Liquid crystalline and light emitting polyacetylenes: Synthesis and properties of biphenyl-containing poly(1-alkynes) with different functional bridges and spacer lengths

Article abstract of DOI:10.1021/ma011406e

Biphenyl-(Biph-) containing 1-alkynes (3 and 4) and their polymers (1 and 2) with varying bridge groups and spacer lengths were synthesized and the effects of the structural variation on their properties, especially their mesomorphism and photoluminescence behaviors, were studied. The acetylene monomers 3(3) [HC≡C(CH₂)₃O-Biph-OCO(CH₂)₁₀CH ₃] and 4(m) [HC≡C(CH₂)_m OCO-Biph-OCO(CH₂)_10-CH₃, m = 3,4] were prepared by sequential etherization and esterification reactions of 1-alkynes. While 3(3) exhibits enantiotropic crystal E and SmB mesophases, its structural cousin 4(3) displays only monotropic SmB phase. Enantiotropic SmA and SmB mesophases are, however, developed when the spacer length is increased to 4. Polymerizations of the monomers are affected by Mo-, W-, Rh-, and Fe-based catalysts, with the WCl₆-Ph₄Sn catalyst giving the best results (isolation yield up to 85% and M_w up to 59000). The polymers were characterized by IR, UV, NMR, TGA, DSC, POM, XRD, and PL analyses. Compared to 1(3), 2(3) shows a red-shifted absorption, a higher T_i, and a better packed interdigitated bilayer SmA_d structure, while the mesophase of 2(4) involves mionolayer-packing arrangements of the mesogens. Upon photoexcitation, 1(3) emits almost no light but 2(m) gives a strong ultraviolet emission (λ_max ～ 350 nm), whose intensity increases with the spacer length.

Full text of DOI:10.1021/ma011406e

Macromolecules 2002, 35, 1229-1240
1229
Liquid Crystalline and Light Emitting Polyacetylenes: Synthesis and
Properties of Biphenyl-Containing Poly(1-alkynes) with Different
Functional Bridges and Spacer Lengths
J a ck y W. Y. La m ,† Yu p in g Don g,† Kevin K. L. Ch eu k ,† J in gd on g Lu o,†
Zh ilia n g Xie,†,‡ Hoi Sin g Kw ok ,‡ Zh ish en Mo,§ a n d Ben Zh on g Ta n g*,†,‡
Department of Chemistry, Center for Display Research, Institute of Nano Science and Technology, and
Open Laboratory of Chirotechnology of the Institute of Molecular Technology for Drug Discovery and
Synthesis,| Hong Kong University of Science & Technology, Clear Water Bay, Kowloon,
Hong Kong, China; and Laboratory of Polymer Physics, Changchun Institute of Applied Chemistry,
Chinese Academy of Sciences, Changchun 130022, China
Received August 6, 2001; Revised Manuscript Received November 9, 2001
ABSTRACT: Biphenyl- (Biph-) containing 1-alkynes (3 and 4) and their polymers (1 and 2) with varying
bridge groups and spacer lengths were synthesized and the effects of the structural variation on their
properties, especially their mesomorphism and photoluminescence behaviors, were studied. The acetylene
monomers 3(3) [HCtC(CH2)3O-Biph-OCO(CH2)10CH3] and 4(m) [HCtC(CH2)mOCO-Biph-OCO(CH2)10-
CH3, m ) 3, 4] were prepared by sequential etherization and esterification reactions of 1-alkynes. While
3(3) exhibits enantiotropic crystal E and SmB mesophases, its structural cousin 4(3) displays only a
monotropic SmB phase. Enantiotropic SmA and SmB mesophases are, however, developed when the spacer
length is increased to 4. Polymerizations of the monomers are effected by Mo-, W-, Rh-, and Fe-based
catalysts, with the WCl6-Ph4Sn catalyst giving the best results (isolation yield up to 85% and Mw up to
59000). The polymers were characterized by IR, UV, NMR, TGA, DSC, POM, XRD, and PL analyses.
Compared to 1(3), 2(3) shows a red-shifted absorption, a higher Ti, and a better packed interdigitated
bilayer SmAd structure, while the mesophase of 2(4) involves monolayer-packing arrangements of the
mesogens. Upon photoexcitation, 1(3) emits almost no light but 2(m) gives a strong ultraviolet emission
(λmax ∼ 350 nm), whose intensity increases with the spacer length.
In tr od u ction
backbone could play an active role in guiding the
orientation of the mesogenic pendants.7 In our previous
work, we studied the mesomorphic properties of a pair
of polyacetylenes with different bridge orientations and
spacer lengths and revealed that the structural vari-
ables affected the mesomorphism of the polymers to a
considerable extent.8 To collect more information and
to gain further insights into how structural variations
affect mesomorphic properties of liquid crystalline poly-
acetylenes, in this study, we investigated the effects of
functional bridge and spacer length on the mesomor-
phism of another pair of polyacetylenes, that is, poly-
(5-{[(4′-{[(undecyl)carbonyl]oxy})-4-biphenylyl]oxy}-1-
pentyne) [1(3)] and poly[m-({[(4′-{[(undecyl)carbonyl]-
oxy})-4-biphenylyl]carbonyl}oxy)-1-alkynes] [2(m); Chart
1].
Liquid crystals and light emitters are complementary
in property; a polymer with the two electrooptical
features (both liquid crystalline and light emitting) is
of practical value, which may offer an array of exciting
opportunities for high-tech innovations. Such a polymer,
for example, may emit polarized light when aligned,
which may be utilized for the construction of lighting
and orientating layers in liquid crystal optical display
devices, thus obviating the use of backlight lamps,
polyimide films, and polarizing sheets. The color and
brightness of the light emitted by the liquid crystalline
polymer may be manipulated by external fields,9 which
may lead to the development of readily tunable electro-
chromic and optical switching systems. If the polymers
can emit ultraviolet (UV) light, that will be even better,
because the UV emitters can act as “color converters”
to generate low-energy visible lights of any colors
through interaction with appropriate phosphors.10
A wealth of side-chain liquid crystalline vinyl poly-
mers has been synthesized and their structure-prop-
erty relationships have been well evaluated.1 In con-
trast, side-chain liquid crystalline acetylenic polymers
have received little attention.2 Akagi and Shirakawa3
and Nuyken4 have synthesized some liquid crystalline
polyacetylenes, whose mesogenic pendants are, how-
ever, attached to the polymer backbones all through an
ether-functional bridge. The limitation in the variety of
the liquid crystalline polyacetylenes has prevented
systematic investigation of their structure-property
relationships. Attracted by the potential of creating
mesomorphic conjugated polymers with exotic electronic
and optical properties, we have worked on the design
and synthesis of new liquid crystalline polyacetylenes.
Through elaborate synthetic efforts,5 we generated a
wide variety of mesogenic polyacetylenes with different
molecular structures.6 Contrary to the “general” belief
that a rigid backbone would distort the packing align-
ments of mesogens, we found that the polyacetylene
* To whom correspondence should be addressed (Department
of Chemistry, Hong Kong University of Science & Technology).
Telephone: +852-2358-7375. Fax: +852-2358-1594. E-mail:
tangbenz@ust.hk.
† Department of Chemistry, Institute of Nano Science and
Technology, and Open Laboratory of Chirotechnology of the
Institute of Molecular Technology for Drug Discovery and Syn-
thesis, Hong Kong University of Science & Technology.
‡ Center for Display Research, Hong Kong University of Science
& Technology.
§ Laboratory of Polymer Physics, Changchun Institute of Ap-
plied Chemistry.
| The University Grants Committee (Hong Kong) Area of
Excellence Scheme.
