Copolymers of methyl methacrylate with N-trifluorophenyl maleimides: High glass transition temperature and low birefringence polymers

Article abstract of DOI:10.1002/pola.26137

Copolymers of methyl methacrylate (MMA) with 2,3,4- and 2,4,6-trifluorophenyl maleimides (TFPMIs) were synthesized by a free radical initiator, azobisisobutyronitrile, in 1,4-dioxane and also in bulk. The refractive indexes of the copolymers were in the range of 1.49-1.52 at 532 nm. The T_gs were 133-195 °C depending on copolymer compositions. In addition, the copolymers were thermally stable, T_d > 350 °C. The orientational and photoelastic birefringence of the copolymers were also investigated. As both of the orientational and photoelastic birefringences of PMMA are negative, whereas those of poly(TFPMI)s are positive, we could obtain nearly zero orientational and photoelastic birefringence polymers when the ratios of 2,3,4-TFPMI/MMA were 15/85 and 5/95 mol %, respectively. For 2,4,6-TFPMI, zero orientational and photoelastic birefringences could be obtained when the ratios of 2,4,6-TFPMI/MMA were 12/88 and 3/97 mol %, respectively. The T_gs of those copolymers with zero birefringences were in the range of 135-140 °C. Copyright

Full text of DOI:10.1002/pola.26137

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Copolymers of Methyl Methacrylate with N-Trifluorophenyl Maleimides:
High Glass Transition Temperature and Low Birefringence Polymers
Liping Lou,1 Akihiro Tagaya,2,3 Yoko Ide,2 Yasuhiro Koike,2,3 Yoshiyuki Okamoto1,2
1Polymer Research Institute, Polytechnic Institute of New York University, 6 MetroTech Center, Brooklyn, New York 11201
2Keio Photonics Research Institute, Keio University, E-Building, Shin-Kawasaki Town Campus, 7-1 Shin-Kawasaki, Saiwai-Ku,
Kawasaki 212-0032, Japan
3Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-Ku, Yokohama 223-8522, Japan
Correspondence to: Y. Okamoto (E-mail: yokamoto@poly.edu)
Received 23 February 2012; accepted 4 April 2012; published online
DOI: 10.1002/pola.26137
ABSTRACT: Copolymers of methyl methacrylate (MMA) with
2,3,4- and 2,4,6-trifluorophenyl maleimides (TFPMIs) were syn-
thesized by a free radical initiator, azobisisobutyronitrile, in 1,4-
dioxane and also in bulk. The refractive indexes of the copoly-
mers were in the range of 1.49–1.52 at 532 nm. The Tgs were 133–
195 ꢀC depending on copolymer compositions. In addition, the
copolymers were thermally stable, Td > 350 ꢀC. The orientational
and photoelastic birefringence of the copolymers were also
investigated. As both of the orientational and photoelastic bire-
fringences of PMMA are negative, whereas those of poly(TFPMI)s
are positive, we could obtain nearly zero orientational and
photoelastic birefringence polymers when the ratios of 2,3,4-
TFPMI/MMA were 15/85 and 5/95 mol %, respectively. For 2,4,6-
TFPMI, zero orientational and photoelastic birefringences could be
obtained when the ratios of 2,4,6-TFPMI/MMA were 12/88 and 3/97
mol %, respectively. The Tgs of those copolymers with zero birefrin-
ꢀ
C
V
gences were in the range of 135–140 C. 2012 Wiley Periodicals,
Inc. J Polym Sci Part A: Polym Chem 000: 000–000, 2012
KEYWORDS: copolymerization;
fluoropolymers;
methyl
methacrylate; N-trifluorophenyl maleimides; orientational and
photoelastic birefringence; thermal properties
INTRODUCTION Maleimide and its derivatives are well
known to give thermally stable polymers and the copolymers
with various vinyl monomers such as methyl methacrylate
(MMA) and styrene.1–7 N-Pentafluorophenyl maleimide
(PFPMI) was colorless, and it was readily copolymerized
with MMA by a free radical initiator such as azobisisobutyro-
nitrile (AIBN) in solution and also in bulk. The copolymers
obtained were thermally stable up to 370 ꢀC, and the water
absorption of these copolymers was greatly reduced because
of the highly hydrophobic nature of the fluorine-substituted
aromatic ring. The refractive index of poly(PFPMI) was
almost the same as that of PMMA, which were 1.4989 and
1.4953 for poly(PFPMI) and PMMA at 532 nm, respectively.
