polyme s
A icle
Re e sible Ac ua ion Abili y upon Ligh S imula ion
o he Sma Sys ems wi h Con ollably G a ed
G aphene Oxide wi h Poly (Glycidyl Me hac yla e)
and PDMS Elas ome : E ec o Compa ibili y and
G aphene Oxide Reduc ion on he
Pho o-Ac ua ion Pe o mance
Jose Osicka 1ID , Mi osla M lik 1ID , Ma ke a Ilciko a 2,*, Ba bo a Hanuliko a 1,
Pa el U banek 1ID , Michal Sedlacik 1,*ID and Ja osla Mosnacek 2,3 ID
1Cen e o Polyme Sys ems, Uni e si y Ins i u e, Tomas Ba a Uni e si y in Zlín, T ida T. Ba i 5678,
760 01 Zlín, Czech Republic; [email p o ec ed] (J.O.); [email p o ec ed] (M.M.); [email p o ec ed] (B.H.);
[email p o ec ed] (P.U.)
2Polyme Ins i u e, Slo ak Academy o Sciences, Dúb a ska ces a 9, 845 41 B a isla a, Slo akia;
[email p o ec ed]
3Cen e o Ad anced Ma e ials Applica ion, Slo ak Academy o Sciences, Dúb a ska ces a 9,
845 11 B a isla a, Slo akia
*Co espondence: [email p o ec ed] (M.I.); [email p o ec ed] (M.S.);
Tel.: +421-232-294-347 (M.I.); +420-576-038-027 (M.S.)
Recei ed: 20 June 2018; Accep ed: 26 July 2018; Published: 28 July 2018


Abs ac :
This s udy is ocused on he con ollable educ ion o he g aphene oxide (GO) du ing
he su ace-ini ia ed a om ans e adical polyme iza ion echnique o glycidyl me hac yla e
(GMA). The success ul modi ica ion was con i med using TGA-FTIR analysis and TEM mic oscopy
obse a ion o he polyme shell. The simul aneous educ ion o he GO pa icles was con i med
indi ec ly ia TGA and di ec ly ia Raman spec oscopy and elec ical conduc i i y in es iga ions.
Enhanced compa ibili y o he GO-PGMA pa icles wi h a polydime hylsiloxane (PDMS) elas ome ic
ma ix was p o en using con ac angle measu emen s. P epa ed composi es we e u he in es iga ed
h ough he dielec ic spec oscopy o p o ide in o ma ion abou he polyme chain mobili y h ough
he ac i a ion ene gy. Dynamic mechanical p ope ies in es iga ion showed an excellen mechanical
esponse on he dynamic s imula ion a a b oad empe a u e ange. The mal conduc i i y e alua ion
also con i med he u he pho o-ac ua ion capabili y p ope ies a ligh s imula ion o a ious
in ensi ies and p o ed ha composi e ma e ial consis ing o GO-PGMA pa icles p o ide sys ems
wi h a signi ican ly enhanced capabili y in compa ison wi h nea GO as well as nea PDMS ma ix.
Keywo ds:
g aphene oxide; educ ion; SI-ATRP; pho o- esponsi e ma e ial; ligh -s imuli ma e ial;
dielec ics; poly (glycidyl me hac yla e); dynamic mechanical analysis
1. In oduc ion
Sma ma e ials belong o a g oup o ma e s. Such physical p ope ies can be changed
upon ex e nal s imulus i.e., elec ic [
1
–
4
] o magne ic ield [
5
–
8
], pH [
9
–
12
], empe a u e [
13
–
16
], o
ligh [
17
–
20
]. The sys ems exhibi ing e e sible pho o-ac ua ion and ligh - esponsi e p ope ies a e
i al o he esea ch communi y only du ing he las decade while he es o he abo e men ioned
p ope ies ha e been pa o he esea ch communi y o e he pas 30 yea s. The e o e, he e a e s ill
Polyme s 2018,10, 832; doi:10.3390/polym10080832 www.mdpi.com/jou nal/polyme s
Polyme s 2018,10, 832 2 o 14
many d awbacks in his opic like s abili y o he sys ems o e en pe o mance, which e e sibly
con ac s o elonga es he polyme composi e sample upon ligh s imula ion. Ma e ials exhibi ing
his phenomenon can ind u iliza ion in a ious sys ems con olling he damping p ope ies [
21
],
sensing [
22
], o hap ic displays [
23
]. The e o e, he b oad applica ions belong o he ield o
elec onic [24], ci il enginee ing [25], o medicine [26], espec i ely.
In hese applica ions, he g aphene oxide (GO) pa icles as a pa o sma sys ems we e p ope ly
in es iga ed due o hei unique p ope ies, i.e., good dispe sibili y in he su ounding media [
27
],
possible pos - unc ionaliza ion [
28
], a e easily educed, and, he e o e, p o ide unabili y o he
elec ical conduc i i y [
29
]. The e a e a ious app oaches ega ding how o educe he GO pa icles
such as ea men wi h hyd azine [
30
], educ ion in he acidic en i onmen [
31
], o simul aneous
educ ion o GO du ing he su ace-ini ia ed a om ans e adical polyme iza ion (SI-ATRP) [32].
Due o he high equi emen s in he abo e men ioned applica ions on he inal ma e ial and om
he mechanical and s abili y poin o iew, he u iliza ion o poly (dime hyl siloxanes) PDMS is e y
equen [
33
]. Such PDMS ma e ial can be ei he ailo ed by c oss-linking densi y o using he addi ion
o silicone oil and a cu ing agen . Howe e , he e is s ill a lack o compa ibili y o PDMS wi h common
ille s such as MWCNT, g aphene, o e en GO and, he e o e, such ille s need o be modi ied in
o de o imp o e compa ibili y and dispe sibili y as well as o e all p ope ies o p epa ed composi e
ma e ials. The e a e a ious echniques o modi ica ion using su ac an s [
34
], bu such sys ems
a e a he ins able o uncon olled polyme iza ion om he su ace, which signi ican ly changes he
p ope ies o ille [
35
] and, he e o e, he SI-ATRP app oach seems o be a e y con enien me hod o
su ace modi ica ion using a a ie y o monome s [
27
,
32
,
36
,
37
] o copolyme s [
38
], which signi ican ly
imp o es he compa ibili y while he basic physical p ope ies such as mechanical o elec ical a e
a ec ed only negligibly.
The e o e, his a icle is ocused on he SI-ATRP o glycidyl me hac yla e (GMA) om he su ace
o GO pa icles in o de o imp o e hei compa ibili y wi h PDMS. Success ul modi ica ion o GO by
sho polyme chains was p o ed using TEM and TGA-FTIR measu emen s. The compa ibili y,
mechanical, dielec ic, and pho o-ac ua ion p ope ies we e in es iga ed when special aim was
concen a ed on he e ec o ligh in ensi y on he inal pho o-ac ua ion pe o mance.
