Synthesis and oxygen permeation of novel polymers of phenylacetylenes having two hydroxyl groups via different lengths of spacers

Article abstract of DOI:10.1016/j.polymer.2014.11.042

Three novel phenylacetylenes having two hydroxyl groups via different kinds of spacers between the two hydroxyl groups and benzyl group were synthesized and polymerized. Two of the resulting polymers having oxyalkylene spacers between the hydroxyl group a

Full text of DOI:10.1016/j.polymer.2014.11.042

Polymer 56 (2015) 199e206
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Polymer
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Synthesis and oxygen permeation of novel polymers of
phenylacetylenes having two hydroxyl groups via different lengths of
spacers
, b,
Yu Zang a, Toshiki Aoki a *, Masahiro Teraguchi b, Takashi Kaneko b, Liqun Ma a,
Hongge Jia a
a Qiqihar University, College of Materials Science and Engineering, Wenhua Street 42, Qiqihar, Heilongjiang 161006, China
b Niigata University, Faculty of Engineering, Ikarashi 2-8050, Nishi-ku, Niigata 950-2181, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Three novel phenylacetylenes having two hydroxyl groups via different kinds of spacers between the two
hydroxyl groups and benzyl group were synthesized and polymerized. Two of the resulting polymers
having oxyalkylene spacers between the hydroxyl group and benzyl group had good membrane forming
ability, relatively high oxygen permselectivity and high oxygen permeability. By introducing the oxy-
alkylene spacers, the membrane forming abilities and oxygen permselectivity were enhanced. Oxygen
permselectivity ðPO =PN ¼ 2:67Þ of the polymer membrane having the longest spacers was higher than
Received 28 August 2014
Received in revised form
14 November 2014
Accepted 18 November 2014
Available online 3 December 2014
2
2
that (2.19) of polymer without any spacers. It may be because the columnar content and then defects
decreased when the cis-cisoid conformation was changed to cis-transoid conformation. In addition, by
decreasing the columnar content of the membrane from the polymer without any spacers, which could
be controlled by conditions in membrane preparation, the membrane forming ability and oxygen
permselectivity were effectively enhanced (from 2.19 to 2.61) without any drop of oxygen permeability.
© 2014 Elsevier Ltd. All rights reserved.
Keywords:
Phenylacetylenes
Two hydroxyl groups
Oxygen permselectivity
1. Introduction
selectivity, the control of the structures is not enough for such
application.
p
-Conjugated polymers like polyacetylenes [1e3] have attrac-
Recently we have been reporting new one-handed helical pol-
y(phenylacetylene)s by helix-sense-selective polymerization of
achiral phenylacetylenes having two hydroxyl groups (for example,
1 in Chart 1) using a chiral catalytic system consisting of [Rh(nor-
bornadiene)Cl]2 (norbornadiene ¼ NBD) as an initiator and (R)-
phenethylamine(PEA) as a cocatalyst [51,52]. The poly(1) adopts a
tight cis-cisoidal helical conformation [52]. We thought the new
types of substituted polyacetylenes having a more regular structure
in their main chains, ie, tight cis-cisoidal helical structures can have
better performance than other polyacetylenes. The high regularity
of poly(1) is expected to be applied to oxygen permeation mem-
brane having high selectivity. However, its oxygen permeability has
not been reported because its membrane forming ability was not
very good. In addition, we thought we needed the new type of
substituted polyacetylenes having a more regular structure in its
main chain, i.e., a tighter cis-cisoidal helical structure, because it
can show better performance than other polyacetylenes. Therefore
we designed three new monomers (2, 3, and 4), which had been
expected to give polymers having cis-cisoidal conformation, and
measured performances of the resulting polymer membranes.
ted increasing attention because of their noteworthy physical
properties such as electric conductivity, nonlinear susceptibility,
high oxygen permeability [4e15] and so on. Among them, poly(-
phenylacetylene)s are useful because they are usually more stable
than other substituted polyacetylenes in the air and can often form
self-supporting membranes [16e24]. Some researchers reported
the synthesis and oxygen permeability of various poly(-
phenylacetylene) membranes showing high oxygen permeabilities
and relatively high oxygen permselectivities [25e50]. On the other
hand, regular structures of poly(phenylacetylene)s such as the
conformation of their polymer main chains and the columnar
structures in their solid state have been reported [51e59]. Although
these regularities are interesting and important because it has
possibility to give oxygen permselective membranes with high
* Corresponding author. Niigata University, Faculty of Engineering, Ikarashi 2-
8050, Nishi-ku, Niigata 950-2181, Japan.
E-mail address: toshaoki@eng.niigata-u.ac.jp (T. Aoki).
http://dx.doi.org/10.1016/j.polymer.2014.11.042
0032-3861/© 2014 Elsevier Ltd. All rights reserved.

