Printability Study of a Conductive Polyaniline/Acrylic Formulation for 3D Printing

polyme s
A icle
P in abili y S udy o a Conduc i e Polyaniline/Ac ylic
Fo mula ion o 3D P in ing
Go e i A ias-Fe ei o 1, Ana A es-Pe nas 1, Au o a Lasagabás e -La o e 2, No a A anbu u 3,
Gonzalo Gue ica-Eche a ia 3, M. Sonia Dopico-Ga cía1and Ma ía-JoséAbad 1,*


Ci a ion: A ias-Fe ei o, G.;
A es-Pe nas, A.; Lasagabás e -La o e, A.;
A anbu u, N.; Gue ica-Eche a ia, G.;
Dopico-Ga cía, M.S.; Abad, M.-J.
P in abili y S udy o a Conduc i e
Polyaniline/Ac ylic Fo mula ion o
3D P in ing. Polyme s 2021,13, 2068.
h ps://doi.o g/10.3390/
polym13132068
Academic Edi o s: Joaquín M.
Ma ínez U eaga, Ma ía Ulaga es de
la O den, Ma ina Pa icia
A ie a Dillon and F eddys R.
Bel án González
Recei ed: 25 May 2021
Accep ed: 19 June 2021
Published: 23 June 2021
Publishe ’s No e: MDPI s ays neu al
wi h ega d o ju isdic ional claims in
published maps and ins i u ional a il-
ia ions.
Copy igh : © 2021 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
1G upo de Políme os, Cen o de In es igacións Tecnolóxicas, Uni e sidade da Co uña, Campus de Fe ol,
15471 Fe ol, Spain; go [email p o ec ed] (G.A.-F.); [email p o ec ed] (A.A.-P.); [email p o ec ed] (M.S.D.-G.)
2
Depa emen o Química O gánica I, Facul ad de Óp ica y Op ome ía, Uni e sidad Complu ense de Mad id,
A cos de Jalón 118, 28037 Mad id, Spain; au [email p o ec ed]
3POLYMAT and Depa men o Ad anced Polyme s and Ma e ials, Physics, Chemis y and Technology,
Facul y o Chemis y, Uni e si y o he Basque Coun y UPV/EHU, 20018 San Sebas ián, Spain;
[email p o ec ed] (N.A.); [email p o ec ed] (G.G.-E.)
*Co espondence: [email p o ec ed]
Abs ac :
The e is need o de eloping no el conduc i e polyme s o Digi al Ligh P ocessing (DLP)
3D p in ing. In his wo k, pho o heology, in combina ion wi h Jacobs wo king cu es, e icaciously
p edic he p in abili y o polyaniline (PANI)/ac yla e o mula ions wi h di e en con en s o PANI
and pho oini ia o . The adjus men o he laye hickness acco ding o cu e dep h alues (C
d
)
allows p in ing o mos o mula ions, excep hose wi h he highes gel poin imes de e mined by
pho o heology. In he wo king condi ions, he maximum amoun o PANI embedded wi hin he esin
was
≃
3 w % wi h a conduc i i y o 10
−5
S cm
−1
, h ee o de s o magni ude highe han he pu e
esin. Highe PANI loadings hinde p in ing quali y wi hou imp o ing elec ical conduc i i y. The
op imal pho oini ia o concen a ion was ound be ween 6 and 7 w %. The mechanical p ope ies o
he ac ylic ma ix a e main ained in he composi es, con i ming he iabili y o hese simple, low-cos ,
conduc i e composi es o applica ions in lexible elec onic de ices.
Keywo ds:
polyaniline; UV cu ing; ac ylic conduc i e composi e; 3D p in ing; a polyme iza-
ion; DLP
1. In oduc ion
Addi i e manu ac u ing (AM) o 3D p in ing echnologies a e gaining impo ance in
he indus y due o he new p oduc ion models ha es ablish he pa adigms o Indus y
4.0. Howe e , one o he majo d awbacks o AM emains—i s limi ed ma e ials selec ion
po olio, wi h low a ailabili y o high-pe o mance ma e ials wi h speci ic p ope ies.
The e o e, mo e esea ch is equi ed on p o iding ma e ials wi h new ea u es [
1
–
3
] wi h
he minimum en i onmen al cos , as demanded by oday’s socie y. In his way, he use o
3D p in ing echnologies in elec onics has g ea po en ial since i allows he in eg a ion o
senso s, conduc o s, de ices wi h di e en elec onic unc ions, e c., in he manu ac u ing
p ocess o h ee-dimensional objec s a an a o dable cos , while main aining eedom in
design [4,5].
Among he di e en 3D p in ing echnologies, he pho ochemical app oach is ex-
emely a ac i e as objec s can be p oduced ia pho opolyme iza ion eac ions o mono-
me s/oligome s, which possess en i onmen al, economic and p oduc ion bene i s [
1
]. This
app oach includes S e eoli hog aphy (SLA) and Digi al Ligh P ocessing (DLP). In DLP,
each laye o he esin is exposed all a once o he ligh sou ce and hen cu ed simul ane-
ously. This allows conside ably sho e building imes han he poin -by-poin p in ing
wi h a lase employed in SLA [2,3,6].
P in able ma e ials a e mainly composed o mono/mul i unc ional monome s and/o
oligome s, pho oini ia ing sys ems and a ious addi i es. When he esin is exposed o UV
Polyme s 2021,13, 2068. h ps://doi.o g/10.3390/polym13132068 h ps://www.mdpi.com/jou nal/polyme s
Polyme s 2021,13, 2068 2 o 20
ligh , he pho oini ia o s decompose in o ee adicals ha eac wi h he monome and
oligome s, causing hem o co alen ly bond o o m long c oss-linked polyme chains [
1
,
3
,
5
].
Abso bing addi i es a e commonly used o adjus he e ical esolu ion, ha is, he small-
es possible laye hickness [
2
]. To ob ain unc ional ma e ials as conduc ing polyme
composi es sui able o 3D p in ing, di e en conduc i e ille s can be added such as me al
nanopa icles, ca bon nano ubes, g aphene, o in insically conduc ing polyme s (ICPs)
such as polypy ole o polyanilines [
7
–
10
]. Polyanilines (PANIs) seem o be excellen
candida es o ab ica ing senso de ices, ene gy con e sion and s o age, o supe capaci-
o s due o hei in insic elec ical p ope ies [
11
–
13
], oge he wi h good en i onmen al
s abili y, simple syn hesis and low cos [
14
]. No wi hs anding, i s use in 3D p in ing ia
a polyme iza ion is sca ce due o challenges such as o e lapping UV–Vis abso bance o
PANI and he pho oini ia o , poo dispe sion in he polyme ma ix and iscosi y a high
ille concen a ions [
3
,
15
]. Only a ew ecen epo s ha e explo ed he possibili y o in-
co po a ing PANI in o o mula ions o DLP p in ing ei he indi idually [
16
] o combined
wi h g aphene [17].
