Functional disubstituted polyacetylenes and soluble cross-linked polyenes: Effects of pendant groups or side chains on liquid crystallinity and light emission of poly(1-phenyl-l-undecyne)s

Article abstract of DOI:10.1021/ma048076t

A group of new poly(1-phenyl-1-undecyne)s with different mesogenic and chromophoric pendant groups or side chains were successfully synthesized and the structural variations were found to greatly affect the mesomorphic and luminescent properties of the po

Full text of DOI:10.1021/ma048076t

3290
Macromolecules 2005, 38, 3290-3300
Functional Disubstituted Polyacetylenes and Soluble Cross-Linked
Polyenes: Effects of Pendant Groups or Side Chains on Liquid
Crystallinity and Light Emission of Poly(1-phenyl-1-undecyne)s
Jacky W. Y. Lam,† Yuping Dong,†, Charles C. W. Law,† Yongqiang Dong,†,|
Kevin K. L. Cheuk,† Lo Ming Lai,† Zhen Li,† Jingzhi Sun,§ Hongzheng Chen,§
Qiang Zheng,§ Hoi Sing Kwok,‡ Mang Wang,§ Xinde Feng,| Jiacong Shen,§ and
Ben Zhong Tang*,†,‡,§,|
Department of Chemistry and Center for Display Research, The Hong Kong University of Science &
Technology, Clear Water Bay, Kowloon, Hong Kong, China, Department of Polymer Science and
Engineering, Zhejiang University, Hangzhou 310027, China, and Department of Polymer Science and
Engineering, Peking University, Beijing 100871, China
Received September 16, 2004; Revised Manuscript Received January 28, 2005
ABSTRACT: A group of new poly(1-phenyl-1-undecyne)s with different mesogenic and chromophoric
pendant groups or side chains were successfully synthesized and the structural variations were found to
greatly affect the mesomorphic and luminescent properties of the polymers. The 1-phenyl-1-undecyne
monomers (C6H5)CtC(CH2)9OCOR with R ) C6H4-C6H10-C5H11 (1), C6H4-OCO-C6H4-OC6H13 (2), and
C6H4-CtC-C6H4-OC7H15 (3) were prepared by simple esterification and/or coupling reactions. The
polymerizations of 1-3 were effected by WCl6-Ph4Sn in toluene at 60-80 °C, giving polymers with high
molecular weights in good isolation yields. The structures and properties of the polymers were
characterized and evaluated by GPC, IR, NMR, TGA, DSC, POM, XRD, UV, and PL analyses. The
polymerizations of 1 and 2 yield linear poly(1-phenyl-1-alkyne)s P1 and P2, respectively, while that of 3
gives a nonlinear macromolecule with its poly(1-phenyl-1-alkyne) main chain cross-linked by the oligo-
(diphenylacetylene) side chains resulted from the partial polymerization of its diphenylacetylene pendants
(P3x). All the polymers are completely soluble in common solvents and are thermally stable with
Td g 390 °C. Polymers P1 and P2 undergo nematic and smectic transitions at ∼100 and ∼170 °C,
respectively, while P3x is nonmesomorphic. Upon excitation, the poly(1-phenyl-1-alkyne) chains of P1
and P2 emit a strong blue light of 460 nm, with their fluorescence quantum efficiencies comparable to or
higher than that of poly(1-phenyl-1-octyne), a highly emissive disubstituted polyacetylene. Polymer P3x
emits a blue-green light of 490 nm, due to the energy transfer from its poly(1-phenyl-1-octyne) main
chain to its oligo(diphenylacetylene) side chains.
Introduction
phenyl-2-phenylacetylene) (PNOPPA)] (Chart 1) are two
typical examples of highly luminescent polyacetylenes.