200
Y. Zang et al. / Polymer 56 (2015) 199e206
To obtain polyphenylacetylenes having regular structures as
precipitate. After removing the red solid by decantation, the su-
pernatant solution was allowed to stand for 2 days to yield a white
solid as a precipitate. The solid was filtered, washed with chloro-
form, and dried to give a white solid. Yield: 63.4% (43.6 g). 1H NMR
(400 MHz, DMSO-d6, d): 8.78 (s, 1H, PhOH), 7.29 (s, 2H, PhH), 5.33 (t,
2H, (CH2OH)2), 4.51 (d, 4H, Ph(CH2OH)2).
membrane materials having good membrane forming ability and
good permselectivities, and to discuss the relationship between the
permselectivity and their regularity containing regular conforma-
tions of their polymer main chains and the columnar contents in
the solid state, three phenylacetylene monomers having two hy-
droxyl groups via different kinds of spacers between the two hy-
droxyl groups and the benzyl group (Chart 1, 2e4) were
synthesized and polymerized in this study. In addition, effects of
extending the length of the spacers on the membrane forming
abilities and their oxygen permselectivity are discussed.
2.3.1.2. 4-Bromo-2,6-bis(hydroxymethyl)-1- dodecyloxybenzene (8).
1-Bromododecane (5.90 mL, 23.6 mmol) was added to the solution
of 7 (5.00 g, 21.5 mmol) and potassium carbonate (8.25 g,
59.7 mmol) in acetone (100 mL). The solution was refluxed under
stirring for 48 h. After cooling to room temperature, unreacted
potassium carbonate was filtered off and the solvent was evapo-
rated to give a crude product. The crude product was purified by
silica-gel column chromatography. Yield: 64.3% (white solid),
Rf ¼ 0.27 (ethyl acetate/hexane ¼ 1/4). 1H NMR(400MHZ, CDCl3,
2. Experimental
2.1. Materials
All the solvents used for synthesis and polymerization of the
monomers were distilled as usual. The polymerization initiator,
[Rh(nbd)Cl]2 (nbd ¼ 2,5 norbornadiene), purchased from Aldrich
Chemical was used as received. Poly(5) and poly(6) were synthe-
sized according to our previous report [53,54].
TMS, d): 7.49 (s, 2H, PhH), 4.70 (d, 4H, Ph(CH2OH)2), 3.85 (t, 2H,
OCH2CH2(CH2)9CH3), 1.97 (t, 2H, (CH2OH)2), 1.80 (m, 2H,
OCH2CH2(CH2)9CH3), 1.50-1.20 (m, 18H, OCH2CH2(CH2)9CH3), 0.88
(t, 3H, OCH2CH2(CH2)9CH3).
2.3.1.3. 1-Dodecyloxy-2,6-bis(hydroxymethyl)-4-(3-hydroxy-3-
methyl-1-butynyl)benzene (9). 2-Methyl-3-butyn-2-ol (2.30 mL,
27.6 mmol) was added to a mixture of 8 (13.8 mmol), tribenzyl-
phosphine (0.430 g, 1.66 mmol), copper(I) iodide (0.290 g,
1.52 mmol) and bis(tribenzylphosphine)palladium(II) chloride
(0.430 g, 0.620 mmol) in dry triethylamine (Et3N, 100 mL). The
solution was stirred at room temperature for 12 h and refluxed for
24 h. The resulting solid was removed by filtration and the solution
was concentrated. The formed brown liquid was purified by silica-
gel column chromatography. The crude solid was recrystallized
from dichloromethane/hexane (1/10). Yield: 81.5% (white solid),
Rf ¼ 0.27 (ethyl acetate/hexane ¼ 1/1). 1H NMR(400MHZ, CDCl3,
2.2. Measurements
2.2.1. Measurement of oxygen and nitrogen permeability
Oxygen and nitrogen permeability coefficients (PO and PN
:
2
2
cm3(STP) cm cmꢀ2 sꢀ1 cm Hgꢀ1) and the oxygen separation factor
ða ¼ PO =PN Þ were measured by a gas chromatographic method by
2
2
using YANACO GTR-10 according to our previous report [47]. The
diffusion coefficient (D: cm2
s
ꢀ1) was calculated by the time-lag
, where L(cm) is the thickness of
method represented by D ¼ L2/6
q
the membrane and q(s) is the time-lag.
2.2.2. Other measurements
TMS, d): 7.45 (s, 2H, PhH), 4.67 (d, 4H, Ph(CH2OH)2), 3.86 (t, 2H,
1H NMR (400 MHz) spectra were recorded on a JEOL LEOLEX-
400 spectrometer. The average molecular weights (Mn and Mw)
were evaluated by gel permeation chromatography (GPC) by using
JASCO liquid chromatography instruments with PU-2080, DG-
2080-53, CO-2060, UV-2070 and two polystyrene gel columns
(Shodex KF-807 L, THF eluent, polystyrene calibration). We recor-
ded CD spectra by using a JASCO J-720WI spectropolarimeter with a
Peltier controller for temperatures at 20 ꢁC (a quartz cell of 1 mm
path length; sample concentration: 0.100e2.00 mM based on the
monomer unit). The infrared spectra were recorded on FT/IR-4200
(JASCO). The elongations at break of the membranes were
measured at a strain rate of 5 mm/min with a TOM-5 Minebea
Co.,Ltd. UV-vis spectra were measured with a JASCO V-550 spec-
tropolarimeter. Elemental Analyses were performed by using
YANACO MT-3, MT-5, MT-6, and J-SCIENCE LAB CO. Ltd. JM-10 at the
Organic Elemental Analysis Research Center (Kyoto University,
Japan). X-Ray diffraction diagrams were measured with a Rigaku
high resolution X-ray diffractometer RINT2500HR/PC Gigerflex
OCH2CH2(CH2)9CH3), 2.14 (s, 1H, C(CH3)2OH), 1.94 (t, 2H, (CH2OH)2),
1.79 (m, 2H, OCH2CH2(CH2)9CH3), 1.60 (s, 6H, C(CH3)2), 1.50-1.20 (m,
18H, OCH2CH2(CH2)9CH3), 0.88 (t, 3H, OCH2CH2(CH2)9CH3).
