Synthesis and optoelectronic properties of novel organosoluble polynorbornenes containing asymmetric pyrenyl and electroactive substituents via ring-opening metathesis polymerization

Article abstract of DOI:10.1002/pola.25024

Novel polynorbornenes, poly(NBPYTPA), and poly(HNBPYTPA), containing chromophoric and electroactive groups were synthesized by ring-opening metathesis polymerization using Grubbs' catalysts and followed hydrogenation, respectively. The glass transition temperatures (T_g) of poly(NBPYTPA) and hydrogenated poly(HNBPYTPA) were 195 and 165 °C, respectively. The 10% weight-loss temperatures of hydrogenated poly(HNBPYTPA) and poly(NBPYTPA) were up to 465 and 420 °C, respectively. The photoluminescence emission spectra of poly(HNBPYTPA) showed strong solvatochromic property, revealing that poly(HNBPYTPA) underwent remarkable bathochromic shifts with an increase in solvent polarity. The cyclic voltammogram of poly(HNBPYTPA) film cast onto an indium tin oxide (ITO)-coated glass substrate exhibited two reversible oxidation redox couples at 0.8 and 1.2 V versus Ag/Ag⁺ in acetonitrile solution. The electrochromic characteristics of poly(HNBPYTPA) showed reversibility, with color changes from yellow to blue and then to red upon the application of potentials from 0 to 1.3 V.

Full text of DOI:10.1002/pola.25024

ARTICLE
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Synthesis and Optoelectronic Properties of Novel Organosoluble
Polynorbornenes Containing Asymmetric Pyrenyl and Electroactive
Substituents via Ring-Opening Metathesis Polymerization
1
2
1
3
4
1
Wei-Ren Lian, Crystal Ho, Ying-Chi Huang, Yi-An Liao, Kun-Li Wang, Der-Jang Liaw,
5
5
Kueir-Rarn Lee, Juin-Yih Lai
1
Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 10607,
Republic of China
2
Department of Chemical Engineering, University of Notre Dame, Notre Dame, Indiana 46556
3
School of Medicine, Faculty of Medicine, National Yang-Ming University, Taipei, Taiwan
4
Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei 10608, Taiwan
5
Department of Chemical Engineering, R&D Center for Membrane Technology, Chung Yuan University, Chung-Li 32023, Taiwan
Correspondence to: D.-J. Liaw (E-mail: liawdj@mail.ntust.edu.tw) or (E-mail: liawdj@gmail.com) or (E-mail: liawdj@ntu.edu.tw) or
(
E-mail: liawdj@yahoo.com.tw)
Received 20 July 2011; accepted 3 September 2011; published online 17 October 2011
DOI: 10.1002/pola.25024
ABSTRACT: Novel polynorbornenes, poly(NBPYTPA), and poly
HNBPYTPA), containing chromophoric and electroactive groups
with an increase in solvent polarity. The cyclic voltammogram of
(
poly(HNBPYTPA) film cast onto an indium tin oxide (ITO)-coated
glass substrate exhibited two reversible oxidation redox couples
were synthesized by ring-opening metathesis polymerization
using Grubbs’ catalysts and followed hydrogenation, respec-
þ
at 0.8 and 1.2 V versus Ag/Ag in acetonitrile solution. The elec-
tively. The glass transition temperatures (T
g
) of poly(NBPYTPA)
trochromic characteristics of poly(HNBPYTPA) showed reversibil-
ity, with color changes from yellow to blue and then to red upon
the application of potentials from 0 to 1.3 V. VC 2011 Wiley Periodi-
ꢀ
and hydrogenated poly(HNBPYTPA) were 195 and 165 C, respec-
tively. The 10% weight-loss temperatures of hydrogenated poly
ꢀ
(
HNBPYTPA) and poly(NBPYTPA) were up to 465 and 420 C,
cals, Inc. J Polym Sci Part A: Polym Chem 49: 5350–5357, 2011
respectively. The photoluminescence emission spectra of poly
HNBPYTPA) showed strong solvatochromic property, revealing
(
KEYWORDS: electrochromism; functionalization of polymers;
that poly(HNBPYTPA) underwent remarkable bathochromic shifts
polynorbornene; pyrene; redox polymers; ROMP
INTRODUCTION Polymers derived from various benzene rings
substituted and N-substituted aniline derivatives were investi-
gated extensively. Polymers of N-substituted aniline derivatives,
such as N-methyl, N-ethyl, N-phenyl, N-naphthyl, and N-benzyl
were important materials in electrochromic (EC) display devi-
attracted much interest because they are highly thermally sta-
ble and are suitable for low cost fabrication processes such as
spin-coating and inkjet printing for large areas and flexible dis-
plays. Therefore, we modified the polymer of N-dipyrenyl ani-
line derivative structure with TPA, which is expected to have
interesting EC behaviors.
