Improving the performance of biobased polyurethane dispersion by the incorporation of photo-crosslinkable coumarin.

Imp o ing he pe o mance o biobased polyu e hane dispe sion
by he inco po a ion o pho o-c osslinkable couma in
Lo ena Ge ma´n-Ayuso ,Jose´ M. Cue as, Rube´n Seoane-Ri e o, Rod igo Na a o, Angel Ma cos-Fe na´ndez,
Jose´ L. Vilas-Vilela
Recei ed: 1 No embe 2022 / Re ised: 3 Feb ua y 2023 / Accep ed: 12 Feb ua y 2023
The Au ho (s) 2023
Abs ac High biobased ca bon con en polyu e hane
dispe sions (PUD) a e a mo e sus ainable al e na i e
o con en ional oil-de i ed wa e bo ne dispe sions in
coa ings. Howe e , he e a e s ill many pe o mance
limi a ions om es ic ed a ailabili y o e ec i e
enewable monome s and oligome s. This wo k
demons a es he imp o emen o he p ope ies o
high biobased con en PUD and de i ed coa ing by
in oducing a pho o- e e sibly c osslinkable couma in
as chain ex ende wi hin he s uc u e. The e ec o
pa ial subs i u ion o 1,3-p opanediol biobased by a
di-hyd oxy pho o- eac i e cyclic couma in on he
pa icle size and he s abili y was analyzed by dynamic
ligh sca e ing (DLS) and mul iple ligh sca e ing
(MLS). The la e al and mo e igid s uc u e o
couma in in ol ed a mode a ed inc emen in pa icle
size wi hou signi ican e ec on he dispe sion s abili y
o a leas 45 days. Associa ed imp o emen in ha d-
ness and oughness was also demons a ed by ensile
es , pendulum ha dness, pencil ha dness and sc a ch
esis ance es . Fu he mo e, con olled UV i adia ion
o he polyu e hane ga e ise o a mechanical pe o -
mance adjus men om e e sible pho o-c osslinking
and scission o he couma in molecules wi hin he
mac omolecula s uc u e. A 70% dime iza ion deg ee
o he couma in wi hin he polyu e hane ilm by UV
ligh p o ided a pa ially e e sible h ee old highe
ensile s eng h han ha o he o iginal biobased
o mula ion as an e ec i e ool o une he esponse o
biobased polyu e hanes.
L. Ge ma
´n-Ayuso (&), J. M. Cue as, R. Seoane-Ri e o
GAIKER Technology Cen e, Basque Resea ch and
Technology Alliance (BRTA), Pa que Tecnolo
´gico de
Bizkaia, Edi icio 202, 48170 Zamudio, Spain
e-mail: [email p o ec ed]
R. Na a o, A. Ma cos-Fe na
´ndez
Ins i u o de Ciencia y Tecnologı
´a de Polı
´me os (CSIC),
Juan de la Cie a 3, 28006 Mad id, Spain
J. L. Vilas-Vilela
Mac omolecula Chemis y G oup (LABQUIMAC),
Depa men o Physical Chemis y, Facul y o Science and
Technology, Uni e si y o he Basque Coun y UPV/EHU,
Ba io Sa iena s/n, 48940 Leioa, Spain
J. L. Vilas-Vilela
BCMa e ials, Basque Cen e o Ma e ials, Applica ions
and Nanos uc u es, UPV/EHU Science Pa k, 48940 Leioa,
Spain
J. Coa . Technol. Res., 20 (5) 1677–1690, 2023
h ps://doi.o g/10.1007/s11998-023-00772-9
1677
G aphical Abs ac
PHOTO-CROSSLINKED COUMARIN
BIOBASED POLYURETHANE
BPU MECHANICAL PERFORMANCE
COUMARIN BIOBASED POLYURETHANE
BIOBASED POLYURETHANE
HO
HO
O
UV
O
O
O
O
0
0
1
2
4
5
6
8
9
S ess (MPa)
10
11
12
7
3
0
1
2
4
5
6
8
9
S ess (MPa)
10
11
12
7
3
50 100 150 200 250 300 350 400 450 500 550 600
%S ain
050
100 150 200 250 300 350 400 450 500 550 600
%S ain
%PUD BIO
%PUD BIO
%PUD BIO_DHEOMC_dime ized
Keywo ds Coa ing, Biobased, Polyu e hane
dispe sion, Couma in
In oduc ion
Polyu e hanes a e one o he mos popula classes o
polyme s o a la ge numbe o coa ing applica ions
hanks o p ope ies ha can be ailo ed o e a wide
ange.