Both polymers can emit efficiently, but the colors of their
emissions are different: the light emitted from the
former is blue while that from the latter is green.12,13
We have been particularly interested in the blue light-
emitting PPA and have synthesized a variety of its
derivatives with an aim of further enhancing its emis-
sion efficiency as well as endowing it with new func-
tionality.5,14 In our previous work, we prepared a series
of new PPAs, in which chromophoric and mesogenic
biphenyl cores were attached to the polyene backbone
as pendants through alkyl spacers of different chain
lengths (m; Chart 2).15 The chain length was found to
greatly affect the properties of the biphenyl-containing
PPAs: for example, the polymer with the shorter chain
length (m ) 4) was not liquid crystalline, whereas that
with the longer chain (m ) 9) packed into a smectic A
(SmA) mesophase in a monolayer arrangement. Both
of the polymers emitted a blue light of 460 nm, but the
fluorescence quantum yield (ΦF) of the polymer with the
longer spacer was higher than that of the one with the
shorter spacer.
Polyacetylene -(HCdCH)n- is well-known as an
electroactive polymer1 but is also notorious for its
instability and intractability.2 Replacements of one or
two hydrogen atoms in the repeat unit of the polymer
by one or two substituents give rise to mono- {-[(R)Cd
CH]n-} or disubstituted polyacetylenes {-[(R)Cd
C(R′)]n-}, respectively, which can be stable and pro-
cessable, provided that the R(′) groups are properly
chosen.3,4 Compared to its monosubstituted counterpart,
a disubstituted polyacetylene often enjoys such advan-
tages as being thermally more stable, better film form-
ing, and mechanically much stronger.5,6 Although poly-
acetylene itself is not luminescent,7 recent investigations
have revealed that its substituted derivatives can be
emissive,5,8,9 with disubstituted polyacetylenes being
generally more luminescent than their monosubstituted
counterparts.10,11 Among disubstituted polyacetylenes,
poly(1-phenyl-1-alkyne)s (PPAs) [e.g., poly(1-phenyl-
1-octyne)
(PPO)]
and
poly(diphenylacetylene)s
(PDPAs) [e.g., poly(1-{p-[(1-naphthyloxy)octyloxy]}-
* Corresponding author. Telephone: +852-2358-7375. Fax:
+852-2358-1594. E-mail: tangbenz@ust.hk.
† Department of Chemistry.
Since the long spacer is good for the mesomorphism
and luminescence of PPAs, in this work, we synthesized
a group of 1-phenyl-1-alkyne monomers with nine
methylene spacers, namely, 1-phenyl-1-undecynes, con-
taining different mesogenic or chromophoric cores
(1-3; Scheme 1). Compared with the biphenyl core in
‡ Center for Display Research.
§ Zhejiang University.
| Peking University.
On leave from School of Chemical Engineering & Materials
Science, Beijing Institute of Technology, Beijing 100081, China.
10.1021/ma048076t CCC: $30.25 © 2005 American Chemical Society
Published on Web 03/09/2005

Macromolecules, Vol. 38, No. 8, 2005
Liquid-Crystalline and Light-Emitting Polyacetylenes 3291
state.16,17 In our previous work, we found that WCl6-
Ph4Sn effected the polymerizations of the biphenyl-
containing 1-phenyl-1-alkynes.15 Polymerization of 1
using the same catalyst was thus attempted. Although
the reaction carried out at room temperature fails to
produce any polymer, the polymerization performed at
60 °C gives a yellow powdery product, which is isolated
in ∼69% yield by precipitation of its toluene solution
into acetone (Table 1, no. 2). Increasing the temperature
to 80 °C did not affect the polymerization result much.
The monomer does not undergo polymerization in the
presence of MoCl5-Ph4Sn. Mixtures of NbCl5- and
TaCl5-Ph4Sn are the most widely used catalysts for the
polymerizations of disubstituted acetylenes3,18 but the
reactions catalyzed by these mixtures give little or no
polymeric products (Table 1, nos. 5 and 6), probably due
to the poisoning interaction of the polar ester groups of
1 with the transition metal compounds. Monomer 2 is
polymerized in a similar way. Although at room-tem-
perature WCl6-Ph4Sn is again ineffective in polymer-
izing 2, the reactions conducted at elevated tempera-
tures yield high molecular weight polymers. The polymer
is isolated in an impressively high yield (∼86%) when
the polymerization is carried out at 80 °C (Table 1, no.