P e ious wo ks ha e s udied he in luence o he composi ion o he pho ocu able
esin on he easibili y o DLP p in ing. Kowsa i e al. [
18
] in es iga ed he e ec o di e en
pa ame e s such as pho oini ia o , abso be , monome molecula weigh o c osslinke on
he esolu ion and quali y o he p in ed s uc u es. Gojzewski e al. [
19
] ocused on he
s udy o he nanomechanical p ope ies a he in e ace o polyme s p in ed by DLP using
a omic o ce mic oscopy (AFM) ha showed he e ec o ligh abso be s on he s i ness
decay ac oss he indi idual laye s. Ho s e e e al. [
20
] s udied he cu ing beha io
o mix u es wi h a iable amoun s o ligh abso be s and pho oini ia o s in ended o
DLP. They combined pho o heology, FTIR and he Jacobs wo king cu es o op imize hei
con en in he o mula ion, al hough no 3D p in ing es s we e ca ied ou . The combina ion
o hese echniques seems especially in e es ing o polyme s wi h low cu ing speed and
educed c oss-linking densi y, whe e he polyme ne wo k and he esul ing mechanical
p ope ies need ime o build up [
20
]. Jacobs wo king cu es a e commonly used o ix
he co ec se ings o DLP [
21
], as hey p o ide wo key pa ame e s o pho ocu able
esins, he pene a ion dep h o he cu ing ligh (D
p
) and he ene gy equi ed o he
polyme iza ion (E
c
) [
22
]. Howe e , al hough E
c
is an impo an alue, he s eng h and
elas ic modulus o a polyme a he gel poin a e no mally oo low o ensu e success ul
ab ica ion du ing he SLA o DLP p ocess [
2
]. Thus, he complemen a y in o ma ion
p o ided by o he echniques as pho o heology o pho o-DSC o de e mine gel ime [
23
]
can help o unde s and he p in ing p ocess.
The main a ge o his wo k is he p in abili y assessmen o a conduc i e, cos -
e ec i e, pho ocu able ac ylic esin o DLP. The p esen pape con inues p e ious esea ch
whe e PANI-HCl was inco po a ed, as conduc i e ille , in o an in-house esin composed
o E hyleneglycolphenyle he ac yla e (EGPEA) as he p incipal monome , 1, 6-Hexanediol
diac yla e (HDODA) as he c osslinke and Diphenyl (2,4,6- i-me hylbenzoyl) phosphine
oxide (TPO) se ing as he pho oini ia o [24].
In he cu en wo k, he e ec o adding PANI on he p in abili y o he esin was
sys ema ically in es iga ed. The concen a ion o he pho oini ia o was also modi ied o
balance he expec ed slowdown o he pho opolyme iza ion eac ion due o abso p ion o
PANI a he p in ing wa eleng h. The o mula ions we e e alua ed by he combina ion
o h ee echniques, namely, pho o heology, Jacobs wo king cu es and DLP p in ing.
F om Jacobs wo king cu es, he pene a ion dep h o cu ing ligh (D
p
) and he ene gy
equi ed o he polyme iza ion (E
c
) we e calcula ed o de ine he bes heo e ical condi ions
o p in ing.
Fu he , o ela e he p in abili y pe o mance o he no el conduc ing esins wi h hei
mic os uc u e and physico-chemical p ope ies, he p in ed samples we e cha ac e ized by
Scanning Elec on Mic oscopy (SEM), A enua ed To al Re lec ance-Fou ie T ans o med
In a ed Spec oscopy (ATR-FTIR), elemen al analysis, elec ical conduc i i y, he mal and
Polyme s 2021,13, 2068 3 o 20
mechanical p ope ies bo h by dynamic mechanical analysis (DMA), di e en ial scanning
calo ime y (DSC) and ensile es .
The p in ing iabili y o di e en PANI composi es was success ully p edic ed based
on he gel poin imes de e mined by Pho o heology, plus he Jacobs cu e pa ame e s,
E
c
and C
d
. The sys ema ic s udy e ealed ha inc easing he concen a ion o TPO al-
lowed o e coming he nega i e e ec o PANI on cu ing pe o mance o a limi ed ex en .
The e o e, o each le el o PANI es ed, he e was an op imal amoun o pho oini ia o s
abo e which no addi ional bene i was obse ed. Fu he , he adjus men o he p in ing
pa ame e s conside ing C
d
enabled p in ing o mos o he es ed o mula ions, excep
hose wi h he highes gel poin imes. In sho , his wo k p o ides aluable guidance
o u u e de elopmen o p in able cos -e ec i e composi es con aining conduc i e UV
abso ben ille s.
2. Expe imen al Sec ion
2.1. Ma e ials
Aniline (ANI, 99.5%) and ammonium pe sul a e (APS, 99%) we e ob ained om
Sigma-Ald ich (S . Louis, MO, USA) and Ac os (Geel, Belgium), espec i ely. Hyd ochlo-
ic acid (37% HCl) and me hanol (MeOH) we e pu chased om Scha lau (Sen mena ,
Spain). Wa e was pu i ied on an Elix 3 sys em (Millipo e, Molsheim, F ance). The
ac ylic monome and c osslinke employed o polyme syn hesis we e E hylene glycol
phenyl e he ac yla e (EGPEA, molecula weigh = 192.21 g mol
−1
) and 1,6-hexanediol
diac yla e (HDODA, molecula weigh = 226.27 g mol
−1
), espec i ely. The pho oini-
ia o used was Diphenyl (2,4,6- ime hylbenzoyl) phosphine oxide (TPO, molecula
weigh = 348.37 g mol
−1
). Monome , c osslinke and pho oini ia o we e pu chased om
Sigma-Ald ich (S . Louis, MO, USA). We employed 2-P opanol ob ained om Scha lau
(Sen mena , Spain) o inse he samples a e 3D p in ing.
P epa a ion o PANI.
The PANI used in his pape was syn he ized in ou labo a o y
as desc ibed in a p e ious a icle [
24
]. The p ocedu e is based on ha published by Pa k
e al. [
25
] and adap ed by Ho a-Roma ís e al. [
11
]. In b ie , he polyme iza ion eac ion
was pe o med unde mechanic s i ing (350 pm) a oom empe a u e o 3 h. The
eac ion was ini ia ed by he d opwise addi ion o he APS oxidan o a ound 30 min.
A e
24 h
, he esul ing p oduc was il e ed unde acuum and washed wi h a mix u e o
1:1 wa e :MeOH. The PANI-HCl was ob ained as a da k g een powde a e d ying o
24 h
a 80
◦
C in acuum in eeze d ying equipmen (Tels a Lyoques , Te assa, Spain). PANI
was cha ac e ized by UV-Vis spec oscopy, SEM, elemen al analysis, FTIR and elec ical
conduc i i y as explained in he co esponding sec ions.
P epa a ion o in-house o mula ion.