2
3
1
–5
ces. Recently, we have reported that the polymer of N-dipyr-
enyl aniline derivatives with high glass transition temperature
However, near-infrared (NIR)-absorbing EC materials are
receiving great attention due to their potential applications
(
T ) show a single color change and remarkable solvatochromic
g
6
properties. EC materials comprise multiple redox-active spe-
cies that exhibit multiple color changes upon the injection or
withdrawal of electrons. Triphenylamine (TPA) derivatives
have showed excellent thermal, electrochemical stability, elec-
tron-donating ability, and optoelectronic properties. They have
been used as advanced materials for polymer memories,
electroluminescence, chemosensor application,
tro-optical devices. Because of a noticeable change of colora-
tion, TPA derivatives are regarded as good EC materials.
24
25
in optical communications,
biomedicine,
camouflage
26
27
materials in warfare, electro-optic switching in devices,
and thermal control and thermal emission detectors for
28
spacecraft. UV–vis-absorbing EC materials have been well
7
29
studied but few NIR EC materials are known to date.
8
–14
1
5
16,17
and elec-
In this report, the norbornene group was selected as the
monomer functionality of macromonomer because its high
reactivity in ring-opening metathesis polymerization allows
1
8
1
9–22
In
3
0,31
for high conversions of macromonomers.
We prepared a
recent years, side-chain polymers with TPA moieties have
Additional Supporting Information may be found in the online version of this article.
2011 Wiley Periodicals, Inc.
V
C
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polynorbornene derivative containing pyrenyl and TPA
groups via ring-opening metathesis polymerization (ROMP)
and followed hydrogenation to afford a saturated polynor-
bornene. To the best of our knowledge, there has been no
report about electrochromism of polynorbornene derivatives
with asymmetric pyrenyl and TPA chromophores. The basic
properties of asymmetric polynorbornene derivatives such as
solubility, thermal, optical, and electrochemical, as well as EC
properties are discussed in this investigation.
ments were carried out with ꢃ3–5 mg samples under nitro-
3
ꢁ1
gen flowing conditions (20 cm min ). UV–vis spectra of
the polymer films were recorded on a JASCO V-550 spectro-
photometer at room temperature in air.
Synthesis of NBMPY
The norbornene derivative NBMA (0.7 g; 6 mmol), sodium
ꢁ
1
tert-butoxide (2.6 g; 27 mmol), Pd(OAc) (0.08 g; 3.6 ꢂ 10
2
ꢁ
1
mmol), tri-tert-butylphosphine (0.14 g; 7.2 ꢂ 10 mmol),
1
-bromopyrene (1.9 g; 6 mmol), and dry toluene (40 mL)
were charged in a three-necked flask and kept stirring under
nitrogen. The mixture was heated to reflux for 3 h. After
completion of the reaction, the solvent was removed under
vacuum and the residue was extracted with dichloromethane
EXPERIMENTAL
Materials
Grubb’s third generation catalyst was obtained from Sigma-
Aldrich. Synthesis of 5-(amino methyl) bicyclo[2.2.1] hept-
4
and water. The organic layer was dried over MgSO and fil-
ꢀ
2
-ene (NBMA) (bp ¼ 60–61 C/11 mmHg) was obtained via
tered. After removing the solvent, the residue was purified
by chromatography (dichloromethane: n-hexane ¼ 1:3). Then
the product was recrystallized from n-hexane, and a light
the Diels–Alder reaction of freshly cracked cyclopentadiene
3
2,33
and allyl amine.