10.1021/ma011406e CCC: $22.00 © 2002 American Chemical Society
Published on Web 01/15/2002

1230 Lam et al.
Macromolecules, Vol. 35, No. 4, 2002
Ch a r t 1
Sch em e 1
To develop such polymers, the first thing to learn is
their structural requirements. Polyacetylenes have,
however, “traditionally” been regarded as nonemissive
polymers.11 Recent studies have revealed that lumines-
cence behaviors of polyacetylenes can be greatly tuned
by changing their molecular structures. Whereas the
(unsubstituted) polyacetylene [-(CHdCH)n-] is almost
nonluminescent,11 its disubstituted cousins [-(CRd
CR′)n-] can be strongly emissive.12,13 Its monosubsti-
tuted derivatives of general structure -[CHdC(Ar)]n-
or poly(1-arylacetylenes) are incapable of emitting
intense light,12-14 but chromophore-containing poly(1-
monomers are examined by differential scanning calo-
rimetry (DSC) and polarized optical microscopy (POM).
Figure 1 shows the DSC thermograms of the monomers,
while the POM textures of 3(3) and 4(m) observed on
cooling from their isotropic states are given in Figure
2.
The first cooling scan of 3(3) shows two sharp peaks
at 113.9 and 47.0 °C (Figure 1A). POM observation
reveals that upon cooling 3(3) from the isotropic state
alkylacetylene) or poly(1-alkynes) {-[CHdC(CmH2m+1
-
Ch)]n-; Ch, light-emitting chromophore} can be highly
luminescent.14 The mesogenic polymers 1(3) and 2(m)
are monosubstituted derivatives of polyacetylene, and
it is of interest to check how the molecular structures
alter their light emitting behaviors. In this work, we
examined their luminescence properties and found that
the polymer with an ether bridge [1(3)] was nonlumi-
nescent but its counterpart with an ester bridge and a
longer methylene spacer [3(4)] emitted strong UV light,
whose intensity is comparable to that of poly(1-phenyl-
1-octyne) (PPO), a highly luminescent disubstituted
polyacetylene.12,13
Resu lts a n d Discu ssion
Syn th esis a n d Mesom or p h ism of Mon om er s. We
synthesized the acetylene monomer 5-{[(4′-{[(undecyl)-
carbonyl]oxy})-4-biphenylyl]oxy}-1-pentyne [3(3)] through
a two-step reaction route. We first etherized 4′,4-
biphenol with 5-chloro-1-pentyne, and the resulting
alcohol (7) was then reacted with lauric acid in the
presence of 1,3-dicyclohexylcarbodiimine (DCC), p-tolu-
enesulfonic acid (TsOH), and 4-(dimethylamino)pyridine
(DMAP) (Scheme 1). We also prepared m-({[(4′-{[(un-
decyl)carbonyl]oxy})-4-biphenylyl]carbonyl}oxy)-1-al-
kynes [4(m), m ) 3, 4], which are the structural cousins
of 3(3) with a different functional bridge group (ester),
through two consecutive esterification of 4′-hydroxy-4-
biphenylcarboxylic acid (9). All the final products (mono-
mers) were isolated in high yields (75-88%) and were
fully characterized by spectroscopic methods, from
which, satisfactory analysis data were obtained (see
Experimental Section for details).
All the acetylene monomers are white crystals at room
temperature and exhibit liquid crystallinity at elevated
temperatures. The thermal transition behaviors of the
F igu r e 1. DSC thermograms of monomers 3(3) and 4(m)
(m ) 3, 4) recorded under nitrogen during the (A) first cooling
and (B) second heating scans at a scan rate of 10 °C/min.

Macromolecules, Vol. 35, No. 4, 2002
Biphenyl-Containing Poly(1-alkynes) 1231
F igu r e 2. Polarized optical microphotographs of 3(3) at (A) 114 °C (mosaic SmB texture with lancet) and (B) 110 °C (paramorphotic
arced mosaic texture of crystal E phase), (C) 4(3) at 66.2 °C (mosaic texture of SmB phase with pseudo π-disclination), and (D)
4(4) at 59.0 °C (mosaic SmB texture).
to 114 °C, mosaic texture of SmB mesophase with
lancet15 is formed (Figure 2A). It is, however, difficult
to identify whether 3(3) enters hexatic or crystal SmB
mesophases because the mosaic textures displayed by
the two phases are indistinguishable.15a When the
temperature is further lowered to 110 °C, continuous
concentric arcs running across the backs of the mosaics
are observed (Figure 2B). Of the different mesophases
evolved from SmB phase, this paramorphotic arced
mosaic texture can only be found in crystal E and G
phases. The arcs in crystal G phase are, however, not
continuous from one area to another and show breaks.
It thus becomes clear that the crystal E phase has
formed at 110 °C, formation of whose arcs is probably
caused by the contraction of the layer ordering at the
SmB-E transition.15 The monomer solidifies at 47 °C.
The crystal-E and E-liquid transitions are enantio-
tropic as the DSC thermogram recorded in the second
heating scan displays two peaks at 73.1 and 116.5 °C.
Monomer 4(3) structurally resembles 3(3) but has a
different functional bridge and it is of interest to study
how it behaves mesomorphically. During the first cool-
ing cycle, 4(3) shows two transition peaks at 66.1 and
61.2 °C (Figure 1A). When 4(3) is allowed to cool from
the isotropic state to 66.2 °C, mosaic texture of the SmB
phase with pseudo π-disclination15b is observed (Figure
2C). The temperature range of the mesophase is,
however, narrow (∼0.5 °C), and the monomer completely
solidifies at 65.5 °C. The exothermic peak at 61.2 °C
may thus be associated with crystal transformation from
one state to another (k-k transition). The second
heating scan records two transition peaks at 76.8 and
83.3 °C but no liquid crystalline texture is observed,
indicating that the mesomorphism is monotropic.
The DSC thermogram of 4(4) shows three transition
peaks at 63.5, 59.7, and 45.5 °C in the first cooling cycle
(Figure 1A). The mesophase in this temperature range
(63.5-59.7 °C) is identified to be SmA because typical
focal-conic fan texture is observed when 4(4) is cooled
to 63.0 °C. The radical lines running across the backs
of the fans, however, disappear upon further cooling to
59.0 °C. Annealing the texture at the same temperature
for 10 minutes results in the formation of mosaic texture
of SmB phase (Figure 2D). Since no transition bars are
observed during the SmA-SmB transition, the me-
sophase formed by 4(4) is thus hexatic in nature.15a The
monomer solidifies at 44.0 °C. Reheating 4(4) regener-
ates the SmB and SmA textures in sequence; that is,
the mesomorphism is enantiotropic.
Table 1 summarizes the thermal transitions and the
corresponding thermodynamic parameters of the acet-
ylene monomers. All the SmA, SmB, and crystal E
transitions involve large enthalpy (∆H) and enthropy
(∆S) changes. These suggest that all the transitions are
first order in nature.15c,16 Although the change in the
functional bridge looks like a subtle structural variation,
it does change the mesomorphic properties of the
acetylene monomers to a great extent, with 3(3) exhibit-
ing better packing order and higher transition temper-
atures. The melting temperature of 4(4) is lower than
that of 4(3), probably due to the plasticization effect of
the longer methylene spacers.
P olym er ization Reaction s. Since Akagi and Shirak-
wa polymerized their mesogenic monomers such as

1232 Lam et al.
Ta ble 1. Th er m a l Tr a n sition s a n d Cor r esp on d in g Th er m od yn a m ic P a r a m eter s of 3(3) a n d 4(m )a
T, °C [∆H, kJ /mol; ∆S, J /(mol K)]
Macromolecules, Vol. 35, No. 4, 2002
no.
monomer
cooling
heating
1
2
3
3(3)
4(3)
4(4)
i 113.9 (-19.34; -49.97)b E 47.0 (-32.81; -102.49) k
i 66.1 (-14.56; -42.92)b k′ 51.2 (-16.99; -52.38) k
i 63.5 (-9.67; -28.73) SmA 59.7 (-5.86; -17.61)
SmB 45.5 (-6.71; -21.06) k
k 73.1 (41.32; 119.34)b E 116.5 (25.21; 64.7) i
k 76.8 (28.32; 80.93) k′ 83.3 (11.67; 33.21) i
k 62.2 (19.0; 56.6)b SmA 65.2 (5.61; 16.58) i
a
Data taken from the DSC thermograms recorded under nitrogen in the first cooling and second heating scans; abbreviations: k )
b
crystalline state, Sm ) smectic phase, i ) isotropic state. Sum of overalpping transitions.