The monome mix u es we e o mula ed ak-
ing as e e ence a p e ious s udy, A ias-Fe ei o e al. [
24
]. A ixed quan i y o he HDODA
c osslinke (15 w %) was added o he p incipal componen , he monome (EGPEA). Di -
e en amoun s o conduc i e ille (PANI 2 w % o 5 w %) and pho oini ia o (TPO, 4 w %
o 10 w %) we e addi ionally inco po a ed. The composi e o mula ions a e compiled in
Table 1.
Wi h he aim o p omo ing homogeneous dispe sion, he componen s we e placed
in o ials and sonica ed o 45 min using a Digi al Soni ie a 15% in ensi y (B anson 450).
Immedia ely p io o use, he liquid o mula ions we e u he mechanically s i ed in a
Vo ex mixe o 10 min a 1000 pm (VELP Scien i ic). A e mixing, he o mula ions we e
cu ed in wo di e en ways, depending on he ype o analysis and cha ac e iza ion: he
i s se o samples was cu ed unde he LED lamp and he second se in he 3D p in e .
In o de o ollow he e olu ion o he ma e ial p ope ies du ing he pho opolyme iza-
ion eac ion, he i s se o samples was polyme ized unde a Visicu e 405 nm lamp wi h
an 8 mm diame e ocus lens connec ed o a LED Spo -Cu ing Sys em (BlueWa e, Dymax
Co p., To ing on, CT, USA). The UV in ensi y was adjus ed o each a inal in ensi y
o 3 mW cm
−2
o e he sample, measu ed wi h a LED adiome e (Dymax ACCU-CAL
50-LED PN40519, Dymax Co p., To ing on, CT, USA). A e being subjec ed o an a e age
Polyme s 2021,13, 2068 4 o 20
exposu e ime o 999 s o ensu e high deg ees o con e sion, discs o 25 mm in diame e
and 200 µm in hickness we e ob ained.
Table 1. Composi e o mula ions, pene a ion dep h (Dp), c i ical exposu e (Ec) and cu e dep h (Cd)
calcula ed om he Jacobs wo king cu es and Viscosi y alues ob ained a 1 s−1.
Sample TPO
(w %)
Theo e ical
PANI (w %)
Dp
(µm)
Ec
(mJ cm−2)
Cd
(µm)
Viscosi y
(Pa.s) 1 s−1
T4P2 4 2 71 42 43 0.047
T4P35 4 3.5 55 42 34 0.072
T4P5 4 5 59 65 10 0.159
T6P2 6 2 63 34 50 0.051
T6P35 6 3.5 48 30 45 0.059
T6P5 6 5 52 51 21 0.153
T7P2 7 2 48 21 62 0.071
T7P35 7 3.5 54 48 25 0.078
T7P5 7 5 46 44 25 0.155
T10P2 10 2 43 21 56 0.025
T10P35 10 3.5 49 45 26 0.078
T10P5 10 5 49 69 5 0.151
A second se o o mula ions we e cu ed wi h a 3D p in e (SLASH PLUS, UNIZ,
San Diego
, CA, USA) which employs LCD S e eoli hog aphy p in ing echnology. The
p in e se ings we e adjus ed based on he p in e echnical equi emen s and he com-
posi ion o he o mula ions es ed. The ligh i adia ion dosage was 76.5 mJ cm
−2
o
each laye , conside ing ha he ligh in ensi y o he 3D p in e was 3 mW cm
−2
and he
exposu e ime was 25.5 s pe laye . The laye hickness was se a 0.05 mm o 0.025 mm
depending on he o mula ion. A e p in ing, he samples we e soaked in 2-p opanol o
10 min in o de o emo e he non-cu ed esin. A pos -cu ing p ocess was pe o med wi h
a pos -cu ing lamp (Fo m Cu e, Fo mlabs, Some ille, MA, USA) o 5 min a 35
◦
C. To
ca y ou he di e en es s, lexible ec angula ilms o 50 mm
×
35 mm
×
0.5 mm we e
p epa ed. The en i e p epa a ion p ocess o 3D p in ing and he aspec o he composi e
samples is illus a ed in Scheme 1. In addi ion, he o mula ions we e alida ed by p in ing
objec s o di e en shapes; he digi al models we e designed and con e ed o STL ile
o ma o 3D p in ing.
Polyme s 2021, 13, 2068 5 o 21
Scheme 1. Diag am o sample p epa a ion.
2.2. Ma e ials Cha ac e iza ion
The UV-Vis spec a o PANI solu ion o 60 ppm in EGPEA: 15 w % HDODA we e
eco ded on a Jasco V-750 double-beam UV-Vis spec opho ome e (Jasco Analí ica S.L.,
Mad id, Spain) be ween 200 and 800 nm.
The iscosi y o he liquid monome o mula ions was de e mined a oom empe a-
u e using a con olled s ain heome e (ARES, TA Ins umen , Newcas le, DE, USA) wi h
pa allel-pla e geome y (25 mm diame e , 1 mm gap). The s eady shea iscosi y (η) was
measu ed in a ange o shea a es be ween 0.3 and 100 s
−1
.
The e olu ion o he pho opolyme iza ion eac ion was moni o ed by in si u pla e o
pla e pho o heology in he a o emen ioned ARES heome e coupled wi h a UV lamp. A
home-made de ice, qui e simila o ha desc ibed by Schmid e al. [26] was employed.
The de ice is depic ed in Scheme 2. I consis s o a 3D-p in ed, home-designed uppe ix-
u e ha allows coupling o he UV sou ce and he uppe pla e. The uppe pla e was made
o qua z o ensu e ansmi ance o UV i adia ion. The liquid sample was placed be-
ween he qua z pla e and a disposable aluminum pa allel pla e, bo h wi h a diame e o
18 mm [26–28].
Scheme 2. Diag am o he pho o heology se -up.
To ollow he e olu ion o he iscoelas ic p ope ies o he composi es, a liquid sam-
ple was placed be ween he wo pla es; hen, he ligh in ensi y and he gap size be ween
he glass pla e and he measu ing sys em we e adjus ed o app oach he condi ions o he
3D p in e . Due o his, an in ensi y o 3 mW.cm
−2
was selec ed and he gap was se a 150
Scheme 1. Diag am o sample p epa a ion.
Polyme s 2021,13, 2068 5 o 20
2.2. Ma e ials Cha ac e iza ion
The UV-Vis spec a o PANI solu ion o 60 ppm in EGPEA: 15 w % HDODA we e
eco ded on a Jasco V-750 double-beam UV-Vis spec opho ome e (Jasco Analí ica S.L.,
Mad id, Spain) be ween 200 and 800 nm.
The iscosi y o he liquid monome o mula ions was de e mined a oom empe a-
u e using a con olled s ain heome e (ARES, TA Ins umen , Newcas le, DE, USA) wi h
pa allel-pla e geome y (25 mm diame e , 1 mm gap). The s eady shea iscosi y (
η
) was
measu ed in a ange o shea a es be ween 0.3 and 100 s−1.
