Synthesis and properties of poly(diphenylacetylenes) having hydroxyl groups

Article abstract of DOI:10.1021/ma050566d

Polymerization of several diphenylacetylene derivatives was carried out by using TaCl₅-n-Bu₄Sn as catalyst. C₆H ₅C≡CC₆H₄-p-OSi(CH₃) ₂t-Bu (3a) and C₆H₅

Full text of DOI:10.1021/ma050566d

4096
Macromolecules 2005, 38, 4096-4102
Synthesis and Properties of Poly(diphenylacetylenes) Having Hydroxyl
Groups
Yuichi Shida,† Toshikazu Sakaguchi,† Masashi Shiotsuki,† Fumio Sanda,†
Benny D. Freeman,‡ and Toshio Masuda*,†
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura
Campus, Kyoto 615-8510, Japan, and University of Texas at Austin, Center for Energy and
Environmental Resources, 10100 Burnet Road, Building 133, Austin, Texas 78758
Received March 17, 2005; Revised Manuscript Received April 4, 2005
ABSTRACT: Polymerization of several diphenylacetylene derivatives was carried out by using TaCl5-
n-Bu4Sn as catalyst. C6H5C≡CC6H4-p-OSi(CH3)2t-Bu (3a) and C6H5C≡CC6H4-m-OSi(CH3)2t-Bu (3b)
provided the corresponding polymers (poly(3a), poly(3b)) with high molecular weights in good yields,
while p-t-Bu(CH3)2SiOC6H4C≡CC6H4-p-OSi(CH3)2t-Bu (3c), p-t-Bu(CH3)2SiOC6H4C≡CC6H4-m-OSi(CH3)2t-
Bu (3d), and m-t-Bu(CH3)2SiOC6H4C≡CC6H4-m-OSi(CH3)2t-Bu (3e) did not satisfactorily. Desilylation of
poly(3a) and poly(3b) membranes catalyzed by trifluoroacetic acid yielded poly(diphenylacetylenes) having
free hydroxyl groups [poly(4a), poly(4b)], which are the first examples of highly polar group-carrying
poly(diphenylacetylenes). Poly(3a) and poly(3b) dissolved in nonpolar solvents such as toluene and
chloroform, while poly(4a) and poly(4b) were insoluble in these solvents. According to TGA in air, poly-
(3a) and poly(3b) were thermally fairly stable among substituted polyacetylenes, and poly(4a) and poly-
(4b) displayed even higher thermal stability. The PCO /PCH and PCO /PN2 permselectivity ratios of poly(4a)
2
4
2
and poly(4b) membranes were as large as 13-46, while keeping relatively high PCO values.
2
Introduction
problem would be to polymerize disubstituted acetylene
monomers possessing protected hydroxyl groups9 and
then to deprotect the polymers formed therefrom. To our
knowledge, there have been no examples of the synthe-
sis of poly(diphenylacetylenes) with highly polar ring
substituents including hydroxyl groups. They are ex-
pected to show interesting properties and functions
since such functional groups would render them more
or less polar and hydrophilic. Thus, we invoke the
protection/deprotection methodology to prepare hy-
droxylated poly(diphenylacetylene) membranes.
The present research deals with the synthesis and
polymerization of novel diphenylacetylene monomers
(3a-e) (Chart 1) possessing hydroxyl groups protected
by bulky silyl groups. We further describe the desily-
lation of the resultant polymers [poly(3a), poly(3b)] to
yield poly(diphenylacetylenes) having hydroxyl groups
[poly(4a),10 poly(4b)], properties of the polymers, and
gas permeability of the polymer membranes. This paper
presents the first synthetic method of poly(diphenyl-
acetylenes) having polar groups.
Polyacetylenes possessing bulky substituents exhibit
useful properties including air stability, good solubility,
easy membrane fabrication, and high gas permeability,
which are not seen in the unsubstituted polyacetylene.1
Especially, these polymers attract much attention as gas
separation membranes applicable to industrial use.2
Poly(diphenylacetylenes) with bulky spherical substit-
uents are especially interesting since they possess
excellent thermal stability and high gas permeability.3
For example, poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]-
acetylene] [poly(1)] is readily soluble in common organic
solvents and exhibits an onset temperature of weight
loss in air up to 450 °C and a large oxygen permeability
coefficient (PO ) of 1550 barrers at 25 °C.4
2
Poly(diphenylacetylene) is an intractable material
because it is insoluble and infusible and hence cannot
be fabricated into a membrane directly.5 Consequently,
the precursor polymers are necessary to prepare poly-
(diphenylacetylene) membrane [poly(2)], and we have
recently succeeded in preparing it by desilylating poly-
(1) membrane (Scheme 1).6 The desilylation reaction
enables the preparation of solvent-insoluble poly(di-
phenylacetylene) and analogous polymer membranes,
which were inaccessible before.7 Furthermore, being
insoluble, this membrane can be used for the separation
of organic mixtures as well as gas separation.8
Ta and Nb catalysts are effective for the polymeriza-
tion of disubstituted acetylenes. They, however, become
inactive upon addition of protic compounds such as
alcohols and carboxylic acids. Accordingly, disubstituted
acetylenes with hydroxyl groups cannot be polymerized
with these catalysts. A possible approach to obviate this
Results and Discussion
Polymerization. The polymerization of dipheny-
lacetylene monomers 3a-e possessing protected hy-
droxyl groups was carried out using a 1:2 mixture of
TaCl5 and n-Bu4Sn as catalyst in toluene solution at
80 °C (Table 1). It has been reported that the TaCl5-
n-Bu4Sn catalyst satisfactorily polymerizes disubstitut-
ed acetylene monomers to give polymers with high
molecular weights in good yields.1a,b The polymerization
of monomer 3a produced a polymer in a good yield,
whose Mw was as high as 4.0 × 106. The polymerization
of monomer 3b also afforded a polymer in an excellent
yield, whose Mw was as high as 1.9 × 106. Thus,
monomers 3a and 3b, which have a bulky siloxy group
in one phenyl group, successfully polymerized to give
high molecular weight polymers in high yields. The
† Kyoto University.