Ta ble 2. P olym er iza tion of
5-{[(4′-{[(Un d ecyl)ca r bon yl]oxy})-4-bip h en ylyl]oxy}-
1-p en tyn e [3(3)]a
Ta ble 3. P olym er iza tion of
5-({[(4′-{[(Un d ecyl)ca r bon yl]oxy})-
4-bip h en ylyl]ca r bon yl}oxy)-1-p en tyn e [4(3)]a
tempc yield
tempb yield
d
d
c
c
no.
catalystb
solvent
toluene
(°C)
(%)
Mw
Mw/Mn
no.
catalyst
solvent
(°C)
(%)
Mw
Mw/Mn
1
2
3
4
5
6
7
8
9
MoCl5-Ph4Sn
[Rh(nbd)Cl]2
[Rh(nbd)Cl]2
Fe(acac)3-3Et3Al dioxane
Fe(acac)3-3Et3Al toluene
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
rt
60
rt
rt
rt
50.8
92.3
91.3
59.7
60.3
9770
4210
4300
3630
4870
1.72
1.20
1.26
1.33
1.43
2.07
2.18
1.78
1
2
3
4
MoCl5-Ph4Sn dioxane
rt
rt
60
rt
7.4 33000
21.4 47400
84.1 37700
84.7 52900
2.02
2.01
1.90
1.95
Et3N
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
dioxane
dioxane
toluene
toluene/Et3Ne
a
toluene
toluene
toluene
toluene
dioxane
dioxane
dioxane
CCl4
rt
77.2 12900
41.7 13500
17.4
Carried out under nitrogen for 24 h; [M]0 ) 0.2 M; [cat.] )
([cocat.] )) 10 mM. b rt ) room temperature. c Determined by GPC
40
60
80
rt
60
80
60
60
9750
in THF on the basis of a polystyrene calibration.
trace
10 WCl6-Ph4Sn
11 WCl6-Ph4Sn
12 WCl6-Ph4Sn
13 Mo(nbd)(CO)4
14 W(mes)(CO)3
68.9 18600
68.6 10800
80.7 12500
36.7 12700
64.0 15700
2.48
2.16
2.65
1.67
1.73
Ta ble 4. P olym er iza tion of
6-({[(4′-{[(Un d ecyl)ca r bon yl]oxy})-
4-bip h en ylyl]ca r bon yl}oxy)-1-h exyn e [4(4)]a
tempc yield
CCl4
d
d
no.
catalystb
solvent
(°C)
(%)
Mw
Mw/Mn
a
Carried out under nitrogen for 24 h; [M]0 ) 0.2 M; [cat.] )
([cocat.] )) 10 mM; for Zielger-Natta catalyst, [AlEt3] ) 3[Fe-
1
2
3
4
5
6
MoCl5-Ph4Sn dioxane
rt
rt
60
rt
60
60
10.8 33500
26.5 71200
82.3 59000
15.9 53600
40.6 13300
52.1 17100
1.97
2.16
1.85
2.07
1.44
1.62
b
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
dioxane
dioxane
toluene
(acac)3]. Abbreviations: mes ) mesitylene, nbd ) 2,5-norborn-
diene, and acac ) acetylacetonate. c rt ) room temperature.
d
Determined by GPC in THF on the basis of a polystyrene
calibration. e Volume ratio of toluene to Et3N ) 4:1.
Mo(nbd)(CO)3 CCl4
W(mes)(CO)4 CCl4
a
Carried out under nitrogen for 24 h; [M]0 ) 0.2 M; [cat.] )
5-[(4′-pentyl-4-biphenylyl)oxy]-1-pentyne [HCtC(CH2)3-
Biph-C5H11] by MoCl5-Ph4Sn, [Rh(nbd)Cl]2, and Fe-
(acac)3-3Et3Al catalysts,3 we checked whether these
catalysts were also effective for the polymerization of
3(3). MoCl5-Ph4Sn initiates the polymerization of 3(3)
in toluene, giving 51% of a polymeric product with a
molecular weight of 9770 (Table 2, no. 1). [Rh(nbd)Cl]2
produces a polymer in 92% yield, whose molecular
weight is, however, low. No increase in the molecular
weight is observed when the polymerization is con-
ducted in a mixture of toluene and Et3N. Polymeriza-
tions of 3(3) can also be achieved by Fe(acac)3-3Et3Al
in toluene and dioxane, but the molecular weights of
the polymers are again low, probably due to the poison-
ing interaction of the polar ester group with the catalyst.
We have previously found that WCl6-Ph4Sn performs
much better than MoCl5-Ph4Sn in the polymerizations
of mesogen-containing acetylene monomers.5 Under
similar conditions, polymerization of 3(3) in toluene
catalyzed by WCl6-Ph4Sn gives a comparatively high
molecular weight polymer in a high yield. In this
solvent, raising the temperature leads to decreases of
both molecular weight and yield, probably due to
instability of the catalytic species and/or activation of
termination reactions. Dioxane is also a good solvent
for the polymerization. Unlike the trend observed in
toluene, the polymer yield and Mw are less sensitive to
the change in temperature; complexation of the polar
solvent molecule(s) of dioxane with the metal center may
have generated a more stable tungsten-oxo catalytic
center, which may be resistant to the attach of detri-
mental terminators.5c W(mes)(CO)3 and Mo(nbd)(CO)4
are air- and moisture-stable metal carbonyl complexes
and can polymerize acetylenes in both halogenated and
b
([cocat.] )) 10 mM. Abbreviations: mes ) mesitylene and
nbd ) 2,5-norborndiene. c rt ) room temperature. Determined
d
by GPC in THF on the basis of a polystyrene calibration.
nonhalogenated solvents.5 Both W(mes)(CO)3 and Mo-
(nbd)(CO)4 effect polymerization of 3(3) in carbon tet-
rachloride, with the latter producing a higher molecular
weight polymer in a higher yield.
Unlike 3(3), 4(3) cannot be effectively polymerized by
MoCl5-Ph4Sn (Table 3, no. 1). WCl6-Ph4Sn, on the
other hand, performs much better under similar condi-
tions. The yield is greatly boosted when temperature is
raised to 60 °C. Toluene is generally a poorer solvent
than dioxane in the polymerizations of functional acety-
lene monomers at high temperatures.5c But at low
temperatures, the solvent is not “bad”: a high molecular
weight polymer is obtained in a high yield when the
polymerization of 4(3) is carried out in toluene at room
temperature.
Similar to 4(3), 4(4) undergoes sluggish polymeriza-
tion when MoCl5-Ph4Sn is used as the catalyst in
dioxane (Table 4, no. 1). Both the yield and molecular
weight are increased when the catalyst is changed to
WCl6-Ph4Sn. Although the molecular weight of the
polymer drops, the yield increases more than three
times when the polymerization is performed at 60 °C.
Surprisingly, polymerization of 4(4) in toluene only gives
15.9% of a polymeric product although it is a good
solvent for the polymerization of 4(3). The reason for
this is unclear at present but will be investigated in the
future. The metal carbonyl catalysts Mo(nbd)(CO)3 and
W(mes)(CO)4 are effective for the polymerization of 4(4),
giving polymers in moderate yields with narrow poly-
dispersities.

Macromolecules, Vol. 35, No. 4, 2002
Biphenyl-Containing Poly(1-alkynes) 1233
F igu r e 3. IR spectra of (A) 3(3) and (B) its polymer 1(3)
(sample taken from Table 2, no. 11).
F igu r e 5. 13C NMR spectra of 3(3) and its polymer 1(3)
(sample from Table 2, no. 11).
at δ 6.05.17 It thus seems reasonable to assign the peak
centered at δ 6.04 to the absorption by the cis olefin
proton in the alternating double-bond backbone of 1(3).
The cis content of the polymer can be calculated accord-
ing to5-8
cis content (%) ) [Acis/(Atotal/9)] × 100
(1)
F igu r e 4. 1H NMR spectra of (A) 3(3) and (B) its polymer
1(3) (sample from Table 2, no. 11).
where Acis and Atotal are respectively the integrated peak
areas of the absorption by the cis olefin proton and of
the total absorption by the aromatic and olefinic protons.