Thus, the refractive indexes of the copolymers (MMA-co-
PFPMI) remained nearly constant (1.4965–1.4970 at 532
nm) regardless of the content of PFPMI in the copolymers,
which minimized light scattering of the copolymers. The
glass transition temperatures (Tg) of the PFPMI-co-MMA
were in the range of 140–180 ꢀC with the PFPMI content
from 18.8 to 65 mol %.8
532 nm, respectively. However, the starting compound for
the preparation of 2,3,4-TFPMI, 2,3,4-trifluoroaniline is much
cheaper than that of 2,3,4,5,6-pentafluoroaniline and it is
more reactive in the preparation of the maleimide. Thus, we
have prepared 2,3,4-TFPMI, and for comparison, the isomer
2,4,6-TFPMI was also prepared. The Tgs of homopolymers of
ꢀ
2,3,4-TFPMI and 2,4,6-TFPMI were more than 230 C.
The utilization of polymers for optical application has one
serious drawback. They exhibit birefringence. The major
types of birefringence are orientational and photoelastic
birefringences. Orientational birefringence is defined as bire-
fringence caused by orientation of the polymer main chains,
which tends to be caused in processes such as injection
molding, extrusion, and heat drawing, in which polymer
main chains are oriented in the molten state and solidify in
the oriented state during the following cooling process to
room temperature because they are generally not relaxed
completely in the process. Photoelastic birefringence is
defined as birefringence caused by elastic deformation below
the Tg. Photoelastic birefringence tends to be caused during
the use of optical polymer devices.9 Several methods have
been investigated to eliminate the birefringence phenomena.
They are the random copolymerization,10,11 the anisotropic
2,3,4-Trifluorophenyl maleimide (2,3,4-TFPMI) was also col-
orless, and the refractive index of poly(2,3,4-TFPMI) was a
little higher than that of poly(PFPMI); 1.5505 vs. 1.4965 at
C
V
2012 Wiley Periodicals, Inc.
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SCHEME 1 Synthesis of 2,3,4-TFPMI and 2,4,6-TFPMI.
molecule dopant,12,13 the birefringent crystal dopant,14,15 and
the polymer blending methods.16 In the random copolymer-
ization method, positive and negative birefringent monomers
that compose positive and negative birefringent homopoly-
mers are randomly copolymerized. As a result, birefringence
is mutually canceled at a specified monomer ratio.
filtered and dried, which was used in the next step without
purification (yield 80%, 53.4 g). The obtained product and
29.3 g (0.22 mol) of anhydrous zinc chloride (ZnCl2) were
dissolved in 200 mL of anhydrous tetrahydrofuran (THF) in
a three-necked flask fitteꢀd with a thermometer. The mixture
was heated up to 45–50 C, and then into the resulting solu-
tion, 66.7 mL (0.32 mol) of HMDS in 60 mL of anhydrous
THF was added dropwise over a period of 0.5 h. After stir-
ring at 45–50 ꢀC for 5 h, the reaction mixture was cooled
and filtered to remove the residue. The pure compound was
obtained by column chromatography on silica gel [eluent,
PMMA exhibits both negative orientational and photoelastic
birefringences, whereas poly(PFPMI) shows both birefringen-
ces positive. Thus, we have obtained the polymer with zero
orientational and photoelastic birefringences by adjusting the
amount of the MMA and PFPMI, MMA/PFPMI 88.9/11.1 mol
% and 93.8/6.2 mol %, respectively. The Tgs of these copoly-
mers were estimated to be about 128 and 122 ꢀC, respec-
tively.17 As poly(TFPMI)s also exhibit both positive orienta-
tional and photoelastic birefringences, TFPMIs were
copolymerized with MMA. Thus, to obtain high Tg and zero
birefringence polymers, we have prepared the copolymers of
TFPMI with MMA of different compositions (Scheme 1), and
we report here the physical and optical properties of these
copolymers.
ꢀ
hexane/THF ¼ 3:1 (v/v); yield 58.5%; m.p. 110–111 C].
1H NMR (CDCl3, 300 MHz): d (s, 2H, CH¼¼CH), (m, 2H, Ph-H).
2,4,6-TFPMI was prepared by similar method as 2,3,4-TFPMI.