2. Ma e ials and Me hods
G aphi e (powde , <20
µ
m, syn he ic), sul u ic acid (H
2
SO
4
, 95%–98%), sodium ni a e (NaNO
3
,
≥
99%), po assium pe mangana e (KMnO
4
, 97%), hyd ogen pe oxide (H
2
O
2
, 29.0–32.0 w %),
α
-b omoisobu y yl b omide (BiBB, 98%), ie hylamine (TEA,
≥
99%), glycidyl me hac yla e (GMA,
98%), e hyl
α
-b omoisobu y a e (EBiB, 98%), N,N,N
0
,N”,N”-pen ame hyldie hylene iamine (PMDETA,
≥
99%), coppe b omide (CuB ,
≥
99%), anisole (99%), and die hyl e he (
≥
99%) we e all pu chased
om Sigma Ald ich and we e used as ecei ed.
The g aphene oxide was ab ica ed om g aphi e powde by a modi ied Humme s me hod [
39
].
The p oduc was sepa a ed in a high-speed cen i uge (So all LYNX 4000, The mo Scien i ic, Wal ham,
MA, USA) ope a ing a 10,000 pm o 20 min a 25
◦
C. The cleaning ou ine was based on he dispe sion
o he GO in 0.1 M HCl and hei e–sepa a ion in a cen i ugal ield. The p ocedu e was epea ed
wi h dis illed wa e se e al imes un il he pH has eached a alue o 7. A e wa d, he pa icles
we e lyophilized in o de o emo e he esidual amoun o wa e a e pu i ica ion and emo e he
b own powde ha was ob ained. The ini ia o BiBB was immobilized, acco ding o he p ocedu e
desc ibed in de ail elsewhe e [
32
]. Two a ious polyme iza ions om he su ace o GO pa icles
in o de o p epa e poly (glycidyl me hac yla e)-modi ied GO (GO-PGMA and GO-PGMA-2), we e
pe o med by he ollowing p ocedu e. The mola a io o eac an s [GMA]:[EBiB]:[CuB ]:[PMDETA]
was [100]:[1]:[1]:[4] and [100]:[1]:[1]:[2] while anisole (50 ol. %) was used as a sol en . The p esence o
oxygen was minimized by degassing he sys em by se e al eeze-pump- haw cycles and a e he
las cycle by illing he sys em wi h a gon. Las ly, he CuB ca alys was added unde a gon low and
polyme iza ion was ca ied ou a 60
◦
C o 4 h and a 50
◦
C o 12 h o polyme iza ions pe o med
Polyme s 2018,10, 832 3 o 14
wi h 4:1 and 2:1 a io o PMDETA o CuB , espec i ely. The p oduc was pu i ied by il a ion using
DMF, ace one, and die hyl e he and d ied using lyophiliza ion.
1
H nuclea magne ic esonance (NMR) spec a we e eco ded a 25
◦
C using an ins umen
(400 MHz VNMRS Va ian, Tokyo, Japan) wi h deu e a ed chlo o o m (CDCl
3
) as a sol en . The
1
H
NMR was used o de e mine he monome con e sion om he a io o a ea o peaks assigned o
PGMA o he a ea o peaks assigned o bo h PGMA and GMA (Figu e 1). The mola mass and
polydispe si y (Ð) o PGMA chains we e in es iga ed using gel pe mea ion ch oma og aphy (GPC)
on he GPC ins umen (PLGPC220, Agilen , Hachioji, Japan) equipped wi h GPC columns (Wa e s
515 pump, wo PPS SDV 5 lm columns (diame e o 8 mm, leng h o 300 mm, 500 Å + 105 Å)) and a
Wa e s 410 di e en ial e ac i e index de ec o empe ed o 30
◦
C. The nea GO and GO wi h a g a ed
PGMA polyme laye we e obse ed using a ansmission elec on mic oscope (TEM, JEM-2100Plus,
Jeol, Tokyo, Japan). The samples o he TEM analysis we e p epa ed by dispe sing he pa icles in
ace one using mechanical s i ing o 5 and 2 min o sonica ion and d opping he esul an suspension
on o a coppe g id. The Raman Shi (3 scans, esolu ion o 2 cm
−1
) we e collec ed on a Nicole DXR
(Nicole , Rhinelande , WI, USA) using an exci a ion wa eleng h o 532 nm. The in eg a ion ime
was 30 s while he lase powe on he su ace was se o 1 mW. The powde s unde in es iga ion
we e comp essed o he o m o pelle s (diame e o 13 mm, hickness app 1 mm). The pelle s we e
used o elec ical conduc i i y measu emen s using a wo-poin me hod (Kei hley 6517B, Cle eland,
OH, USA). The con ac angle (CA) alues we e e alua ed om he s a ic sessile d op me hod on
he pelle s ca ied ou on a Su ace Ene gy E alua ion sys em equipped wi h a CCD came a (Ad ex
Ins umen s, B no, Czech Republic). A d ople (5
µ
L) o PDMS was ca e ully d ipped on o he su ace
and he CA alue was eco ded. The p esen ed CA esul s a e he a e age alues om 10 independen
measu emen s. The he mo-oxida ion decomposi ion o he samples was on-line moni o ed using
a he mog a ime ic analyze (TGA) ope a ing in an oxygen a mosphe e coupled wi h FTIR wi h a
help o Nicole iS10 equipped wi h TGA-IR module (The mo Scien i ic, Wal ham, MA, USA). In he
Figu e 2, he highligh ed bands a e hose whe e he FTIR signal was collec ed in o de o p o e he
p esence o he a ious componen s in he GO-based powde s.
The composi es con aining a ious amoun o GO-based pa icles we e p epa ed using he
ollowing s anda d p ocedu e: PDMS (Sylga d 184, A lan a, GA, USA) was mixed wi h silicone oil
and subsequen ly a c oss-linke was added in a ios o PDMS: silicone oil: c oss-linke 7/3/1 and,
las ly, 0.1 ol. % o he pa icles was added be o e he cu ing. In he case o he nea PDMS ma ix, we
u he in es iga ed he same a io o PDMS in his pape . Silicone oil and a c oss-linke was used bu
wi hou he addi ion o he pa icles. In he case o all samples, he mix u es we e degassed using a
acuum o en in he ou cycles a 10 mba a oom empe a u e and hen placed in o he o en and
cu ed a an ele a ed empe a u e se o 60 ◦C o 6 h.