Dicyclopentadiene and allyl amine were
purchased from Merck. Palladium acetate, sodium tert-butox-
ide, tri-tert-butylphosphine, and 1,4-dibromobenzene were
purchased from Aldrich and used without further purifica-
tion. Pyrene and n-bromosuccinimide were purchased from
Acros and used as received. Hydroquinone and 6-di-tert-
butyl-4-methyl-phenol were purchased from Janssen and
used without further purification. 4-Bromo-TPA was pur-
chased from TCI and used as received. Solvents, such as
xylene, toluene, and benzene were purified by normal proce-
dures and handled in a moisture-free atmosphere. N,N-dime-
thylformamide was dried and distilled over calcium hydride
under an inert atmosphere. The polymerization solvent, tet-
rahydrofuran, was dried over sodium metal and benzophe-
none, and then distilled before use.
ꢀ
green solid was obtained in a 62% yield; mp: 106 C by DSC
ꢀ
(
10 C/min).
ꢁ
1
IR (KBr pellet, cm ): 3422 (NAH, stretching), 1047 (CAN,
aromatic amine), 1601 (C ¼¼ C, cyclic alkene), 3045 (CAH, aro-
1
matic stretching). H NMR (CDCl
(
3
): d (ppm) ¼ 0.79–0.82
H ; 1H), 1.34–1.38 (H ; 1H), 1.36–1.38 (H ; 1H), 1.47–
n3 X3 n7
1
1
.51 (Hx3 and H ; 3H), 1.57–1.59 (H ; 1H), 1.87–1.92 (H ;
x7 n7 x2
H), 2.02–2.07 (H ; 1H), 2.54–2.60 (H ; 1H), 2.89 (H ;
n3
n2
x1
1H), 2.94 (Hx4 and Hn4; 2H), 3.11–3.22 (Hn8; 2H), 3.36–3.49
(Hx8; 2H), 4.70–4.90 (H ; 1H), 6.10 (Hn6; 1H), 6.20 (Hx5 and
x6; 2H), 6.29–6.30 (Hn5; 1H), 7.31–8.07 (H10; 9H). C NMR
9
1
3
H
(
3
4
CDCl ): d (ppm) ¼ 30.49 (C ), 31.32 (C ), 38.77 (C ),
3
n3
x3
n2
9.01 (C ), 41.71 (C ), 42.41 (C ), 44.42 (C ), 44.61 (C ),
x2 x4 n4 n1 x1
5.30 (C ), 48.63 (C ), 49.62 (C ), 49.96 (C ), 132.40
x7
n8
n7
x8
Measurements
The glass transition temperatures (T ) and melting points
(
C ), 136.35 (C ), 136.83 (C ), 137.8 (C ), 108.92–142.61
n6 x6 x5 n5
g
(C ) ELEM. ANAL. Calcd. for C H N:C, 89.13%; H, 6.54%; N,
9 24 21
4.33%. Found: C, 88.86%; H, 6.61%. N, 4.53%.