‡ University of Texas at Austin.
* Corresponding author: Tel +81-75-383-2589; Fax +81-75-383-
2590; e-mail masuda@adv.polym.kyoto-u.ac.jp.
10.1021/ma050566d CCC: $30.25 © 2005 American Chemical Society
Published on Web 04/19/2005

Macromolecules, Vol. 38, No. 10, 2005
Poly(diphenylacetylenes) 4097
Scheme 1. Synthesis of Poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene] [Poly(1)] and Membrane of
Poly(diphenylacetylene) [Poly(2)]
Chart 1. Diphenylacetylene Monomers Having Siloxy Groups
Scheme 2. Synthesis of Poly(diphenylacetylenes) Having Hydroxyl Groups
Table 1. Polymerization of 3a-e by TaCl5-n-Bu4Sna
Table 2. Desilylation of Poly(3a) and Poly(3b) with
Trifluoroacetic Acid (TFA)
polymerb
treatment medium
c
run
monomer
[M]0 (M)
yield (%)
Mw/103 c
Mw/Mn
run
polymer
(vol ratio)
time (h)
conv (%)a
1
2
3
4
5
6
7
3a
3b
3c
3c
3d
3e
3e
0.10
0.10
0.10
0.50
0.50
0.10
0.50
61
72
0
4000
1900
12.1
5.8
1
2
3
4
5
6
poly(3a)
poly(3a)
poly(3a)
poly(3a)
poly(3a)
poly(3b)
TFA/H2O (4/1)
TFA/H2O (2/1)
TFA/methanol (4/1)
TFA/methanol (2/1)
TFA
24
48
48
48
48
24
100
90
80
0
30
48
0
0
250
7.6
80
TFA/H2O (4/1)
100
a Determined by TGA (see text for details).
a In toluene at 80 °C for 24 h; [TaCl5] ) 20 mM, [n-Bu4Sn] )
40 mM. b Toluene-soluble and methanol-insoluble product. c Mea-
sured by GPC.
sessed high molecular weights (Mw > 1.0 × 106), they
afforded tough free-standing membranes by casting
from toluene solution. The membranes formed from
poly(3a) and poly(3b) were uniform, transparent and
yellow. On the other hand, it was difficult to prepare a
free-standing membrane from poly(3d) because of its
rather low molecular weight.
The membrane of poly(3a) was immersed in a mixture
of trifluoroacetic acid (TFA)/water or TFA/methanol
(Table 2). Poly(3a) was completely desilylated by using
a mixture of TFA/water (4/1) (run 1). After workup by
washing with aqueous NaHCO3 solution and water and
by the subsequent drying, the desilylation product was
dark green and kept the membrane form. The comple-
molecular weight distributions of the polymers were
appreciably broad (Mw/Mn ) 5.8-12.1). On the other
hand, the polymerization of monomers 3c and 3e did
not produce polymers. Monomer 3d provided a lower
molecular weight polymer (Mw ) 2.5 × 105; DPw ) 570)
in a moderate yield even at a high monomer concentra-
tion ([M]0 ) 0.50 M). The inactivity of monomers 3c and
3e and the low polymerizability of 3d may be due to
the stetic and/or electronic effect of the two substituents.
Desilylation of Polymer Membranes. High mo-
lecular weight is essential for the fabrication of free-
standing membranes. As poly(3a) and poly(3b) pos-

4098 Shida et al.
Macromolecules, Vol. 38, No. 10, 2005
Figure 1. IR spectra of poly(3a) and its desilylation product
[poly(4a)] (KBr pellet).
Figure 2. TGA curves of the polymers (in air, heating rate
10 °C min-1).
Table 3. Solubility of the Polymersa
dissolved in many relatively nonpolar solvents such as
toluene, chloroform, and THF, similarly to other poly-
(diphenylacetylene) derivatives.3 In contrast, poly(4a)
was insoluble in such solvents but partly soluble in
methanol and ethanol. Poly(4b) was insoluble in the
nonpolar solvents, methanol and ethanol, while soluble
in highly polar solvents such as DMSO and DMF. This
variation in solubility with desilylation is remarkable
and noteworthy, which should be reflective of incorpora-
tion of hydroxyl groups.
poly(3a)
poly(3b)
poly(4a)
poly(4b)
hexane
cyclohexane
toluene
CHCl3
(
(
+
+
+
-
-
-
+
+
+
+
+
-
-
-
-
-
-
-
-
-
-
(
-
-
-
-
-
+
+
-
THF
DMF
DMSO
methanol
a +: soluble; (: partly soluble; -: insoluble.