The he mal conduc i i y was measu ed by one side con ac me hod using he TCi model (C-Te m
Technologies, Vancou e , BC, Canada). The iscoelas ic p ope ies o bo h he nanocomposi e and
pu e polyme ma ix we e s udied h ough he dynamic mechanical analysis (DMA) in ensile mode.
All measu emen s we e pe o med a a linea iscoelas ic egion. The measu emen was done a 1 Hz
in he empe a u e ange om
−
150 o 150
◦
C. To p o ide in o ma ion abou how he modi ica ion o
he GO wi h PGMA g a s in luences he s ain o he ma e ials, a dependence o he s o age and loss
moduli was plo ed agains he change in he leng h
∆
L, i.e., pa ame e speci ied in he expe imen al
pho o-ac ua ion in es iga ions. The measu emen s we e pe o med a 1 Hz and a 25
◦
C. The dielec ic
spec oscopy anged om a empe a u e o
−
150 o 100
◦
C and anged in equency om 10
−1
o
107Hz, which we e employed o in es iga e he polyme chains dynamics.
The glass ansi ion p ocess was e alua ed h ough ac i a ion ene gies calcula ed om he
A henius equa ion (Equa ion (1)) in o de o see he e ec o modi ica ion on he elaxa ion p ocesses
in he PDMS based composi es.
β= ∞expEa
kBT, (1)
Polyme s 2018,10, 832 4 o 14
whe e E
a
is he ac i a ion ene gy,
∞
is he p e-exponen ial ac o , Tis he modynamic empe a u e,
and kBis he Bol zmann cons an .
In o de o p ope ly in es iga e he polyme chains dynamics, he loss pe mi i i y need o be
ecalcula ed o he loss modulus. This ecalcula ion was based acco ding o Equa ion (2) [40].
M∗=1
ε∗
M0=ε0
ε02+ε00 2
M00 =ε00
ε02+ε00 2
(2)
whe e
ε
* is complex pe mi i i y and
ε0
and
ε
” a e ela i e pe mi i i y and loss pe mi i i y,
espec i ely. M* is he complex dielec ic modulus and M
0
and M” a e s o age and dielec ic loss
moduli, espec i ely.
Polyme s 2018, 10, x FOR PEER REVIEW 4 o 14
whe e Ea is he ac i a ion ene gy, 𝑓
∞is he p e-exponen ial ac o , T is he modynamic empe a u e,
and kB is he Bol zmann cons an .
In o de o p ope ly in es iga e he polyme chains dynamics, he loss pe mi i i y need o be
ecalcula ed o he loss modulus. This ecalcula ion was based acco ding o Equa ion (2) [40].
22
22
*
*1


















M
M
M
(2)
whe e ε* is complex pe mi i i y and ε′ and ε″ a e ela i e pe mi i i y and loss pe mi i i y,
espec i ely. M* is he complex dielec ic modulus and M′ and M″ a e s o age and dielec ic loss
moduli, espec i ely.
Figu e 1. Rep esen a i e 1 H NMR spec um om il e ed polyme iza ion mix u e o glycidyl
me hac yla e pe o med wi h [GMA]:[EBiB]:[CuB ]:[PMDETA] a io o [100]:[1]:[1]:[4] a 60 °C o
4 h. The monome con e sion was 43%.
The pho o-ac ua ion abili y o bo h he ma ix and composi e samples was in es iga ed using
he mal mechanical analysis (TMA, Me le Toledo, Columbus, OH, USA), which was p e iously
published [15]. Red LED diode (Luxeon Rebell, Philips, Ams e dam, he Ne he lands) was used o
i adia ion. I adia ion was applied o 10 s a 627 nm wi h 6, 9, and 12 mW ligh sou ce in ensi y
unde 10% p e-s ain o he samples. The maximum alue o ac ua ion is cha ac e ized by a change
in sample leng h du ing he exposi ion o ligh , ΔL = (L0 − L)/L0, whe e L0 is he leng h o non-i adia ed
sample and L is he leng h o an i adia ed sample.
Figu e 1.
Rep esen a i e
1
H NMR spec um om il e ed polyme iza ion mix u e o glycidyl
me hac yla e pe o med wi h [GMA]:[EBiB]:[CuB ]:[PMDETA] a io o [100]:[1]:[1]:[4] a 60
◦
C o 4 h.
The monome con e sion was 43%.
The pho o-ac ua ion abili y o bo h he ma ix and composi e samples was in es iga ed using
he mal mechanical analysis (TMA, Me le Toledo, Columbus, OH, USA), which was p e iously
published [
15
]. Red LED diode (Luxeon Rebell, Philips, Ams e dam, he Ne he lands) was used o
i adia ion. I adia ion was applied o 10 s a 627 nm wi h 6, 9, and 12 mW ligh sou ce in ensi y
unde 10% p e-s ain o he samples. The maximum alue o ac ua ion is cha ac e ized by a change in
sample leng h du ing he exposi ion o ligh ,
∆
L= (L
0−
L)/L
0
, whe e L
0
is he leng h o non-i adia ed
sample and Lis he leng h o an i adia ed sample.
Polyme s 2018,10, 832 5 o 14
3. Resul s and Discussion
Success ul polyme iza ion o GMA om he su ace o GO was con i med by a ious echniques
such as
1
H NMR, GPC, TEM, and TGA-FTIR. The con e sion o GMA was calcula ed o be 43% and
46%, acco ding o
1
H NMR spec a and he mola mass and Ð o PGMA chains de e mined om
GPC we e 5900 g
·
mol
−1
and 1.28 and 6100 g
·
mol
−1
and 1.26 o he GO-PGMA 1 and GO-PGMA 2,
espec i ely, i he expe imen al mola mass wi h he heo e ical one. Fu he mo e, om he TEM
in es iga ion, he 2D na u e o he nea GO pa icles (Figu e 2a) can be clea ly seen. Mo eo e , he
2D s uc u e was also obse ed in he case o GO-PGMA while he p esence o he PGMA chains
exhibi a he lossy-like s uc u es, which p o ided subs an ial coa ing o he GO pa icle (Figu e 2b).
The change in he eac ion mix u e o GO modi ica ion (Figu e 2c) does no lead o a signi ican change
in he mo phology and p o ides nea ly he same mo phology han he p e ious one (Figu e 2b).