9).
Similar to monomers 1 and 2, monomer 3 can also be
readily polymerized into high molecular weight poly-
mers by the W catalyst at high temperatures (Table 1,
nos. 10 and 11), with the Mo, Nb, and Ta mixtures being
again ineffective catalysts. However, different from the
polymers of 1 and 2, those of 3 show multipeaked GPC
chromatograms. As can be seen from Figure 1, the
polymer obtained from the polymerization of 3 at 60 °C
gives several peaks: one main peak in the “normal”
molecular weight region and a few minor peaks in the
very high molecular weight region. The high molecular
weight fractions are increased when the polymerization
temperature is increased to 80 °C.
Chart 1
Chart 2
the polymers shown in Chart 2, the phenylcyclohexane
core in 1 is less conjugated and the phenyl benzoate core
in 2 is more polarized, while the diphenylacetylene core
in 3 is, on the other hand, more conjugated. In this
paper, we demonstrate that the variation in the core
structure greatly affects the polymerization behaviors
of the monomers as well as the physical properties of
the resultant polymers. Thus, monomers 1 and 2 are
polymerized into linear PPA chains of P1 and P2,
respectively, whereas a linear PPA of P3 is not yielded
by the polymerization of monomer 3; instead, a nonlin-
ear polyacetylene with a PPA backbone and oligo-
(diphenylacetylene) (ODPA) pendants (P3x) is obtained
(Chart 3). The linear polyacetylene bearing the phenyl-
cyclohexane- (P1) and phenyl benzoate-cored pendants
(P2) are nematogenic and smectogenic, respectively, but
the nonlinear, cross-linked polyene with the diphenyl-
acetylene-cored pendants and ODPA branches (P3x) are
completely nonmesomorphic. Furthermore, P1 and P2
are blue emitters, while P3x emits a blue-green light.
The multipeaked GPC chromatograms suggest that
both of 1-phenyl-1-alkyne and diphenylacetylene triple
bonds of 3 have undergone polymerizations. The
WCl6-Ph4Sn mixture is a good catalyst for the poly-
merizations of 1-phenyl-1-alkynes (e.g., 1 and 2), and
the PPA chains formed by the polymerization of the
1-phenyl-1-alkyne triple bonds of 3 are thus believed
to be the backbone of the polymer of 3. Although it has
been reported that the WCl6-Bu4Sn mixture is not a
catalyst for the polymerizations of diphenylacetylenes,19
the triple bonds of the diphenylacetylene pendants of
the polymer of 3 may have been partially polymerized
by WCl6-Ph4Sn, because our recent investigations
found that this catalyst could polymerize diphenylacety-
lene derivates of C6H5CtCC6H4O(CH2)mOAr, with Ar
being naphthyl and carbazolyl groups.20 The partial
polymerization of diphenylacetylene triple bonds in the
pendants of the polymer of 3 should result in the
formation of cross-linked gels, which would normally be
insoluble. The products of the polymerizations of 3 are,
however, completely soluble in common solvents such
as toluene, THF, and chloroform. The syntheses of
soluble polymers with cross-linked molecular structures
have been accomplished in certain polymerization sys-
tems under well-controlled conditions.21 It is amazing
that soluble, cross-linked polyacetylenes can be pre-
pared under the normal conditions of acetylene polym-
erization.
Results and Discussion
Monomer Preparations and Polymer Syntheses.
1-Phenyl-1-undecyne monomers 1 and 2 were prepared
by single-step, room-temperature esterifications of
11-phenyl-10-undecyn-1-ol (4)15 with 4-(4-pentylcyclo-
hexyl)benzoic acid (5) and 4-(4-hexyloxyphenylcarbony-
loxy)benzoic acid (6), respectively, in the presence of
a
mixture of 1,3-dicyclohexylcarbodiimine (DCC),
p-toluenesulfonic acid (TsOH), and 4-(dimethylamino)-
pyridine (DMAP; Scheme 1). Monomer 3 was prepared
by esterification of 4-ethynylbenzoic acid (7) with
11-phenyl-10-undecyn-1-ol (4) in the presence of a
mixture of DCC, TsOH, and DMAP, followed by the
coupling of the resultant diyne (8) with 4-heptyloxy-
iodobenzene (9) catalyzed by a palladium complex. All
of the monomers were isolated in good yields (∼56-90%)
after purification by column chromatography and re-
crystallization. The monomers were characterized by
spectroscopic methods, from which satisfactory analysis
data were obtained (see Experimental Section for de-
tails). While 1 is a colorless liquid, 2 and 3 are white
solids but do not exhibit liquid crystallinity at elevated
temperatures.