(
Tm) were measured on a Dupont 9000 differential scanning
calorimeter (TA Instruments TA 910) at a heating rate of
ꢀ
ꢁ1
1
0 C min , under a steady flow of nitrogen. Cyclic Voltam-
Synthesis of NBPYTPA
metry (CV) was performed on a CHI model 619A with
indium-tin oxide (ITO) used as a working electrode and a
platinum wire used as an auxillary electrode at a scanning
rate of 50 mV s against a Ag/Ag reference electrode in a
solution of 0.1 M tetrabutylammonium perchlorate (TBAP)/
4-Bromotriphenylamine (1.0 g; 3.1 mmol), NBMPY (1.0 g;
3.1), palladium acetate (0.02 g; 1.03 mmol), sodium tert-
butoxide (0.88 g; 9.1 mmol), and tri-tert-butylphosphine
(20 lgL; 0.09 mmol) were combined with 10 mL of anhy-
drous toluene in a 200 mL round bottom flask in a nitrogen
ꢁ
1
þ
ꢀ
acetonitrile(CH CN). The spectroelectrochemical cell com-
atmosphere. The reaction mixture was heated to 120 C and
3
posed of a 1 cm cuvette, ITO, and the auxillary and reference
electrodes. Absorption spectra for spectrochemical analysis
were measured with a UV–vis-NIR spectrophotometer. Ele-
mental analysis was performed on a Perkin-Elmer 2400 ana-
lyzer. The H and C NMR spectra were recorded on a
Bruker DRX_500 instrument operating at 500 MHz for pro-
stirred for 2 h. Then, the solution was filtered and the sol-
vent was removed under reduced pressure. The product was
purified by chromatography (dichloromethane: n-hexane ¼ 1:4)
and recrystallized with cosolvent [ethanol/acetone (v/v) ¼
1:20] to afford a yellow crystal in a 74% yield (1.3 g; 2.3
1
13
ꢁ
1
mmol). IR (KBr pellet, cm ): 1049 (CAN; aromatic amine),
1600 (C ¼¼ C, cyclic alkene), 3044 (CAH, aromatic stretching).
tons and 125 MHz for carbons. The weight-average (M ) and
w
1
number average (M ) molecular weights were determined
H NMR (CDCl , d, ppm): 0.62–0.065 (H ; 2H), 1.19–1.21
n
3
n5
using gel permeation chromatography (GPC). Five Waters
(H ; 2H), 1.26–1.28 (H ; 2H), 1.35–1.36 (H and H ; 2H),
n4 x5 n4 x4
1.87–1.92 (H ; 2H), 1.94–1.96 (H ; 1H), 2.65–2.69 (H ;
n5 x7 n7
1H), 2.72–2.74 (H ; 1H), 2.79–2.81 (H and H ; 2H), 2.87–
n3 x5 x3
3
4
(
Ultrastyragel) columns 300 ꢂ 7.7 mm (guard, 500, 10 , 10 ,
5
and 10 Å in a series) were used for GPC analysis with THF
ꢁ
1
(1 mL min ) as an eluent. The eluents were monitored
2.88 (Hn5; 1H), 3.71–3.81 (Hn8; 2H), 4.04–4.07 (Hx8; 2H),
5.54–5.56 (H ; 1H), 6.01–6.02 (H and H ; 2H), 6.04–6.08
with a refractive index detector (RI 2000) with polystrene
used as a standard. Thermogravimetric data was measured
with a Perkin-Elmer TG/DTA (Diamond TG/DTA). Experi-
n2
x1
x2
(H ; 1H), 6.61–6.65 (Hn13; 2H) 6.95–7.01 (Hn12; 4H), 7.12–
n1
7.14 (H ; 2H), 7.23–7.26 (H
n9
and Hn11; 6H), 8.12–8.51
n10
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SCHEME 1 Synthetic route of hydrogenated novel polynorbornenes.
(
pyrene). ELEM. ANAL. Calcd. for C H N:C, 89.01%; H, 6.05%;
filled dry box. The monomer NBPYTPA (0.95 g; 1.8 mmol)
was added to 3 mL of THF and then degassed via several
freeze-pump-thaw cycles. After degassing, the catalyst solu-
tion was injected into the monomer solution by a syringe.
2
4 21
N, 4.94%. Found: C, 88.75%; H, 6.26%. N, 4.86%.