2.3.1.4. 4-Dodecyloxy-3,5-bis(hydroxymethyl)phenylacetylene
(1).
A mixture of 9 (11.4 mmol) and sodium hydride (60% in oil, 0.450 g,
11.3 mmol) in dry toluene (400 mL) was refluxed for 20 min. After
cooling the mixture to room temperature, the resulting solid was
removed by filtration and the solvent was concentrated. The crude
product was dissolved in diethyl ether, and then the solution was
washed with 0.1 M HCl aqueous solution. The organic layer was
dried with anhydrous sodium sulfate. After removing the formed
salt by filtration, the organic layer was concentrated. The obtained
solid was purified by silica-gel column chromatography and by
recrystallization from hexane. Yield: 67.2% (white solid), Rf ¼ 0.24
(ethyl acetate/hexane ¼ 1/4). 1H NMR(400MHZ, CDCl3, TMS,
d): 7.49
(s, 2H, PhH), 4.70 (d, 4H, Ph(CH2OH)2), 3.90 (t, 2H,
OCH2CH2(CH2)9CH3), 3.04 (s, 1H, C^CH), 1.96 (t, 2H, (CH2OH)2), 1.81
RAD-gVA.
(m,
2H,
OCH2CH2(CH2)9CH3),
1.50-1.20
(m,
18H,
OCH2CH2(CH2)9CH3), 0.88 (t, 3H, OCH2CH2(CH2)9CH3). Anal.calcd
for C22H34O3: C 76.26, H 9.89; Found: C 76.56, H 9.76.
2.3. Synthesis of the poly(2)-poly(4) (Scheme 1)
2.3.1. Synthesis of new monomers 2-4 (Scheme 1)
2.3.1.1. 4-Bromo-2,6-bis(hydroxymethyl)-1-phenol (7). A formalde-
hyde aqueous solution (37.0 wt%, 300 mL, 4.00 mol) was added
dropwise to a solution of 4-bromophenol (51.1 g, 0.295 mol) and
potassium hydroxide (18.5 g, 0.393 mol) in 2-propanol (100 mL),
and the solution was heated and stirred at 40 ꢁC for 89 h. The
resulting solution was cooled to room temperature and poured into
0.1 mol/L hydrochloric acid (1000 mL) with stirring. The solution
was allowed to stand for about 6 h to give a red viscous solid as a
2.3.1.5. 4-Dodecyloxy-3,5-bis(bromomethyl)phenylacetylene
(10).
1 (1.00 g, 2.89 mmol), CBr4 (3.23 g, 9.73 mmol), PPh3 (2.27 g,
8.67 mmol), and CH2Cl2 (40.0 mL) were put in a 100 mL flask. The
solution was stirred for 4 h in an ice bath and then the solvent was
removed by evaporation. The crude solid was purified by silica-gel
column chromatography to give compound 10. Yield: 88.5% (white
solid), Rf ¼ 0.14 (Hexane). 1H NMR(400MHZ, CDCl3, TMS,
d): 7.50 (s,
2H, PhH), 4.48 (s, 4H, PhCH2Br), 4.09 (t, 2H, PhOCH2CH2), 3.06 (s,1H,

Y. Zang et al. / Polymer 56 (2015) 199e206
201
≡CH),
1.89(tt,
2H,
OCH2CH2CH2),
1.54-1.27
(m,18H,
Poly(2): 1H NMR(400MHZ, CDCl3, TMS,
d): 6.74 (br, PhH and
OCH2CH2(CH2)9CH3), 0.88 (t,3H, OCH2CH2(CH2)9CH3).
trans proton in the main chain), 5.57 (br, cis proton in the main
4-Dodecyloxy-3,5-bis(2-hydroxyethyloxymethyl)phenyl-
acetylene (2)
chain), 4.25 (br, PhCH2O), 3.74-3.30 (br, PhOCH2CH2 and OCH2
-
CH2OH),1.85-1.26 (br, CH2CH2OH and OCH2(CH2)10CH3), 0.88 (s, 3H,
OCH2(CH2)10CH3). IR(KBr): 3310(OH), 2840(CH).