The e olu ion o he pho opolyme iza ion eac ion was moni o ed by in si u pla e o
pla e pho o heology in he a o emen ioned ARES heome e coupled wi h a UV lamp. A
home-made de ice, qui e simila o ha desc ibed by Schmid e al. [
26
] was employed.
The de ice is depic ed in Scheme 2. I consis s o a 3D-p in ed, home-designed uppe
ix u e ha allows coupling o he UV sou ce and he uppe pla e. The uppe pla e was
made o qua z o ensu e ansmi ance o UV i adia ion. The liquid sample was placed
be ween he qua z pla e and a disposable aluminum pa allel pla e, bo h wi h a diame e
o 18 mm [26–28].
Polyme s 2021, 13, 2068 5 o 21
Scheme 1. Diag am o sample p epa a ion.
2.2. Ma e ials Cha ac e iza ion
The UV-Vis spec a o PANI solu ion o 60 ppm in EGPEA: 15 w % HDODA we e
eco ded on a Jasco V-750 double-beam UV-Vis spec opho ome e (Jasco Analí ica S.L.,
Mad id, Spain) be ween 200 and 800 nm.
The iscosi y o he liquid monome o mula ions was de e mined a oom empe a-
u e using a con olled s ain heome e (ARES, TA Ins umen , Newcas le, DE, USA) wi h
pa allel-pla e geome y (25 mm diame e , 1 mm gap). The s eady shea iscosi y (η) was
measu ed in a ange o shea a es be ween 0.3 and 100 s
−1
.
The e olu ion o he pho opolyme iza ion eac ion was moni o ed by in si u pla e o
pla e pho o heology in he a o emen ioned ARES heome e coupled wi h a UV lamp. A
home-made de ice, qui e simila o ha desc ibed by Schmid e al. [26] was employed.
The de ice is depic ed in Scheme 2. I consis s o a 3D-p in ed, home-designed uppe ix-
u e ha allows coupling o he UV sou ce and he uppe pla e. The uppe pla e was made
o qua z o ensu e ansmi ance o UV i adia ion. The liquid sample was placed be-
ween he qua z pla e and a disposable aluminum pa allel pla e, bo h wi h a diame e o
18 mm [26–28].
Scheme 2. Diag am o he pho o heology se -up.
To ollow he e olu ion o he iscoelas ic p ope ies o he composi es, a liquid sam-
ple was placed be ween he wo pla es; hen, he ligh in ensi y and he gap size be ween
he glass pla e and he measu ing sys em we e adjus ed o app oach he condi ions o he
3D p in e . Due o his, an in ensi y o 3 mW.cm
−2
was selec ed and he gap was se a 150
Scheme 2. Diag am o he pho o heology se -up.
To ollow he e olu ion o he iscoelas ic p ope ies o he composi es, a liquid sample
was placed be ween he wo pla es; hen, he ligh in ensi y and he gap size be ween he
glass pla e and he measu ing sys em we e adjus ed o app oach he condi ions o he 3D
p in e . Due o his, an in ensi y o 3 mW cm
−2
was selec ed and he gap was se a 150
µ
m.
The chosen gap was highe han he size o he PANI agglome a es in he esin suspension.
In addi ion, his is an op imum sample gap o heological cha ac e iza ion because a a
sample hickness <50
µ
m, he heological in o ma ion becomes un eliable, and a a sample
hickness o >500 µm, a uni o m pho ocu ing eac ion canno be ensu ed [29].
A ime-sweep measu emen was ca ied ou o each o mula ion and he e ec o
bo h PANI and TPO concen a ions we e s udied. The es s we e pe o med in dynamic
mode wi h a equency o 10 ad s
−1
and a s ain o 30%. P io o his, s ain and equency
scans we e pe o med o de e mine i hese condi ions lie in he linea iscoelas ic ange o
he ma e ials. The es p ocedu e was di ided in wo s ages. In he i s one, he sample
was main ained be ween he pla es 300 s wi hou UV ligh exposu e in o de o equilib a e
i and ob ain he baseline o he uncu ed composi e. In he second s age, he pho opolyme
was cu ed wi h a ligh in ensi y o 3 mW cm
−2
o 1300 s [
20
,
30
]. Du ing he ime-sweep
measu emen s, he e olu ion o he elas ic modulus (G
0
) and loss modulus (G
00
) and an

Polyme s 2021,13, 2068 6 o 20
δ
we e moni o ed o he composi es. A leas h ee measu emen s a oom empe a u e
we e made o each o mula ion.
The Jacobs wo king cu es we e calcula ed o all o mula ions desc ibed in
Table 1
.
To elabo a e, he Jacobs wo king cu es he liquid monome o mula ions we e u he
p epa ed ollowing he p ocedu e desc ibed in he Sec ion 2.1. Ci cula ilms o 18 mm
diame e and 1 mm hickness we e cu ed be ween wo glasses unde a 405 nm Visicu e
lamp, wi h a cons an in ensi y o 3 mW cm
−2
and a ying he exposu e imes. E e y
sample was pe o med in duplica e. A e polyme iza ion, he uncu ed ma e ial was
emo ed om he ci cula ilms by sp aying wi h 2-P opanol and he emaining sol en
was e apo a ed a oom empe a u e o e nigh in a ume hood. The hicknesses o he
samples we e measu ed wi h a hickness gauge (Milli as 1080, MAHR GmbH, Gö ingen,
Ge many) and plo ed as a unc ion o Exposu e (Emax) (mJ cm−2).
The Jacobs wo king cu e p o ides in o ma ion on wo key pa ame e s o pho ocu -
able esins: he pene a ion dep h o he cu ing ligh and he ene gy equi ed o polyme -
iza ion (Equa ion (1)) [22].
Cd=Dp·lnEmax
Ec(1)
whe e C
d
(
µ
m) is he cu ed dep h, E
max
(mJ cm
−2
) is he ligh i adia ion dosage on he
su ace, E
c
(mJ cm
−2
) is he s a ing poin o he ansi ion om liquid o solid and
D
p
(
µ
m) ep esen s he pene a ion dep h. This exp ession equa es o a linea line on a
semiloga i hmic plo o C
d
in y-axis e sus E
max
in x-axis. The in e cep ion o he Jacobs
wo king cu e wi h he x-axis ep esen s Ec, whe eas Dpis he slope o he linea line.
The mo phology o PANI powde and he p in ed composi e ilms was e alua ed
using Scanning Elec on Mic oscopy (SEM). P in ed specimens we e b oken unde c yo-
genic condi ions and hen examined using a JEOL JSM-7200F Field Emission Scanning
Elec on Mic oscope (JEOL L d, Tokyo, Japan) a an accele a ing ol age o 10 kV, equipped
wi h an Ene gy Dispe si e X- ays Spec ome y Sys em (EDS) o chemical mic oanalysis
(AZ ecLi e Nanoanalysis, Ox o d Ins umen s, Ox o d, UK). P io o obse a ion, he
samples we e spu e -coa ed wi h a hin palladium/pla inum laye (C essin ong 208HR).