General Procedure for ROMP of NBPYTPA via Grubbs’
first-(I), second-(II), and third-generation catalysts (III)
A solution of the catalyst was prepared by dissolving the me-
ꢀ
The polymerization was carried out at 30 C for 1 h. The
reaction was terminated by the addition of 1 mL of ethyl
vinyl ether. Then, poly(NBPYTPA) was obtained by precipitat-
ing in excess methanol and further purified by dissolving in
ꢁ
3
tathesis catalyst Ru (G3), (1.5 mg; 1.8 ꢂ 10
mmol) in
0
.5 mL of anhydrous tetrahydrofuran (THF) in an argon-
5
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1
3
FIGURE 1 H NMR spectrum of NBPYTPA in CDCl .
THF and reprecipitating from methanol. Poly(NBPYTPA) was
dissolved in benzene, filtered, and then frozen drying was
carried out. The yield of poly(NBPYTPA) was 95%. The poly-
be 4:1 from the NMR spectrum shown in Figure 1. As the poly-
merization proceeded, the vinylic proton peaks of NBPYTPA at
1
13
5.54–6.04 ppm were disappeared in the H NMR and C NMR
spectrum of poly (NBPYTPA) shown in Figure 2 and Figure S2.
The vinyl protons peaks appeared as broad signals between
4.6 and 5.6 ppm due to the double bond in the polymer main
chain. Poly(NBPYTPA) was reduced using hydrogenating agent
merizations of the monomer NBPYTPA with catalysts Ru
1
(
G1) and Ru (G2) were carried out in the same manner. H
NMR (CDCl ; d, ppm): 0.8–3.1 (H ), 3.7–4.2 (H ), 4.6–5.6
3
3–7
8
(
H
1
and H
2
), 6.3–7.2 (H9–13), and 7.7–8.4 (pyrene).
1
to afford poly (HNBPYTPA) as shown in Scheme 1. From H
Hydrogenation of Poly(NBPYTPA)
Poly(NBPYTPA) (0.66 g; 1.2 mmol) was dissolved in 8 mL of
dried xylene in a Schlenk tube. To the above solution, 1.64 g
13
NMR and C NMR spectrum of poly(HNBPYTPA) shown in
Figure 3 and Figure S3, the resonance signals of olefinic pro-
tons of poly(NBPYTPA) between d (ppm) 4.6 and 5.6 were dis-
appeared completely. The aromatic resonance signals of
poly(HNBPYTPA) between d (ppm) 6.5 and 8.3, which indi-
cated the remaining protons in pyrene and TPA side groups
(
8.8 mmol) of hydrogenating agent, p-toluenesulfonhydrazide
(
7.3 equiv relative to the repeating unit), and a trace amount
of 2,6-di-tert-butyl-4-methylphenol (inhibitor) were added.
The polymer solution containing the hydrogenating agent was
then degassed three times via freeze-pump-thaw cycles and
ꢀ
sealed. The solution was stirred at 120 C for 12 h until the
evolution of nitrogen stopped. The hydrogenated polymer
poly (HNBPYTPA) was obtained by precipitating in excess
methanol and further purified by dissolving in tetrahydrofu-
ran and reprecipitating in methanol. Poly(HNBPYTPA) was
dissolved in benzene, filtered, and frozen drying was carried
out. The yield of the hydrogenated polymer poly(HNBPYTPA)
1
was 90%. H NMR (CDCl , d, ppm): 0.9–2.9 (H1–7), 3.6–4.3
3
(
H ), 6.5–7.3 (H9–13), and 7.7–8.3 (pyrene).
8
RESULTS AND DISCUSSION
Synthesis and Characterization
The novel norborene monomer (NBPYTPA) containing a py-
rene and a TPA substituent was successfully synthesized. The
1
13
synthesis route is shown in Scheme 1. The H NMR and
C
NMR of NBPYTPA is shown in Figure 1 and Figure S1. The ra-
tio of the NBPYTPA endo- and exo-isomers was calculated to
1
FIGURE 2 H NMR spectrum of poly(NBPYTPA) in CDCl
3
.