1
Howe e , he en i onmen al policies, he
wo ldwide c ude oil p ice luc ua ions, he deple ion
o he ossil uel ese es, as well as global wa ming,
a e p essing o achie e mo e sus ainable p oduc s able
o subs i u e he con en ional sol en -based coa ings.
In he las decades, hus, wa e bo ne polyu e hane
dispe sions (PUDs) ha e gained majo ele ance
because hey success ully supe sede hei con en ional
sol en bo ne coun e pa s.
2–4
In his scena io, ano he na u al s ep o wa d is o
inc ease he biocon en in PUD om using biopolyols
g adually becoming comme cially a ailable.
5,6
The e-
o e, se e al s udies ha e been published in ecen
yea s ega ding wa e bo ne polyu e hane dispe sions
(PUDs) syn hesized om polyols based on na u al
oils.
7–12
Ne e heless, high biobased ca bon con en wi h
sui able pe o mance s ill emains a challenge o high-
demanding polyu e hane indus ies om ce ain limi-
a ions in p ope ies.
13
The highe he a ge echnical
pe o mance, he mo e likely a manu ac u e is no
able o come up wi h sui able biobased compounds o
be di ec ly used.
Couma ins a e cha ac e ized by di e en in e es ing
physical, biological, pho o-physical and pho ochemical
p ope ies om a wide ange o chemical s uc u es
and side subs i uen s, which u ns hem in o molecules
able o p o ide new unc ions o polyu e hanes.
14
Then, biobased solu ions could also exploi hose
ea u es o imp o e pe o mance o o achie e new
unc ions o enla ge hei use ulness. Couma in con-
sis s o a la ge amily o benzo-a-py ones cha ac e ized
by used benzene and py one ings ha can be easily
ob ained om many species o plan s, bac e ia and
ungi (Fig. 1). These molecules can be pho o- eac i e
chemicals able o expe ience e e sible [2p+2p]
cycloaddi ion eac ions o cause a cyclobu ane ing
upon UV i adia ion.
15
In pa icula , cycloaddi ion
eac ion occu s a »365 nm, whe eas pho o-clea age
eac ion a 254 nm ende s he o iginal couma in
moie ies. I is clea ha hese eac ions in he solid
s a e can be ex emely use ul o su ace coa ings,
al hough e e sible pho o- eac ions show con inuous
cycle by cycle loss o e iciency, pa icula ly o pho o-
scission p ocesses.
14
Couma ins ha e p o ided in insic healing ea u es
o polyu e hanes (be ween 16 and 78% o damage
eco e y as a unc ion o he s uc u e).
16,17
Besides,
he pho o- eac i i y o couma in has been s udied o
c osslink polyu e hane linea chains
18–20
(Fig. 2).
This cu en wo k s udies a non-p e iously epo ed
app oach o enhance he pe o mance o a high
con en o biogenic ca bon PUD by inco po a ing a
1678
J. Coa . Technol. Res., 20 (5) 1677–1690, 2023
couma in diol in he syn hesis as a pho o- eac i e chain
ex ende in a p epolyme mixing p ocess. The esul s
demons a e he possibili y o designing coa ings
de i ed om pho o-c osslinkable biobased wa e bo ne
polyu e hane dispe sions wi h enhanced pe o mance,
which could ind wide applica ions in sec o s as ex ile,
wood, o packaging, among o he s, whe e PUD a e
widely used.