Sodium hydride (144 mg, 3.00 mmol) was added to a solution of
compound 10 (300 mg, 0.600 mmol) and ethylene glycol (0.330 mL,
6.00 mmol) in THF (60.0 mL). The mixture was refluxed for 3 days,
and water (60 mL) was added. The resulting aqueous layer was
extracted with ethyl acetate. The organic layer was dried over
MgSO4, and evaporated to dryness. The product was purified with
silica gel chromatography to give monomer 2. Yield: 68.6% (white
solid), Rf ¼ 0.23 (ethyl acetate/hexane ¼ 1/2). 1H NMR(400MHZ,
Poly(3): 1H NMR(400MHZ, CDCl3, TMS,
d), 6.51 (br, PhH and
trans proton in the main chain), 5.44 (br, cis proton in the main
chain), 4.08(br, PhCH2O), 3.36-2.97 (br, PhOCH2 CH2, OCH2(CH2)2
-
CH2OH and CH2CH2OH), 1.37-1.20 (br, CH2(CH2)2CH2OH and
OCH2(CH2)10CH3), 0.81 (s, 3H, OCH2(CH2)10CH3). IR(KBr): 3397(OH),
2840(CH).
Poly(4): 1H NMR(400MHZ, THF-d8, TMS,
d), 6.47 (br, PhH and
CDCl3, TMS,
d): 7.43 (s, 2H, PhH), 4.50 (d, 4H, PhCH2O), 3.76 (t, 2H,
trans proton in the main chain), 5.60 (br, OPhOH and cis proton in
the main chain), 4.50 (br, PhCH2O), 3.43(br, OCH2CH2(CH2)9CH3),
1.17-1.00 (br, OCH2CH2(CH2)9CH3 and OCH2CH2(CH2)9CH3), 0.81 (s,
3H, OCH2CH2(CH2)9CH3). IR(KBr): 3340(OH), 2840(CH).
PhOCH2), 3.70(td, 4H, OCH2CH2OH), 3.55 (t, 4H, OCH2CH2OH), 2.96
(s, 1H, C^CH), 1.93 (t, 2H, OCH2CH2OH), 1.72(tt, 2H, OCH2CH2CH2),
1.45-1.19 (m, 18H, (CH2)9CH3)，0.81 (t, 3H, (CH2)9CH3). IR(KBr):
3310(OH), 3280(HeC≡)，2840(CH), 2095(C^C). Anal.calcd for
C
26H42O5: C 71.85, H 9.74, O 18.41; found: C 71.89, H 9.75, O 18.21.
2.4. Membrane preparation
2.3.1.6. 4-Dodecyloxy-3,5-bis(4-hydroxybutyloxymethyl)phenyl-
acetylene (3). Sodium hydride (150 mg, 3.20 mmol) was added to a
solution of compound 10 (300 mg, 0.640 mmol) and 1,4-butanediol
(0.560 mL, 6.35 mmol) in THF (60.0 mL). The mixture was refluxed
for 3 days, and water (60 mL) was added. The resulting aqueous
layer was extracted with ethyl acetate. The organic layer was dried
over MgSO4, and evaporated to dryness. The product was purified
with silica gel chromatography. Yield: 76.0% (colorless liquid),
Rf ¼ 0.12 (ethyl acetate/hexane ¼ 1/2). 1H NMR(400MHZ, CDCl3,
A typical membrane fabrication method for poly(2) was as fol-
lows: A solution of the poly(2) (0.0600-10.0 wt%) in dry toluene
(40.0 mg/mL) was cast on a poly(tetrafluoroethylene) sheet (4 cm2).
After evaporating of the solvent for 12 h at 25 ꢁC, the membranes
were detached from the sheet and dried in vacuo for 24 h. Thickness
(L) of the membranes was 50.0e80.0
mm. Other polymer mem-
branes were carried out similarly.
3. Results and discussion
TMS, d), 7.48 (s, 2H, PhH), 4.50 (s, 4H, PhCH2O), 3.81 (t, 2H, PhOCH2),
3.64(td, 4H, CH2(CH2)2CH2OH), 3.53 (t, 4H, OCH2(CH2)2CH2OH),
3.01 (s, 1H, C^CH), 1.93 (t, 2H, CH2CH2OH), 1.78(tt, 2H,
OCH2CH2CH2), 1.65 (m, 8H, CH2(CH2)2CH2OH), 1.45-1.26 (m, 18H,
OCH2CH2(CH2)9CH3)，0.81 (t, 3H, OCH2CH2(CH2)9CH3).IR(KBr):
3397(OH), 3296(HeC≡)，2840(CH), 2095(C^C). Anal.calcd for
3.1. Synthesis and polymerization of novel phenylacetylene
monomers having two hydroxyl groups (Table 1, Scheme 1)
As described in the introduction part, we reported a phenyl-
acetylene(1) (Chart 1) having two hydroxyl groups without any
spacers between the two hydroxyl groups and benzyl group was
polymerized to give the corresponding tight cis-cisoidal one
handed helical polymer [51,52]. In addition, the solid from this
regular polymer was reported to include a columnar structure
[55e59]. However its oxygen permeability has not been reported
because its membrane forming ability was not very good. To obtain
polymers as membrane materials having good membrane forming
ability from such novel phenylacetylenes having two hydroxyl
groups, three novel phenylacetylenes having two hydroxyl groups
via different kinds of the spacers between the two hydroxyl groups
and benzyl group (Chart 1, 2e4) were synthesized and polymerized
by using the [Rh(nbd)Cl]2/(R)-PEA as catalytic system (Scheme 1).