Polyme s 2018, 10, x FOR PEER REVIEW 5 o 14
3. Resul s and Discussion
Success ul polyme iza ion o GMA om he su ace o GO was con i med by a ious echniques
such as 1H NMR, GPC, TEM, and TGA-FTIR. The con e sion o GMA was calcula ed o be 43% and
46%, acco ding o 1H NMR spec a and he mola mass and Ð o PGMA chains de e mined om GPC
we e 5900 g·mol−1 and 1.28 and 6100 g·mol−1 and 1.26 o he GO-PGMA 1 and GO-PGMA 2,
espec i ely, i he expe imen al mola mass wi h he heo e ical one. Fu he mo e, om he TEM
in es iga ion, he 2D na u e o he nea GO pa icles (Figu e 2a) can be clea ly seen. Mo eo e , he
2D s uc u e was also obse ed in he case o GO-PGMA while he p esence o he PGMA chains
exhibi a he lossy-like s uc u es, which p o ided subs an ial coa ing o he GO pa icle (Figu e
2b). The change in he eac ion mix u e o GO modi ica ion (Figu e 2c) does no lead o a signi ican
change in he mo phology and p o ides nea ly he same mo phology han he p e ious one (Figu e
2b).
Figu e 2. TEM images o (a) nea GO; (b) GO-PGMA; and (c) GO-PGMA-2.
The TGA-FTIR echnique u ilizing he on-line moni o ing o he FTIR spec a du ing he mal
decomposi ion o he nea GO (Figu e 3a,b), GO wi h bonded ini ia o (Figu e 3c,d), and GO-PGMA
(Figu e 3e, ) pa icles was employed o u he p o e he success ul coa ing o GO wi h PGMA chains.
In his case, he TGA spec a o he le side o Figu e 3 co espond o he FTIR spec a on he igh
side o Figu e 3. Fo he nea GO pa icles and GO wi h an ini ia o , he de ailed desc ip ion was
al eady published elsewhe e [41]. Howe e , he ollowing desc ip ion is no el o GO-PGMA
pa icles. I can be clea ly seen ha he pa icles peak a ound 200 °C, which co esponds o oxygen-
con aining g oups ha dec ease as side in o ma ion o p o e he pa ial educ ion o he GO-PGMA
pa icles. Mo eo e , he p esence o he success ul coa ing is ema kable om Figu e 3e when, in he
ange om 250 o 450 °C, we obse ed wo peaks bo h co esponding o he he mal decomposi ion
o PGMA. A simila ange o PGMA decomposi ion was also ound in he case o modi ica ion o
ca bonyl i on [42] as well as in he case o GO-PGMA modi ied h ough SI-ATRP whe e he mass loss
in Figu e 3e is e y simila o he ollowing e e ence [27]. In case o GO-PGMA-2, he TGA-FTIR scan
looked nea ly iden ical because, om he s uc u al poin o iew, he FTIR spec a in Figu e 3
ep esen he collec ion o he signal du ing he pe iod highligh ed in Figu e 3e by a cyan colo .
Speci ic abso p ion bands we e ound a 1722 cm−1 (ca bonyl), 1318 cm−1 C-O-C s e ching, 2961, and
2791 cm−1 (alkyl ib a ions). Fu he mo e, he sha p peak a 750 cm−1 is based on an epoxy ing
abso p ion and, he e o e, con i ms he p esence o PGMA polyme chains g a ed on he su ace o
GO.
G aphene oxide educ ion is a e y impo an ac o om i s applicabili y poin o iew. I he
ma e ial has a highe elec ic conduc i i y, he he mal conduc i i y is highe . The he mal ene gy
edis ibu ion in he sample is a c ucial ac o o he inal pho o-ac ua ion pe o mance. In addi ion,
he composi e ma e ial upon i s de o ma ion can show a sensing capabili y only i ce ain esis i i y
o he ma e ial is eached. The e o e, he high conduc i i y o he inal composi e is e y impo an .
This is simila ly obse ed in he s udy by Geo gousiss e al. [43]. The e o e, he conduc i i y and
Raman spec oscopy (Figu e 4) we e in es iga ed o p o e he deg ee o educ ion o GO and
Figu e 2. TEM images o (a) nea GO; (b) GO-PGMA; and (c) GO-PGMA-2.
The TGA-FTIR echnique u ilizing he on-line moni o ing o he FTIR spec a du ing he mal
decomposi ion o he nea GO (Figu e 3a,b), GO wi h bonded ini ia o (Figu e 3c,d), and GO-PGMA
(Figu e 3e, ) pa icles was employed o u he p o e he success ul coa ing o GO wi h PGMA chains.
In his case, he TGA spec a o he le side o Figu e 3co espond o he FTIR spec a on he igh side
o Figu e 3. Fo he nea GO pa icles and GO wi h an ini ia o , he de ailed desc ip ion was al eady
published elsewhe e [
41
]. Howe e , he ollowing desc ip ion is no el o GO-PGMA pa icles. I can
be clea ly seen ha he pa icles peak a ound 200
◦
C, which co esponds o oxygen-con aining g oups
ha dec ease as side in o ma ion o p o e he pa ial educ ion o he GO-PGMA pa icles. Mo eo e ,
he p esence o he success ul coa ing is ema kable om Figu e 3e when, in he ange om 250 o
450
◦
C, we obse ed wo peaks bo h co esponding o he he mal decomposi ion o PGMA. A simila
ange o PGMA decomposi ion was also ound in he case o modi ica ion o ca bonyl i on [
42
] as well
as in he case o GO-PGMA modi ied h ough SI-ATRP whe e he mass loss in Figu e 3e is e y simila
o he ollowing e e ence [
27
]. In case o GO-PGMA-2, he TGA-FTIR scan looked nea ly iden ical
because, om he s uc u al poin o iew, he FTIR spec a in Figu e 3 ep esen he collec ion o
he signal du ing he pe iod highligh ed in Figu e 3e by a cyan colo . Speci ic abso p ion bands we e
ound a 1722 cm
−1
(ca bonyl), 1318 cm
−1
C-O-C s e ching, 2961, and 2791 cm
−1
(alkyl ib a ions).
Fu he mo e, he sha p peak a 750 cm
−1
is based on an epoxy ing abso p ion and, he e o e, con i ms
he p esence o PGMA polyme chains g a ed on he su ace o GO.
G aphene oxide educ ion is a e y impo an ac o om i s applicabili y poin o iew. I he
ma e ial has a highe elec ic conduc i i y, he he mal conduc i i y is highe . The he mal ene gy
edis ibu ion in he sample is a c ucial ac o o he inal pho o-ac ua ion pe o mance. In addi ion,
he composi e ma e ial upon i s de o ma ion can show a sensing capabili y only i ce ain esis i i y
o he ma e ial is eached. The e o e, he high conduc i i y o he inal composi e is e y impo an .