Expe imen al
Ma e ials
Acco ding o he syn hesis p ocess p e iously epo ed
by he au ho s o ob ain he couma in monome ,
18
2,2-
bis(hyd oxyme hyl)p opionic acid, 2,2-dime hoxyp o-
pane, p- oluenesul onic acid monohyd a e, 1,3-dicyclo-
hexylca bodiimide, eso cinol, e hyl ace oace a e, 2-
b omoe hanol (B E OH), anhyd ous py idine and
dowex H + esin we e supplied by Sigma-Ald ich and
used as ecei ed. P iplas 3294 (C oda), a 100%
biobased polyes e polyol wi h an app oxima e molec-
ula weigh (Mw) o 2000 g mol
–1
, was used as polyol,
whe eas a 100% biobased 1,3 p opanediol om
Dupon was used as chain ex ende . Dime hylolp opi-
onic acid (DMPA) as in e nal emulsi ie , ie hylamine
(TEA) as he neu alize , dibu yl in dilau a e
(DBTDL) as he ca alys and N-me hyl py olidone
(NMP) as a cosol en we e supplied by Sigma-Ald ich.
Alipha ic diisocyana e o he syn hesis o he poly-
u e hane was isopho one diisocyana e (IPDI) (sup-
plied by Me ck).
Syn hesis o 2,2-bis(hyd oxyme hyl)p opiona e
o 7-hyd oxye hoxy-4-me hylcouma in
(DHEOMC diol)
The syn hesis p ocess o he couma in diol was
p e iously published by he au ho s.
18
Isop opyli-
dene-2,2-bis-(me hoxy)p opionic anhyd ide
(DMPAA) was syn hesized acco ding o li e a u e.
21,22
7-Hyd oxye hoxy-4-me hylcouma in (HEOMC) was
syn hesized by eac ing 7-hyd oxy-4-me hylcouma in
wi h B E OH and po assium ca bona e in DMF.
A e wa ds, DMPAA and HEOMC we e eac ed o
p oduce an es e . Finally, he dep o ec ion o he
hyd oxyl g oups was pe o med by in oduced he
p o ona ed esin o ob ain he a ge DHEOMC diol
(Fig. 3). Solu ion liquid 1H NMR spec um was
eco ded a oom empe a u e in a Va ian Uni y Plus
400 ins umen using deu e a ed chlo o o m (CDCl
3
)
o deu e a ed dime hylsul oxide (DMSO-d6) as sol-
en . Spec um was e e enced o he esidual sol en
p o ons a 7.26 o 2.50 ppm.
Syn hesis o he wa e bo ne polyu e hane
dispe sions
Wa e polyu e hane dispe sions (PUD) we e p epa ed
by p epolyme mixing p ocess.
23
NMP cosol en was
used (12 w %) o educe he iscosi y o he eac ion
media. The o mula ions used in he di e en eac ions
a e summa ized in Table 1.
The polyme was designed acco ding o he ollow-
ing ea u es: he a io [NCO]/[OH] in p epolyme is
1.5, in e nal emulsi ie , DMPA, was se o 7 w % based
on he weigh o he p epolyme , and he co espond-
OO
Fig. 1: Couma in s uc u e
UV
Fig. 2: Pho o-c osslinking diag am
HO
HO
O
OOOO
Fig. 3: Chemical s uc u e o DHEOMC (in ed pho o-
c osslinkable bond)
1679
J. Coa . Technol. Res., 20 (5) 1677–1690, 2023
ing ca boxylic g oups we e 100% neu alized by he
addi ion o TEA. The solid con en in he inal
wa e bo ne PUD was 30 w %. In he syn hesis o
polyu e hane wi h couma in, his compound,
DHEOMC, was in oduced dissol ed in NMP as chain
ex ende subs i u ing pa ially 1,3 p opanediol. A 5
w % con en o couma in was selec ed as e ec i e
enough modi ica ion wi h sui able dispe sion qual-
i y.
28,29
A low pa icle size dis ibu ion, wi h he
associa ed long pe iod s abili y o he dispe sion, a e
impe a i e o use ul sui able wa e bo ne coa ings.
The e o e, couma in con en mus be limi ed o a oid
any undesi able e ec on he dispe sion bu wi h
enough pho o- eac i e e ec o p o ide a ia ions in
polyu e hane pe o mance by i adia ion.