The Fou ie T ans o med In a ed (FTIR) da a we e eco ded on a Jasco 4700 spec-
ome e equipmen (Jasco Analí ica S.L., Mad id, Spain). Th ee abso p ion spec a o
PANI-HCl we e pe o med in Po assium B omide (KB ) pelle s and he a e age spec um
examined. The ec angula p in ed ilms we e analyzed in he A enua ed Re lec ance
Mode (ATR) by using a MIRacle ZnSe Single Re lec ion Ho izon al ATR accesso y (PIKE
Technologies, Madison, WI, USA). Th ee indi idual spec a we e collec ed on each ilm. All
he spec a we e ca ied ou om 4000 o 600 cm
−1
wi h a 4 cm
−1
esolu ion o e 64 scans
and subjec ed o baseline and ATR co ec ion. The spec a we e analyzed using he B uke
OPUS
®
so wa e e sion 5.5 (B uke Española S.A, Mad id, Spain). The deg ee o he
ac yla e double bonds con e sion (DBC%) in he pos -cu ed p in ed ilms was calcula ed
om he IR peak a ea o he band loca ed a 810 cm
−1
, no malized o he ca bonyl es e
s e ching band (
νC=O
) o he ac ylic polyme a 1728 cm
−1
, as in e nal e e ence, acco ding
o Equa ion (2) [31]:
Deg ee o con e sion (DBC%)=(A810/A1728) =0−(A810/A1728)
(A810/A1728) =0
×100% (2)
The elemen al analysis o C, H, N and S o PANI and he composi es we e conduc ed
in duplica e using The moFinnigan FlashEA1112 elemen al analyze (Conque Scien i ic,
Poway, CA, USA).
The elec ical conduc i i y (
σ
) a oom empe a u e was calcula ed om he elec ical
esis ance da a by he ou -p obe me hod (MCP-T610 LORESTA-GP, Mi subishi Chemical
Co p, Tokyo, Japan) in he samples ob ained by 3D p in e p ocess. In he case o PANI, he
elec ical esis ance was de e mined on h ee squa e comp ession molded pelle s o 2.5 cm
Polyme s 2021,13, 2068 7 o 20
×
2.5 cm
×
0.5 mm. The elec ical conduc i i ies (
σ
) epo ed o each polyme o mula ion
a e he mean alues o a leas 12 eadings measu ed on h ee di e en samples.
Dynamic mechanical analysis (DMA) was pe o med on a DMA model Q800 om TA
ins umen s (Newcas le, Delawa e, USA). The analysis was used o de e mine he modulus,
glass ansi ion empe a u e (T
g
) and c oss-linking densi y. The c oss-linking densi y,
νc
, is
de ined as he numbe o moles o elas ically e ec i e ne wo k chains pe cubic cen ime e
o ilm. I was calcula ed using Equa ion (3) [
31
–
33
], whe e E’
min
is he minimum s o age
modulus and TE0min is he empe a u e a minimum s o age modulus:
νc=E0min
3RTE0min
(3)
The a e age molecula weigh o chain segmen s be ween he c oss-links,
Mc
, was
calcula ed o each o mula ion using Equa ion (4) [
31
], whe e
ρ
is he ilm densi y and
R is he uni e sal gas cons an .
ρ
was de e mined by he A chimedes p inciple wi h
a Sa o iusLA230S elec onic balance equipped wi h a densi y measu emen ki , using
dis illa e wa e as he e e ence liquid.
Mc=3ρRTE0min
E0min
(4)
Rec angula es specimens 15
×
6
×
0.5 mm we e p epa ed o DMA measu emen s
in he 3D p in e . The es me hod was a ension- ilm mode unde he ollowing condi ions:
equency o 1 Hz, ampli ude o 15
µ
m and empe a u e om
−
40
◦
C o 80
◦
C a a hea ing
a e o 4 ◦C min−1.
The glass ansi ion empe a u es (T
g
) we e also e alua ed by Di e en ial Scanning
calo ime y (DSC) (2010 TA Ins umen s, Newcas le, Delawa e, USA) unde ni ogen
a mosphe e. Then, 10–12 mg o he composi es ilms we e pu in aluminum pans and
hea ed om −40 ◦C o 200 ◦C a a a e o 10 ◦C min−1.
Tensile s ess–s ain p ope ies we e cha ac e ized using an Ins on 5569 uni e sal
es ing machine (Ins on Can on, No wood, MA, USA) ope a ing a oom empe a u e
and a c oss-head speed o 10 mm
·
min
−1
un il ailu e. Young modulus (E), s eng h
and s ain a b eak poin we e calcula ed om s ess–s ain cu es as he a e age o i e
dumbbell-shaped specimens o each ma e ial o dimensions 30.0 ×3.2 ×1.2 mm.
3. Resul s
3.1. Rheological Resul s
3.1.1. Viscosi y o Liquid Fo mula ions
Ini ially, he e ec o bo h PANI and TPO concen a ions on he iscosi y o he liquid
o mula ion was s udied a oom empe a u e. An adequa e iscosi y mus be uned o
success ul 3D-p in ing. O he wise, i he iscosi y alue is oo high, he liquid o mula ion
canno ill he gap be ween he a and he p e ious polyme ized laye homogeneously
in he speci ied ime, esul ing in ailu e when he building pla o m is aised du ing he
p in ing p ocess [7].
By way o example, Figu e S1 depic s he e ec o he ille addi ion on s eady shea
iscosi y as a unc ion o shea a e o a cons an TPO ini ia o con en o 4 w %, whe eas
Figu e S2 desc ibes he e ec o he pho oini ia o con en o a cons an PANI concen a ion
o 5 w %. Fu he , he iscosi y alues ob ained a 1 s
−1
o all o mula ions assayed a e
summa ized in Table 1.
A clea augmen in iscosi y was shown wi h inc easing ille concen a ion. The
p esence o PANI pe u bed he no mal polyme low; consequen ly, he iscosi y o he
illed polyme inc eased om 0.005 Pa s up o 0.150 Pa s a 1 s
−1
upon aising PANI loadings
om 0 o 5 w %. These alues ep esen ed an inc ease o wo o de s o magni ude. By
con as , no ema kable e ec o he pho oini ia o concen a ion on s eady shea iscosi y
Polyme s 2021,13, 2068 8 o 20
as a unc ion o shea a e was obse ed. This esul can be app ecia ed in Figu e S2, in
which he co esponding g aphs emain close h oughou he es ed ange.