This is simila ly obse ed in he s udy by Geo gousiss e al. [
43
]. The e o e, he conduc i i y and
Raman spec oscopy (Figu e 4) we e in es iga ed o p o e he deg ee o educ ion o GO and a iously
educed GO-PGMA pa icles. The in ensi ies a ios (I
D
/I
G
) we e ound o be 0.9 o nea GO (Figu e 4a)

Polyme s 2018,10, 832 6 o 14
and 1.08 and 1.26 o GO-PGMA 1 (Figu e 4b) and GO-PGMA 2 (Figu e 4c) co esponding o he
de e mined conduc i i ies o 1.2
×
10
−8
, 5
×
10
−7
, and 2.3
×
10
−3
S
·
cm
−1
, espec i ely. The a ios
indica e a signi ican and con ollable educ ion du ing he SI-ATRP p ocess, which is e y p omising
o u he indus ial applica ions.
Compa ibili y o he ille wi h a ma ix is a c ucial ac o o imp o emen o he physical as well
as mechanical p ope ies o he inal composi e ma e ial. Inhomogenei y p esen in he sample due
o he weak compa ibili y can be mainly esponsible o mechanical ins abili ies du ing a epea able
mechanical load o , in he case o ma e ials wi h desi ed elec ical o he mal conduc i i ies, can lead
o hei su e ed pe o mances. The e o e, he con ac angle alues o PDMS d ops, as he elas ome ic
ma ix used in his s udy, on o he su ace o pelle s p epa ed om he nea GO o GO-PGMA pa icles,
which we e in es iga ed (Figu e 5). I can be clea ly seen ha he con ac angle o nea GO was
de e mined o be 49.9
◦±
3.2
◦
, which showed ela i ely poo compa ibili y while he modi ica ion
o he GO wi h sho polyme chains o PGMA dec eased he con ac angle o 40.1
◦±
1.3
◦
and,
he e o e, imp o ed he we abili y be ween he PDMS and GO-PGMA su ace due o he p esence o
he alipha ic polyme backbone. In his case, he in luence o a ious conduc i i ies was no p o en
and con ac angles we e in he ange o e o . Howe e , he con ac s angles we e no so low as was
p e iously ound by ou esea ch g oup o PMMA o PBMA g a s [36].
Polyme s 2018, 10, x FOR PEER REVIEW 6 o 14
a iously educed GO-PGMA pa icles. The in ensi ies a ios (ID/IG) we e ound o be 0.9 o nea GO
(Figu e 4a) and 1.08 and 1.26 o GO-PGMA 1 (Figu e 4b) and GO-PGMA 2 (Figu e 4c) co esponding
o he de e mined conduc i i ies o 1.2 × 10−8 S·cm−1, 5 × 10−7 S·cm−1, and 2.3 × 10−3 S·cm−1, espec i ely.
The a ios indica e a signi ican and con ollable educ ion du ing he SI-ATRP p ocess, which is e y
p omising o u he indus ial applica ions.
Compa ibili y o he ille wi h a ma ix is a c ucial ac o o imp o emen o he physical as
well as mechanical p ope ies o he inal composi e ma e ial. Inhomogenei y p esen in he sample
due o he weak compa ibili y can be mainly esponsible o mechanical ins abili ies du ing a
epea able mechanical load o , in he case o ma e ials wi h desi ed elec ical o he mal
conduc i i ies, can lead o hei su e ed pe o mances. The e o e, he con ac angle alues o PDMS
d ops, as he elas ome ic ma ix used in his s udy, on o he su ace o pelle s p epa ed om he nea
GO o GO-PGMA pa icles, which we e in es iga ed (Figu e 5). I can be clea ly seen ha he con ac
angle o nea GO was de e mined o be 49.9° ± 3.2°, which showed ela i ely poo compa ibili y while
he modi ica ion o he GO wi h sho polyme chains o PGMA dec eased he con ac angle o 40.1°
± 1.3° and, he e o e, imp o ed he we abili y be ween he PDMS and GO-PGMA su ace due o he
p esence o he alipha ic polyme backbone. In his case, he in luence o a ious conduc i i ies was
no p o en and con ac angles we e in he ange o e o . Howe e , he con ac s angles we e no so
low as was p e iously ound by ou esea ch g oup o PMMA o PBMA g a s [36].
Figu e 3. TGA analysis (a,c,e) wi h on-line moni o ing o he FTIR spec a (b,d, ) o nea GO (a,b);
GO-inicia o , and (c,d) and GO-PGMA (e, ) pa icles.
Figu e 3.
TGA analysis (
a
,
c
,
e
) wi h on-line moni o ing o he FTIR spec a (
b
,
d
,
) o nea GO (
a
,
b
);
GO-inicia o , and (c,d) and GO-PGMA (e, ) pa icles.
Polyme s 2018,10, 832 7 o 14
Polyme s 2018, 10, x FOR PEER REVIEW 7 o 14
Figu e 4. Raman spec a o he nea GO (a) GO-PGMA 1; (b) GO-PGMA 2; and (c) pa icles and
co esponding chemical s uc u es.
Figu e 5. Images om CCD came a o he 5 µL PDMS d ople s on he nea GO (a) and GO-PGMA (b).
In o de o show how he op ical p ope ies o he composi es we e changed a e adding a ious
ille s, he images o nea PDMS as well as he GO-based composi es we e pe o med (Figu e 6a). I
can be seen ha he bes op ical p ope ies had a nea PDMS. Howe e , he modi ica ion using he
SI-ATRP app oach p o ided he composi es wi h be e dispe sed ille in compa ison o he nea GO
due o he ac ha nea GO/PDMS composi es seem o be o highe anspa ency wi h ela i ely big
agglome a es and less uni o m ille dispe sion compa ed o he GO-PGMA g a ed pa icles. In
addi ion, he change o he con ac angles be ween he wa e and composi es is nea ly negligible and
is mo e a ec ed by he modi ica ion han he ime o s o age (Figu e 6b). This means ha he
p ope ies ha we e changing o e 7 days did so negligibly. The con ac angle o nea as-p epa ed
PDMS and a e 7 days o s o age is 105.4° and 105.1°, espec i ely. Simila esul s we e ound o
o he composi es whe e he as-p epa ed GO-PGMA 1 a e 7 days o s o age show con ac angles o
98.7° and 98.2°, espec i ely. The longe g a s p o ided composi es wi h a sligh ly lowe con ac
angle o 97.4° and 96.8° o as-p epa ed GO-PGMA 2 and a e 7 days o s o age, espec i ely, due o
he highe amoun o he hyd ophilic epoxy g oups p esen ed on he GO-PGMA 2 pa icles su ace.
The lowe con ac angle was obse ed o nea GO, which was expec ed due o he p esence o
hyd oxyl, ca boxyl, and epoxy g oups on i s su ace. The e o e, showing con ac angle o 87.7° and
87.1° o as-p epa ed GO composi e a e 7 days o he s o age, espec i ely.