The new monomers 2e4, were obtained via the monomer 1 in
23e38% yields according to Scheme 1. The polymerization gave
high Mw of poly(2) and poly(3) in high yields(Table 1, Nos. 2 and 3).
Especially Mw of poly(3) was 20 times higher than that of poly(1)
(Table 1, Nos. 1 and 3), although the Mw of poly(4) was lower than
that of poly(1).
C
30H50O5: C 73.43, H 10.27, O 16.30; found: C 72.77, H 10.28, O
16.43.
2.3.1.7. 4-Dodecyloxy-3,5-bis(2-hydroxybenzyl-1-oxy)methyl-
phenylacetylene (4). Catechol (349 mg, 3.18 mmol), compound 10
(300 mg, 0.635 mmol), potassium carbonate (439 mg, 3.18 mmol),
and acetone (60.0 mL) were put in a 100 mL flask. The solution was
refluxed for 48 h and cooled to room temperature. Unreacted po-
tassium carbonate was removed by filtration and the solution was
concentrated by evaporation. The crude product was purified by
silica-gel column chromatography. Yield: 80% (white solid),
Rf ¼ 0.38 (ethyl acetate/hexane ¼ 1/4). 1H NMR(400MHZ, THF-d8,
TMS,
d), 7.57 (s, 2H, PhH), 6.95-6.81 (m, 8H, (OPhHOH)2), 5.71 (s, 2H,
(OPhOH)2),
5.08 (s, 4H, (PhCH2O)2), 3.87 (t, 2H,
OCH2CH2(CH2)9CH3), 3.05 (s, 1H, C^CH), 1.78 (m, 2H,
OCH2CH2(CH2)9CH3), 1.34-1.17 (m, 18H, OCH2CH2(CH2)9CH3), 0.86
(t, 3H, OCH2CH2(CH2)9CH3). IR(KBr): 3340(OH), 3285(HeC≡)，
2840(CH), 2095(C^C). Anal.calcd for C34H42O5: C 76.95, H 7.98, O
15.07; found: C 76.95, H 8.62, O 15.07.
While the formed poly(1) was partly precipitated during poly-
merization i.e., the polymerization solution could not maintain its
homogeneity, no precipitation was observed by the end of poly-
merization of 2 and 3.
2.3.2. Polymerization of new monomers 2e4 (Scheme 1)
A typical procedure for 2 was as follows: A solution of [Rh(nbd)
Cl]2 (2.12 mg, 4.60
(118 l, 0.920 mmol) in dry toluene (1.44 mL) was added to a dry
toluene (1.44 mL) solution of 2 (100 mg, 230 mol). The reaction
solution was stirred at room temperature for 4 h. The crude poly-
mer was purified by reprecipitation of the toluene solution into a
large amount of methanol and the formed solid was dried in vacuo
to give a red solid.
m
mol) and (S)- or (R)-phenethylamine (PEA)
It is thought to be caused by the fact that the introduction of
longer flexible spacers between the two hydroxyl groups and the
benzyl group in 2 and 3 enhanced the solubilities of the monomers
and their polymers compared with those of 1 and poly(1) which
has no spacers, and therefore homogeneity of the polymerization
system could be kept during polymerization. The polymerization
system of 4 could not keep its homogeneity during polymerization
since the benzene ring as a spacer decreased the solubility of the
monomer and its polymer. Therefore, the polymerization gave a
m
m
Other polymerization of new monomers 3 and 4 were carried
out similarly.

202
Y. Zang et al. / Polymer 56 (2015) 199e206
Scheme 1. Synthetic routes to new polymers (poly(2)-poly(4)).
low Mw poly(4) in a low yield. In the case of 5 having a shorter alkyl
group than 1, the yield and Mw were also low (Table 1, No. 5)
because solubilities of 5 and poly(5) were low. The yield of poly-
merization of 6 having a benzyloxy group as a spacer, and Mw and
solubility of poly(6) were similar to those of 1 and poly(1).
