K.-S. Lee et al. / Polymer 51 (2010) 632–638
633
One of the defects for polymeric waveguide applications is their
appreciably high birefringence. In fact, the polarization-dependent
loss which is induced by the optical components with large bire-
fringence can cause degradation of the transmission quality or failure
of the optical data. For example, the birefringence of polarization-
independent wavelength division multiplexing (WDM) should even
close to be zero. Hence, the design of waveguide materials with zero
birefringence is important and has still remained a challenge.
In this study, we focused on the synthesis and characterization
of novel crosslinkable fluorinated poly(arylene ether sulfide)s with
the goals of achieving low birefringence (for clarity of information
transportation at the telecommunication region of 1550 nm),
sufficient thermal stability, and a chemical resistance to withstand
the typical fabrication processing and operating conditions of
waveguide materials. In order to achieve these properties, pendant
diphenylated dihydroxy monomer and fluorinated monomer were
used to increase the glass transition temperature and to lower the
refractive index and birefringence of the polymer. In addition,
a crosslinkable polymer system was employed to improve the
thermal stability and chemical resistance, as well as to lower the
birefringence with giving more amorphous structure.
aqueous solution (25 mL), the catalyst Pd(PPh
3
)
4
(0.50 g, 5 mol%)
ꢀ
was added. The reaction mixture was refluxed at 80 C under
a nitrogen atmosphere for 8 h. The solution was extracted with
methylene chloride and water and dried over anhydrous magne-
sium sulfate. Evaporation in a vacuum gave a white solid. The crude
product was purified by column chromatography. The analytical
ꢀ
1
data obtained were as follows: Yield: 93%. mp: 147–149 C. H NMR
(300 MHz, CDCl , ppm): 3.79 (s, 6H), 6.98 (s, 2H), 7.35 (t, 2H,
J ¼ 7.34 Hz), 7.44 (t, 4H, J ¼ 7.26 Hz), 7.59 (d, 4H, J ¼ 6.97 Hz).
NMR (75 MHz, CDCl , ppm): O–), 114.81 (s,
¼ 56.41 (s, CH
CH O–C–CH–), 127.08 (s, –CH–CH–CH–CH–CH–), 128.06 (s, –CH–
CH–CH–CH–CH–), 129.43 (s, –CH–CH–CH–CH–CH–), 130.43 (s,
3
, d
13
C
3
,
d
d
3
3
CH
(EI, m/z): calcd for C20
for C20
3
O–C–C–), 138.31 (s, CH
3
O–C–C–C–), 150.65 (s, CH
, 290.36; found, 290 [M] . Anal. calcd.
3
O–C–). MS
þ
18
H O
2
H
18
O
2
: C, 82.73; H, 6.25. Found: C, 82.77; H, 6.28.
0
0
00
2.2.2. (1,1 ; 4 ,1 )-terpheny-2,5-diol (4)
A solution of the monomer 3 in glacial acetic acid (100 mL) was
reacted with hydrobromic acid (50 mL) for 48 h at 125 C. The
ꢀ
solution was poured into deionized water (1 L) and filtered to obtain
a white powder. The material was recrystallized from methylene
chloride. The analytical data were as follows: Yield: 90%. mp: 222–
ꢀ
1
2
. Experimental
224 C. H NMR (300 MHz, CDCl
3
, d, ppm): 6.85 (s, 2H), 7.30 (t, 2H,
J ¼ 7.32 Hz), 7.41 (t, 4H, J ¼ 7.51 Hz), 7.55 (d, 4H, J ¼ 4.03 Hz), 8.96 (s,
13
2
.1. Materials
2H). C NMR (75 MHz, CDCl
s, –CH–CH–CH–CH–CH–),128.45 (s, –CH–CH–CH–CH–CH–),128.68
(s, HO–C–C–),129.55 (s, –CH–CH–CH–CH–CH–),138.74 (s, HO–C–C–
3
, d, ppm): 118.21 (s, HO–C–CH–),127.14
(
Pentafluorophenyl sulfide, potassium carbonate, methylene
ꢁ1
chloride, bromine, iodine, 1,4-dimethoxybenzene, tetrahydrofuran
C–), 147.53 (s, HO–C–). IR (KBr, thin film, cm ): 3438 (–OH). MS (EI,
þ
(
(
THF), 1,2-dibromoethane, trimethyl borate, hydrobromic acid
48%), acetic acid (glacial), tetrakis(triphenylphosphine)palla-
m/z): calcd for C18
H
14
O
2
, 262.30; found, 262 [M] . Anal. calcd. for
18 14 2
C H O : C, 82.42; H, 5.38. Found: C, 82.58; H, 5.60.
dium(0), N,N-dimethylacetamide (DMAc), and benzene were
purchased from Aldrich Chemical Co. and used without further
purification. Magesium (Mg) powder was obtained from Kanto
Chemical Co. Magnesium was used after activation and vacuum
2.3. Synthesis of FPAESI and E-FPAESI
As shown in Scheme 2, FPAESIs were synthesized via the step-
growth polymerization of compound 4 with pentafluorophenyl
sulfide. Dihydroxy monomer 4 (1.85 mmol) and pentafluorophenyl
sulfide (0.68 g, 1.86 mmol) with K CO (0.28 g, 1.10 equiv), in
a DMAc (10 mL) and benzene (10 mL) mixture, were placed in
a 50 mL 2-neck flask equipped with a magnetic stirrer, a nitrogen
ꢀ
drying at 100 C for 24 h. Magnesium sulfate and hydrochloric acid
were obtained form Oriental Chemical Industries (Korea). 3-Ethy-
nylphenol was prepared according to the literature [17,30]. 1,4-
Dibromo-2,5-dimethoxybenzene (1) and 2,5-dimethoxy-1,4-ben-
zenediboronic acid (2) were prepared according to the methods
reported in the literature [18].
2
3
ꢀ
inlet, and a Dean–Stark trap. The mixture was reacted at 120 C for
2 h to ensure complete dehydration with refluxing benzene into
1
2
2
.2. Synthesis of monomer
the Dean–Stark trap. E-FPAESI was synthesized by capping the end
of the FPAESI with an ethynyl group. Typically, 3-ethynylphenol
(0.87 g, 4.00 equiv) and benzene (10 mL) were added to the reac-
0
0
00
.2.1. 2,5-Dimethoxy-(1,1 ; 4 ,1 )-terphenyl (3)
ꢀ
With a stirred solution of the monomer 2 (1.50 g, 6.64 mmol),
tion mixture, and the reaction was allowed to proceed at 120 C for
bromobenzene (2.08 g, 13.25 mmol) in THF (50 mL) and 2 M K
2
CO
3
2 h. After removing benzene, the reaction mixture was cooled and
Br
B(OH)2
Br2/CH2Cl2
1) Mg/THF
H3CO
OCH3
H3CO
OCH3
H3CO
(HO)2B
OCH3
r.t.
2) B(OCH3)3/H2SO4
Br
1
2
Br
Pd(PPh3)4/THF/H2O/K2CO3
HBr/CH3COOH
125 o
H3CO
OCH3
HO
OH
C
3
4
Scheme 1. Synthesis of the dihydroxy monomer.