The onset temperatures (T0) of weight loss of poly-
(3a) and poly(3b) were 320 and 390 °C in air, respec-
tively, which indicates fair thermal stability among
substituted polyacetylenes (Table 4). These polymers
showed two-stage weight loss in TGA measured in air,
suggesting that the silyl group is at first eliminated
(Figure 2). The T0 values of poly(4a) and poly(4b) were
360 and 420 °C and even higher than those of poly(3a)
and poly(3b).
tion of desilylation was confirmed by IR spectroscopy;
i.e., the absorption peaks assignable to the siloxy group
at 1260, 912, 855, and 812 cm-1 disappeared, and a
broad peak due to the hydroxyl group appeared at 3300
cm-1 (Figure 1). The degree of desilylation was evalu-
ated by thermogravimetric analysis (TGA) in air; namely,
when the silyl group had been partly or completely
removed, the amount of ash of SiO2 remaining above
700 °C in air in TGA decreased proportionally, and
hence the degree of desilylation was determined from
the amount of ash. The change of the weights of the
membranes before and after desilylation was also useful
to comfirm the complete desilylation (e.g., poly(3a): 53.6
mg; poly(4a): observed weight 33.5 mg, calculated
weight 33.5 mg). Under the conditions other than those
in run 1, poly(3a) was not completely desilylated. Poly-
(3b) was completely desilylated by using TFA/water
(4/1) in the same way as poly(3a). The yellow color of
poly(3b) membrane turned orange upon desilylation.
Thus, the bulky silyl group could be removed using a
mixture of TFA/water (4/1) irrespective of the position
of the substituents.
Poly(3a) exhibited two absorption maxima at λmax
)
373 and 429 nm in the UV-vis spectrum (Table 4)
similarly to other poly(diphenylacetylene) derivatives;
e.g., for poly(1) λmax ) 375 and 430 nm.4 Poly(3b) also
showed a UV-vis spectrum close to that of poly(3a).
As seen in Table 4, the Young’s moduli (E), tensile
strengths (σB), and elongations at break (γB) of poly-
(3a) and poly(3b) resembled those of poly(1); that is, all
these polymers were very hard and brittle and could
hardly be elongated. This seems to be common in poly-
(diphenylacetylene) derivatives.11 Poly(4a) and poly(4b)
were mechanically even harder due to the presence of
hydroxyl groups.
Density and Fractional Free Volume (FFV) of
the Polymers. The densities of polymer membranes
were measured to calculate the fractional free volume
(FFV). FFV (cm3 of free volume/cm3 of polymer) is often
used to estimate the efficiency of chain packing and the
General Properties of the Polymers. The solubil-
ity of the present polymers was examined (Table 3).
Poly(3a) and poly(3b) possessing bulky siloxy groups
Table 4. Comparison of Properties of the Polymersa
poly(1)b
poly(3a) poly(3b)
420
poly(4a)
poly(4b)
T0c (°C)
320
390
360
420
λmax (nm)
ꢀmax (M-1 cm-1
Ef (MPa)
σBf (MPa)
γBf (%)
375, 430
4300, 4800
1460
373, 429d
4800, 5400d
920
370, 421e
5200, 5800e
1800
)
2160
26
1.2
1.217
0.0805
3500
46
1.3
1.189
0.102
19
19
2.2
17
1.0
1.5
0.91
densityg (g/cm3)
FFVh
0.993
0.177
0.976
0.190
0.26
a Obtained with TaCl5 as catalyst at 80 °C for 24 h. b Data from refs 4, 11, and 14. c Onset temperature of weight loss in TGA measured
in air. d Measured in CHCl3, concentration 1.27 × 10-4 mol/L. e Measured in CHCl3, concentration 1.34 × 10-4 mol/L. f E ) Young’s
modulus, σB ) tensile strength, and γB ) elongation at break. g Determined by hydrostatic weighing. h FFV values were calculated from
membrane densities (see text).