3.1.2. Pho o heology
To u he cha ac e ize he pho opolyme iza ion p ocess, he e olu ion o he cu ing
eac ion was s udied in si u. This me hod moni o s he change in modulus du ing he liquid
o solid ansi ion in pho ocu able composi es and can hus de e mine he gel poin . The
measu ed bulk modulus co ela es wi h he deg ee o polyme iza ion and he c osslinking
densi y [
34
]. The obse ed beha io was exac ly he same in all pho ocu ed composi es. As
an example, he e olu ion o he elas ic modulus (G
0
), loss modulus (G
00
) and an
δ
in he
sample labelled T4P5 is shown in Figu e 1A. A he beginning, be o e u ning on he UV
lamp and du ing he i s seconds o illumina ion, G
0
was smalle han G
00
, co esponding
o a liquid-like beha io . Then, he shapes o he G
0
and G
00
plo s changed o e he cou se o
i adia ion. A e se e al seconds o exposu e ime, which was di e en o each sample, he
elas ic componen inc eased apidly; G
0
and G
00
cu es app oached each o he , indica ing
he gel poin . F om he s a o he UV exposu e, an
δ
alues dec eased apidly due o a
es ic ion in molecula mobili y and o he ecombina ion eac ions ha p edomina e in
g ea leng h as he pho o-oxida i e eac ion p oceeds. G
0
inc eased apidly, pa allel o he
dec ease in an
δ
exceeding G
00
. This inc ease was due o he ans o ma ion o a iscous
New onian luid in o an elas ic solid du ing he o ma ion o he ne wo k. In he las pa
o he cu e, G
0
con inued o inc ease sligh ly indica ing he aging p ocess o he gel, while
G
00
emained almos cons an . This beha io showed again he dominan elas ici y o he
sys em and indica ed he o ma ion o a pe manen h ee-dimensional ne wo k.
Fo cla i y, as all composi es p esen ed he same ea u es, only he e olu ion o G
0
will be shown o samples o inc easing PANI con en and a selec ed TPO concen a ion.
Speci ically, Figu e 1B epo s he con e sion cu es as a unc ion o i adia ion ime o
composi es o inc easing PANI loading and 7 w % TPO. I is e iden ha by inc easing
he PANI con en , he equi ed i adia ion ime o each he maximum s o age modulus
inc eases; hence, he e is an impo an dec ease in he a e o pho opolyme iza ion. The
same beha io was obse ed o he emaining amoun s o pho oini ia o es ed (4%, 6%
and 10%) (g aphs no shown). The pho opolyme iza ion pa ame e s we e u he modi ied
by a ying he amoun o pho oini ia o o a cons an PANI w %. The shapes o he cu es
ob ained upon inc easing he TPO con en we e simila o hose o depic ed in Figu e 1A,B
(g aphs no shown).
Hence, o be e compa e he e ec o he addi ion o bo h PANI and he pho oini ia o ,
he gel poin s we e de e mined in he icini y o he G
0
and G
00
c osso e [
29
,
35
–
39
].
The esul s a e plo ed in Figu e 1C. Fi s o all, in acco dance wi h Figu e 1B, he a e o
polyme iza ion clea ly dec eased a he same a e he gel poin ime linea ly inc eased, upon
augmen ing PANI con en (R
2
= 0.92–0.99). Speci ically, he gel poin ime inc eased 2- old,
2.6- old, 2.8- old and 2.8- old when he amoun o PANI ose om 2% o 5% o amoun s o
TPO o 4, 6, 7 and 10 w %, espec i ely. This is a e y well-known phenomenon, mainly
due o he s ong abso p ion o ligh by he PANI ille a ound 405 nm as desc ibed in he
abso p ion spec um o Figu e S3. This is he c i ical wa eleng h on which he UV lamps
used o pho opolyme iza ion ha e hei highes adia ion powe . As a esul , he le el o
ligh a ailable o he pho oini ia o diminishes [31] and hinde s he p in ing p ocess.
Polyme s 2021,13, 2068 9 o 20
Polyme s 2021, 13, 2068 9 o 21
Figu e 1. (A) Elas ic modulus (G’), loss modulus (G”) and an δ e sus i adia ion ime o he composi es wi h 4 w %.
TPO and 5 w % PANI (T4P5). (B) Elas ic modulus (G’) e sus i adia ion ime o composi es wi h 7 w % TPO and PANI
con en s om 2 w % up o 5 w % (T7P2, T7P35 and T7P5). (C) Gel poin ime (s) e sus PANI w % upon inc easing TPO
concen a ion. (D) Wo king cu es o composi es wi h 7 w % TPO and PANI con en s om 2 w % up o 5 w % exposed
o 405 nm ligh (3 mW cm−2).
Fo cla i y, as all composi es p esen ed he same ea u es, only he e olu ion o G’
will be shown o samples o inc easing PANI con en and a selec ed TPO concen a ion.
Speci ically, Figu e 1B epo s he con e sion cu es as a unc ion o i adia ion ime o
composi es o inc easing PANI loading and 7 w % TPO. I is e iden ha by inc easing
he PANI con en , he equi ed i adia ion ime o each he maximum s o age modulus
inc eases; hence, he e is an impo an dec ease in he a e o pho opolyme iza ion. The
same beha io was obse ed o he emaining amoun s o pho oini ia o es ed (4%, 6%
and 10%) (g aphs no shown). The pho opolyme iza ion pa ame e s we e u he modi-
ied by a ying he amoun o pho oini ia o o a cons an PANI w %. The shapes o he
cu es ob ained upon inc easing he TPO con en we e simila o hose o depic ed in Fig-
u es 1A,B (g aphs no shown).
Hence, o be e compa e he e ec o he addi ion o bo h PANI and he pho oini i-
a o , he gel poin s we e de e mined in he icini y o he G’ and G’’ c osso e [29,35–39].
The esul s a e plo ed in Figu e 1C. Fi s o all, in acco dance wi h Figu e 1B, he a e o
polyme iza ion clea ly dec eased a he same a e he gel poin ime linea ly inc eased,
upon augmen ing PANI con en (R
2
= 0.92–0.99). Speci ically, he gel poin ime inc eased
2- old, 2.6- old, 2.8- old and 2.8- old when he amoun o PANI ose om 2% o 5% o
Figu e 1.
(
A
) Elas ic modulus (G
0
), loss modulus (G
00
) and an
δ
e sus i adia ion ime o he composi es wi h 4 w %.
TPO and 5 w % PANI (T4P5). (
B
) Elas ic modulus (G
0
) e sus i adia ion ime o composi es wi h 7 w % TPO and PANI
con en s om 2 w % up o 5 w % (T7P2, T7P35 and T7P5). (
C
) Gel poin ime (s) e sus PANI w % upon inc easing TPO
concen a ion. (
D
) Wo king cu es o composi es wi h 7 w % TPO and PANI con en s om 2 w % up o 5 w % exposed o
405 nm ligh (3 mW cm−2).