Polyol, IPDI, DMPA, ca alys and cosol en eac ed
in a 250 mL glass-jacke ed eac o equipped wi h a
mechanical s i e a 80C o 2.5 h, unde ni ogen
a mosphe e, o syn hesize he NCO- e mina ed p e-
polyme . TEA was added a lowe empe a u e o
pe o m he neu aliza ion p ocess o 0.5 h. Subse-
quen ly, he chain ex ende (1,3-p opanediol o /and
DHEOMC diol) was added, and he syn hesis o he
polyu e hane occu ed o 1.5 h. Dispe sion was
Table 1: Amoun o eagen s used in he syn hesis o di e en biobased PUD
PUD P iplas w % IPDI w % DMPA w % TEA w % 1,3PD w % DHEOMC w %
PUD_BIO 52 33 6 5 4 –
PUD_BIO_DHEOMC 50 32 6 5 3 5
HO HO OCN
H
O
O
O
O
O
O
HO OH
R
HO OH
O
OOH
R3
OH
3
O
OCN
PREPOLYMER-
NEUTRALIZATION
CHAIN EXTENSION
C
3
COO
CH
O
R
R
R
O
OO
O
NCO
R1
R1
R1
R1R1R1R1
R2
R1
R2
R2N
H
N
H
N
H
N
H
N
NH NH
O
OO
O
OO
H2
OO
O
O
O
OHO
CH3
O
O
O
C
COO
RR
R
H
N
H
NH
NH
NH
N
H
NH
N
H
N
H
N
HC
C
3
R2OH OH NCO
R1
COOH
DBTDL
TEA COSOLVENT
COSOLVENT
DHEOMC
POLYURETHANE DISPERSION
1,3 PROPANEDIOL
DISPERSION
-
NH+
NH+
Fig. 4: Reac ion scheme o PUD wi h DHEOMC syn hesis
1680
J. Coa . Technol. Res., 20 (5) 1677–1690, 2023
achie ed by g adually inco po a ing wa e o he
polyu e hane a 30C unde igo ous s i ing. The
eac ion scheme can be seen in Fig. 4.
Polyu e hane ilms we e p epa ed by cas ing 4 g o
polyu e hane dispe sion in a mould and allowing
e apo a ion o he wa e a oom empe a u e o
7 days. A e wa ds, he polyu e hane was d ied a 50C
o 24 h. T anspa en ilms ob ained we e 0.3–0.5 mm
hick.
Pho o-dime iza ion o polyu e hane
I adia ion o pho o-dime iza ion/pho o-clea age o
polyu e hane ilm wi h couma in in he ha d segmen
was ca ied ou in an ul a iole c osslinke (ul a iole
p oduc s) equipped wi h wo se o 5 (8 W) lamps o
354 nm o 254 nm i adia ions (354 and 254 nm a e he
wa eleng hs on he maxima o he i adia ion spec a
o he lamps, espec i ely). Pho o-dime iza ion o
couma in and he o ma ion o cyclobu ane o c oss-
link he polyu e hane chains occu when i adia ed a
354 nm. The ligh - igge ed cyclobu ane clea age eac-
ion occu s by i adia ing again dime ized polyu -
e hanes a 254 nm.
Cha ac e iza ion
Cha ac e iza ion o he polyu e hane dispe sions
Pa icle size and -po en ial
The pa icle size dis ibu ion was e alua ed by Dy-
namic Ligh Sca e ing (DLS) echnique om measu -
ing a ia ions in he ligh sca e ed by he polyu e hane
dispe sions. The ze a ( ) po en ial was es ablished by
Phase Analysis Ligh Sca e ing om he elec-
opho e ic mobili y o he dispe sions. Bo h pa ame-
e s we e measu ed wi h a B ookha en Ze aPALS
ins umen . PUD samples we e dilu ed wi h deionized
wa e be o e measu emen a 25C.
Medium e m s abili y
Medium e m s abili y analysis was ca ied ou wi h
Tu biscaneLAB S abili y Analyse om Fo mulac-
ion SA. The echnology embedded in Tu biscan
LABeis based on he Mul iple Ligh Sca e ing
(MLS) echnique, which enables as and sensi i e
iden i ica ion o des abiliza ion mechanisms (such as
c eaming, sedimen a ion, loccula ion, coalescence,
e c.). Tu biscan LAB calcula es Tu biscan

S abili y
Index (TSI), which is a speci ic pa ame e de eloped o
compa e and cha ac e ize he physical s abili y o
samples. TSI alue can be associa ed o he des abi-
liza ion kine ics analyzing i s e olu ion o e he ime.
S abili y o PUD was e alua ed wi hou dilu ion a
di e en imes o de ec des abiliza ion mechanisms
and ob ain des abiliza ion kine ics cu es.