Macromolecules, Vol. 38, No. 10, 2005
Table 5. Gas Permeability Coefficients (P) of the Polymersa
P (barrerb)
O2
Poly(diphenylacetylenes) 4099
polymer
H2
He
CO2
N2
50
67
2.4
5.1
CH4
PO /PN
PCO /PCH
PCO /PN
2
2
2
4
2
2
poly(3a)c
poly(3b)c
poly(4a)d
poly(4b)d
330
380
56
170
210
38
810
880
110
130
160
190
8.0
15
160
170
2.3
9.6
3.2
2.8
3.3
2.9
5.1
5.2
47.8
13.5
16.2
13.1
45.8
25.5
86
46
a P values measured at 25 °C. b 1 barrer ) 1 × 10-10 cm3 (STP) cm cm-2 s-1 cmHg-1
.
c Methanol-conditioned. d Hexane-conditioned.
amount of space (free volume) available for gas perme-
ation in a polymer matrix. It is defined as12
vSP - v0 vSP - 1.3vW
FFV )
≈
vSP
vSP
where vsp and v0 are the specific volume and occupied
volume (or zero-point volume at 0 K) of the polymer,
respectively. It is usually assumed that v0 is 1.3 times
as large as the van der Waals volume (vW), which is
calculated by the group contribution methods.13
The FFV values of poly(3a) and poly(3b) were 0.18-
0.19, which are more or less smaller than that of poly-
(1)14 (FFV ) 0.26). Desilylation of poly(3a) and poly(3b)
resulted in shrinkage of the polymer membranes, and
the densities became higher than those before desily-
lation (Table 4). Simultaneously, the FFV of poly(3a)
decreased from 0.177 to 0.0805, and that of poly(3b) did
from 0.190 to 0.102. This is explicable by the idea that
the shrinkage of the membranes due to intermolecular
hydrogen bonding predominates over the formation of
microvoids due to elimination of the bulky silyl groups
in the solid state.
Figure 3. Plot of diffusion coefficient (D) vs solubility coef-
ficient (S) of poly(3a) and poly(4a).
Gas Permeability of the Polymer Membranes.
The polymer membranes were conditioned beforehand
by immersing in methanol [for poly(3a) and poly(3b)]
or in hexane [for poly(4a) and poly(4b)] for 24 h and
subsequently drying to constant weight at room tem-
perature. Then their gas permeability was measured at
25 °C (Table 5).
Figure 4. Plot of diffusion coefficient (D) vs solubility coef-
ficient (S) of poly(3b) and poly(4b).
The oxygen permeability coefficient (PO ) of poly(3a)
was 160 barrers, which is relatively small 2among those
of poly(diphenylacetylene) derivatives; e.g., poly(1): PO
2
) 1550 barrers, PO /PN ) 3.0;6 poly[1-phenyl-2-[p-
2
(isopropyldimethylsil2yl)phenyl]acetylene: PO ) 500
indicating that the separation performance for CO2
remarkably improves upon desilylation. The increases
of separation factors of poly(4a) against poly(3a) were
fairly larger than those with poly(4b) vs poly(3b). It is
barrers, PO /PN ) 2.3.15 The permeability of2poly(3a)
2
to other gas2es was also relatively low. The permeability
of poly(3b) with meta-hydroxyl group was somewhat
higher to every gas than of the para-counterpart, poly-
(3a). The PO values of desilylated polymers poly(4a) and
poly(4b) we2re 8.0 and 15 barrers, respectively, which
demonstrate significant decreases of gas permeability
after desilylation, presumably owing to the decrease of
FFV. In general, polymers bearing hydroxyl groups such
especially noteworthy that the PCO /PCH value of poly-
4
(4a) is located out of the Robeson’s2upper bound.18 The
methane permeability, PCH , remarkably decreases com-
4
pared to those of not only CO2 but also small-size gases
(H2, He) upon desilylation. This is reasonable because
methane is nonpolar and fairly bulky.
The gas permeability coefficient (P) was inspected in
more detail by dividing into the gas solubility coefficient
(S) and gas diffusion coefficient (D). The calculation
method is explained in the experimental part. The D
and S of poly(3a) and poly(4a) are plotted in Figure 3
and those of poly(3b) and poly(4b) in Figure 4.
The S of every gas except CO2 hardly changed upon
desilylation, while the D significantly decreased. The
decrease of D can be accounted for both by the elimina-
tion of the silyl groups possessing high mobility and by
the decrease of FFV. The obvious increase of S of CO2
in both poly(3a) and poly(3b) can be explained by the
idea that the CO2 molecule strongly interacts with the
hydroxyl groups of the polymers.
as poly(vinyl alcohol) (PO ) 0.00665 barrers) commonly
2
show very low gas permeability and can be utilized as
gas barrier membranes.16 When this is taken into
account, the relatively high gas permeability of poly-
(4a) and poly(4b) suggests fairly sparse structures as
are common for sterically crowded substituted poly-
acetylenes.
The gas separation factors for oxygen and nitrogen
(PO /PN ) of poly(3a) and poly(4a) were 3.2 and 3.3,
2
2
which are very close to each other. A similar tendency
was observed in the case of poly(3b) and poly(4b). In
contrast, the gas separation factors of CO2 and methane
(PCO /PCH ) and of CO2 and nitrogen (PCO /PN ) of poly-
4
2
2
(4a) 2and poly(4b) were 14-48 and appreciably large,17