Following an opposi e end, he pho oini ia o concen a ion has also a g ea in luence
on he ime needed o he polyme iza ion p ocess. A small concen a ion o TPO means
less eac i e species in he solu ion, esponsible o slowe ini ia ion and p opaga ion
a es [
40
], so he ime o achie ing he gel poin is highe , and ice e sa. Speci ically,
he e ec o inc easing he TPO con en om 4 up o 10 w % educed he gel poin ime
0.47- old, 0.54- old and 0.67- old o PANI loadings o 2, 3.5 and 5 w %, espec i ely.
Thus, by inc easing he pho oini ia o con en , i is possible o o e come he compe i i e
abso p ion e ec o PANI and an inc ease in bo h ac ylic double bond con e sion and
he a e o pho ocu ing can be achie ed [
7
]. The e ec was mo e e iden o he samples
wi h a high amoun o PANI. Mo eo e , as can be obse ed in Figu e 1C, he bigges
educ ion in he gel poin ime was ound a e changing he TPO concen a ion om 6 o
7 w % o a gi en PANI con en , whe eas a u he inc ease in he pho oini ia o con en
did no p o ide a clea bene i in e ms o cu ing ime ( he gel poin imes o T7P5 and
T10P5 we e simila , wi hin expe imen al e o ). As s a ed by p e ious au ho s, when a
c i ical concen a ion o pho oini ia o is exceeded, compe i i e chain p opaga ion and/o
gel e ec s, associa ed wi h he highe concen a ion o ee adicals, delay he eac ion
p opaga ion and he gel poin [
40
]. Simul aneously, he e ec o c osslinking may be
Polyme s 2021,13, 2068 16 o 20
Table 4.
The a e age molecula weigh o chain segmen s be ween he c oss-links (M
c
), c oss-link
densi y (
υc
) and ansi ion empe a u e (T
g
) calcula ed om DMA da a o samples ob ained by
3D p in e .
Sample
Fo mula ion
υc(·10−3)
(mol.cm−3)
Mc
(g·mol)
Tg
(◦C)
Re e ence 1.58 ±0.12 757 ±59 27.1 ±0.5
T4P2 1.89 ±0.21 636 ±72 25.5 ±0.6
T4P35 2.00 ±0.07 589 ±19 24.4 ±1.3
T6P2 1.40 ±0.39 895 ±248 25.5 ±0.8
T6P35 1.96 ±0.18 602 ±55 25.4 ±0.1
T7P2 1.75 ±0.01 687 ±2 26.1 ±0.1
T7P35 2.04 ±0.09 588 ±26 25.7 ±0.6
T7P5 2.21 ±0.01 543 ±4 24.7 ±0.7
T10P2 1.34 ±0.17 910 ±116 25.0 ±0.2
T10P35 1.72 ±0.22 705 ±92 25.9 ±0.2
T10P5 2.11 ±0.10 562 ±26 25.2 ±0.2
As shown in Table 4, he T
g
o he pu e ac ylic esin is 2
◦
C highe han he co e-
sponding alues o he composi es; besides, no a ia ion is obse ed in he T
g
alues o
he composi es (a ound 25
◦
C) as unc ion o PANI o TPO con en , wi hin expe imen al
e o . This beha io is no su p ising due o he ac ha all he o mula ions ha e 15%
by weigh o HDODA c osslinke . The small inc ease in he T
g
o he pu e ac ylic esin
may be ela ed o he highe deg ee o double bond con e sion in he absence o PANI.
The same end is pe cei ed when analyzing he T
g
da a ob ained by DSC, despi e he
g ea e expe imen al e o and he ac ha he a e age T
g
calcula ed by his echnique
(a ound 13
◦
C) is lowe han ha ob ained by DMA, p o ing he ubbe y na u e o he
ilms (Supplemen a y Ma e ials, Table S1).
F om ano he poin o iew, he c oss-link densi y (
υc
) co ela es wi h he s o age
modulus in he ubbe y s a e in homogeneous ne wo ks [
35
]. In composi e samples o
complex sys ems, he s i ness is he esul o a complex in e play be ween physical and
chemical c oss-links and he in insic igidly o he ille [
47
]. Speci ically, he
υc
alues
compiled in Table 4 e lec bo h he co alen bonds be ween ac ylic chains and he H-bond
in e ac ions be ween he ac ylic ma ix and PANI ille . As seen in Table 4, he c oss-link
densi y (
υc
) sligh ly inc eased, whe eas he leng h be ween he c oss-links (M
c
) dec eased,
upon adding PANI o he o mula ion. Hence, despi e he same c osslinke con en and
mino di e ences in DBC%, his enhancemen is expec ed owing o he igidi y o PANI
clus e s dispe sed among he c oss-linked ac ylic ma ix [
48
] and he addi ional H-bond
in e ac ion, desc ibed in he FTIR sec ion, which inc ease he in e acial adhesion be ween
PANI and he ac ylic ne wo k.
Conce ning he ole o he pho oini ia o ,
υc
and M
c
a e app oxima ely cons an , wi hin
expe imen al e o , o a gi en PANI loading. Fu he , he highe DBC% and he absence
o he igid ille explain he in e media e alues o he pu e ac ylic esin. As a esul , he
di e ences a e small, and all he composi e ilms and he pu e ac ylic esin ha e simila
dynamic mechanical beha io .
To assess he p ac ical applica ion o p in ed ilms, mechanical ensile es s we e
ca ied ou . F om he s ess–s ain cu es depic ed in Figu e S6, he modulus, s ess a
b eak and elonga ion a b eak o p in ed composi es we e calcula ed and p esen ed in
Table S1 (Supplemen a y Ma e ials) in compa ison wi h p is ine ac ylic esin. Rega ding
he la e , i has simila elonga ion a b eak bu supe io modulus and ensile s eng h
han analogous EGPEA-HDODA copolyme s p epa ed by cas ing by Bo ello e al. [
49
].
The same au ho s had obse ed di e ences in ensile modules be ween p in ed and cas

Polyme s 2021,13, 2068 17 o 20
specimens o he same chemical composi ion, showing he in luence o manu ac u ing
condi ions in mechanical pe o mance.
In ela ion wi h PANI composi es, no signi ican ends a e obse ed upon a ying he
PANI loading o he ini ia o con en . The andom a ia ions a e asc ibed o expe imen al
e o , excep o he dec ease in he elonga ion a b eak o T7P35 and T7P5. Fi s o all, he
sub le di e ences obse ed in he s o age modulus by DMA as a unc ion o PANI loading
canno be de ec ed in ensile es s. The igidi y o PANI chains could be coun e poised by
small a ia ions in DBC% o mic os uc u al de ec s. Mo eo e , he lowe elonga ion a
b eak alues o TP35 and T7P5 can be asc ibed o he obse ed c acks and po es, mos ly
loca ed a he in e ace be ween laye s, due o uncu ed esin be ween laye s as o en
obse ed in a polyme iza ion, abo e all in he e ogeneous composi es [
45
]. Likewise, no
signi ican di e ences in bo h he ensile s eng h and Young’s modulus we e ound by Joo
and Cho o polyu e hane-PANI p in ed composi es wi h PANI con en s up o 6 w %. The
au ho s sugges ed ha he o ma ion o PANI clus e s e a ds he ein o cing e ec s on he
ul ima e s eng h o he PU/PANI composi es [
16
]. On he con a y, g aphene shee s o
ca bon nano ubes p o ide be e mechanical s eng h and lexibili y as ille s o UV-cu able
p in ed esins [7,16,50].