We tried to polymerize the nonmesomorphic mono-
mers in the hope that polymerization will enable the
mesogenic pendants to enter the liquid crystalline

3292 Lam et al.
Macromolecules, Vol. 38, No. 8, 2005
Scheme 1
Chart 3
of 3 at δ 7.39 and 7.25 shift upfield to δ 6.84 upon
polymerization,22 as observed in the case of polymeri-
zation of the biphenyl-containing 1-phenyl-1-alkynes
(Chart 2).15 The resonance of the protons of the meth-
ylene group directly linked to the triple bond (tCCH2
or propargyl protons) becomes very weak after polym-
erization (cf., panels A and B of Figure 3) because the
allenic protons (dCCH2) are attached to a rigid polymer
backbone.5,6b,23,24
In the 13C NMR spectrum of 3, the carbon atoms of
its 1-phenyl-1-alkyne triple bond resonate at δ 80.6 (b)
and 90.3 (c), while those of its diphenylacetylene one
are located at δ 92.6 (i) and 87.4 (j) (Figure 4A). After
polymerization, the resonance peaks of the 1-phenyl-1-
alkyne triple bond disappear, and that of the propargyl
carbon (d) downfield shits due to its transformation to
allenic structure (Figure 4B). This confirms that the
1-phenyl-1-alkyne triple bonds of molecules of 3 have
all been consumed by the acetylene polymerization. The
resonance peaks of the diphenylacetylene triple bond
(i and j), on the other hand, do not disappear but are
weakened in intensity, spectroscopically proving that
not all but part of the diphenylacetylene triple bonds of
the molecules of 3 have been polymerized. The olefinic
carbon atoms b and c of the PPA backbone and the
ODPA branches resonate in a broad chemical shift
range owing to the rigid nature of the polyacetylene
chains.6b,22-24
Thermal Stability and Oxidative Resistance. The
monosubstituted polyacetylenes such as poly(1-alkyne)s
-{HCdC[(CH2)mCH3]}n- are thermally unstable.5,6 Poly-
(1-hexyne) (PH), for example, starts to lose its weight
at a temperature (Td) as low as 150 °C (Figure 5).
Thermal stability of the biphenyl-containing poly-
(1-alkyne)s is much higher and their Td’s move up to
∼300 °C.24,25 As shown in Figure 5, the PPA derivatives
of P1, P2, and P3x are thermally very stable and their
Td’s are as high as ∼390 °C. Clearly, the resistance of
the polyacetylenes to thermolytic decomposition is
boosted by the replacement of the hydrogen atom in the
repeat unit of a poly(1-alkyne) with a phenyl ring. It is
worth noting that ∼40% of the original weight of P3x is
left when it is pyrolyzed at 550 °C, at which almost all
of the weights of P1 and P2 are lost. Thermally induced
acetylene polymerization26 of the triple bonds of the
unpolymerized diphenylacetylene pendants of P3x fur-
ther cross-links the polymer, and the resultant thermo-
set gel may have graphitized upon pyrolysis, resulting
in the high weight residue at the high temperature.