Using eq 1, the cis content of 1(3) is calculated to be
45% (or 55% trans). The polymer thus consists of
comparable amounts of cis and trans stereoisomers, as
evidenced by its relatively broad absorption peaks.
Figure 5 shows the 13C NMR spectrum of 3(3) along
with that of its polymer 1(3). While the acetylene carbon
atoms of 3(3) absorb at δ 83.3 and 66.1, these absorp-
tions disappear in the spectrum of 1(3). The absorption
of the propargyl carbon of 3(3) at δ 15.1 also disappears
owing to its transformation to the allylic structure in
1(3) by the acetylene polymerization. The absorptions
of the olefin carbon atoms of the backbone are, however,
not distinguishable because of their overlapping with
the peaks of the carbon atoms of the aromatic pendants.
The UV absorption spectra of chloroform solutions of
the polymers are given in Figure 6. None of the
monomers shows any peaks at wavelengths longer than
325 nm; the absorption in the long-wavelength visible
spectral region is thus obviously from the double-bond
Str u ctu r a l Ch a r a cter iza tion . All the purified po-
lymerization products give satisfactory spectroscopic
data corresponding to their expected molecular struc-
tures (see Experimental Section for details). An example
of the IR spectrum of 1(3) is given in Figure 3. The
spectrum of its monomer 3(3) is also shown in the same
figure for comparison. The tC-H stretching and bend-
ing vibrations of the monomer are observed at 3200 and
630 cm-1. All these acetylene absorption bands disap-
pear in the spectrum of its polymer, indicating that the
triple bonds have been consumed by the polymerization
reaction.
NMR analysis proves that the acetylene triple bonds
have been transformed to polyene double bonds. Figure
4 shows the 1H NMR spectra of 3(3) and its polymer
1(3) in chloroform. There is no peak in the acetylene
absorption region (δ ∼ 2.0) in the spectrum of the
polymer. Instead, a new broad peak appears in the olefin
absorption region (δ 6.5-5.8). Masuda and Higashimura
have reported that the cis olefin proton of an aliphatic
poly(1-alkyne), poly(3,3-dimethyl-1-pentyne), absorbs

1234 Lam et al.
Macromolecules, Vol. 35, No. 4, 2002
F igu r e 7. TGA thermograms of 1(3) (sample from Table 2,
no. 11), 2(3) (Table 3, no. 3), 2(4) (Table 4, no. 3), and poly(1-
hexyne) (PH; data taken from ref 18b) recorded under nitrogen
at a heating rate of 10 °C/min.
F igu r e 6. UV spectra of chloroform solutions of 1(3) (sample
from Table, 2, no. 11), 2(3) (Table 3, no. 3), and 2(4) (Table 4,
no. 3).
backbones of the polymers. The absorptivity is low,
probably owing to the reduction of the effective conjuga-
tion lengths along the polyacetylene backbone by the
bulky pendant groups. The undecylcarbonyloxybiphen-
ylyloxy pendants of 1(3) absorb at 265 nm, which is ∼12
nm blue-shifted from those of 2(m). The biphenylyl
chromphores of 2(m) are well polarized by the push-
pull interaction of the electron-donating undecylcarbon-
yloxy and electron-withdrawing carbonyloxy groups.8
The polarizability of the pendants in 1(3) is, however,
low because both undecylcarbonyloxy and ether groups
are electron-donating.
Sta bility, Mesom or p h ism , a n d Lu m in escen ce.
Since the formation of mesophases of a thermotropic
liquid crystalline polymer is realized by the application
of heat, the thermal stability of the polymer is thus of
primary importance. Poly(1-hexyne) (PH), which may
be regarded as the parent form of the mesogen-contain-
ing poly(1-alkynes), is so unstable that it starts to lose
its weight at ∼150 °C (Figure 7; with the starting Mw
and Mw/Mn of PH being 410 000 and 3.2, respectively).18
On the other hand, all the mesogenic polyacetylenes
almost do not lose any weights at a temperature as high
as ∼300 °C. Clearly, the introduction of the mesogenic
units into the macromolecular structures has dramati-
cally enhanced the resistance of the polymers to ther-
molysis, probably due to the protective “jacket effect”
of the thermally stable mesogenic pendants.6-8 The
thermal stability of the polymers is further substanti-
ated by the DSC analysis: no irreversible peaks suspi-
ciously associated with polymer degradation are ob-
served at the high temperatures during the cycles of
repeated heating-cooling scans.
After confirming the stability of the polymers by the
thermal analyses, we studied their mesomorphic prop-
erties. Figure 8 shows the DSC thermograms of 1(3) and
2(m) recorded under nitrogen during the first cooling
and second heating scans. In the first cooling cycle, a
broad exothermic peak associated with i-SmA is ob-
served at 121.5 °C in 1(3) and the corresponding SmA-i
transition is detected at 137.7 °C. Polymer 2(3) enters
the SmA phase from its isotropic state at 198.8 °C. The
mesophase is stable in a temperature range over 48 °C
before 2(3) finally solidifies at 150.3 °C. The associated
F igu r e 8. DSC thermograms of the mesomorphic poly(1-
alkynes) 1(3) (sample from Table 2, no. 11), 2(3) (Table 3, no.
3), and 2(4) (Table 4, no. 3) recorded under nitrogen during
the (A) first cooling and (B) second heating scans at a scan
rate of 10 °C/min.
g-SmA and SmA-i transitions are observed at 164.3
and 210.4 °C. The transition profiles of 2(4) are similar
to those of 2(3) and i-SmA and SmA-g transitions are
found at 199.0 and 161.7 °C. Peaks corresponding to
g-SmA and SmA-i transitions are observed at 199.4
and 166.7 °C.
Figure 9 shows the POM microphotographs of the
mesomorphic textures of 1(3) and 2(m). When 1(3) is
cooled from its isotropic state, small anisotropic rhombic

Macromolecules, Vol. 35, No. 4, 2002
Biphenyl-Containing Poly(1-alkynes) 1235
F igu r e 9. Mesomorphic textures observed on cooling (A) 1(3) (sample from Table 2, no. 11) to 165 °C, 2(3) (Table 3, no. 3) (B) to
200 and (C) 170 °C, and (D) 2(4) (Table 4, no. 3) to 160 °C from their isotropic melts.
Ta ble 5. Th er m a l Tr a n sition s a n d Cor r esp on d in g Th er m od yn a m ic P a r a m eter s of 1(3) a n d 2(m )a
T, °C [∆H, kJ /mru; ∆S, J /(mru K)]b
no.
polymer
cooling
heating
1
2
3
1(3)
2(3)
2(4)
i 121.5 (-6.86; -17.38) SmA
i 198.8 (-2.52; -5.34) SmA 150.3 (-0.30; -0.71) g
i 199.0 (-3.71; -7.84) SmA 161.3 (-0.78; -1.80) g
SmA 137.7 (6.56; 15.97) i
g 164.3 (0.20; 0.46) SmA 210.4 (3.09; 6.39) i
g 166.7 (0.38; 0.86) SmA 199.4 (3.77; 7.98) i
a
Data taken from the DSC thermograms recorded under dry nitrogen in the first cooling and second heating scans. Abbreviations:
b
k ) crystalline state, Sm ) smectic phase, g ) glassy state, and i ) isotropic liquid. Abbreviation: mru ) monomer repeat unit.
entities emerge from the dark background of the iso-
tropic liquid. The fine textures grow into fanlike struc-
tures upon further cooling (Figure 9A) but the exact
nature of the mesophase is difficult to identify. We
repeatedly tried to grow the liquid crystals with care
but failed to obtain any readily identifiable character-
istic textures. With the aid of X-ray diffraction (XRD)
measurements, the textures are identified to be associ-
ated with a SmA phase (see below).
