple ely whi e egions a e holes in he ilm, in oduced du ing ul a mic o ome cu ing. Simila o wha was he case wi h expe imen s conduc ed in chap e 4.3.4 we a e awa e o he ac ha sol en e apo a ion will ap he sys em in a me as able s a e and such p epa ed ilms can only show he quali a i e aspec o compa ibiliza ion achie ed by ou hyb id pa icles. To de e mine indus ially ele an quan i a i e e ec s, like mechanical p ope ies o compa ibilized blends, i is necessa y o conduc ex usion expe imen s and mechanical es s. Fo pu e PS/PMMA blend ilms o compa able molecula weigh ha con ain no compa ibilize s, i is known, ha la ge (se e al µm in diame e ) sphe ical domains o he mino i y phase inside a ma ix o med by he majo i y phase esul om phase seg ega ion.51 Wi h unmodi ied kaolini e we obse e mac ophase sepa a ion (Fig. 5.7a). No dispe sion is achie ed, only la ge agg ega es o clay pa icles can be ound, sepa a ing om he ma ix, apped inside he polyme phase whe e hey happen o be upon d ying (Fig. 5.7a). This beha iou is expec ed due o he clay’s hyd ophilic Chap e 5 73 na u e (cha ged on one side and pola hyd oxy g oups on he o he side) and he ac ha i does no o m s able dispe sions in THF (and hus is ha d o dispe se in he Polyme mix u e o s a wi h). In ano he expe imen we modi ied he TS o kaolini e wi h dodecylamine, which is compa able in s uc u e o he alkyl ammonium sal s used o p epa e comme cial o ganoclay like he widely used Cloisi e 20A. He e we can obse e clus e ing in he PMMA phase (Fig. 5.7b). Like in he Lumi uge expe imen s we expec he kaolini e o o m sandwich s uc u es wi h he alkyl chains o he o ganophilized TS agg ega ed ia hyd ophobic in e ac ions in he inside and he pola OS a he ou side o he o he way ound. In none o he cases we could ind a su ace which has high compa ibili y wi h any o he polyme phases and hus is no dispe sed homogeneously. This obse a ion is in good ag eemen wi h li e a u e abou o he o ganoclay (e.g. Cloisi e 20A), which dispe ses only in he PMMA phase o a PS/PMMA blend and o ms s ong clus e s in PS homopolyme blends.75 Ob iously modi ica ion o one side is no su icien o align he pa icles a he in e ace unde hese condi ions. Hyb id Janus Pa icles 74 Fig. 5.7 TEM images o 3:7 (w /w ) PS/PMMA blend ilms. a) wi h p is ine kaolini e, b) wi h unila e ally o ganophilized kaolini e, c) wi h D16-b-S115/PCM-kaolini e, and d) close up a an in e - ace. The ac ion o he clay is 5w % and he scale ba ep esen s 500 nm. In con as , in he ilm p epa ed wi h he Janus- ype D16-b-S115/PCM-kaolini e (Fig. 5.7c, d) he kaolini e pa icles a e assembled exac ly a he in e ace be ween bo h polyme phases. A nea ly ull co e age o he in e ace by compa ibilize is ealized. Due o he Janus cha ac e o he modi ied kaolini e he in e acial ension o he pla ele s in he blend in e ace should be e y low. The e o e, he assembly o he pa icles a he in e ace is ene ge ically highly a o ed. As a consequence, he PS domains a e no longe sphe ical bu appea polygonal ollowing he shape o he clay pla ele s (Fig. 5.7c, d). Chap e 5 75 5.3 Conclusion A synopsis o all expe imen al da a p esen ed con i ms ha he ex e nal basal planes o kaolini e pla ele s can be selec i ely add essed by polys y ene and PMMA, simila o wha has been s udied in de ail o he molecula modi ica ion wi h Ru(bpy)32+ and a phospho ous-labelled ca echol (3-Diphenylphosphinyloxyp opyl-3,4- dihyd oxybenzoa e) in li e a u e21. Janus- ype D16-b-S115/PCM-kaolini e pla ele s ob ained by dual modi ica ion showed in e acial ac i i y in a sol en -cas PS/PMMA blend ilm. Ob iously, blend p epa a ion ia mel ex usion would be ad an ageous. Wo k in ha di ec ion is on he way bu he esul s ob ained by sol en -cas ing al eady gi e a s ong indica ion on he e iciency o he hyb id Janus pa icles as blend compa ibilize s. While he p esen ed wo k ep esen s a p oo o p inciple, he app oach is, o cou se, highly modula and should allow o acile and a o dable ine- uning o app op ia e compa ibilize s o a b oad ange o blend sys ems. The in insically pola s uc u e o kaolini e se es as e sa ile co e o hese Janus pla ele s. Adjus men o he su ace ensions o bo h basal planes can easily and selec i ely be ailo ed o each speci ic blend composi ion. Mo eo e , pa icle size dis ibu ion and mo phology (aspec a io) may be a ied o e a wide ange by he choice o he kaolini e sou ce. Fu he mo e, ha concep is no es ic ed o kaolini e bu can be ans e ed o any o he ino ganic ma e ial which possesses a pola c ys al s uc u e and whe e opposing c ys al aces a e unca ed by chemically di e en unc ional g oups, pa ing he way o selec i e modi ica ion. An addi ional ad an age o he concep should be an inhe en ein o cemen o he blend by he ino ganic ille , which, mo eo e , is concen a ed a he blends in e aces. This should c ea e a syne gis ic e ec s e ching a beyond a pu e Picke ing e ec and should boos he mechanical p ope ies o he blend. Re e ences 76 6 Chap e 6: Re e ences 1. Hussain, F.; Hojja i, M.; Okamo o, M.; Go ga, R. E., Jou nal o Composi e Ma e ials 2006, 40, (17), 1511-1575. 2. Ga y W. Beall, C. E. P., Fundamen als o Polyme -Clay Nanocomposi es. Camb idge Uni e si y P ess: 2011. 3. B iga i, M. F.; Galan, E.; Theng, B. K. G.; Fayza Be gaya, B. K. G. T. a. G. L., Chap e 2 S uc u es and Mine alogy o Clay Mine als. 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