We previously reported that polymers from monomers having
no spacers between the hydroxyl groups and benzyl group, i.e.,
poly(1) [51], poly(5) [53] and poly(6) [54], were optically active
(Table 1, Nos. 1, 5 and 6; [G] ¼ 54, 59 and 7deg, Fig. S1) and their
main chain took cis-cisoid one-handed helical conformations
which are maintained by intramolecular hydrogen bonds of the
hydroxyl groups [52]. On the other hand, three novel polymers of
the corresponding monomers having two hydroxyl groups in this
study, i.e., poly(2), poly(3), and poly(4) were optically inactive
([G] ¼ 0, Table 1, Nos. 2e4). Because we found most of polymers
prepared from achiral phenylacetylenes having two hydroxyl
groups by using chiral catalytic system such as poly(1) showed CD
signals based on their stable one handed tight cis-cisoidal confor-
mation, this finding can indicate that these polymers' main chain
consisted of more extended and unstable cis-transoid helical con-
formations. We also reported that in 1H NMR spectra, the peaks of
polymers having tight cis-cisoidal conformations were very broad
because of their very low molecular motion. In fact, the peaks for
poly(5) and poly(6) in 1H NMR spectra were very broad similar to
poly(1). However, the peaks of poly(2), poly(3), and poly(4) were
sharp in 1H NMR spectra. To discuss the broadness, the peak
width(W1/2) at the half-height of the methyl peak in 1H NMR
spectra of poly(1)-poly(4) are shown in Table 1. The W1/2 values of
poly(2), poly(3), and poly(4) were much smaller than that of
poly(1). The finding indicates the molecular motion of poly(2)-
Table 1
Polymerization of novel phenylacetylenes (1e6) having two hydroxyl groups.
Mw (106)
Mw/Mn
W1/2b (ppm)
jGj307c (deg)
nOHd (cmꢀ1
)
Solubilitye
Membrane forming abilityf
a
a
No.
Monomer
Yield (%)
1
2
3
4
5
6
1
2
3
92.0
85.5
89.5
42.0
24.8
92.5
2.5
2.3
39
0.57
1.0
7.9
3.8
4.0
6.5
3.1
5.0
4.0
0.22
0.034
0.036
0.056g
e
54
0
0
0
59
7
3300
3438
3400
3352
e
þþ
þþþ
þþ
þþ
þ
þ
þþþ
þþ
e
4
5h
6i
e
e
e
þþ
þ
a
By GPC correlating polystyrene standard (eluent: THF).
b
c
d
e
f
Peak width at hꢀa1lf-height of eCH3 in 1H NMR spectra in CDCl3.
jGj307 ¼ [
q]
3
ꢂ 102 at 307 nm in THF.
307
The OeH vibration absorption bands from IR spectra at r.t. (3.0 g/L) in CHCl3.
In CHCl3; þþþ: high soluble; þþ: soluble; þ:partly soluble.
þþþ: Very flexible; þþ: flexible; þ: brittle; ꢀ: no membrane forming ability.
g
h
i
In THF-d8.
From Ref. [53].
From Ref. [54].

Y. Zang et al. / Polymer 56 (2015) 199e206
203
Table 2
Oxygen permeation through membranes of novel polymers of polyphenylacetylenes
(1e3) having two hydroxyl groups.
b
c
No. Membrane Solvent Membrane
forming abilitya
PO
PO =PN
DO
DO =DN
2
2
2
2
2
2
1
2
3
Poly(1)
Poly(2)
Poly(3)
CHCl3
THF
THF
þ
1.39 2.19
0.13 2.60
0.16 2.67
1.16 1.04
0.41 1.45
0.50 1.34
þþþ
þþ
a
b
c
þþþ: Very flexible; þþ: flexible; þ: brittle.
In 10ꢀ8 cm3 (STP) cm cmꢀ2 sꢀ1 cm Hgꢀ1
In 10ꢀ6 cm2 sꢀ1
.
.
Fig. 2. XRD of novel polymers of phenylacetylenes (1e4) having two hydroxyl groups.
converted to cis-transoid racemic helical structure. Therefore, the
main chains became more flexible by extending the spacers of the
side groups.
3.2. Fabrication and characterization of their membranes (Table 1)
Poly(2) and poly(3) could be easily fabricated into self-
supporting membranes which were tough enough to be applied
as oxygen permselective membranes. Their good membrane
forming abilities are attributed to the good solubility and high Mw,
respectively (Table 1). On the other hand, poly(4) and poly(5)
showed no self-supporting membrane forming ability due to their
low Mw and poor solubility, respectively. Although poly(1) and
poly(6) had self-membrane forming ability, they were much brit-
tler than poly(2) and poly(3). Poly(2) and poly(3) membranes have
higher flexibility and higher elongation at break than those of
poly(1) whose reason is discussed later.
Fig. 1. Oxygen permeation through membranes of novel polymers of phenylacetylenes
(1e3) having two hydroxyl groups.
3.3. Enhancement of oxygen permselectivities of the membranes by
changing the chemical structures of the polymers (Table 2, Fig. 1)
poly(4) is higher than that of poly(1). We also reported the stable
cis-cisoidal conformation in poly(1) was maintained only by their
intramolecular hydrogen bonds. In the IR spectra of poly(1)-poly(4)
in chloroform (Fig. S2), the wavenumber of OeH vibration ab-
sorption bands of poly(2), poly(3), and poly(4) were higher than
that of poly(1). The observation shows their hydrogen bonds in
poly(2), poly(3), and poly(4) were weaker than those in poly(1). In
conclusion, all the results on CD, UV, NMR, and IR above mentioned
indicate that with increase of the spacer length, the hydrogen
bonds had become weaker and their tight cis-cisoidal one-handed
helical main chain structures could not be maintained and was
Oxygen and nitrogen permeability coefficients (PO and PN
)
2
2
through the membranes of polyphenylacetylenes, poly(1), poly(2)
and poly(3) were newly determined as shown in Table 2 and Fig. 1.