Polymer 2(3), however, exhibits typical SmA textures
in the mesomorphic temperature region. When 2(3) is
cooled from the isotropic state to 200 °C, many small
baˆtonnets appear. The baˆtonnets grow to bigger do-
mains when the sample is further cooled. Interestingly,
inside the layer, parallel bands normal to the director
of the baˆtonnets are clearly seen (Figure 9B). Such
banded textures have often been observed in other liquid
crystalline polyacetylenes that form SmA mesophase,6-8
suggesting that it is a common phenomenon observable
in smectic polyacetylene systems. Further lowering the
temperature encourages further growth of the baˆton-
nets. Coalescence of the anisotropic domains results in
the formation of well-developed characteristic focal-
conic fan texture (Figure 9C). The banded textures
observed in the early stage of the mesomorphic transi-
tion are, however, completely buried. The mesomorphic
textures formed in 2(4) are similar to those of 2(3) and
as shown in Figure 9D, very large baˆtonnets with
banded textures are also observed upon cooling the
isotropic liquid of 2(4).
The thermal transitions and their corresponding
enthalpy and entropy changes of 1(3) and 2(m) are
summarized in Table 5. The large ∆H and ∆S changes
involved in the mesomorphic transitions of 1(3) and 2(m)
rule out the possibility of nematic phase and further
support the assignment of smecticity to the mesophases
of the polyacetylene liquid crystals. It is of interest to
note that the polymer having an ester-functional bridge
[2(3)] shows higher Ti than the one with an ether bridge
[1(3)] (∆T ∼ 77 °C), in agreement with the POM
observation that 2(3) displays better developed meso-
morphic textures. On the other hand, the change in
spacer length [2(3) vs 2(4)] has little influence on the
Ti of the polymers.
We carried out powder XRD experiments in order to
gain more information concerning the molecular ar-

1236 Lam et al.
Macromolecules, Vol. 35, No. 4, 2002
F igu r e 11. Photoluminescence spectra of chloroform solutions
of 1(3) (sample from Table 2, no. 11), 2(3) (Table 3, no. 3), 2(4)
(Table 4, no. 3), and poly(1-phenyl-1-octyne) (PPO). Concentra-
tion: 0.05 mM. Excitation wavelengths (nm): 320 [1(3)], 315
[2(3) and 2(4)], and 350 (PPO).
F igu r e 10. X-ray diffraction patterns of the mesogenic
polyacetylenes quenched with liquid nitrogen from their liquid
crystalline states: 1(3) (sample from Table 2, no. 11) at 150
°C, 2(3) (Table 3, no. 3), and 2(4) (Tables 4, no. 3) at 170 °C.
acetylenes are sensitive to their molecular structures.
Will the structural variations of functional bridge and
spacer length affect the luminescence behaviors of the
liquid crystalline poly(1-alkynes)? The answer is a firm
yes: While a weak emission peaked at 370 nm is
observed when 1(3) is photoexcited at 320 nm (Figure
11), 2(3) emits a strong UV light of 353 nm, whose
intensity is ∼20 times higher than that from 1(3).
Polymer 2(4) emits even more strongly at 347 nm and
its luminescence intensity is comparable to that of PPO,
a well-known highly fluorescent disubstituted poly-
acetylene.12,13
Ta ble 6. X-r a y Diffr a ction An a lysis Da ta of 1(3) a n d 2(m )a
molecular
ratio
polymer T (°C) d1 (Å) d2 (Å) length (l; Å)b d1/l
phase
1(3)
2(3)
2(4)
150
170
170
27.16
41.06
26.35
4.26
4.27
4.26
28.36
30.21
31.46
0.96 SmA
1.36 SmAd
0.84 SmA
a
The mesophases in the liquid crystalline states at the given
temperatures were frozen by the rapid quenching with liquid
nitrogen. b Calculated from the monomer repeat units in their fully
extended conformation.
Whereas the emission of PPO at 460 nm is by the
polyarylalkyne backbone,12,13 we have previously clearly
demonstrated that the polyene backbone of a poly(1-
alkyne) emits faintly in the red spectral region with a
rangements, modes of packing, and types of order in the
mesophases of the polyacetylene liquid crystals. The
diffractogram of 1(3) shows a sharp reflection and a
broad halo at 2θ ) 3.25 and 20.85°, respectively, from
which d spacings of 27.16 and 4.26 Å are derived (Figure
10). The existence of long-range positional order in the
polymer again rules out the possibility of nematic
classification.19 The calculated molecular length of one
monomer repeat unit (mru) of 1(3) is 28.36 Å, which is
close to the experimentally obtained layer thickness
(Table 6). This confirms the SmA nature of the me-
sophase and suggests that the mesogens are packed in
a monolayer structure.
λ
max of ∼740 nm.14b The UV light emitting by polymers
1 and 2 thus must be from their pendant chromophores.
The pendants of 1(3) are not good lumophores because
of their unfavorable electronic structures, as discussed
above (cf., Figure 6). On the other hand, the chro-
mophoric pendants in 2(3) are well polarized by the
electron-donating and -withdrawing groups. This push-
pull interaction increases the mobility of the π-electrons,
thus leading to the enhanced emission. The increase of
emission intensity with the spacer length in the series
of 2(m) is in agreement with the observations of
Yoshino12 and Kabayashi,13 who have found that longer
alkyl chains favor stronger emission in the photolumi-
nescence and electroluminescence of poly(1-phenyl-1-
alkynes). The longer alkyl chains may have better
segregated the chromophoric pendants, which effectively
hampers the excitons from traveling to the quenching
sites of the polyacetylene backbone and hence enhances
the chances for the confined excitons to recombine
radiatively.12,13
The XRD diffractogram of 2(3) also displays Bragg
reflections at low and middle angles. The sharp reflec-
tion at the low angle (2θ ) 2.15°) corresponds to a layer
spacing of 41.06 Å, which is in considerable excess of
the molecular length (30.21 Å). The mesophase in 2(3)
thus involves a bilayer packing arrangement, in which
the alkoxy tails are interdigitated in an antiparallel
fashion.5c,8 Interestingly, when the spacer length is
increased by one methylene unit, 2(4) forms SmA
mesophase of a monolayer structure. Clearly, the type
of the functional bridge and length of the methylene
spacer dramatically affect the layer structure of the
liquid crystalline polyacetylenes.
Con clu sion s
In this work, the mesogenic and chromophoric acety-
lene monomers and polymers with different functional
bridges and spacer lengths are designed and synthe-
sized. The structural variations on the chemical and
Previous studies by us14 and others12,13 have revealed
that light-emitting efficiencies of monosubstituted poly-

Macromolecules, Vol. 35, No. 4, 2002
Biphenyl-Containing Poly(1-alkynes) 1237
min. A set of monodisperse polystyrene standards covering the
molecular weight range of 103-107 was used for the molecular
weight calibration.
The thermal stability of the polymers was evaluated on a
Perkin-Elmer TGA 7 under dry nitrogen at a heating rate of
10 °C /min. A Setaram DSC 92 was used to measure the phase
transition thermograms. An Olympus BX 60 POM equipped
physical properties of the monomers and polymers are
investigated and the results can be summarized as
follows:
(1) All the acetylene monomers 3(3) and 4(m) are
liquid crystalline, and the monomer with the ether-
functional bridge shows better ordered mesophase and
higher transition temperatures than its counterpart
with the ester-functional bridge.
(2) WCl6-Ph4Sn and MoCl5-Ph4Sn catalysts are good
at polymerizing 3(3) in toluene and dioxane. For 4(m),
the best polymerization results are obtained in dioxane
using WCl6-Ph4Sn as catalyst.
(3) The spacer length exerts little influence on the
absorption properties of 2(m). The functional bridge,
however, affects the polarizability of the biphenyl me-
sogen, with the pendant absorption in 1(3) being con-
siderably blue-shifted from that of 2(3).
with
a Linkam TMS 92 hot stage was used to observe
anisotropic optical textures. The XRD patterns were recorded
on a Philips PW1830 powder diffractometer with a graphite
monochromator using 1.5406 Å Cu KR wavelength at room
temperature (scanning rate, 0.05°/s; scan range, 2-30°). The
polymer samples for the XRD measurements were prepared
by freezing the molecular arrangements in the liquid crystal-
line states by liquid nitrogen as previously reported.6-8
Mon om er Syn th esis. The alkyne monomer 3(3) was
synthesized by etherization of 4′,4-biphenol with 5-chloro-1-
pentyne followed by esterification of the resulting alcohol with
lauric acid in the presence of DCC, TsOH, and DMAP (cf.,
Scheme 1). The monomers 4(m) with a different functional
bridge group were prepared by esterifications of 4′-hydroxy-
4-biphenylcarboxylic acid with lauric acid and n-alkyn-1-ol.