Structural Characterizations by Spectroscopic
Methods. Spectroscopic analyses readily confirm that
the polymers of 1 and 2 are linear PPA chains bearing
phenylcyclohexane- and phenyl benzoate-cored pen-
dants, whose molecular structures can be respectively
represented by P1 and P2 shown in Chart 3. Since the
analysis of linear polyacetylene structures has been a
routine job in our laboratories and has been reported
in many of our previous papers,9,11,15 the structural
characterizations of P1 and P2 will not be discussed
here in detail (their numeric spectroscopic data can,
however, be readily found in Experimental Section). Our
discussion will instead be focused on the spectroscopic
verification of the nonlinear molecular structure of the
polymer of 3 suggested by its GPC trace, that is, a
macromolecule with a PPA backbone cross-linked by the
ODPA branches resulted from the partial polymeriza-
tion of its diphenylacetylene pendants (P3x).
Figure 2 shows the IR spectrum of P3x. For compari-
son, the spectrum of its monomer 3 is also given in the
figure. The vibration band of CtC stretching of a
1-phenyl-1-alkyne is normally very weak and can only
be occasionally observed at ∼2230 cm-1 15,22
,
while that
of a diphenylacetylene is strong enough to be visible at
∼2200 cm-1 19
. Monomer 3 exhibits a readily identifiable
band at 2217 cm-1, which is clearly associated with the
CtC stretching of its diphenylacetylene group. This
absorption band is still observable in the spectrum of
P3x, indicating that the polymer contains diphenyl-
acetylene triple bonds in its molecular structure. This
proves that the diphenylacetylene triple bonds have
been only partially polymerized by the W-catalyzed
acetylene polymerization.
1
Figure 3 shows the H NMR spectra of P3x and its
To further evaluate the stability of the polymers, we
checked the changes of their molecular weights with
monomer 3. The resonance peaks of the phenyl protons

Macromolecules, Vol. 38, No. 8, 2005
Table 1. Polymerizations of 1-Phenyl-1-undecynes (1-3)a
temp (°C) yield (%)
Liquid-Crystalline and Light-Emitting Polyacetylenes 3293
b
b
no.
catalyst
Mw
Mw/Mn
11-[4-(4-Pentylcyclohexyl)phenylcarbonyloxy]-1-phenyl-1-undecyne (1)
1
2
3
4
5
6
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
MoCl5-Ph4Sn
NbCl5-Ph4Sn
TaCl5-Ph4Sn
room tempc
0
60
80
60
60
60
68.5
64.5
0
trace
0
62 400
87 200
2.3
2.7
11-[4-(4-Hexyloxyphenylcarbonyloxy)phenylcarbonyloxy]-1-phenyl-1-undecyne (2)
7
8
9
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
room tempc
0
60
80
25.8
86.2
44 100
36 100
1.7
1.6
11-[4-(4-Heptyloxyphenylethynyl)phenylcarbonyloxy]-1-phenyl-1-undecyne (3)
10
11
12
13
14
WCl6-Ph4Sn
WCl6-Ph4Sn
MoCl5-Ph4Sn
NbCl5-Ph4Sn
TaCl5-Ph4Sn
60
80
60
60
60
32.2
42.3
0
trace
0
50 500d
57 700d
1.7d
1.9d
a Carried out under nitrogen in toluene for 24 h; [M]0 ) 0.2 M, [MtClx] ) [Ph4Sn] ) 10 mM (Mt ) W, Mo, Nb, Ta; x ) 5, 6). b Determined
by gel permeation chromatograph (GPC) in THF on the basis of a polystyrene calibration. c Room temperature. d Values for the main
peaks of the multipeaked GPC curves (cf., Figure 1).
Figure 1. GPC chromatograms of P3x prepared by
WCl6-Ph4Sn in toluene at 60 °C and 80 °C.
Figure 3. 1H NMR spectra of chloroform-d solutions of (A) 3
and (B) its polymer P3x (sample taken from Table 1, no. 10).
The solvent peak is marked with an asterisk (/).
to thermolysis caused by oxidative chain scission. The
high stability of the polymer is possibly due to the
“jacket effect” of its pendant groups,5 which sterically
shields the polyene backbone from the thermolytic
attack.