Figu e 6. (a) Images o he nea PDMS and p epa ed composi es and (b) Images om CCD came a o
he 5 µL wa e d ople s on he nea PDMS and a ious composi es. Line 1 ep esen s measu emen s
o as-p epa ed samples while line 2 ep esen s he measu emen s o he samples a e 7 days o
s o age a RT.
Figu e 4.
Raman spec a o he nea GO (
a
) GO-PGMA 1; (
b
) GO-PGMA 2; and (
c
) pa icles and
co esponding chemical s uc u es.
Polyme s 2018, 10, x FOR PEER REVIEW 7 o 14
Figu e 4. Raman spec a o he nea GO (a) GO-PGMA 1; (b) GO-PGMA 2; and (c) pa icles and
co esponding chemical s uc u es.
Figu e 5. Images om CCD came a o he 5 µL PDMS d ople s on he nea GO (a) and GO-PGMA (b).
In o de o show how he op ical p ope ies o he composi es we e changed a e adding a ious
ille s, he images o nea PDMS as well as he GO-based composi es we e pe o med (Figu e 6a). I
can be seen ha he bes op ical p ope ies had a nea PDMS. Howe e , he modi ica ion using he
SI-ATRP app oach p o ided he composi es wi h be e dispe sed ille in compa ison o he nea GO
due o he ac ha nea GO/PDMS composi es seem o be o highe anspa ency wi h ela i ely big
agglome a es and less uni o m ille dispe sion compa ed o he GO-PGMA g a ed pa icles. In
addi ion, he change o he con ac angles be ween he wa e and composi es is nea ly negligible and
is mo e a ec ed by he modi ica ion han he ime o s o age (Figu e 6b). This means ha he
p ope ies ha we e changing o e 7 days did so negligibly. The con ac angle o nea as-p epa ed
PDMS and a e 7 days o s o age is 105.4° and 105.1°, espec i ely. Simila esul s we e ound o
o he composi es whe e he as-p epa ed GO-PGMA 1 a e 7 days o s o age show con ac angles o
98.7° and 98.2°, espec i ely. The longe g a s p o ided composi es wi h a sligh ly lowe con ac
angle o 97.4° and 96.8° o as-p epa ed GO-PGMA 2 and a e 7 days o s o age, espec i ely, due o
he highe amoun o he hyd ophilic epoxy g oups p esen ed on he GO-PGMA 2 pa icles su ace.
The lowe con ac angle was obse ed o nea GO, which was expec ed due o he p esence o
hyd oxyl, ca boxyl, and epoxy g oups on i s su ace. The e o e, showing con ac angle o 87.7° and
87.1° o as-p epa ed GO composi e a e 7 days o he s o age, espec i ely.
Figu e 6. (a) Images o he nea PDMS and p epa ed composi es and (b) Images om CCD came a o
he 5 µL wa e d ople s on he nea PDMS and a ious composi es. Line 1 ep esen s measu emen s
o as-p epa ed samples while line 2 ep esen s he measu emen s o he samples a e 7 days o
s o age a RT.
Figu e 5.
Images om CCD came a o he 5
µ
L PDMS d ople s on he nea GO (
a
) and GO-PGMA (
b
).
In o de o show how he op ical p ope ies o he composi es we e changed a e adding a ious
ille s, he images o nea PDMS as well as he GO-based composi es we e pe o med (Figu e 6a).
I can be seen ha he bes op ical p ope ies had a nea PDMS. Howe e , he modi ica ion using he
SI-ATRP app oach p o ided he composi es wi h be e dispe sed ille in compa ison o he nea GO
due o he ac ha nea GO/PDMS composi es seem o be o highe anspa ency wi h ela i ely
big agglome a es and less uni o m ille dispe sion compa ed o he GO-PGMA g a ed pa icles.
In addi ion, he change o he con ac angles be ween he wa e and composi es is nea ly negligible
and is mo e a ec ed by he modi ica ion han he ime o s o age (Figu e 6b). This means ha he
p ope ies ha we e changing o e 7 days did so negligibly. The con ac angle o nea as-p epa ed
PDMS and a e 7 days o s o age is 105.4
◦
and 105.1
◦
, espec i ely. Simila esul s we e ound o o he
composi es whe e he as-p epa ed GO-PGMA 1 a e 7 days o s o age show con ac angles o 98.7
◦
and 98.2
◦
, espec i ely. The longe g a s p o ided composi es wi h a sligh ly lowe con ac angle o
97.4
◦
and 96.8
◦
o as-p epa ed GO-PGMA 2 and a e 7 days o s o age, espec i ely, due o he highe
amoun o he hyd ophilic epoxy g oups p esen ed on he GO-PGMA 2 pa icles su ace. The lowe
con ac angle was obse ed o nea GO, which was expec ed due o he p esence o hyd oxyl, ca boxyl,
and epoxy g oups on i s su ace. The e o e, showing con ac angle o 87.7◦and 87.1◦ o as-p epa ed
GO composi e a e 7 days o he s o age, espec i ely.
Polyme s 2018, 10, x FOR PEER REVIEW 7 o 14
Figu e 4. Raman spec a o he nea GO (a) GO-PGMA 1; (b) GO-PGMA 2; and (c) pa icles and
co esponding chemical s uc u es.
Figu e 5. Images om CCD came a o he 5 µL PDMS d ople s on he nea GO (a) and GO-PGMA (b).
In o de o show how he op ical p ope ies o he composi es we e changed a e adding a ious
ille s, he images o nea PDMS as well as he GO-based composi es we e pe o med (Figu e 6a). I
can be seen ha he bes op ical p ope ies had a nea PDMS. Howe e , he modi ica ion using he
SI-ATRP app oach p o ided he composi es wi h be e dispe sed ille in compa ison o he nea GO
due o he ac ha nea GO/PDMS composi es seem o be o highe anspa ency wi h ela i ely big
agglome a es and less uni o m ille dispe sion compa ed o he GO-PGMA g a ed pa icles. In
addi ion, he change o he con ac angles be ween he wa e and composi es is nea ly negligible and
is mo e a ec ed by he modi ica ion han he ime o s o age (Figu e 6b). This means ha he
p ope ies ha we e changing o e 7 days did so negligibly. The con ac angle o nea as-p epa ed
PDMS and a e 7 days o s o age is 105.4° and 105.1°, espec i ely. Simila esul s we e ound o
o he composi es whe e he as-p epa ed GO-PGMA 1 a e 7 days o s o age show con ac angles o
98.7° and 98.2°, espec i ely. The longe g a s p o ided composi es wi h a sligh ly lowe con ac
angle o 97.4° and 96.8° o as-p epa ed GO-PGMA 2 and a e 7 days o s o age, espec i ely, due o
he highe amoun o he hyd ophilic epoxy g oups p esen ed on he GO-PGMA 2 pa icles su ace.