Typical synthetic procedures are given below.
(4) All the polymers are thermally stable, irrespective
of the type of the functional bridge and the spacer
length.
(5) While 1(3) with the ether bridge forms SmA phase
of monolayer structure, its counterpart with the ester
bridge 2(3) displays better developed mesomorphic
textures, exhibits higher transition temperatures, and
shows interdigitated packing arrangements of me-
sogenic pendants. The mesogens in the polymer with a
longer spacer [2(4)] is, however, packed in a monolayer
structure.
(6) Polymer 1(3) is almost nonluminescent; in sharp
contrast, 2(3) is highly emissive. The emission intensity
is further enhanced (almost doubled) when the spacer
length is increased from 3 to 4.
The structure-property relationship gained in this
study will help design liquid crystalline and light
emitting polyacetylenes for high-tech applications. The
efficient UV emission from the liquid crystalline poly-
acetylenes is of particular technological implications.10
We are currently investigating polarized emission from
the polyacetylenes 2(m), in particular 2(4), and explor-
ing the possibility of utilizing the polymers for the
construction of optical display systems with simple
device configurations, high emission efficiency, and full
color tunability.20
5-[(4′-Hyd r oxy-4-bip h en ylyl)oxy]-1-p en tyn e (7). In a
1000-mL Erlenmeyer flask equipped with a condenser were
dissolved 10 g (53.7 mmol) of 4,4′-biphenol and 3 g of KOH
(58.8 mmol) in 400 mL of acetone/DMSO mixture (10:1 by
volume) under gentle heating and stirring. To the homoge-
neous solution were added 5 g (53.6 mmol) of 5-chloro-1-
pentyne and a catalytic amount of potassium iodide. The
resulting mixture was then refluxed for 30 h. The reaction
mixture was poured into 300 mL water and acidified with 15
mL of 37% hydrochloric acid. The precipitate was collected by
suction filtration. The crude product was purified on a silica
gel column using chloroform as eluent followed by recrystal-
lization from toluene. White crystal was obtained in 33% yield
(5 g). IR (KBr), ν (cm-1): 3375 (br, OH), 3304 (s, H-Ct), 636
1
(m, H-Ct bending). H NMR (300 MHz, DMSO-d6), δ (ppm):
9.57 (s, OH), 7.59 (d, 2H, Ar-H meta to OH), 7.50 (d, 2H,
Ar-H meta to OC5H7), 7.07 (d, 2H, Ar-H ortho to OH), 6.94
(d, 2H, Ar-H ortho to OC5H7), 4.14 (t, 2H, OCH2), 2.92 (t,
1H, H-Ct), 2.44 (td, 2H, tC-CH2), 1.99 (m, 2H, OCH2CH2).
13C NMR (75 MHz, DMSO-d6), δ (ppm): 157.6 (aromatic carbon
linked with OC5H7), 156.7 (aromatic carbon linked with OH),
131.0 (aromatic carbon para to OH), 130.9 (aromatic carbon
para to OC5H7), 127.4 (aromatic carbons meta to OH), 127.2
(aromatic carbons meta to OC5H7), 115.9 (aromatic carbons
ortho to OH), 115.0 (aromatic carbons ortho to OC5H7), 83.9
(tC), 71.9 (OCH2), 66.1 (HCt), 28.0 (tC-CH2CH2), 14.7
(tC-CH2).
Exp er im en ta l Section
Ma ter ia ls. Dioxane (Nacalai Tesque), THF (Lab-Scan), and
toluene (BDH) were predried over 4 Å molecular sieves and
distilled from sodium benzophenone ketyl immediately prior
to use. Dichloromethane (Lab-Scan) was dried over molecular
sieves and distilled over calcium hydride. 4-Pentyn-1-ol,
5-hexyn-1-ol, and 5-chloro-1-pentyne were the products of
Farchan Laboratory and were used as received. Except mo-
lybdenum(V) chloride (Acros), all other reagents and solvents
were purchased from Aldrich and used without further puri-
fication.
In str u m en ta tion . The IR spectra were measured on a
Perkin-Elmer 16 PC FT-IR spectrophotometer. The 1H and 13C
NMR spectra were recorded on a Bruker ARX 300 NMR
spectrometer using chloroform-d as solvent and tetramethyl-
silane (δ ) 0) or chloroform (7.26) as internal reference. The
UV spectra were measured on a Milton Roy Spectronic 3000
Array spectrophotometer and the molar absorptivity (ꢀ) of the
polymers was calculated on the basis of their monomer repeat
units. The mass spectra were recorded on a Finnigan TSQ
7000 triple quadrupole mass spectrometer operating in a
chemical ionization (CI) mode using methane as carrier gas.
The elemental analyses were performed by M-H-W, Phoenix,
AZ. The number- and weight-average molecular weights of the
polymers were estimated by a Waters Associates GPC system.
Degassed THF was used as eluent at a flow rate of 1.0 mL/
5-{[(4′-{[(Un d ecyl)ca r bon yl]oxy})-4-bip h en ylyl]oxy}-1-
p en tyn e [3(3)]. In a typical run, lauric acid (2.9 g, 14.5 mmol),
5-[(4′-hydroxy-4-biphenylyl)oxy]-1-pentyne (3.6 g, 14.3 mmol),
TsOH (0.6 g, 3.5 mmol), and DMAP (0.4 g, 3.3 mmol) were
dissolved in 250 mL of dry THF in a 500-mL, two-necked flask
in an atmosphere of nitrogen. The solution was cooled to 0-5
°C with an ice-water bath, to which 4.6 g of DCC (22.3 mmol)
dissolved in 50 mL of THF was added under stirring via a
dropping funnel. The reaction mixture was stirred overnight.
After the formed urea solid was filtered out, the solution was
concentrated by a rotary evaporator. The product was purified
by a silica gel column using chloroform as eluent. Recrystal-
lization from absolute ethanol gave 5.0 g of white crystals
(yield: 87%). IR (KBr), ν (cm-1): 3300 (s, H-Ct), 1748 (vs,
1
CdO), 630 (m, H-Ct bending). H NMR (300 MHz, CDCl3),
δ (ppm): 7.55 (d, 2H, Ar-H meta to OCO), 7.49 (d, 2H, Ar-H
meta to OC5H7), 7.14 (d, 2H, Ar-H ortho to OCO), 6.99 (d,
2H, Ar-H ortho to OC5H7), 4.12 (t, 2H, OCH2), 2.57 (t, 2H,
OCOCH2), 2.43 (td, 2H, tC-CH2), 2.01 (m, 3H, HCt and
OCH2CH2), 1.77 (m, 2H, OCOCH2CH2), 1.43-1.28 [m, 16H,
(CH)2], 0.89 (t, 3H, CH3). 13C NMR (75 MHz, CDCl3), δ (ppm):
172.4 (CdO), 158.4 (aromatic carbon linked with OC5H7), 149.6
(aromatic carbon linked with OCO), 138.4 (aromatic carbon
para to OCO), 132.9 (aromatic carbon para to OC5H7), 128.0
(aromatic carbons meta to OCO), 127.6 (aromatic carbons meta

1238 Lam et al.
Macromolecules, Vol. 35, No. 4, 2002
to OC5H7), 121.7 (aromatic carbons ortho to OCO), 114.7
(aromatic carbons ortho to OC5H7), 83.3 (tC), 68.9 (OCH2),
66.1 (HCt), 34.5 (OCOCH2), 31.9 (CH2C2H5), 29.6 (OCOC2H4-
CH2), 29.4 (OCOC5H10CH2), 29.3 (OCOC4H8CH2 and OCOC6-
H12CH2), 29.2 (OCOC3H6CH2), 29.1 (CH2C3H7), 28.1 (tC-
CH2CH2), 24.9 (OCOCH2CH2), 22.7 (CH2CH3), 15.1 (tC-CH2),
14.1 (CH3). MS (CI): m/e 435.3 [(M + 1)+; calcd 435.3)]. Anal.