4. Conclusions
A sys ema ic heological and Jacobs wo king cu e cha ac e iza ion allowed de ining
he UV-3D p in abili y window o a se ies o ac ylic conduc i e esins o mula ed using
inc easing loadings o PANI as conduc i e ille and TPO as pho oini ia o .
The pho o heology p o ed o be a aluable echnique o measu ing he e olu ion o
gel imes as a unc ion o PANI and TPO. Due o i s high UV abso p ion, he augmen in
PANI con en s inc eased gel imes and E
c
bu lowe ed C
d
. These changes we e, o some
ex en , coun e ac ed by he pho oini ia o . The op imal amoun o TPO ha maximized
cu e dep h and minimized c i ical ene gy was be ween 6 and 7 w %, ega dless o PANI
loading. Mos o he o mula ions could be p in ed wi h p e ious adjus men o he p in e
se ings conside ing C
d
, excep hose wi h he highes gel imes. The p in ing es con i med
he bes o mula ion selec ed acco ding o i s Ecand Cd alues, namely T7P2.
The mic os uc u e o composi es wi h high PANI con en s and/o low TPO amoun s
was he e ogeneous, and he SEM images depic ed po es and c acks, mos ly a he laye
in e ace, possibly caused by incomple e cu ing. These po ous pa e ns can nega i ely a ec
in e laye adhesion, in line wi h he g ea e di icul ies encoun e ed du ing he p in ing
p ocess and p edic ed by Jacobs wo king cu e pa ame e s. In addi ion, ATR-FTIR spec a
showed a high deg ee o cu ing in all he p in ed composi es, al hough sligh ly lowe han
nea ac ylic esin.
The elemen al analysis ou comes e ealed ha he maximum amoun o nano ille
embedded wi hin he esin was app oxima ely 3 w %, which led o an inc ease in elec ical
conduc i i y o h ee o de s o magni ude ela i e o pu e esin (up o σ≈10−5S/cm).
The emaining PANI, unbounded o he polyme ma ix, was ca ied away in he
washing s ep. An inc ease in iscosi y, he endency o PANI o agglome a e and he
slowing down o he polyme iza ion a e upon inc easing ille loading explained his
ac . PANI loadings abo e 3.5 w % hinde ed p in abili y and p omo ed mic os uc u e
he e ogenei y, wi hou imp o ing elec ical pe o mance.
The mechanical and dynamo-mechanical p ope ies o he p in ed composi es mainly
e lec ed he esponse o he c osslinked ac ylic ma ix wi h ha dly any di e ence ega dless
he amoun o PANI o TPO. Mino di e ences in duc ili y ha e been asc ibed o he
samples’ he e ogenei y due o he o ma ion o PANI clus e s and i s in luence on he
po osi y pa e n. As a inal poin , he small dec ease in he T
g
compa ed o he ac ylic esin
was asc ibed o a lowe deg ee o con e sion.
In summa y, he de eloped s a egy will p o ide a p ac ical app oach o AM o
cos -e ec i e, lexible ac ylic nanocomposi es wi h mul i- unc ional p ope ies. Speci i-
Polyme s 2021,13, 2068 18 o 20
cally, he conduc i e composi es de eloped in he cu en esea ch p o ed good o e all
pe o mances, opening new possibili ies o applica ion in DLP p in ing.
Supplemen a y Ma e ials:
The ollowing a e a ailable online a h ps://www.mdpi.com/a icle/10
.3390/polym13132068/s1, Figu e S1. Viscosi y alues as a unc ion o shea a e and PANI con en
a oom empe a u e o a cons an TPO ini ia o con en o 4 w %. Figu e S2. Viscosi y alues as a
unc ion o shea a e and TPO con en a oom empe a u e o a cons an PANI con en o 5 w %.
Figu e S3. UV- isible abso p ion spec um o PANI-HCl in EGPEA: 15 w % HDODA a 60 ppm.
Figu e S4. SEM image showing he nano od mo phology o PANI-HCl wi h magni ude ampli ica ion
3000
×
. Figu e S5. SEM images o he su ace o p in ed ilms (A) Pu e ac ylic esin, (B) T7P2, (C)
T7P35 and (D) T7P5 wi h magni ude ampli ica ion 1500
×
. Table S1. In luence o sample o mula ion
on T
g
, de e mined by DSC, and mechanical p ope ies o p in ed samples measu ed by ensile es
(E= Young’s modulus,
σ
= s ess a b eak and
ε
= elonga ion a b eak). Figu e S6. S ess-s ain cu e
o Pani-ac ylic composi es.
Au ho Con ibu ions:
Concep ualiza ion, M.-J.A. and M.S.D.-G.; me hodology, A.A.-P., M.S.D.-G.,
G.G.-E. and A.L.-L.; alida ion, M.-J.A., M.S.D.-G., and A.A.-P.; o mal analysis, G.A.-F.; in es iga ion,
G.A.-F.; A.A.-P. and N.A.; da a cu a ion, G.A.-F. and A.A.-P.; w i ing—o iginal d a p epa a ion,
A.L.-L., G.A.-F., N.A. and A.A.-P.; w i ing— e iew and edi ing, A.L.-L., M.S.D.-G. and G.G.-E.;
supe ision, M.-J.A. and M.S.D.-G.; unding acquisi ion, M.-J.A. All au ho s ha e ead and ag eed o
he published e sion o he manusc ip .
Funding:
Go e i A ias-Fe ei o hanks he inancial unding ecei ed om he Xun a de Galicia and
he Eu opean Union (P og am o suppo he p edoc o al s age a SUG 2019 (ED481A-2019/001)).
The au ho s would like o hank he inancial suppo om Xun a de Galicia-FEDER (P og am o
Consolida ion and s uc u ing compe i i e esea ch uni s (ED431C 2019/17)).
Ins i u ional Re iew Boa d S a emen : No applicable.
In o med Consen S a emen : No applicable.
Da a A ailabili y S a emen :
The da a p esen ed in his s udy a e a ailable on eques om he
co esponding au ho .
Acknowledgmen s:
The au ho s g a e ully acknowledge M. Vic o ia González Rod íguez (G upo
de Políme os, Cen o de In es igacións Tecnolóxicas, Uni e sidade da Co uña) o he help and
assis ance in he syn hesis o PANI and p epa a ion o he composi es.
Con lic s o In e es : The au ho s decla e no con lic o in e es .
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