The yield of 2,4,6-TFPMI was a little higꢀher than its afore-
mentioned analog (yield 64.6%; m.p. 105 C).
1H NMR (CDCl3, 300 MHz): d (s, 2H, CH¼¼CH), (m, 2H, Ph-H).
Homopolymerization and Copolymerization of
2,3,4-TFPMI and 2,4,6-TFPMI with MMA
The homopolymerizatioꢀns of 2,3,4-TFPMI and 2,4,6-TFPMI
were carried out at 60 C for 72 h using AIBN as the initia-
tor. Copolymerizations of 2,3,4-TFPMI and 2,4,6-TFPMI with
MMA were carried out in 1,4-dioxane solutions and also in
bulk with AIBN as the initiator. Monomer solutions and ini-
tiator were transferred into a glass tube and subjected to
three freeze-pump-thaw cycles, which were followed by seal-
ing under vacuum. The copolymers were purified by
repeated precipitation from THF solution into a large amount
of methanol. For the bulk copolymerization, after polymeriz-
EXPERIMENTAL
Materials
Zinc chloride, hexamethyldisilazane (HMDS), MMA, maleic
anhydride, AIBN, and solvents were purchased from Aldrich.
2,3,4-Trifluoroaniline and 2,4,6-trifluoroaniline were pur-
chased from SynQuest Laboratory.
Synthesis of Fluorinated Phenyl Maleimides: 2,3,4-TFPMI
and 2,4,6-TFPMI
2,3,4-TFPMI and 2,4,6-TFPMI were synthesized according to
reported method with some modifications.18,19 In a 500-mL
three-necked flask provided with a stirrer, a reflux con-
denser, and a dropping funnel, 26.8 g (0.27 mol) of maleic
anhydride and 140 mL of 1,4-dioxane were placed. The 1,4-
dioxane solution (90 mL) of 40 g of 2,3,4-trifluoroaniline
(0.27 mol) was added to the flask using a dropping funnel
for 1 h at ambient temperature. The reaction was completed
in 5 h at room temperature. The precipitate formed was
ꢀ
ing at 60–80 C for 24 h, the polymer produced was purified
by the precipitation from THF solution into a large amount
of methanol. The polymer collected was dried under vacuum
at 60 ꢀC for 48 h. The monomer conversions were in the
range of 85–90%.
Characterization
1H NMR spectra were determined on a Brucker AC 300 spec-
trometer, at 300 MHz, using CDCl3 as a solvent. Chemical
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TABLE 1 Copolymerization of 2,4,6-TFPMI with MMA in 1,4-Dioxanea
Mole Fraction of
2,4,6-TFPMI
Refractive Index
b
Feed
Copolymer
(mol %)c
Conversion
(%)
Mn
Sample
(mol %)
(ꢂ104)
PDIb
Tg (ꢀC)
Td (ꢀC)
532 nm
839 nm
2,4,6-TFPMI-co-MMA-1
2,4,6-TFPMI-co-MMA-2
2,4,6-TFPMI-co-MMA-3
2,4,6-TFPMI-co-MMA-4
a
20
40
60
80
17.8
33
92.5
83.6
65.7
43.0
3.0
2.62
2.80
3.78
4.56
148
165
181
200
344
350
360
370
1.5095
1.5105
1.5140
1.5220
1.4985
1.5000
1.5015
1.5080
3.2
46.5
60
2.35
0.98
b
c
All the copolymerizations were carried out at 60 ꢀC, using AIBN as
initiator.
Determined by GPC, using THF as eluent.
Calculated by 1H NMR.
RESULTS AND DISCUSSION
shifts were reported in d (ppm) from internal tetra-
methylsilane (TMS). The refractive indexes of the poly-
mers were measured using a Metricon model 2010 prism
coupler. The measurement accuracy was 60.0005.
The probe wavelengths in the prism were 532, 633, and
839 nm. Molecular weights were determined by gel
permeation chromatography (GPC; Waters 510) using THF
as the eluent at a flow rate of 1.0 mL/min. The molecu-
lar calibration curves were obtained using polystyrene
standards. The Tg of polymers was measured using a DSC
2920 module with the TA Instrument 5100 system, with
a scan rate of 10 ꢀC/min. The Tg was taken in the sec-
ond heating scan as the midpoint of the heat capacity
transition between the upper and lower points of
deviation from the extrapolated liquid and glass lines.