Figure 2. IR spectra of (A) 3 and (B) its polymer P3x (sample
Nematic and Smectic Mesomorphisms. To know
taken from Table 1, no. 10).
whether the 1-phenyl-1-alkyne derivatives become liq-
time and temperature. GPC analyses of the polymer
samples stored under ambient conditions in air for more
than 4 years find no changes in their molecular weights,
revealing that the polymers are very stable at room
temperature. We annealed P1 in air for 2 h at different
temperatures and plotted its Mw against the annealing
temperature in Figure 6. Almost no change in Mw is
observed when P1 is annealed at temperatures up to
150 °C, although further heating to 200 °C leads to a
slight increase in Mw. This confirms that P1 is resistant
uid crystalline after polymerization, we studied thermal
transitions of their polymers by differential scanning
calorimeter (DSC). Disappointedly, no liquid crystalline
transitions are detected by DSC for P3x in either
heating or cooling cycle. This is probably caused by its
nonlinear, irregularly cross-linked structure, in which
the ODPA branches segregate the unpolymerized di-
phenylacetylene mesogens in a random fashion. De-
lightfully, however, linear polymers P1 and P2 both
exhibit liquid crystallinity, as indicated by their DSC

3294 Lam et al.
Macromolecules, Vol. 38, No. 8, 2005
Figure 5. Thermogravimetric analysis (TGA) thermograms
of P1 (sample taken from Table 1, no. 2), P2 (Table 1, no. 8),
P3x (Table 1, no. 10), and poly(1-hexyne) (PH)6b recorded under
nitrogen at a heating rate of 20 °C/min.
Figure 6. Effect of temperature on the molecular weight (Mw)
of P1 (sample taken from Table 1, no. 2). The polymer samples
were annealed in air at given temperatures for 2 h.
with the nematic phase of P1.27 It is noted that all of
the monosubstituted polyacetylenes bearing the similar
mesogenic pendants prepared so far exhibit SmA
phases.28 The formation of the nematic phase in P1 is
probably caused by its more rigid disubstituted poly-
acetylene backbone, which hampers its mesogenic pen-
dants from packing into SmA phase. Compared to the
phenylcyclohexane mesogens in P1, the phenyl benzoate
mesogens in P2 have a stronger tendency to enter into
an SmA phase.17a,29 Thanks to this propensity for
smecticity, baˆtonnets, indicative of the formation of SmA
phase, are observed when the isotropic liquid of P2 is
cooled. The baˆtonnets could readily grow into the focal-
conic fan textures of SmA phases in the monosubsti-
tuted polyacetylene systems17a,29,30 but are difficult to
develop into the typical SmA texture in P2 (Figure 6B),
again due to the rigidity of its PPA backbone.
Table 2 summarizes the thermal transitions of P1 and
P2 as well as their corresponding enthalpy and entropy
changes. The small changes in ∆H (< |0.7| kJ/mru) and
∆S [< |1.7| J/(mru K)] involved in the mesophase
transitions of P1 suggest a poor ordering of its phenyl-
cyclohexane-cored mesogenic units and support the
assignment of nematicity to its Schlieren textures.31 The
Figure 4. 13C NMR spectra of chloroform-d solutions of (A) 3
and (B) its polymer P3x (sample taken from Table 1, no. 10).
The solvent peaks are marked with asterisks (/).
thermograms (Figure 7). In the first cooling cycle of P1,
an exothermic peak associated with its i-n transition
is observed at 108.4 °C. Its corresponding n-i transition
is detected as a broad endothermic bump peaked at
95.0 °C during the second heating scan. The nematic
phase is thus enantiotropic. Polymer P2 displays a
better-ordered SmA phase at 168.3 °C in the first cooling
cycle. The mesophase is again enantiotropic with the
corresponding SmA-i transition observed at 169.2 °C in
the second heating scan.
When the isotropic liquid of P1 is cooled, typical
Schlieren textures are formed. An example of the
polarized optical microscope (POM) photographs of the
Schlieren textures is given in Figure 8A, where four
brushes radiate from a disclination point. The polymer
also displays Schlieren texture containing a singularity
with two brushes or s ) (1/2 (data not shown). Since
disclination with s ) (1/2 is incompatible with SmC
phase, the Schlieren textures thus should be associated

Macromolecules, Vol. 38, No. 8, 2005
Liquid-Crystalline and Light-Emitting Polyacetylenes 3295
Figure 7. DSC thermograms of mesomorphic PPA derivatives
of (A) P1 (sample taken from Table 1. no. 2) and (B) P2 (Table
1, no. 8) recorded under nitrogen during the first cooling and
second heating scans at a scan rate of 10 °C/min.