Calcd for C29H38O3: C; 80.13, H; 8.82. Found: C; 80.00, H;
8.49.
NMR (300 MHz, CDCl3), δ (ppm): 8.12 (d, 2H, Ar-H ortho to
CO2C6H9), 7.6 (m 4H, Ar-H para to CO2C6H9 and OCOC11H23),
7.19 (d, 2H, Ar-H ortho to OCOC11H23), 4.37 (t, 2H, CO2CH2-
C5H7), 2.58 (t, 2H, OCOCH2), 2.30 (td, 2H, tC-CH2), 1.98 (t,
1H, HCt), 1.93 (m, 2H, OCOCH2CH2), 1.75 (m, 4H, OCOCH2-
CH2 and tCCH2CH2), 1.27 [m, 16H, (CH2)8], 0.88 (t, 3H, CH3).
13C NMR (75 MHz, CDCl3), δ (ppm): 172.3 (OCO C11H23), 166.4
(CO2C6H9), 150.9 (aromatic carbon linked with OCO C11H23),
144.8 (aromatic carbons para to CO2C6H9), 134.6 (aromatic
carbon para to OCOC11H23), 130.1 (aromatic carbons ortho to
CO2C6H9), 129.2 (aromatic carbon linked with CO2C6H9), 128.3
(aromatic carbons meta to CO2C6H9), 127.0 (aromatic carbons
meta to OCOC11H23), 122.1 (aromatic carbons ortho to
OCOC11H23), 83.9 (tC), 68.8 (HCt), 64.5 (CO2CH2C5H7), 34.3
(OCOCH2), 31.9 (OCOC8H16CH2), 29.6 (OCOC2H4CH2), 29.5
(OCO2CH2CH2), 29.3 (OCOC5H10CH2), 29.2 (OCOC4H8CH2),
29.1 (OCOC3H6CH2), 27.8 (OCO 2C7H14CH2), 25.1 (tC-
CH2CH2), 25.0 (OCOCH2CH2), 22.7 (CH2CH3), 17.5 (tC-CH2),
14.1 (CH3). MS (CI): m/e 477.3 [(M + 1)+; calcd 477.3]. Anal.
Calcd for C31H40O4: C, 78.10; H, 8.46. Found: C, 78.24; H,
8.32.
(4′-{[(Un d ecyl)ca r b on yl]oxy})-4-b ip h en ylca r b oxylic
a cid (10). Into a 100-mL, two- necked, round-bottomed flask
were added 4.0 g (20 mmol) of lauric acid, 3 mL of thionyl
chloride, and 20 mL of THF. After refluxing for 2 h, the excess
thionyl chloride was distilled off under reduced pressure. The
solid left in the flask was dissolved in 20 mL of THF and cooled
using an ice bath. A solution of 4′-hydroxy-4-biphenylcarboxylic
acid (4.5 g, 21 mmol) and pyridine (2 mL) in 30 mL of THF
was injected into the flask, and the mixture was slowly
warmed to room temperature and stirred overnight. THF was
then distilled off using a rotary evaporator. Recrystallization
of the solid residue from absolute ethanol gave 5.6 g of
product: white crystal; yield 69.6%. IR (KBr), ν (cm-1): 1746
(vs, CdO stretching in OCOC11H23), 1684 (vs, CdO stretching
P olym er iza tion . All the polymerization reactions and
manipulations were carried out under nitrogen using Schlenk
techniques in a vacuum line system or an inert-atmosphere
glovebox (Vacuum Atmospheres), except for the purification
of the polymers, which was done in an open atmosphere. A
typical experimental procedure for the polymerization of 3(3)
is given below.
1
in CO2H). H NMR (300 MHz, DMSO-d6), δ (ppm): 13.01 (s,
1H, CO2H), 8.13 (d, 2H, Ar-H ortho to CO2H), 7.80 (m, 4H,
Ar-H), 7.30 (d, 2H, Ar-H ortho to OCOC11H23), 2.70 (t, 2H,
OCOCH2), 1.80 (m, 2H, OCOCH2CH2), 1.40 [m, 16H, (CH2)8],
1.00 (t, 3H, CH3). 13C NMR (75 MHz, DMSO-d6), δ (ppm):
171.8 (OCOC11H23), 170.2 (CO2H), 150.3 (aromatic carbon
linked with OCOC11H23), 143.5 (aromatic carbon para to
CO2H), 136.6 (aromatic carbon para to OCOC11H23), 123.0
(aromatic carbons ortho to CO2H), 129.8 (aromatic carbon
linked with CO2H), 128.2 (aromatic carbons meta to CO2H),
126.8 (aromatic carbons meta to OCOC11H23), 122.5 (aromatic
carbons ortho to OCOC11H23), 33.6 (OCOCH2), 31.3 (CH2CH2-
CH3), 29.1 (OCOC2H4CH2), 29.0 (OCOC5H10CH2) 28.8 (OCO-
C4H8CH2 and OCOC6H12CH2), 28.7 (OCOC3H6CH2), 28.5
(CH2C3H7), 24.5 (OCOCH2CH2), 22.2 (CH2CH3), 14.0 (CH3).
5-({[(4′-{[(Un d ecyl)ca r b on yl]oxy})-4-b ip h en ylyl]ca r -
Into a baked 20 mL Schlenk tube with a stopcock in the
sidearm was added 375.0 mg (0.8 mmol) of 3(3). The tube was
evacuated under vacuum and then flushed with dry nitrogen
three times through the sidearm. Freshly distilled 1,4-dioxane
(2 mL) was injected into the tube to dissolve the monomer.
The catalyst solution was prepared in another tube by dis-
solving 16.0 mg of tungsten(VI) chloride and 17.0 mg of
tetraphenyltin in 2 mL of 1,4-dioxane. The two tubes were aged
at 60 °C for 15 min and the monomer solution was transferred
to the catalyst solution using a hypodermic syringe. The
reaction mixture was stirred at room temperature under
nitrogen for 24 h. The solution was then cooled to room
temperature, diluted with 5 mL of chloroform, and added
dropwise to 500 mL of acetone through a cotton filter under
stirring. The precipitate was allowed to stand overnight, which
was then filtered with a Gooch crucible. The polymer was
washed with acetone and dried in a vacuum oven to a constant
weight.
bon yl}oxy)-1-p en tyn e [4(3)]. In
a 500-mL, two-necked,
round-bottom flask were dissolved (4′-{[(undecyl)carbonyl]-
oxy})-4-biphenylcarboxylic acid (1.25 g, 3.2 mmol), 4-pentyn-
1-ol (0.32 g, 3.8 mmol), DCC (0.98 g, 4.8 mmol), TsOH (0.12 g,
0.70 mmol), and DMAP (0.08 g, 0.65 mmol) in 250 mL of dry
dichloromethane. After the solution was stirred for 24 h, the
formed urea was filtered out and the solvent was removed by
a rotary evaporator. The residue was purified by a silica gel
column using dichloromethane as eluent followed by recrys-
tallization from absolute ethanol.
Ch a r a cter iza tion Da ta . 4(3). White crystal; yield 74.6%.