Homopolymerization of 2,3,4-TFPMI and 2,4,6-TFPMI and
Their Copolymerizations with MMA in Solution
2,3,4-TFPMI was polymerized in benzene at 60 ꢀC using
AIBN as initiator, and the polymer produced was rather in-
soluble in benzene and precipitated.21 On the other hand,
under similar conditions, 2,4,6-TFPMI was polymerized with-
out precipitation. The copolymerization of 2,3,4-TFPMI and
2,4,6-TFPMI with MMA were carried out in 1,4-dioxane solu-
tion using AIBN as the initiator at 60 ꢀC. The results of
copolymerizations are summarized in Tables 1 and 2. The
feed ratios of TFPMIs were in the range of 0.2–0.8. As is
shown in Tables 1 and 2, the number–average molecular
weights of the copolymers decreased, whereas the polydis-
persity of copolymers increased with increase in the amount
of TFPMIs added, which was due to the low reactivity of
TFPMIs when compared with that of MMA. As shown in
Tables 1 and 2, the monomer conversion and the molecular
weights of 2,4,6-TFPMI copolymers were slightly higher than
that of copolymers of asymmetrically substituted TFPMIs,
which indicated that 2,4,6-TFPMI was more reactive than its
analogs.
Birefringence Measurement
Birefringence of polymer was measured on thin films.20
The THF solutions were spread onto a glass plate using a
knife coater, then dried at room temperature for 1 h fol-
lowed by drying at 90 ꢀC under reduced pressure for 24
h. The sample polymer films were cut into a dumbbell
shape. For the orientational birefringence measurements,
polymer films with a thickness of about 40 lm were uni-
axially drawn above Tg temperature at ꢁ157 ꢀC and a
rate of 4–20 mm/min with a universal tensile testing
machine (Tensile RTC-1210A, A&D). The orientational
degrees of the main chains of the polymers f were con-
firmed from an IR dichroic ratio measured by polarized
Fourier transform infrared spectroscopy. The orientational
birefringence Dnor of the uniaxially drawn films was meas-
ured at a wavelength of 633 nm by optical heterodyne
interferometry with birefringence measurement equipment
(ABR-10A, Uniopt Corp., Japan). The photoelastic birefrin-
gence Dnph was measured by using the same equipment
with adding stress. The photoelastic birefringence Dnph is
expressed as follows:
The compositions of copolymers produced were calculated
from the characteristic proton resonance signals of TFPMIs
and MMA repeat units in 1H NMR spectra of TFPMI-co-
MMAs (Figs. 1 and 2), which were the protons from phenyl
ring (d ¼ 6.75–7.0 ppm for 2,4,6-TFPMI and 6.9–7.2 ppm for
2,3,4-TFPMI, respectively) and methoxy groups in the side
chains of MMA (d ¼ 3.43–3.87 for MMA), respectively. In
addition, as shown in Figures 1 and 2, the signal of phenyl
ring protons in both of the TFPMI are shifted to higher field,
and the methoxy group of MMA first splits into two peaks
and then shifts to downfield when the content of TFPMI in
copolymers increases, which may be due to the interaction
between the electron-deficient trifluorophenyl group of
TFPMI and carbonyl group of MMA in the solution.
To obtain the monomer reactivity, the copolymerization was
terminated at low conversion (<10%). The monomer reac-
tivity ratios were calculated using Fineman-Ross method.21
For 2,4,6-TFPMI-co-MMA, the values of r1 (2,4,6-TFPMI) and
r2 (MMA) were 0.26 and 0.95, and for 2,3,4-TFPMI-co-MMA,
the values were 0.37 (r1, 2,3,4-TFPMI) and 0.97 (r2, MMA),
Dnph ¼ Cr;
(1)
where C is the photoelastic coefficient of the polymer and r
is the stress. A positive polymer has C > 0, and a negative
polymer has C < 0. The C values of the polymers were deter-
mined on the basis of the results for Dn.