4100 Shida et al.
Macromolecules, Vol. 38, No. 10, 2005
Scheme 3. Synthesis of Diphenylacetylene Monomers Having Siloxy Groups
phenylphosphine)palladium dichloride (0.80 g, 1.1 mmol),
triphenylphosphine (1.2 g, 4.6 mmol), cuprous iodide (1.3 g,
6.8 mmol), and triethylamine (300 mL) were placed in the
flask. The reaction mixture was stirred at room temperature
for 2 h. After the triethylamine in the reaction mixture was
evaporated, ether (300 mL) was added, and then the insoluble
salt was filtered off. The solution was washed with 1 N
hydrochloric acid and then with water. The ethereal solution
was dried over anhydrous sodium sulfate followed by rotary
evaporation of ether. Purification of the crude product by flash
column chromatography (eluent: hexane/ethyl acetate ) 9/1)
provided the desired product [1-phenyl-2-(p-hydroxyphenyl)-
acetylene] (yield 14 g, 61%) as a white solid. As the second
step,20 a 500 mL three-necked flask was equipped with a
dropping funnel and a magnetic stirring bar and flushed with
nitrogen. 1-Phenyl-2-(p-hydroxyphenyl)acetylene (13 g, 65
mmol), imidazole (13 g, 200 mmol), and N,N-dimethylforma-
mide (100 mL) were placed in the flask. Then, a solution of
tert-butyldimethylchlorosilane (13.6 g, 90 mmol) in N,N-
dimethylformamide (80 mL) was added dropwise at 0 °C for
30 min, and then the reaction mixture was stirred for an
additional 10 h at room temperature. After ether (100 mL)
was added, the solution was washed with water and then with
1 N aqueous sodium hydroxide. The ethereal solution was
dried over anhydrous sodium sulfate and then concentrated
at reduced pressure. The crude product was purified by flash
column chromatography (eluent: hexane) to provide the
desired product (new compound; yield 13.3 g, 67%) as a
colorless liquid. Purity >99% (1H NMR). IR (KBr): 2957, 1595,
1490, 1260, 880, 852, 843, 615, 497 cm-1. 1H NMR (CDCl3): δ
7.67 (d, 2H, Ar), 7.57 (d, 2H, Ar), 7.37-7.47 (m, 3H, Ar), 6.93
(d, 2H, Ar), 1.13 (s, 9H), 0.33 (s, 6H). 13C NMR (CDCl3): δ
155.9, 133.0, 131.4, 128.3, 127.9, 123.5, 120.2, 116.0, 89.4, 88.2,
25.6, 18.2, -4.5. Anal. Calcd for C20H24OSi: C, 77.9; H, 7.8.
Found: C, 78.0; H, 7.9.
Conclusions
In this article, we have demonstrated the synthesis
of novel poly(diphenylacetylene) derivatives possessing
hydroxyl groups protected with bulky silyl groups and
their transformation into poly(diphenylacetylenes) hav-
ing hydroxyl groups by desilylation using a mixture of
TFA/water (4/1). Thus, the synthesis of a new class of
polar poly(diphenylacetylene) membranes was achieved.
The poly(diphenylacetylenes) with hydroxyl groups
showed unique solubility properties. The gas perme-
ability of the poly(diphenylacetylenes) having hydroxyl
groups was lower than that of the polymers before
desilylation, probably owing to the decrease of micro-
voids resulting from intermolecular hydrogen bonding.
Nevertheless, the relatively high gas permeability of the
hydroxylated poly(diphenylacetylenes) among hydroxyl
group-bearing polymers suggests a fairly sparse struc-
ture as seen in many substituted polyacetylenes. In
addition, the membranes of the hydroxylated poly-
(diphenylacetylenes) exhibited outstanding CO2 perme-
ability as well as separation performance for CO2
against methane and nitrogen, which could be explained
by the increase of solubility of CO2 in the polymer
membranes, resulting from strong interaction between
CO2 molecules and the hydroxyl groups. Thus, poly-
(diphenylacetylenes) with polar groups proved to show
unique properties, and syntheses of other polar group-
containing polymers are in progress.
Experimental Section
Materials. TaCl5 as main catalyst was commercially ob-
tained (Strem) and used without further purification. n-Bu4-
Sn (Wako, Japan) as cocatalyst was used after distillation.
p-Iodophenol, m-iodophenol, and common solvents such as
toluene, ether, and methanol (Wako, Japan) were employed
without further purification. Phenylacetylene and tert-but-
yldimethylchlorosilane were purchased from Aldrich. Mono-
mers were synthesized according to Scheme 3, referring to the
literature for ethynylation19 and silylation.20 Their synthesis
and analytical data are detailed below.
1-Phenyl-2-p-(tert-butyldimethylsiloxy)phenyl-
acetylene (3a). As the first step,19 a 500 mL three-necked
flask was equipped with a three-way stopcock and a magnetic
stirring bar and flushed with dry nitrogen. p-Iodophenol (25
g, 110 mmol), phenylacetylene (12 g, 110 mmol), bis(tri-
1-Phenyl-2-m-(tert-butyldimethylsiloxy)phenyl-
acetylene (3b). This monomer was prepared by the same
method as for 3a using m-iodophenol as the starting compound
instead of p-iodophenol. Yield 70%, colorless liquid, purity
>99% (1H NMR). IR (KBr): 2956, 1590, 1494, 1264, 973, 878,
839, 537, 457 cm-1. 1H NMR (CDCl3): δ 7.53 (d, 2H, Ar), 7.32-
7.34 (m, 3H, Ar), 7.18 (t, H, Ar), 7.14 (d, H, Ar), 7.00 (s, H,
Ar), 6.81 (d, H, Ar), 0.99 (s, 9H), 0.21 (s, 6H). 13C NMR
(CDCl3): δ 155.9, 133.0, 131.4, 128.3, 127.9, 123.5, 120.2, 116.0,
89.4, 88.2, 25.6, 18.2, -4.5. Anal. Calcd for C20H24OSi: C, 77.9;
H, 7.8. Found: C, 78.0; H, 7.9.