Cha ac e iza ion o he polyu e hane ilms
Molecula weigh
The molecula mass dis ibu ion o he PUD ilms was
de e mined by gel pe mea ion ch oma og aphy, using
GPC WATERS equipmen , wi h e ac i e index
de ec o 2414 and wo columns TOSOH HR1 and
HR3, calib a ed wi h espec o polys y ene s anda ds.
Polyme we e dissol ed in e ahyd o u an (THF) and
70 lL o he sample was injec ed wi h a olume a e o
ca ie sol en o 1 mL min
1
a 40C empe a u e.
The a e age molecula masses, Mn, Mw and polydis-
pe si y index we e de e mined.
Pho o- eac i i y o polyu e hanes
UV expe imen s we e pe o med in a Pe kin Elme
Lambda 35 UV/Vis spec ome e . Abso bance o he
hin ilm was measu ed om 380 o 250 nm. The pho o-
e e sibili y o he syn hesized polyu e hane was cha -
ac e ized in he coa ings by UV. Du ing dime iza ion,
he UV peak wi h maximum in abso bance a 320 nm
in he polyu e hane UV spec um ela ed o he
conjuga ed p-sys em dec eased due o he disappea -
ance o he double bond in he couma in wi h
o ma ion o a cyclobu ane ing by [2p+2p] cycload-
di ion. The maximum abso bance a 320 nm was used
o desc ibe he pho o- eac ion deg ee,
24,25
whe e con-
e sion is
Con e sion UV ¼1A =Ao
A : abso bance a 320 nm a ime since s a o UV
adia ion.
Ao: abso bance a 320 nm a ime 0.
Raman echnology was also used o s udy he pho o-
dime iza ion kine ic. Spec oscopy measu emen s we e
ca ied ou by a Renishaw in Via Lase mic o-Raman
Spec ome e (Wo on-unde -Edge, UK). A lase
beam wi h wa eleng h o 785 nm se ed as he
exci a ion ligh . The es ing a ea on he ilm was abou
1lm
2
. Con e sion quan i ica ion was done by aking
he a io o he peak ela ed o he double bond a
1617 cm
1
and he peak a 1442 cm
1
ela ed o
me hylene g oups.
18,24
The gel con en (GC) o he esul an ilms was
measu ed by g a ime ical analysis soaking he cu ed
ilms in e ahyd o u an (THF) o 24 h and d ying he
insoluble pa in an o en a 40C o 24 h o cons an
weigh .
26
1681
J. Coa . Technol. Res., 20 (5) 1677–1690, 2023

The mal p ope ies
Modula ed DSC expe imen s we e ca ied ou in
Me le Toledo DSC 1 ins umen . All samples we e
hea ed and cooled o se e al imes a he a e o
1C min
1
in a ni ogen a mosphe e. The e e sible
and non- e e sible hea low in o ma ion can be
simul aneously ob ained in his modula ed DSC expe -
imen . The empe a u e o he midpoin o e e sible
hea low, co esponding o he change in he speci ic
hea , was aken as he glass ansi ion empe a u e ( g).
Mechanical p ope ies
Tensile p ope ies we e measu ed in a FTM-50 1000N
es ing machine (Techlab Sys ems, S.L.) equipped wi h
a 500 N load cell. Tes pieces we e cu om he
samples. A c osshead speed o 50 mm min
1
was used.
S ain was measu ed om c osshead sepa a ion and
e e ed o 10 mm ini ial leng h. A minimum o 5
samples we e es ed o each ma e ial.
Polyu e hane coa ings pe o mance
Polyu e hane dispe sions we e applied on poly(me hyl
me hac yla e) (PMMA) subs a e by au oma ic ilm
applica o wi h a ba o 64 lm. D ying p ocess was
es ablished in 7 days a ambien empe a u e be o e
es ing.
Su ace mo phology
The s udy o coa ings su ace opog aphy was ca ied
ou using an PLu neox op ical p o ile om Senso a .
Con ocal scanning echnology was used o analyze he
oughness. The su ace opog aphy ob ained was
ea ed and oughness pa ame e s we e calcula ed by
Senso iew so wa e acco ding o ISO 25178.