The lowe con ac angle was obse ed o nea GO, which was expec ed due o he p esence o
hyd oxyl, ca boxyl, and epoxy g oups on i s su ace. The e o e, showing con ac angle o 87.7° and
87.1° o as-p epa ed GO composi e a e 7 days o he s o age, espec i ely.
Figu e 6. (a) Images o he nea PDMS and p epa ed composi es and (b) Images om CCD came a o
he 5 µL wa e d ople s on he nea PDMS and a ious composi es. Line 1 ep esen s measu emen s
o as-p epa ed samples while line 2 ep esen s he measu emen s o he samples a e 7 days o
s o age a RT.
Figu e 6.
(
a
) Images o he nea PDMS and p epa ed composi es and (
b
) Images om CCD came a o
he 5
µ
L wa e d ople s on he nea PDMS and a ious composi es. Line 1 ep esen s measu emen s o
as-p epa ed samples while line 2 ep esen s he measu emen s o he samples a e 7 days o s o age
a RT.
Polyme s 2018,10, 832 8 o 14
In es iga ions o dielec ic p ope ies (Figu e 7) is e y impo an due o he ac ha , wi h he
help o measu emen in a b oad empe a u e ange and equency-dependen pe mi i i y, i is possible
o calcula e E
a
o he glass ansi ion and T
g
, which p o ides in o ma ion abou he polyme chain
lexibili y in he p esence o GO pa icles. In ou s udy, howe e , he p epa ed composi es exhibi ed a
a he s ong elec ical esponse o he applied elec ic ield and, he e o e, ob ained
ε0
and
ε
”exhibi ed
elec ode pola iza ion and we e no sui able o E
a
calcula ion [
40
]. The e o e, he exp ession o M
0
and
M” was used, which was mainly M” acco ding o Equa ion (2). The e o e, his quan i y was also used
o he in e p e a ion o he dielec ic spec a in Figu e 5. He e he peak a ound
−
120
◦
C indica ing he
p esence o Tgcan be seen o all in es iga ed samples.
Polyme s 2018, 10, x FOR PEER REVIEW 8 o 14
In es iga ions o dielec ic p ope ies (Figu e 7) is e y impo an due o he ac ha , wi h he
help o measu emen in a b oad empe a u e ange and equency-dependen pe mi i i y, i is
possible o calcula e Ea o he glass ansi ion and Tg, which p o ides in o ma ion abou he polyme
chain lexibili y in he p esence o GO pa icles. In ou s udy, howe e , he p epa ed composi es
exhibi ed a a he s ong elec ical esponse o he applied elec ic ield and, he e o e, ob ained ε′
and ε″ exhibi ed elec ode pola iza ion and we e no sui able o Ea calcula ion [40]. The e o e, he
exp ession o M′ and M″ was used, which was mainly M″ acco ding o Equa ion (2). The e o e, his
quan i y was also used o he in e p e a ion o he dielec ic spec a in Figu e 5. He e he peak
a ound −120 °C indica ing he p esence o Tg can be seen o all in es iga ed samples.
Figu e 7. 3D plo s o he dielec ic p ope ies o he nea PDMS ma ix, (a) nea GO-PDMS; (b) GO-
PGMA 1; (c) and GO-PGMA 2; (d) All a 0.1 ol. % con en in PDMS.
F om he posi ion o he maxima o his peak a a ious empe a u es, he Ea o Tg was calcula ed
acco ding o Equa ion (1) and esul s a e lis ed in Table 1. I can be clea ly seen ha he highes Ea o
45.70 kJ·mol−1 was ound o nea PDMS by ollowing he nea GO composi e wi h Ea o 36.57 kJ·mol−1.
The sample GO-PGMA 1 wi h 0.1 olume pe cen age o pa icles o lowe conduc i i y possess only
a sligh dec ease in Ea showing an imp o ed PDMS chain mobili y a e modi ica ion while he
sample GO-PGMA 2 wi h same pa icle loading. Howe e , wi h signi ican ly highe conduc i i y
possesses signi ican ly be e chain mobili y and, las ly, he lowes Ea o 23.80 kJ·mol−1 u he
enhanced he pho o-ac ua ion capabili y. These esul s indica e ha he p esence o he GO-PGMA
pa icles in he composi e signi ican ly imp o es he lexibili y o he PDMS chains due o he ac
ha he ene gy necessa y o he polyme chain mo emen is lowe . As i will be shown below, hese
esul s we e also con i med by he in es iga ion o DMA and pho o-ac ua ion pe o mance since he
esul s om hese expe imen s well-co ela es wi h hese dielec ic in es iga ions.
Figu e 7.
3D plo s o he dielec ic p ope ies o he nea PDMS ma ix, (
a
) nea GO-PDMS; (
b
)
GO-PGMA 1; (c) and GO-PGMA 2; (d) All a 0.1 ol. % con en in PDMS.
F om he posi ion o he maxima o his peak a a ious empe a u es, he E
a
o T
g
was calcula ed
acco ding o Equa ion (1) and esul s a e lis ed in Table 1. I can be clea ly seen ha he highes E
a
o
45.70 kJ
·
mol
−1
was ound o nea PDMS by ollowing he nea GO composi e wi h E
a
o 36.57 kJ
·
mol
−1
.
The sample GO-PGMA 1 wi h 0.1 olume pe cen age o pa icles o lowe conduc i i y possess only a
sligh dec ease in E
a
showing an imp o ed PDMS chain mobili y a e modi ica ion while he sample
GO-PGMA 2 wi h same pa icle loading. Howe e , wi h signi ican ly highe conduc i i y possesses
signi ican ly be e chain mobili y and, las ly, he lowes E
a
o 23.80 kJ
·
mol
−1
u he enhanced he
pho o-ac ua ion capabili y. These esul s indica e ha he p esence o he GO-PGMA pa icles in he
composi e signi ican ly imp o es he lexibili y o he PDMS chains due o he ac ha he ene gy
necessa y o he polyme chain mo emen is lowe . As i will be shown below, hese esul s we e also
con i med by he in es iga ion o DMA and pho o-ac ua ion pe o mance since he esul s om hese
expe imen s well-co ela es wi h hese dielec ic in es iga ions.
Polyme s 2018,10, 832 9 o 14
Table 1.
Ac i a ion ene gies o a glass ansi ion p ocess o pu e PDMS and PDMS composi es wi h
a iously conduc ing pa icles.