By extending the length of the spacers between the two hydroxyl
groups and benzyl group, membrane forming abilities and oxygen
permselectivities were highly enhanced. In particular, the polymer
membrane from the monomer (3) having the longest spacer, i.e.,
butyloxy, showed the highest oxygen permselectivity
(PO =PN ¼ 2.67) which was 1.2 times higher than poly(1) without
2
2
spacers (PO =PN ¼ 2.19), although the PO values of poly(2) and
2
2
2
Table 3
Characterization of membranes of novel polymers of phenylacetylenes (1e6) having two hydroxyl groups.
No. Polymer Lattice spacing (d)a (Å) Columnar diameterb (Å) Columnar contentc (%) Tensile strength (Kg/cm2) Elongation at break (%) Membrane
forming abilityd
1
2
3
4
5
6
Poly(1)
Poly(2)
Poly(3)
Poly(4)
Poly(5)e
Poly(6)f
20.42
26.74
26.58
28.65
17.90
25.70
23.58
30.88
30.69
33.08
20.70
29.70
85.9
43.6
36.8
13.8
65.5
60.3
113.7
103.3
223.1
e
10.8
175
50.0
þ
þþþ
þþ
e
e
e
e
e
128.5
7.60
þ
a
b
c
d
e
f
Calculated from the following equations: 2d sin
d/sin 60.
The ratio of the area of columnar region to the area of the entire region.
q
¼ n
l
, where n ¼ 1 and
l
¼ 1.54 Å.
þþþ: Very flexible; þþ: flexible; þ: brittle; ꢀ: no membrane forming ability.
From Ref. [53].
From Ref. [54].

204
Y. Zang et al. / Polymer 56 (2015) 199e206
Table 4
3.4. Reasons for the improvements of oxygen permselectivities by
changing the chemical structures of the polymers (Table 3, Fig. 2)
Oxygen permeation through membranes of novel polymers of polyphenylacetylenes
(1) having two hydroxyl groups prepared by using different solvents.
a
b
No. Membrane Solvent
P
O2
P
O2
=P
D
D =D
O2 N2
N2
O2
As described above (Table 1), although 1 was reported to pro-
duce a tight cis-cisoidal one handed helical polymer by the same
polymerization condition as that in this study [51,52], it was esti-
mated that the polymers from 2e4 did not have tight cis-cisoidal
one handed helical main chains but had loose cis-transoidal
racemic helical main chains, judging from their sharper peaks in
NMR(W1/2) and the absorption bands for OH at higher wave lengths
and the UV absorption peaks(Fig. S1). In addition, poly(2) and
poly(3) showed better membrane forming abilities and oxygen
permselectivitie than poly(1). Therefore, it is thought that one of
the reason for these improvements were change of a tight cis-cisoid
helicity to a loose cis-transoid helicity in the main-chain confor-
mation. Table 3 lists the results of measurements of XRD (Fig. 2) and
mechanical strength for the six polymer membranes. The columnar
content of poly(2), poly(3), and poly(4) (Table 3, Nos. 2e4) were
much lower than that of poly(1), poly(5) and poly(6) (Table 3, Nos.
1, 5 and 6) whose main chain took regular cis-cisoidal helical
conformation. Poly(2) and poly(3) membranes had higher flexi-
bility and higher elongation at break (175 and 50%) than poly(1)
(10.8%). It may be caused by their loose helical conformation and
lower columnar contents. Although usually polymer membranes
having a higher crystallinity show higher permeability and lower
permselectivity, these results for poly(1), poly(2), and poly(3) were
opposite. It may be caused by the presence of some molecular size
defects in poly(1).
1
2
3
Poly(1-a)
Poly(1-b)
Poly(1-c)
CHCl3
toluene/CHCl3 (1/1 (v/v)) 1.41 2.61
pyridine 1.46 2.07
1.39 2.19
1.16 1.04
1.80 1.19
1.37 1.19
a
In 10ꢀ8 cm3 (STP) cm cmꢀ2 sꢀ1 cmHgꢀ1
.
b
In 10ꢀ6 cm2 sꢀ1
.
In conclusion, by changing the length of the spacers of the
monomers between the two hydroxyl groups and benzyl group, the
conformations of the polymer main chains were controlled from
cis-cisoid to cis-transoid, resulting in decrease of their columnar
contents. As a result, the membrane forming ability and oxygen
permselectivity were highly enhanced, although the oxygen
permeability decreased.
Fig. 3. Oxygen permeation through membranes of phenylacetylene (1) having two
hydroxyl groups prepared by using different solvents.
poly(3) were lower than that of poly(1). To discuss the reason of this
change in PO and PO =PN , diffusion coefficients (D) were deter-
3.5. Enhancements of oxygen permselectivities of the membranes
from the same polymers by changing preparation conditions
(Table 4, Fig. 3)
2
2
2
mined from the time lags (Table 2). The higher PO =PN values and
2
2
lower PO values of poly(2) and poly(3) membranes were caused by
2
the higher DO =DN values and lower DO2 values of them. Judging
2
2
from this fact and the better membrane forming ability of poly(2)
and poly(3), these higher PO =PN and lower PO may be caused by
dense and defect-free structures of poly(2) and poly(3) membranes.