Su ace gloss
The gloss o he polyu e hane coa ings on PMMA
pieces was measu ed acco ding o ISO2813:1994 s an-
da d in a Mic o-TRI-Gloss ins umen (BYK-Ga dne
GmbH). Gloss was ob ained by di ec ing a cons an
in ensi y ligh beam a 60on he coa ing su ace and
measu ing he e lec ed ligh . The alues ob ained we e
he a e age o en eplica es.
Su ace ha dness
Pendulum ha dness measu es he numbe o oscilla-
ions o a pendulum on a coa ing su ace un il i s ops.
The Ko
¨nig ha dness o he polyu e hane coa ings on
PMMA pieces was measu ed based on ISO 1522:2006
s anda d wi h Ko
¨nig Pendulum Ha dness Tes e
(Neu ek. Ins umen s S.L). The alues ob ained we e
he a e age o en eplica es. Sc a ch esis ance was
quan i ied by measu emen s o he Pencil Ha dness.
The pencil ha dness scale ex ends om 9H (ha d) o
9B (no ha d). We ollowed ISO 15184, using a Wol -
Wilbu n Pencil Ha dness es e (BYK-Ga dne , Ge -
e s ied, Ge many).
Resul s and discussion
Syn hesis o 2,2-bis(hyd oxyme hyl)p opiona e
o 7-hyd oxye hoxy-4-me hylcouma in
(DHEOMC diol)
A e he dep o ec ion eac ion o he ace onide g oup,
he chemical composi ion o DHEOMC was de e -
mined by
1
H NMR. Apa om a ge DHEOMC
(couma in diol wi h a molecula weigh o 292 g
mol
1
), in he NMR spec um o his p oduc , a signal
was de ec ed a 3.74 ppm co esponding o he s a ing
mono unc ional p oduc HEOMC. Fo he de e mina-
ion o he weigh con en o each p oduc , he
a oma ic signals o he couma in moie y (> 6.0 ppm)
we e used as a e e ence because hey emain cons an
in bo h p oduc s.
F om he a io o a eas be ween he signals loca ed a
4.36 and 3.74 ppm, (Fig. 5) he mola a io be ween bo h
p oduc s is de e mined, conside ing ha he i s signal
con ained ou hyd ogens o DHEOMC, while he
second signal came om wo hyd ogens o HEOMC.
F om his a ea a io, i was ob ained ha he e was
66.5% mole o DHEOMC and 33.5% mole o HEOMC.
Then, om he molecula weigh s o bo h p oduc s
(DHEOMC, 336.34 g mol
1
and HEOMC, 220.22 g
mol
1
), i was deduced ha he weigh a io be ween
bo h p oduc s was 75.21 w % DHEOMC and 24.79 w %
HEOMC. The e o e, he pho o- eac i e couma in
monome ob ained was composed o a di unc ional
(75.21 w %) and a mono unc ional (24.79 w %) species.
In he syn hesis o he polyu e hane, hus, he e ec o
he mono unc ional 7-hyd oxye hoxy-4-me hyl-
couma in as end-capping agen in he chain ex ension
s age should be conside ed. While i is ue ha he
pho o- eac i i y o he unc ionalized polyu e hane
should keep p ope om HEOMC demons a ing sim-
ila dime iza ion and clea age con e sions han
DHEOMC.
27
This monome exhibi ed close o a 75%
dime iza ion con e sion in polyu e hane ilms.
19
Syn hesis o he wa e bo ne polyu e hane
dispe sions
Pho o- eac i e PU was ob ained by subs i u ing pa o
biobased chain ex ende by he DHEOMC o ob ain a
5 w % concen a ion o couma in in he inal poly-
u e hane, as i was de ailed abo e.
1682
J. Coa . Technol. Res., 20 (5) 1677–1690, 2023
As shown in Table 2, i was ound ha he a e age
pa icle size o he biobased dispe sion inc eased wi h
he inco po a ion o he pho o- eac i e couma in, as
was obse ed in li e a u e o pe oleum based PUD.
17
S e ic impedimen s in pa icle o ma ion mechanism
by he oluminous couma in side g oups esul ed in a
signi ican inc ease in pa icle sizes. The same ca boxyl
con en om DMPA in couma in unc ionalized o -
mula ion p o ided enough elec os a ic epulsion
be ween hese nega i ely cha ged bigge nanopa icles
o achie e s able dispe sions wi h a ze a po en ial well
below 30 mV, which is cha ac e is ic o elec os a -
ically s able dispe sions.