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5
ꢁ1
ꢁ1
4
00 [e ¼ 1.12 ꢂ 10 (L mol cm )] nm (curve c). TPA
5 ꢁ1
exhibited strong absorption at 322 [e ¼ 1.12 ꢂ 10 (L mol
ꢁ
1
cm )] nm in THF solution (curve d). It means that the UV–vis
5
ꢁ1
ꢁ1
absorption at 322 [e ¼ 1.80 ꢂ 10 (L mol cm )] nm of
poly (HNBPYTPA) is assignable to a p–p* transition resulting
from the conjugated TPA structure
1
9,21,22
and it is not related
to cyclic norbornene and pyrene structure (curve a). The UV–
vis absorption of poly(HNBPYTPA) in solid state also shows
similar absorbance peaks with a little red-shift at 323 [e ¼
5
ꢁ1
ꢁ1
1
.63 ꢂ 10 (L mol cm )] nm (curve b). The PL spectrum
of poly(HNBPYTPA) in solid state showed the maximum band
1
3
FIGURE 3 H NMR spectrum of poly(HNBPYTPA) in CDCl .
still appeared. The molecular weight of the ring-opened poly-
norbornenes was determined by GPC using the polystyrene as
the standard. The number-average molecular weights (M ) of
n
poly(NBDTPA) obtained by Ru (G1), Ru (G2), and Ru (G3)
5
were 1.02, 2.88, and 3.45 ꢂ 10 , respectively, with yields of
25, 85, and 88 %. The ROMP of NBPYTPA using the Ru (G1)
was attempted but suffers from the drawback of lower activ-
3
4
ity. Ru (G2) exhibited good activity to the polymerization of
NBPYTPA, but gave polymer with uncontrolled molecular
weight and broad PDI (1.82), due to slower initiation and
3
5
faster propagation rates. It has been widely known that Ru
G3) exhibited better control due to faster initiation and inhib-
(
3
6
its side reaction like back-biting. The results also showed
that Ru (G3) promoted higher activity than Ru (G1) and Ru
3
7
(
G2) initiators in this study.
Basic Properties
Solubility
Poly(NBPYTPA) is not indefinitely stable in air atmosphere.
When being stored under ambient condition for 10 weeks,
poly(NBPYTPA) became insoluble while the polymers stored
under nitrogen were still soluble. This phenomenon might
suggest the unsaturated polymer carried out some kind of
chemical reaction (such as crosslinking, oxidation, etc) due
3
8
to the unsaturated C ¼¼ C double bonds in poly(NBPYTPA).
Poly(NBPYTPA) and poly(HNBPYTPA) are both highly soluble
in common organic solvents such as toluene, xylene, tetrahy-
drofuran (THF), benzene, chlorobenzene, and 1,2-dichloro-
benzene, and at room temperature. The excellent solubility
makes the hydrogenated ring-opened polynorbornene poly
(
HNBPYTPA), a potential candidate for practical applications
ꢁ
5
of spin-coating, dip-coating, or inject-printing processes to
obtain the thin film for optoelectronic devices.
FIGURE 4 (A) UV–vis spectra of (a) poly(HNBPYTPA) (1 ꢂ 10
ꢁ
1
ꢁ
5
mol L ; THF), (b) poly(HNBPYTPA) film, (c) NBMPY (1 ꢂ 10
ꢁ1
ꢁ5
ꢁ1
mol L ; THF) (d) TPA (1 ꢂ 10 mol L ; THF) (e) NBMA (1 ꢂ
ꢁ
5
ꢁ1
L ;
Optical Properties
1
0
mol
THF) and emission spectra of (f) poly
(HNBPYTPA) (1 ꢂ 10ꢁ mol L ; kexc ¼ 320 nm; film). (B) Nor-
5
ꢁ1
In Figure 4(A), there is no UV–vis absorption bands for mono-
mer NBMA (curve e) and the absorption spectrum of mono-
mer NBMPY containing pyrene substituent showed two char-
acteristic peaks at 285 [e ¼ 2.17 ꢂ 10 (L mol cm )] and
malized PL spectra of dilute solutions of poly(HNBPYTPA) (1 ꢂ
ꢁ
3
ꢁ1
mol L ) in various solvents. Photographs were taken
10
5
ꢁ1
ꢁ1
under illumination of 365-nm UV light.