Sample Code Ea(kJ·mol−1) o Tg(−120 ◦C)
pu e PDMS 45.70
0.1 ol % nea GO/PDMS 36.57
0.1 ol % GO-PGMA 1/PDMS 31.32
0.1 ol % GO-PGMA 2/PDMS 23.80
Dynamic mechanical p ope ies (Figu e 8) a e one o he mos c ucial ac o s in luencing he
applicabili y o ma e ials as pho o-ac ua ion sys ems. Re e sible con ac ion/elonga ion o he sample
by ligh s imula ion is a a he dynamic p ocess and, he e o e, in es iga ion upon dynamic condi ions
is e y impo an . As can be seen in Figu e 8a, he s o age moduli below T
g
we e nea ly he same o
all in es iga ed samples. The i s di e ence can be seen abo e T
g
when he lowes s o age modulus
was ob ained o nea PDMS and was ollowed by he GO-PGMA sample. The highes alues we e
obse ed o samples con aining nea GO pa icles. A simila si ua ion occu s abo e he mel ing
egion when he nea GO possessed he highes s o age modulus. This obse a ion can be explained
by possible co alen bonding be ween he PDMS and hyd oxyl g oups o GO pa icles [
44
]. Since he
amoun o he hyd oxyl g oups signi ican ly dec eased due o bo h he modi ica ion wi h PGMA chains
and he educ ion o he GO (clea ly seen om Figu es 3and 4), he mechanical esponse is mos ly
based on he good compa ibili y o he GO-PGMA pa icles wi h he PDMS. F om he empe a u e
dependence o he an
δ
(Figu e 8b), i can be seen ha he peak o an
δ
o he sample con aining
GO-PGMA dec eased when compa ed wi h pu e PDMS o PDMS illed wi h nea GO, which indica ed
enhanced compa ibili y o GO-PGMA wi h he PDMS ma ix. Ye , he absolu e alue o an
δ
a e all
ansi ions was highe o GO-PGMA han o PDMS ma ix and PDMS con aining nea GO due o
he ac ha physical en anglemen s o PGMA sho polyme chains p o ide mo e lexible s uc u e
han in he case o GO wi h possible co alen bonding o he PDMS. Composi es consis ing o a ious
GO-PGMA wi h di e en conduc i i ies show nea ly he same mechanical beha io . The di e ences
we e in he ange o e o . The e o e, only he one consis ing o GO-PGMA pa icles wi h highe
conduc i i ies a e shown in Figu e 8. The e o e, i can be s a ed ha GO-PGMA/PDMS composi e
p o ides a sys em wi h enhanced damping and also wi h imp o ed lexibili y o he composi e sys em,
which well-co ela es wi h dielec ic s udies and which is in he same ime highly sui able o he
pho o-ac ua ion poin o iew.
Polyme s 2018, 10, x FOR PEER REVIEW 9 o 14
Table 1. Ac i a ion ene gies o a glass ansi ion p ocess o pu e PDMS and PDMS composi es wi h
a iously conduc ing pa icles.
Sample Code
Ea (kJ·mol−1) o Tg (−120 °C)
pu e PDMS
45.70
0.1 ol % nea GO/PDMS
36.57
0.1 ol % GO-PGMA 1/PDMS
31.32
0.1 ol % GO-PGMA 2/PDMS
23.80
Dynamic mechanical p ope ies (Figu e 8) a e one o he mos c ucial ac o s in luencing he
applicabili y o ma e ials as pho o-ac ua ion sys ems. Re e sible con ac ion/elonga ion o he sample
by ligh s imula ion is a a he dynamic p ocess and, he e o e, in es iga ion upon dynamic
condi ions is e y impo an . As can be seen in Figu e 8a, he s o age moduli below Tg we e nea ly
he same o all in es iga ed samples. The i s di e ence can be seen abo e Tg when he lowes
s o age modulus was ob ained o nea PDMS and was ollowed by he GO-PGMA sample. The
highes alues we e obse ed o samples con aining nea GO pa icles. A simila si ua ion occu s
abo e he mel ing egion when he nea GO possessed he highes s o age modulus. This obse a ion
can be explained by possible co alen bonding be ween he PDMS and hyd oxyl g oups o GO
pa icles [44]. Since he amoun o he hyd oxyl g oups signi ican ly dec eased due o bo h he
modi ica ion wi h PGMA chains and he educ ion o he GO (clea ly seen om Figu es 3 and 4), he
mechanical esponse is mos ly based on he good compa ibili y o he GO-PGMA pa icles wi h he
PDMS. F om he empe a u e dependence o he an δ (Figu e 8b), i can be seen ha he peak o an
δ o he sample con aining GO-PGMA dec eased when compa ed wi h pu e PDMS o PDMS illed
wi h nea GO, which indica ed enhanced compa ibili y o GO-PGMA wi h he PDMS ma ix. Ye , he
absolu e alue o an δ a e all ansi ions was highe o GO-PGMA han o PDMS ma ix and
PDMS con aining nea GO due o he ac ha physical en anglemen s o PGMA sho polyme chains
p o ide mo e lexible s uc u e han in he case o GO wi h possible co alen bonding o he PDMS.
Composi es consis ing o a ious GO-PGMA wi h di e en conduc i i ies show nea ly he same
mechanical beha io . The di e ences we e in he ange o e o . The e o e, only he one consis ing o
GO-PGMA pa icles wi h highe conduc i i ies a e shown in Figu e 8. The e o e, i can be s a ed ha
GO-PGMA/PDMS composi e p o ides a sys em wi h enhanced damping and also wi h imp o ed
lexibili y o he composi e sys em, which well-co ela es wi h dielec ic s udies and which is in he
same ime highly sui able o he pho o-ac ua ion poin o iew.
Figu e 8. Dependence o he s o age modulus (a) and an δ (b) o b oad empe a u e ange o nea
PDMS (black solid line) and o PDMS composi es con aining 0.1 ol % o nea GO ( ed dash do line)
and GO-PGMA 2 (blue dashed line).
In o de o in es iga e he mechanical p ope ies o he p epa ed composi es, dependence on he
change in he leng h ∆L in he ange o po en ial pho o-ac ua ion on he iscoelas ic moduli we e
measu ed. Va ious na u es o he ille can p o ide he sys em wi h mul iple mechanical
pe o mances a he s ain de o ma ion ob ained du ing ligh -s imula ion. As can be seen in Figu e
Figu e 8.
Dependence o he s o age modulus (
a
) and an
δ
(
b
) o b oad empe a u e ange o nea
PDMS (black solid line) and o PDMS composi es con aining 0.1 ol % o nea GO ( ed dash do line)
and GO-PGMA 2 (blue dashed line).
In o de o in es iga e he mechanical p ope ies o he p epa ed composi es, dependence on
he change in he leng h
∆
Lin he ange o po en ial pho o-ac ua ion on he iscoelas ic moduli we e
measu ed. Va ious na u es o he ille can p o ide he sys em wi h mul iple mechanical pe o mances