30
The a e age pa icle size
(d50) o bo h aw biobased o mula ion and couma in
based PUD ba ely inc eased a 3 and 5% a e 45 days
o s o age, espec i ely. The dispe sions, hus, kep
s able wi h ime, as demons a ed no only by he ze a
po en ial, bu also by he e y sligh e olu ion o TSI
index (Fig. 6). The couma in unc ionalized PUD jus
exhibi ed a sligh ly highe TSI han o iginal biobased
sample om highe ini ial pa icle size and sligh ly
mo e p onounced inc ease wi h ime. Dispe sion
emained s ables o a leas 45 days, no des abiliza ion
p ocesses like sedimen a ion o c eaming we e de-
ec ed.
Pho o-dime iza ion/pho o-clea age con e sion
Ob ained polyme ilm was exposed o UV adia ion in
an ul a iole c osslinke o en du ing di e en i adi-
a ion imes o p omo e he dime iza ion and clea age
o pho o-ac i e couma in molecules in polyu e hane,
as shown in Fig. 7. Pho o-dime iza ion/pho o-clea age
Table 2: Polyu e hane dispe sion p ope ies
PUD Pa icle size dis ibu ion DLS (nm) -po en ial (mV)
PDI d 10 (nm) d 50 (nm) d 90 (nm)
PUD_BIO 0.21 81.1 ±1.5 141.3 ±1.5 246.5 ±2.6 53.4
PUD_BIO + 45 days 0.19 84.9 ±2.9 145.8 ±3.5 250.3 ±6.1 43.7
PUD_BIO_DHEOMC 0.23 125.8 ±3.9 226.9 ±4.3 409.7 ±4.7 48.1
PUD_BIO_DHEOMC + 45 days 0.20 138.8 ±5.2 239.6 ±2.1 414.0 ±13.6 60.2
DMSO
HEOMC
0
1.00
2.12
0.95
1.37
2.81
1.13
0.69
3.27
2.99
7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0
ppm
3.5 2.5 0.5
1.5
3.0 2.0 1.0
HO
2
DHEOMC
Fig. 5: P o on NMR spec um o he DHEOMC syn hesized
1683
J. Coa . Technol. Res., 20 (5) 1677–1690, 2023
eac ions we e s udied by UV VIS spec oscopy and
Raman spec oscopy.
24
The c osslinking deg ee
achie ed was analyzed by gel con en es .
UV–Vis spec oscopy e ealed ha pho o-dime iza-
ion eac ion achie ed a con e sion o 0.70 by i adia ion
a 354 nm. Howe e , a e excision p ocess by 1.5 min
i adia ion a 254 nm, he couma in dime ized con e -
sion dec eased un il 0.18. Tha means ha he pho o-
dime iza ion o polyu e hane syn hesized was no com-
ple ely e e sible, jus he 74% o dime ized couma in
was clea ed by i adia ion a 254 nm, see Fig. 8.
Rega ding Ramam analysis, con e sion quan i ica-
ion was calcula ed by a ioing he peak ela ed o he
double bond a 1617 cm
1
and he peak a 1442 cm
1
ela ed o me hylene g oups, which emained cons an
du ing he UV adia ion o polyme (Fig. 9). The
pho o-dime iza ion con e sion calcula ed by Raman
spec oscopy was 0.70 a e 240 min i adia ion a
354 nm. Subsequen i adia ion a 254 nm o 1.5 min
(pho o-scission p ocess) led o con e sion dec eased o
0.16 (which means a pho o-clea age yield o a 77%),
Fig. 10. Gene ally, clea age yield d ops mo e sha ply
wi h i adia ion om exis ing an equilib ium be ween
couma in and i s dime s and om o ming non-
clea able dime s when lac one ing opens.
14,17
As
obse ed p e iously in pe ol based polyu e hanes,
18,20
highe con e sions we e no expec ed o longe
exposu e imes once asymp o ic beha io o con e sion
cu e was obse ed.