5
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at 560 nm. Poly(HNBPYTPA) also exhibits solvatochromic
characteristics. Figure 4(B) showed the normalized PL spectra
of poly(HNBPYTPA) in various solvents, together with fluores-
cence images of the solutions. The PL emission spectra of poly
(
HNBPYTPA) showed strong solvent-polarity dependence, and
underwent remarkable bathochromic shifts with an increase
of the solvent polarity. The solvatochromism could be attrib-
uted to the fast intramolecular charge-transfer process result-
3
9
ing in a large change of dipole moment in the excited state.
The onset wavelength of poly(HNBPYTPA) in solid state from
the UV–vis transmittance spectrum is about 370 nm, by which
the energy gap of poly(HNBPYTPA) is estimated to be 3.3 eV.
Thermal Properties
The polynorbornenes obtained by the three different Grubbs’
ruthenium catalysts have glass transition temperatures (T )
g
ꢀ
between 189 and 195 C and no remarkable difference was
observed. In many applications, the instability of the unsatu-
rated polymers to chemical and thermal degradation is a
4
0,41
concern.
The thermogravitivity spectra of poly(NBPYTPA)
FIGURE 6 Cyclic voltammograms of poly(HNBPYTPA) in films
and hydrogenated poly(HNBPYTPA) in nitrogen shows in
Figure 5. The unsaturated poly(NBPYTPA) and saturated
cast on indium tin oxide (ITO)-coated glass substrates in
3
CH CN containing 0.1 M TBAP. The scanning rate is 0.1 V/s.
poly(HNBPYTPA) showed 10% weight-loss temperatures
ꢀ
(
Td10%) at 420 and 465 C under nitrogen, respectively. Under
air, unsaturated poly(NBPYTPA) and saturated poly
(
HNBPYTPA) showed 10% weight-loss temperatures (Td10%)
lyte. Oxidative and reductive cycles of poly(NBPYTPA) and
poly(HNBPYTPA) are shown in Figure 6. Poly(NBPYTPA)
showed two reversible oxidation redox couples with E1/2 val-
ues of 0.68 and 1.15 V. The unsaturated poly(NBPYTPA)
ꢀ
at 390 and 430 C, respectively. The glass transition tempera-
tures (Tg) of poly(NBPYTPA) and hydrogenated poly
(
T caused by the hydrogenation was about 30 C. Obviously,
the rotation around the hydrogenated carbon–carbon single
bond made the mobility of the polymer chain easier.
ꢀ
HNBPYTPA) were 195 and 165 C, respectively. A decrease in
ꢀ
g
exhibited the similar electrochemical behavior with saturated
43
poly(HNBPYTPA).
Poly(NBPYTPA) and poly(HNBPYTPA)
4
2
showed color changes from yellow to blue then to red at
applied potentials ranging over 0.80 and 1.20 V in the oxida-
tive scan, respectively. From the oxidation potential relative
to ferrocene/ferrocenenium, which can correspond to ꢁ4.8 eV
Electrochemical Properties
The electrochemical behaviors of poly(NBPYTPA) and poly
HNBPYTPA) are investigated by CV conducted by films cast
on ITO-coated glass substrates as the working electrode in
dry CH CN solution containing 0.1 M of TBAP as the electro-
(
4
4
for ferrocene below the vacuum level, we can approximately
calculate the HOMO energy level of poly(HNBPYTPA). The
LUMO levels of poly(HNBPYTPA) were calculated to be ꢁ1.5
3
eV according to the equation: LUMO ¼ HOMO þ E . The HOMO
g
energy level is ꢁ4.8 eV derived from energy gap.