p,p′-Bis(tert-butyldimethylsiloxy)diphenylacetylene
(3c). p-(tert-Butyldimethylsiloxy)iodobenzene and p-(tert-but-
yldimethylsiloxy)phenylacetylene were prepared according to
a literature procedure.21 A 500 mL three-necked flask was

Macromolecules, Vol. 38, No. 10, 2005
Poly(diphenylacetylenes) 4101
equipped with a three-way stopcock and a magnetic stirring
bar and flushed with dry nitrogen. p-(tert-Butyldimethyl-
siloxy)iodobenzene (5.2 g, 15.6 mmol), p-(tert-butyldimethyl-
siloxy)phenylacetylene (3.0 g, 13.0 mmol), bis(triphenylphos-
phine)palladium dichloride (0.090 g, 0.13 mmol), triphenylphos-
phine (0.14 g, 0.52 mmol), cuprous iodide (0.15 g, 0.78 mmol),
and triethylamine (80 mL) were placed in the flask. The
reaction mixture was stirred at room temperature for 2 h. After
the triethylamine in the reaction mixture was evaporated,
ether (150 mL) was added, and then the insoluble salt was
filtered off. The solution was washed with 1 N hydrochloric
acid and then with water. The ethereal solution was dried over
anhydrous sodium sulfate followed by rotary evaporation of
ether. Purification of the crude product by flash column
chromatography (eluent: hexane) provided the desired product
(new compound; yield 4.0 g, 72%) as a white solid. Purity >99%
(1H NMR). IR (KBr): 2957, 1603, 1260, 916, 855, 812, 690
poly(4a) and poly(4b) were not observed because of either
insolubility or high viscosity of solution. Poly(4a); IR (film):
3300, 1595, 1490, 1232, 777, 690, 524 cm-1. Poly(4b); IR
(film): 3300, 1579, 1482, 1230, 780, 689, 523 cm-1
.
Measurements. The molecular weights of polymers were
estimated by gel permeation chromatography (CHCl3 as elu-
ent, polystyrene calibration). IR spectra were recorded on a
Shimadzu FTIR-8100 spectrophotometer. NMR spectra were
observed on a JEOL EX-400 spectrometer. Thermogravimetric
analyses (TGA) were conducted in air with a Parkin-Elmer
TGA7 thermal analyzer. Tensile tests were carried out at 25
°C at a strain rate of 0.5 mm/min on a Tensilon model RTM-
500 (Orientec Co.). A typical specimen was 50 mm in length,
5.0 mm in width, and 30 µm in thickness.
The densities of membranes were determined by hydrostatic
weighing using a Mettler Toledo balance (model AG204,
Switzerland) and a density determination kit.22 In this method,
a liquid with known density (F0) is needed, and the membrane
density (F) is given by the following equation:
1
cm-1. H NMR (CDCl3): δ 7.37 (d, 4H, Ar), 6.79 (d, 4H, Ar),
0.98 (s, 18H), 0.20 (s, 12H). 13C NMR (CDCl3): δ 155.6, 132.8,
120.1, 116.3, 88.1, 25.6, 18.3, -4.4. Anal. Calcd for C20H24-
OSi: C, 77.9; H, 7.8. Found: C, 78.0; H, 7.9.
MA
F )
× F0
p,m′-Bis(tert-butyldimethylsiloxy)diphenylacetylene
(3d). This monomer was prepared by the same method as for
3c using m-(tert-butyldimethylsiloxy)iodobenzene instead of
p-(tert-butyldimethylsiloxy)iodobenzene. Yield 82%, colorless
liquid, purity >99% (1H NMR). IR (KBr): 2956, 1600, 1494,
MA - ML
where MA is membrane weight in air and ML is membrane
weight in the auxiliary liquid. Aqueous Na2NO3 solution was
used as the auxiliary liquid.
The gas permeability coefficients (P) of polymers were
measured with a Rikaseiki K-315-N gas permeability ap-
paratus at 25 °C. The P values were calculated from the slopes
of time-pressure curves in the steady state where Fick’s law
holds.23 The D values were determined by the time lag method
using the following equation:
1
1257, 973, 878, 839, 617, 543, 462 cm-1. H NMR (CDCl3): δ
7.40 (d, 2H, Ar), 7.17 (t, H, Ar), 7.10 (d, H, Ar), 6.98 (d, H, Ar),
6.81 (d, H, Ar), 6.79 (d, 2H, Ar), 0.99 (s, 9H), 0.98 (s, 9H), 0.21
(s, 12H). 13C NMR (CDCl3): δ 155.9, 155.4, 133.0, 129.5, 129.3,
125.7, 124.7, 123.8, 122.9, 121.7, 120.2, 116.0, 89.1, 88.1, 25.7,
18.2, -4.4. Anal. Calcd for C20H24OSi: C, 77.9; H, 7.8. Found:
C, 78.0; H, 7.9.