As we discussed above, to enhance the membrane forming
ability and oxygen permselectivity, the columnar content should be
lower. It has been achieved by changing the monomer structures,
2
2
2
Chart 1. Chemical structures of monomers having two hydroxyl groups in this study (1e6).

Y. Zang et al. / Polymer 56 (2015) 199e206
205
Table 5
Characterization of membranes of novel polymers of polyphenylacetylene (1) having two hydroxyl groups prepared by using different solvents.
No.
Membrane
Solvent
Condition
Lattice spacing (d)a (Å)
Columnar diameterb (Å)
Columnar contentc (%)
Membrane strengthd
1
2
3
Poly(1-a)
Poly(1-b)
Poly(1-c)
CHCl3
25ꢁC/101 KPa
25ꢁC/101 KPa
45ꢁC/61 KPa
20.42
20.53
20.62
23.58
23.71
23.81
85.9
67.8
29.0
þ
toluene/CHCl3 (1/1 (v/v))
pyridine
þþþ
þþ
a
Determined by XRD, calculated from the following equations: 2d sin
d/sin 60.
The ratio of the area of columnar region to the area of the entire region.
þþþ:Very flexible; þþ: flexible; þ:brittle.
q
¼ n
l
, where n ¼ 1 and
l
¼ 1.54 Å.
b
c
d
i.e., the length of the spacer. Although poly(1) had highly regular
chemical structures, their membrane performance was poor
because of very high columnar content (85.9%) when it was pre-
pared from chloroform solution. Therefore, we tried to decrease of
the columnar content of poly(1) by changing solvents in membrane
preparation. Solvents with different polarities and boiling points,
such as toluene and pyridine, were used for membrane fabrication.
Table 4 and Fig. 3 show the results of measurement of oxygen
permeation behavior for the three poly(1) membranes prepared by
three different conditions, i.e., poly(1-a), poly(1-b), and poly(1-c).
The PO =PN was successfully improved from 2.19(poly(1-a)) to
times higher than that of poly(1) having no spacers. These polymers
could be easily fabricated into self-supporting membranes which
were tough enough to be applied as oxygen permselective mem-
branes. By extending the length of the spacers, the membrane
forming abilities and oxygen permselectivities were highly
enhanced. In particular, the poly(2) having the longest spacers, i.e.,
butyloxy groups showed the highest oxygen permselectivity
(PO =PN ¼ 2.67) which was 1.2 times higher than that of poly(1)
2
2
(PO =PN ¼ 2.19). Because the conformation of poly(2) and poly(3) is
2
2
an extended cis-transoidal and that of poly(1) is a tight cis-cisoidal,
the columnar contents of poly(2) and poly(3) were lower than that
of poly(1). In addition, by using solvents having lower solubilities,
i.e., toluene, the columnar contents of poly(1) (85.9%) were
decreased to 67.8, respectively. As a result, oxygen permselectivities
were also substantially enhanced without any drop of oxygen
permeability. This may be because the intermediate columnar
content decrease the defects in the membrane and as a result the
regular structure was effectively used for the separation. This is an
ideal improvement.
2
2
2.61(poly(1-b)) with no decrease of PO when toluene/CHCl3 (1/1(v/
2
v)) was used as a two component solvent (Table 4, Nos.1 and 2). The
increase in PO =PN was caused by increase in DO =DN . When we
2
2
2
2
used pyridine as a solvent (Table 4, No. 3), PO increased but PO =PN
2
2
2
decreased (poly(1-c)).
3.6. Reason for the improvements of oxygen permselectivities by
changing preparation conditions(Table 5, Fig. S3)
Acknowledgments
To discuss the reason for the improvement of PO =PN for poly(1)
2
2
and the best performance of poly(1-b), XRD for the three mem-
branes were measured(Fig. S3). Table 5 shows the results of XRD
measurement for the three poly(1) membranes prepared by three
different conditions, i.e., poly(1-a), poly(1-b), and poly(1-c). By
changing the polarity and boiling point of the casting solvent for
the membrane fabrication, the columnar contents were highly
changed. When solvents having a high boiling point, i.e., toluene
and pyridine were used, the original columnar content of poly(1a)
(85.9%) largely decreased to 67.8 and 29.0%. Contrary to the
decrease, the membrane forming ability highly increased. Poly(1-b)
membrane having an intermediate columnar content, showed the
best performance as an oxygen permselective membrane. By
decreasing the columnar contents, the membrane became denser
and flexible and as a result the defects, which had been included in
the original membrane poly(1-a), may be decreased. Therefore the
potential ability of the regular structure in poly(1), which can
efficiently separate oxygen and nitrogen, could be used and
emerged in poly(1-b) membrane.
Partial financial support through the Overseas Scholars Foun-
dation of the Education Department of Heilongjiang province of
China (1254HQ008) is gratefully acknowledged.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.polymer.2014.11.042.
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