Figure 8. Mesomorphic textures observed on cooling (A) P1
(sample taken from Table 1, no. 2) to 100 °C and (B) P2 (Table
1, no. 8) to 160 °C from their isotropic melts. Scale bar:
20 µm.
mesomorphic transitions of P2, however, involve bigger
changes in ∆H and ∆S [up to ∼12 kJ/mru and
∼27 J/(mru K), respectively], in agreement with the
smecticity of its mesophase revealed by the POM
observation.
bump at ∼332 nm with an ꢀ of ∼2550 mol-1 L cm-1
,
which is assigned to the absorption of its PPA backbone.
This assignment is supported by the observation that
poly(1-phenyl-1-nonyne), a parent form of P1, absorbs
at a similar wavelength (λ ∼325 nm) with a similar
absorptivity (ꢀ ∼3000 mol-1 L cm-1).32 This is further
attested by the overlapping of the absorption spectrum
of P1 with that of PPO, another parent form of P1, in
the wavelength range ∼300-350 nm. The PPA back-
bone of P2 shows similar absorption behaviors in the
similar spectral region (λ ∼ 330 nm, ꢀ ∼ 2110 mol-1
L cm-1).
We carried out X-ray diffraction (XRD) experiments
with the aim of further verifying the mesophase assign-
ments and gaining insights into the packing arrange-
ments of the mesogens in the polymers. It is known that
a typical XRD diffractogram of a nematic liquid crystal
is characterized by a diffuse halo and broad bumps in
the high- and low-angle regions, respectively.31 As can
be seen from Figure 9, the diffractogram of the sample
of P1 rapidly quenched from 100 °C by liquid nitrogen
possess these two features, thus substantiating the
nematicity assignment to its mesophase at this tem-
perature. Polymer P2, however, shows not only a diffuse
halo in the high-angle region but also Bragg reflection
peaks in the low-angle region. The sharp reflection at
2θ ) 2.65° corresponds to a layer spacing of 33.31 Å,
close to the molecular length for the repeat unit of P2
at its most extended conformation (l ) 35.52 Å). Its
mesogens are thus packed in a monolayer fashion.
The high-order secondary reflection at 2θ ) 5.25°
(d ) 16.82 Å) is readily detected by the XRD diffratom-
eter, indicative of good packing arrangements in this
liquid crystal system. The reflection at 2θ ) 7.7° (d )
11.47 Å) may be associated with the packing of the
appendages without the flexible tails.
The absorption spectrum of P3x is, however, different
from those of P1 and P2. The chromophoric pendant of
P3x absorbs at ∼316 nm. This absorption is strong
(ꢀ ∼ 25120 mol-1 L cm-1), owing to the molecular
polarization induced by the push-pull interaction ex-
erted on the chromophore by the electron-donating ether
group (-O-) and electron-withdrawing ester group
(-CO2-) attached to the two ends of the diphenylacety-
lene core. The appearance of this strong absorption peak
confirms that P3x bears the diphenylacetylene pen-
dants, or in other words, not all of the diphenylacetylene
triple bonds have been polymerized by the W-catalyzed
acetylene polymerization. Because of the overlapping
with this strong pendant absorption peak, the absorp-
tion peak of the PPA backbone of P3x now appears as a
shoulder at ∼332 nm with an apparent absorptivity of
∼21980 mol-1 L cm-1
.