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TABLE 2 Copolymerization of 2,3,4-TFPMI with MMA in 1,4-Dioxanea
Mole Fraction of
2,4,6-TFPMI
Refractive Index
b
Copolymer
(mol %)c
Conversion
(%)
Mn
Sample
Feed (mol %)
(ꢂ104)
PDIb
Tg (ꢀC)
Td (ꢀC)
532 nm
839 nm
2,3,4-TFPMI-co-MMA-1
2,3,4-TFPMI-co-MMA-2
2,3,4-TFPMI-co-MMA-3
2,3,4-TFPMI-co-MMA-4
a
20
40
60
80
18.0
39.3
48.6
63.8
87.7
71.6
56.7
30.0
b
2.4
2.7
1.3
0.8
3.0
146
164
176
195
352
360
374
378
1.5030
1.5125
1.5190
1.5260
1.4990
1.5020
1.5080
1.5145
2.82
3.69
4.52
All the copolymerizations were carried out at 60 ꢀC, using AIBN as
initiator.
Determined by GPC, using THF as eluent.
Calculated by 1H NMR.
c
respectively. The Q and e values for both of fluoro-substituted
phenyl maleimide were also calculated using the Alfrey-Price
equation.22 The Q2 and e2 values for MMA were taken from
the literature.23 The results were found to be 1.23 (Q1) and
1.58 (e1) for 2,4,6-TFPMI-co-MMA and 1.13 (Q1) and 1.40 (e1)
for 2,3,4-TFPMI-co-MMA, respectively. The Q and e values of
N-phenylmaleimide (PMI) were reported to be 1.29 and 1.54,
respectively. The slightly lower Q and e values for TFPMI
when compared with that of PMI are due to the electron-
withdrawing property of pentafluorophenyl group.
Gordon-Taylor equation, which indicated that there was no
significant interaction between the partially fluorinated phe-
nyl rings and MMA moieties of the copolymers in the solid
state. To investigate the effect of substituted fluorine in the
molecular structures on their thermal properties, we plotted
the Tgs of 2,3,4-and 2,4,6-TFPMI with 2,3,4,5,6-PFPMI and
nonfluorine-containing PMI-based copolymers versus their
contents in corresponding copolymers in Figure 3. It is
shown that the trifluorinated N-substituted phenyl malei-
mides exhibit the higher Tgs than their perfluoro and non-
fluoro N-substituted analogs, and the position of fluorine on
phenyl ring has no effects on their Tg.
Thermal and Optical Properties of Copolymers
of N-TFPMIs with MMA
Thermal stability of the copolymers was determined by ther-
mogravimetric analysis in a nitrogen atmosphere. The results
are also summarized in Table 1. It can be seen that introduc-
ing TFPMIs as comonomer significantly ameliorated the
decomposition temperature of PMMA.24
Polymers of N-substituted maleimides were reported to have
high Tg and thermal stability. The Tgs for 2,3,4 TFPMI-co-
MMA and 2,4,6-TFPMI-co-MMA were measured, and their
values are shown in Tables 1 and 2, respectively. The Tgs of
copolymers were found to increase linearly with the increas-
ing amount of the TFPMIs in the copolymers, and the rela-
tionship between Tg and the polymer composition fits the
In our previous study, it was found that the PFPMI homopol-
ymer had almost the same refractive index with PMMA, as a
result of which the refractive indexes of the copolymers
FIGURE 1 1H NMR spectra of 2,4,6-TFPMI-co-MMA containing
FIGURE 2 1H NMR spectra of 2,3,4-TFPMI-co-MMA containing
17.5 (A), 25.6 (B), 36.5 (C), and 50.0 mol % (D) of TFPMI.
16.7 (A), 27.1 (B), 35.4 (C) and 43.5 mol % (D) of TFPMI.
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FIGURE 4 Refractive indexes of 2,3,4-TFPMI-co-MMA, 2,4,6-
TFPMI-co-MMA, PFPMI-co-MMA, and PMI-co-MMA.
FIGURE 3 Tg of 2,3,4-TFPMI-, 2,4,6-TFPMI, PFPMI-, and PMI-co-
MMA.
indexes when compared with its symmetrically substituted
analog at the same content of TFPMI in copolymers.