IR (KBr), ν (cm-1): 3288 (s, H-Ct), 1746 (vs, CdO stretching
in OCOC11H23), 1714 (vs, CdO stretching in CO2C5H7), 654
(m, H-Ct bending). 1H NMR (300 MHz, CDCl3), δ (ppm): 8.12
(d, 2H, Ar-H ortho to CO2C5H7), 7.62 (d, 4H, Ar-H para to
CO2C5H7 and OCOC11H23), 7.21 (d, 2H, Ar-H ortho to
OCOC11H23), 4.56 (t, 2H, CO2CH2C4H5), 2.58 (t, 2H, OCOCH2-
Ch a r a cter iza tion Da ta . 1(3). Red powdery solid; yield
68.9%. Mw 9750; Mw/ Mn 1.78 (GPC; Table 2, no. 11). IR (KBr),
ν (cm-1): 1756 (vs, CdO). 1H NMR (300 MHz, CDCl3), δ
(ppm): 7.35, 7.00, 6.82 (Ar-H and trans H-C)), 6.14 (cis
H-C)), 3.87 (OCH2), 2.56 (OCOCH2), 2.1 (dC-CH2), 1.81
(OCOCH2CH2), 1.35 [(CH2)9], 0.96 (CH3). 13C NMR (75 MHz,
CDCl3), δ (ppm): 172.1 (CdO), 158.5 (aromatic carbon linked
with OC5H7), 149.7 (aromatic carbon linked with OCOC11H23),
138.0 (aromatic carbon para to OCOC11H23), 132.5 (aromatic
carbon para to OC5H7), 127.9 (aromatic carbons meta to
OCOC11H23), 127.4 (aromatic carbons meta to OC5H7), 121.8
(aromatic carbons ortho to OCOC11H23), 114.7 (aromatic
carbons ortho to OC5H7), 67.4, (OCH2), 34.4 (OCOCH2 and
dC-CH2), 31.9 (CH2C2H5), 29.7 (OCOC2H4CH2), 29.4 (OCOC5-
C
10H21), 2.41 (td, 2H, tC-CH2), 2.02 (m, 3H, tCCH2CH2 and
HCt), 1.78 (m, 2H, OCOCH2CH2) 1.55-1.40 [m, 16H, (CH2)8],
0.88 (t, 3H, CH3). 13C NMR (75 MHz, CDCl3), δ (ppm): 172.1
(OCOC11H23), 169.3 (CO2C5H7), 150.9 (aromatic carbon linked
with OCOC11H23), 144.8 (aromatic carbon para to CO2C5H7),
137.5 (aromatic carbon para to OCOC11H23), 130.1 (aromatic
carbon ortho to CO2C5H7), 129.0 (aromatic carbon linked with
CO2C5H7), 128.3 (aromatic carbons meta to CO2C5H7), 127.0
(aromatic carbons meta to OCOC11H23), 122.1 (aromatic car-
bons ortho to OCOC11H23), 83.0 (tC), 69.1 (HCt), 63.5
(CO2CH2), 34.4 (OCOCH2), 31.9 (CH2C2H5), 29.6 (OCOC2H4CH2),
29.4 (CH2C5H11), 29.3 (OCOC4H8CH2 and OCOC6H12CH2), 29.2
(OCOC3H6CH2), 29.1 (CH2C3H7), 27.7 (tC-CH2CH2), 24.9
(OCOCH2CH2), 22.6 (CH2CH3), 15.4 (tC-CH2), 14.0 (CH3). MS
H
10CH2, OCOC4H8CH2, OCOC6H12CH2 and OCOC3H6CH2),
29.2 (OCOC3H6CH2 and CH2C3H7), 25.0 (OCOCH2CH2), 22.7
(CH2CH3), 14.1 (CH3). UV (CHCl3, 1.13 × 10-4 mol /L), λmax
(nm)/ꢀmax (mol-1 L cm-1): 265/2.23 × 104, 360 (sh)/1.33 × 103.
2(3). Yellow powdery solid; yield 84.1%. Mw 37 700; Mw/Mn
1.9 (GPC, Table 3, no. 3). IR (KBr), ν (cm-1): 1758 (CdO
stretching in OCOC11H23), 1716 (CdO stretching in CO2C5H7).
1H NMR (300 MHz, CDCl3), δ (ppm): 7.93, 7.39, 6.97 (Ar-H
and trans H-Cd), 5.96 (cis H-Cd), 4.32 (CO2CH2), 2.59
(OCOCH2), 2.06 (dC-CH2), 1.80 (OCOCH2CH2 and dC-
CH2CH2), 1.36 [(CH2)8], 0.96 (CH3). 13C NMR (75 MHz, CDCl3),
δ (ppm): 171.8 (OCOC11H23), 165.9 (CO2C5H7), 150.5 (aromatic
carbon linked with OCOC11H23), 144.0 (aromatic carbon para
to CO2C5H7), 137.1 (aromatic carbon para to OCOC11H23), 129.9
(aromatic carbons ortho to CO2C5H7), 128.8 (aromatic carbon
(CI): m/e 463.3 [(M + 1)+; calcd 463.3]. Anal. Calcd for C30
38O4: C, 77.88; H, 8.28. Found: C, 77.53; H, 7.85.
4(4). White crystal; yield 88.2%. IR (KBr), ν (cm-1): 3256
-
H
(s, H-Ct), 1754 (vs, CdO stretching in OCOC11H23), 1716 (vs,
CdO stretching in CO2C6H9), 674 (m, H-Ct bending). 1H

Macromolecules, Vol. 35, No. 4, 2002
Biphenyl-Containing Poly(1-alkynes) 1239
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linked with CO2C5H7), 128.0 (aromatic carbons meta to
CO2C5H7), 126.8 (aromatic carbons meta to OCOC11H23), 121.8
(aromatic carbons ortho to OCOC11H23), 64.3 (CO2CH2), 34.3
(OCOCH2 and dC-CH2), 31.8 (CH2C2H5), 29.6 (OCOC2H4CH2),
29.5 (OCOC5H10CH2), 29.3 (OCOC4H8CH2 and OCOC6H12CH2),
29.1 (OCOC3H6CH2 and OCOC7H14CH2), 24.8 (OCOCH2CH2),
22.6 (CH2CH3), 14.0 (CH3). UV (CHCl3, 9.00 × 10-5 mol/L),
λ
max/ꢀmax: 277 nm/2.56 × 104 mol-1 L cm-1
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2(4). Red powdery solid; yield 82.3%. Mw 59 000, Mw/Mn 1.85
(GPC; Table 4, no. 3). IR (KBr), ν (cm-1): 1756 (vs, CdO
stretching in OCOC11H23), 1716 (vs, CdO stretching in
CO2C6H9). 1H NMR (300 MHz, CDCl3), δ (ppm): 7.87, 7.35,
6.97 (Ar-H and trans H-Cd), 5.75 (cis H-Cd), 4.22 (CO2CH2),
2.34 (OCOCH2), 2.06 (dC-CH2), 1.71-1.27 [(CH2)12], 0.88
(CH3). 13C NMR (75 MHz, CDCl3), δ (ppm): 171.9 (OCOC11H23),
166.0 (CO2C6H9), 150.7 (aromatic carbon linked with OCO-
C
11H23), 144.7 (aromatic carbon para to CO2C6H9), 137.7
(aromatic carbon para to OCOC11H23), 129.9 (aromatic carbons
ortho to CO2C6H9), 129.0 (aromatic carbon linked with
CO2C6H9), 128.1 (aromatic carbons meta to CO2C6H9), 126.7
(aromatic carbons meta to OCOC11H23), 121.9 (aromatic car-
bons ortho to OCOC11H23), 64.8 (CO2CH2), 34.3 (OCOCH2 and
dC-CH2), 31.9 (CH2C2H5), 29.6 (OCOC2H4CH2), 29.5 (OCO-
CH2CH2), 29.3 (OCOC5H10CH2), 29.2 (OCOC4H8CH2 and
OCOC3H6CH2), 24.9 (OCOCH2CH2), 22.7 (CH2CH3), 14.1 (CH3).
UV (CHCl3, 8.80 × 10-5 mol/L), λmax/ꢀmax: 276 nm/2.34 × 104
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Ack n ow led gm en t. The work described in this paper
was partially supported by the Research Grants Council
of the Hong Kong Special Administrative Region, China,
through Grants HKUST 6062/98P, 6187/99P, and 6121/
01P. This project was also benefited from the financial
support of the Industry Department of the Hong Kong
SAR Government, the Center for Display Research, and
the Institute of Nano Science and Technology of the
Hong Kong University of Science & Technology and the
Open Laboratory of Chirotechnology of the Institute of
Molecular Technology for Drug Discovery and Synthesis
administrated by the University Grants Committee
(Hong Kong) under the Area of Excellence Scheme.
B.Z.T. thanks the National Science Foundation of China
for the Oustanding Young Investigator Award (No.
20129001).
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