m,m′-Bis(tert-butyldimethylsiloxy)diphenylacet-
ylene (3e). This monomer was prepared by the same method
as for 3c using m-(tert-butyldimethylsiloxy)iodobenzene and
m-(tert-butyldimethylsiloxy)phenylacetylene instead of p-(tert-
butyldimethylsiloxy)iodobenzene and p-(tert-butyldimethyl-
siloxy)phenylacetylene. Yield 71%, colorless liquid, purity
>99% (1H NMR). IR (KBr): 2956, 1596, 1494, 1262, 970, 878,
839, 542, 460 cm-1. 1H NMR (CDCl3): δ 7.18 (t, 2H, Ar), 7.12
(d, 2H, Ar), 7.00 (s, 2H, Ar), 6.81 (d, 2H, Ar), 0.99 (s, 18H),
0.21 (s, 12H). 13C NMR (CDCl3): δ 155.4, 129.3, 124.9, 124.2,
123.0, 120.5, 88.9, 25.7, 18.2, -4.4. Anal. Calcd for C20H24-
OSi: C, 77.9; H, 7.8. Found: C, 78.0; H, 7.9.
D ) l2/6θ
Here, l is the membrane thickness, and θ is the time lag, which
is given by the intercept of the asymptotic line of the time-
pressure curve to the time axis. The membrane thickness was
controlled so that the time lag would be in the range 10-300
s, preferably 30-150 s. When the time lag was <10 s, the error
of measurement became relatively large. If the time lag was,
on the contrary, >300 s, the error based on baseline drift
became serious. The S values were calculated by using the
equation S ≡ P/D.
Polymerization. Polymerizations were performed in a
Schlenk tube equipped with a three-way stopcock under dry
nitrogen. Unless otherwise specified, the polymerizations were
carried out at 80 °C for 24 h at the following concentrations:
[M]0 ) 0.10 M, [TaCl5] ) 20 mM, [n-Bu4Sn] ) 40 mM. The
formed polymers were isolated by precipitation into a large
amount of methanol, and the polymer yields were determined
by gravimetry. Sharp 1H and 13C NMR spectra of these
polymers was not observed because of too high viscosity of the
solutions. Poly(3a); IR (film): 2960, 1605, 1490, 1263, 912, 855,
812, 781, 690, 548 cm-1. Poly(3b); IR (film): 2959, 1597, 1481,
Acknowledgment. The authors thank Professor
Tamejiro Hiyama at Kyoto University for his valuable
suggestions and Professor Toshikazu Takigawa for
measurement of mechanical properties. Thanks are also
due to NOF Corp. and Matsue-Matsushita Electric
Industrial Co., Ltd., for their financial support. This
research was supported by a grant-in-aid for scientific
research from the Ministry of Education, Science,
Culture and Sports (Japan).
1270, 968, 880, 839, 780, 688, 527 cm-1
.
Membrane Fabrication and Desilylation. Membranes
(thickness ca. 30-80 µm) of poly(3a) and poly(3b) were
fabricated by casting toluene solution of the polymers (con-
centration ca. 0.50-1.0 wt %) onto a Petri dish. The dish was
covered with a glass vessel to slow down solvent evaporation
(ca. 3-5 days). With reference to the method described in the
literature,6 the desilylation reaction of the membranes of poly-
(3a) and poly(3b) was carried out using trifluoroacetic acid as
acid catalyst. A detailed method of desilylation of membranes
is as follows: A membrane of polymer was immersed in a
mixture of trifluoroacetic acid and water (volume ratio 4:1) at
room temperature for 24 h. To neutralize the remaining acid
in the polymer matrix, the membrane was then immersed in
aqueous NaHCO3 solution at room temperature for 24 h,
washed with water, and then dried in air at room temperature.
Finally, the membrane was immersed in hexane for 24 h to
remove residual impurities and dried to constant weight at
room temperature for 24 h. Sharp 1H and 13C NMR spectra of
References and Notes
(1) (a) Masuda, T.; Sanda, F. In Handbook of Metathesis; Grubbs,
R. H., Ed.; Wiley-VCH: Weinheim, 2003; Vol. 3, Chapter 3.11.
(b) Nomura, R.; Masuda, T. In Encyclopedia of Polymer
Science and Technology; Kroshwitz, J. I., Ed.; Wiley: New
York, 2003; Vol. IA, p 1. (c) Sedlacek, J.; Vohlidal, J. Collect.
Czech. Chem. Commun. 2003, 68, 1745. (d) Choi, S. K.; Gal,
Y. S.; Jin, S. H.; Kim, H. K. Chem. Rev. 2000, 100, 1645.
(2) For reviews of gas separation membranes, see: (a) Pinnau,
I.; Freeman, B. D. Advanced Materials for Membrane Sepa-
rations; ACS Symposium Series 876; American Chemical
Society: Washington, DC, 2004. (b) Baker, R. W. Ind. Eng.