EC Characteristics
For the EC investigations, poly(HNBPYTPA) was cast onto
ITO-coated glass slides, and a homemade electrochemical
cell was built from a commercial UV–visible cuvette. The cell
was placed in the optical path of the sample light beam in a
UV–vis-NIR spectrophotometer, which allowed us to acquire
electronic absorption spectra in situ under potential control
in a 0.1 M TBAP/ CH
3
CN solution. The results for the poly
(
HNBPYTPA) film (thickness about 10 lm) are presented in
Figure 7 as a series of UV–vis-NIR absorbance curves corre-
lated to electrode potentials. When the applied potentials
were increased positively from 0 to 0.80 V, the new bands
rose at 680 and 1200 nm due to the first oxidation. When
the potential was increased to 1.20 V, corresponding to the
second oxidation step, the peak at 500 nm increased, and
another peak at 800 nm increased. The film exhibited a color
change from yellow to blue and then to red as shown in
FIGURE 5 TGA curves for poly(NBPYTPA) and hydrogenated
poly(HNBPYTPA) measured under nitrogen. Temperature was
ꢀ
ꢁ1
raised at rate of 10 C min
.
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ARTICLE
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1
FIGURE 7 Absorption spectra of poly(HNBPYTPA) in films cast
K.; Wang, K. L.; Chen, W. T.; Lee, K. R.; Lai, J. Y.; Chan, L. H.; Chen,
C. T. J. Polym. Sci. Part A: Polym. Chem. 2009, 47, 6231–6245.
on ITO-coated glass substrate (thickness ꢃ11 lm; in CH
3
CN
with 0.1 M TBAP as the supporting electrolyte) (A) Eappl: (a)
1
2
6 Wang, K. L.; Liou, W. T.; Liaw, D. J.; Chen, W. T. Dyes Pigm.
008, 78, 93–100.
0
1
.0, (b) 0.50, (c) 0.55, (d) 0.6, (e) 0.7, (f) 0.8, (g) 0.9, (h) 1.0, (i)
.1, (j) 1.2, (k) 1.3, and (l) 1.4 V.
1
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7 Wang, K. L.; Liou, W. T.; Liaw, D. J.; Huang, S. T. Polymer
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Figure 7 due to the oxidations. The observed UV–vis-NIR
absorption changes in the poly(HNBPYTPA) film at various
potentials are fully reversible and are associated with strong
color changes. The poly(NBPYTPA) film showed similar spec-
tral changes.
18 Wang, K. L.; Huang, S. T.; Hsieh, L. G.; Huang, G. S. Poly-
mer 2008, 49, 4087–4093.
19 Wu, H. Y.; Wang, K. L.; Liaw, D. J.; Lee, K. R.; Lai, J. Y. J.
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2
0 Wu, H. Y. U.; Wang, K. L. I.; Jiang, J. C.; Liaw, D. J.; Lee, K.
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CONCLUSIONS
2
1 Chen, W. H.; Wang, K. L.; Liaw, D. J.; Lee, K. R.; Lai, J. Y.
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2 Chen, W. H.; Wang, K. L.; Hung, W. Y.; Jiang, J. C.; Liaw, D.
High thermally stable polymers based on polynorbornene
with asymmetric electroactive moieties were designed and
prepared via ring opening metathesis polymerization and fol-
lowed hydrogenation to obtain saturated polynorbornene
with good solubility and thermal stability. The polynorbor-
nenes shows multiple colors and strong absorbance at NIR
region under applied voltages. The polynorbornenes also
show solvatochromic properties. Thus, these outstanding
characteristics suggest that the prepared organosoluble satu-
rated polynorbornene is a good candidate in the NIR-absorb-
ing EC materials.
2
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