remained nearly constant regardless of the polymer composi-
tion. In this study, we have found that the refractive indexes of
TFPMI-co-MMA are in between of those of the PFPMI and PMI
and increase linearly with increase in the content of TFPMI in
copolymers (Fig. 4). In addition, the asymmetrically substituted
phenyl ring in poly(TFPMI) possesses slightly higher refractive
Physical Properties of the Copolymers Prepared in Bulk
To investigate the physical properties of TFPMI-co-MMA
polymer for the application in the optical devices, we pre-
pared copolymers in bulk using AIBN as radical initiator. The
copolymers obtained were purified by reprecipitation from
TABLE 3 Copolymerization of TFPMI with MMA in Bulka
Refractive Index
Conversion
Feed Ratio
(mol %)
TFPMI Content in
Copolymers (%)b
Sample
(%)
Tg (ꢀC)
532 nm
633 nm
839 nm
2,3,4-TFPMI-co-MMA-1
2,3,4-TFPMI-MMA-2
2,3,4-TFPMI-MMA-3
2,4,6-TFPMI-MMA-1
2,4,6-TFPMI-MMA-2
2,4,6-TFPMI-co-MMA-3
a
5
10
20
5
3.0
9.0
95.3
90.4
83.2
93.4
91.2
85.8
133
137
145
134
135
147
1.4970
1.5030
1.5080
1.4955
1.4975
1.5090
1.4930
1.4980
1.5030
1.4910
1.4925
1.5025
1.4880
1.4925
1.4965
1.4855
1.4870
1.4970
17.5
3.0
10
20
5.0
17.3
b
All the copolymerizations were carried out at 60 ꢀC, using AIBN as
initiator.
Calculated from 1H NMR spectra.
TABLE 4 Birefringence Properties of Copolymers
Polymer
Intrinsic Birefringence (10ꢃ3
)
Photoelastic Coefficient (TPaꢃ1
)
2,3,4-TFPMI-co-MMA (9.0/91.0 mol %)
2,3,4-TFPMI-co-MMA (17.5/82.5 mol %)
Poly(2,3,4-TFPMI)
ꢃ0.8
4.2
0.2
12
13 (calculated)
ꢃ4.0
ꢃ3.2
17 (calculated)
47 (calculated)
0.03
2,4,6-TFPMI-co-MMA (3.0/97.0 mol %)
2,4,6-TFPMI-co-MMA (5.0/95.0 mol %)
Poly(2,4,6-TFPMI)
2.5
69 (calculated)
ꢃ5.3
PMMA
ꢃ5.7
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FIGURE 5 Orientational birefringence of TFPMI-co-MMA versus
FIGURE 6 Photoelastic birefringence of TFPMI-co-MMA versus
orientation degree of polymer chains.
stress.
Birefringence
the THF solution into a large amount of methanol and dried
under vacuum oven at 60 ꢀC. The physical properties of
TFPMI-co-MMA are summarized in Table 3.
Figure 5 shows the orientational birefringence versus the
orientation degree of the polymer chains. PMMA exhibits a
negative orientational birefringence. Its birefringence is com-
pensated by the copolymerization with TFPMI, which has a
positive orientational birefringence effect. Orientational bire-
fringence Dnor can be written as follows:
It is found that the conversions of copolymerization were
generally more than 80%, and the number–average molecu-
lar weights of copolymers were higher than those produced
in 1,4-dioxane solution. The thermal properties of PMMA
were effectively improved by being copolymerized with
TFPMI monomers. The Tg of PMMA (ꢁ110 ꢀC) was
increased to 133 ꢀC for copolymer containing 3 mol % of
TFPMI.24
Dnor ¼ f Dn0:
(2)
Here, Dn0 is intrinsic birefringence that means birefringence
of polymer is in the completely oriented state (f ¼ 1.0).
FIGURE 7 Intrinsic birefringence and photoelastic coefficient of copolymers as a function of the composition of the copolymers:
(a) 2,3,4-TFPMI-co-MMA and (b) 2,4,6-TFPMI-co-MMA.
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Based on this relation and experimental results, intrinsic
birefringences of the polymers were obtained (Table 4).
copolymers with zero birefringence were in the range of
135–140 C.
ꢀ
The photoelastic birefringence versus the stress of the polymers
is shown in Figure 6. PMMA exhibited negative photoelastic bire-
fringence, and photoelastic birefringence constant C was approx-
imately ꢃ5.3 (TPaꢃ1). Its negative birefringence was shifted
to positive birefringence with an increase of TFPMI content.
Photoelastic coefficients of the copolymers are listed in Table 4.
ACKNOWLEDGMENTS
This research is supported by the Japan Society for the Promo-
tion of Science (JSPS) through its ‘‘Funding Program for World-
leading Innovative R&D on Science and Technology (FIRST
Program).’’