Chem. Res. 2002, 41, 1393. (c) Nagai, K.; Masuda, T.;
Nakagawa, T.; Freeman, B. D.; Pinnau, I. Prog. Polym. Sci.
2001, 26, 721. (d) Nunes, S. P.; Peinemann, K.-V. Membrane
Technology in the Chemical Industry; Wiley: New York, 2001.
(e) Aoki, T. Prog. Polym. Sci. 1999, 24, 951.
(3) (a) Masuda, T.; Teraguchi, M.; Nomura, R. In Polymer
Membranes for Gas and Vapor Separation; ACS Symposium

4102 Shida et al.
Macromolecules, Vol. 38, No. 10, 2005
Series 733; Freeman, B. D., Pinnau, I., Eds.; American
Chemical Society: Washington, DC, 1999; Chapter 2. (b)
Masuda, T.; Tachimori, H. J. Macromol. Sci. 1994, 11, 1675.
(4) (a) Tsuchihara, K.; Masuda, T.; Higashimura, T. J. Am.
Chem. Soc. 1991, 113, 8548. (b) Tsuchihara, K.; Masuda, T.;
Higashimura, T. Macromolecules 1992, 25, 5816.
(5) Niki, A.; Masuda, T.; Higashimura, T. J. Polym. Sci., Part
A: Polym. Chem. 1987, 25, 1553.
(6) Teraguchi, M.; Masuda, T. Macromolecules 2002, 35, 1149.
(7) (a) Sakaguchi, T.; Shiotsuki, M. Masuda, T. Macromolecules
2004, 37, 4104. (b) Sakaguchi, T.; Kwak, G.; Masuda, T.
Polymer 2002, 43, 3937.
(8) Sakaguchi, T.; Yumoto, K.; Kwak, G.; Yoshikawa, M.;
Masuda, T. Polym. Bull. (Berlin) 2002, 48, 271.
(9) (a) Robertson, J. Protecting Group Chemistry; Oxford Uni-
versity Press: New York, 2000. (b) Kocienski, P. J. Protecting
Groups; Georg Thieme Verlag: Stuttgart, 1994.
(10) Shida, Y.; Sakaguchi, T.; Shiotsuki, M.; Wagener, K. B.;
Masuda, T. Polymer 2005, 46, 1.
(11) Seki, H.; Tang, B.-Z.; Tanaka, A.; Masuda, T. Polymer. 1994,
35, 3456.
(12) (a) Pixton, M. R.; Paul, D. R. In Polymeric Gas Separation
Membranes; Paul, D. R., Yampolskii, Y. P., Eds.; CRC Press:
Boca Ration, FL, 1994; pp 83-153. (b) Lee, W. M. Polym. Eng.
Sci. 1980, 20, 65. (c) van Krevelen, D. W. Properties of
Polymers: Their Correlation with Chemical Structure; Their
Numerical Estimation and Prediction from Additive Group
Contributions, 3rd ed.; Elsevier Science: Amsterdam, 1990;
pp 71-107.
(13) Bondi, A. Physical Properties of Molecular Crystals, Liquids,
and Glasses; John Wiley and Sons: New York, 1968; pp 25-
97.
(14) Toy, L. G.; Nagai, K.; Freeman, B. D.; Pinnau, I.; He, Z.;
Masuda, T.; Teraguchi, M.; Yampolskii, Y. P. Macromolecules
2000, 33, 2516.
(15) Sakaguchi, T.; Yumoto, K.; Shiotsuki, M.; Sanda, F.; Yoshika-
wa, M.; Masuda, T. Macromolecules, in press.
(16) (a) Robeson, L. M.; Burgoyne, W. F.; Langsam, M.; Savoca,
AC.; Tien, C. F. Polymer 1994, 35, 4970. (b) Nagai, K.;
Nakagawa, T. J. Membr. Sci. 1995, 105, 261. (c) Pauly, S. In
Polymer Handbook, 4th ed.; Brandrup, J., Immergut, E. H.,
Grulke, E. A., Eds.; Wiley: New York, 1999; VI/543.
(17) (a) Kazama, S.; Teramoto, T.; Haraya, K. J. Membr. Sci. 2002,
207, 91. (b) Koros, W. J.; Mahajan, R. J. Membr. Sci. 2000,
175, 181.
(18) Robeson, L. M. J. Membr. Sci. 1991, 62, 165.
(19) (a) Sonogashira, K. J. Organomet. Chem. 2002, 653, 46. (b)
Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N.
Synthesis 1980, 627.
(20) Suzuki, T.; Sato, E.; Unno, K.; Kametani, T. J. Chem. Soc.,
Perkin Trans. 1 1986, 2263.
(21) Yashima, E.; Huang, S.; Matsushima, T.; Okamoto, Y.
Macromolecules 1995, 28, 4184.
(22) Lin, H.; Freeman, B. D. J. Membr. Sci. 2004, 239, 105.
(23) Masuda, T.; Iguchi, Y.; Tang, B.-Z.; Higashimura, T. Polymer
1988, 29, 2041.
MA050566D