The pa ial pho o-dime iza ion eac ion o
DHEOMC in he ha d segmen s (0.7 con e sion o a
5 w % o couma in) caused he o ma ion o some
c osslinking poin s ha p omo ed a low gel con en
(3% gel ac ion). As desc ibed abo e, educed con en
o couma in p ese ed he p ope ies o he dispe sion
and as will be shown, he inal aes he ic p ope ies o
he coa ings. Howe e , his pho o-induced ligh ly
c osslinked s uc u e may lead o ailo made imp o e-
men o he mechanical pe o mance o elas ome ic
biobased polyu e hanes o lexible applica ions like
packaging o ex ile, among o he s.
Polyu e hane p ope ies
The analysis o he molecula weigh con i med he
po en ial e ec o he mono unc ional couma in specie
(HEOMC iden i ied by NMR) as an end-capping agen
on he chain ex ension p ocess. The 24.79% o mono-
hyd oxyl couma in monome en ailed a educ ion in
he molecula weigh o he polyu e hane om pa -
ially s opping he polyme g ow h
31,32
(Table 2).
The dynamic scan calo ime ic e ealed a single
glass ansi ion empe a u e indica ing ha he poly-
me s did no show he cha ac e is ic phase sepa a ion
o hese ma e ials. The i egula i y s uc u e o IPDI
isocyana e along wi h he p esence o couma in la e al
mo i di icul he ha d segmen s o seg ega e and he
c ys alliza ion o he polyu e hane.
33
DSC analysis (Table 2and Fig. 11) demons a ed
ha glass ansi ion empe a u es ( g) o he s udied
polyme s we e no signi ican ly a ec ed by he p es-
ence o he couma in monome . On he one hand, he
e ec o modi ying he chain ex ende on he g is
eally cons ained in polyu e hane s uc u es wi h a
balance a io be ween ha d and so segmen s (mod-
e a e ha d segmen con en ), e en u he when so
segmen s a e o med by high molecula weigh polyols,
like P iplas (2000 g mol
1
) in his s udy.
34
On he
o he hand, he glass ansi ion empe a u e was no
10
8
6
TSI
4
2
0
0102030
Time (days)
% PUD_BIO
% PU_BIO_DHEOMC
40 50
Fig. 6: TSI des abiliza ion and pho og aphs o syn hesized
PUD
Pho o-dime iza ion
Pho o-clea age
OO
O
O
OO
OO
O
O
O
O
Fig. 7: Pho o-dime iza ion/pho o-clea age eac ions o couma in molecules
1684
J. Coa . Technol. Res., 20 (5) 1677–1690, 2023
signi ican ly al e ed by he low c osslinking deg ee
33,35–37
when he 5 w % ac ion o DHEOMC wi hin he ha d
segmen was dime ized. As expec ed, he long chain
biobased so segmen was bea ing he g ea es e ec
on g i compa ed o chain ex ende o ligh ly c oss-
linked s uc u e.
Di e en coa ing p ope ies o he syn hesized
biobased polyu e hanes we e s udied (Table 3). Side
couma in moie ies wi hin he polyu e hane chain
ba ely a ec ed he ilm o ma ion and he ela ed
aes he ic p ope ies om su ace mo phology. The
p esence o oluminous couma in species could ha e
some ad e se e ec on he low beha io and su ace
oughness du ing coalescing and d ying o PUD. Then,
signi ican aise in oughness would gene a e a gloss
e ec , i.e. enhanced mic o oughness inc eases di usely
280
1
0
1
0
300 320 340 360
= 0 = 0 s
= 60 s
= 90 s
= 13 min
= 49 min
= 45 min
= 205 min
= 240 min
Wa eleng h /nm
Abso bance
Abso bance
280 300 320 340 360
Wa eleng h /nm
Fig. 8: UV–Vis spec a o PUD_BIO_DHEOMC, le pho o-dime iza ion a 350 nm and igh pho o-clea age upon i adia ion
a 254 nm
1450
30000
25000
1617 cm
p is ine
dime iza ion
clea age
–1
Coun s
20000
15000
1500 1550
Raman shi (cm–1)
1600 1650
Fig. 9: Raman spec a o PUD_BIO_DHEOMC non i adia ed (black line), polyu e hane dime ized (blue line) and
polyu e hane clea ed ( ed line)
1685
J. Coa . Technol. Res., 20 (5) 1677–1690, 2023