Figure 7 shows intrinsic birefringence and photoelastic coeffi-
cient of TFPMI-co-MMA as a function of content of MMA unit
in the copolymers. Those relations can be written as follows:
REFERENCES AND NOTES
1 Brydson, J. A. Plastic Materials; Butterworth Scientific:
London, 1982; p 376–377.
Poly(2,3,4-TFPMI-co-MMA):
2 Kine, B. B.; Novak, R. W. In Encyclopedia of Polymer Science
and Engineering, 2nd ed.; Mark, H. F., Ed.; Wiley: New York,
1986; Vol. 1, pp 234–235.
Dnor ¼ ꢃ0:18MMMA þ 13:13;
C ¼ ꢃ0:53MMMA þ 47:43:
(3)
(4)
3 Otsu, T.; Matsumoto, A.; Kubota, T.; Mori, S. Polym. Bull.
1990, 23, 43–50.
Poly(2,4,6-TFPMI-co-MMA):
4 Matsumoto, A.; Kubota, T.; Otsu, T. Macromolecules 1990,
23, 4508–4513.
Dnor ¼ ꢃ0:2MMMA þ 17:46;
C ¼ ꢃ0:74MMMA þ 69:03:
(5)
(6)
5 Otsu, T.; Tatsumi, A.; Matsumoto, A. J. Polym. Sci Polym.
Lett. Ed. 1986, 24, 113–117.
6 Matsumoto, A.; Kubota, T.; Otsu, T. Polym. Bull. 1990, 24,
459–466.
Here, MMMA is the content of MMA unit in the copolymers.
The ratios of 2,3,4-TFPMI/MMA for zero orientational bire-
fringence and zero photoelastic birefringence were calculated
to be 15/85 mol % (28/72 wt %) and 5/95 mol % (10/90 wt
%), respectively, by eqs 3 and 4. The intrinsic birefringence
and the photoelastic birefringence of poly(2,3,4-TFPMI) were
calculated to be 13 ꢂ 10ꢃ3 and 47 (TPaꢃ1) (Table 4).
7 Otsu, T.; Matrumoto, A.; Tatsumi, A. Polym. Bull. 1990, 24,
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Phys. 1996, 35, 3896–3901.
The ratios of 2,4,6-TFPMI/MMA for zero orientational birefrin-
gence and zero photoelastic birefringence were calculated to
be 12/88 mol % (24/76 wt %) and 3/97 mol % (7/93 wt
%), respectively, by eqs 5 and 6. The intrinsic birefringence
and the photoelastic birefringence of poly(2,4,6-TFPMI) were
calculated to be 17 ꢂ 10ꢃ3 and 69 (TPaꢃ1) (Table 4).
These results show that 2,4,6-TFPMI unit exhibits higher ori-
entational and photoelastic birefringence effects than those
of 2,3,4-TFPMI.
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CONCLUSIONS
17 Tagaya, A.; Lou, L.; Ide, Y.; Koike, Y.; Okamoto, Y. Chin. Sci.
B, in press.
2,3,4- and 2,4,6-TFPMIs were synthesized and copolymerized
with MMA using AIBN as initiator in 1,4-dioxane or in bulk.
The glass transition temperatures of the copolymers were
high (133–195 ꢀC) depending on copolymer compositions.
The copolymers obtained were thermally stable. The orienta-
tional and photoelastic birefringences of copolymers of
TFPMIs and MMA were measured. The copolymers of MMA/
2,3,4-TFPMI would exhibit zero orientational and photoelas-
tic birefringences when the ratio of 2,3,4-TFPMI/MMA were
15/85 and 5/95 mol %, respectively. For the copolymers of
2,4,6-TFPMI/MMA, the ratios of copolymers with zero orien-
tational and photoelastic birefringences were determined to
be 12/88 and 3/97 mol %, respectively. The Tgs of these
18 Bruynes, C. A.; Jurriens, T. K. J. Org. Chem. 1982, 47,
3966–3969.
19 Teddy, P. Y.; Kondo, S.; Toru, T.; Ueno, Y. J. Org. Chem.
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22 Alfrey, T., Jr.; Young, L. J. Copolymerization; Wiley-Inter-
science: New York, 1964; Chapter 2.
23 Matsumoto, A.; Kubota, T.; Otsu, T. Macromolecules 1990,
23, 4508–4513.
24 Hirata, T.; Kashiwagi, T.; Brown, J. E. Macromolecules 1985,
18, 1410–1418.
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