Electronic Absorption and Light Emission. The
absorption spectra of the polymer solutions in THF are
shown in Figure 10. The mesogenic pendants of P1 and
P2 absorb at ∼240 and ∼264 nm with molar absorp-
Absorption spectrum of a PDPA chain is characterized
by its absorptions in the longer wavelength region
(λ > 400 nm),19 where a PPA chain does not absorb. For
example, PNOPPA, a PDPA derivative, absorbs at
λ > 400 nm, with absorption peak at ∼425 nm
tivities (ꢀ) of ∼18630 and ∼22150 mol-1 L cm-1
,
respectively. The UV spectrum of P1 exhibits a broad

3296 Lam et al.
Macromolecules, Vol. 38, No. 8, 2005
Table 2. Thermal Transitions and Packing Arrangements of P1 and P2
T, °C [∆H, kJ/mru; ∆S, J/(mru K)]c (by DSC)a
no.
polymer
cooling scan
heating scan
1
2
P1
P2
i 108.4 (-0.63; -1.64) n
i 168.3 (-7.58; -17.18) SmA
n 95.0 (0.40; 1.35) i
SmA 169.2 (11.78; 26.65) i
molecular packing arrangements (by XRD)
no.
polymer
T (°C)b
d1 (Å)
d2 (Å)
d3 (Å)
d4 (Å)
l (Å)d
ratio d1/l
phase
3
4
P1
P2
100
155
4.36
4.39
29.90
35.52
n
SmA
33.31
16.82
11.47
0.94
a Data taken from the DSC thermograms recorded under nitrogen in the first cooling and second heating scans; abbreviations:
n ) nematic phase, SmA ) smectic A phase, and i ) isotropic liquid. b The mesomorphic structure in the liquid crystalline phase at the
given temperature was frozen by the rapid quenching with liquid nitrogen. c Abbreviation: mru ) monomer repeat unit. d Molecular
length (l) calculated from the monomer repeat units in their fully extended conformation.
Figure 10. UV absorption spectra of THF solutions of P1
(sample taken from Table 1, no. 2), P2 (Table 1, no. 8), and
P3x (Table 1, no. 10). The spectral data for poly(1-phenyl-1-
octyne) (PPO)5 and poly(1-{p-[(1-naphthyloxy)octyloxy]}phenyl-
2-phenylacetylene) (PNOPPA)20 are shown for comparison.
Figure 9. X-ray diffraction patterns of mesomorphic PPA
derivatives quenched by liquid nitrogen from their liquid
crystalline states: P1 (sample taken from Table 1, no. 2) at
100 °C and P2 (Table 2, no. 8) at 155 °C.
absorbed by the PPA backbone of P3x is transferred to
its ODPA side chains, which pumps the oligomers to
their excited states. When the excitons decay back to
their ground state, a blue-green light is emitted from
the ODPA chains. There is no shoulder at 460 nm in
the photoluminescence spectrum of P3x, indicating that
the energy transfer from the PPA backbone to the ODPA
side chains is efficient. The emission spectrum of a
PDPA chain is normally peaked at >500 nm:5,12,13 for
example, the λmax of the spectrum of PNOPPA is located
at ∼509 nm (Figure 11B).20 The blue shift of the λmax of
P3x from that of a normal PDPA chain confirms the
finding by the UV spectral analysis: the effective
conjugation length of the ODPA side chains of P3x is
short.
(ꢀ ∼3000 mol-1 L cm-1). No absorption peak is, however,
observed at this wavelength in the spectrum of P3x.
What one can see from Figure 10 is a weak tail start-
ing from ∼360 nm and ending at ∼450 nm with
ꢀ < 4000 mol-1 L cm-1. This indicates that only has a
portion of the diphenylacetylene pendants of P3x been
polymerized into ODPA side chains with low degrees
of polymerization (or small numbers of repeat units) and
short conjugation lengths. The inhomogeneity in the
conjugation lengths of the ODPA side chains as well as
their random distributions along the PPA backbone of
P3x have smoothened the defined absorption peak19 into
a gradually decaying tail.
As discussed in the Introduction, PPA and PDPA can
efficiently emit blue and green lights, respectively, upon
photoexcitation.12,13 PPO is a typical example of PPA,5
which emits a blue light of 460 nm in a high quantum
efficiency (ΦF 43%).12,13 Both P1 and P2 can be consid-
ered to be derivatives of PPO. Because of this structural
similarity, P1 and P2 emit blue light of 460 nm with
spectral profiles similar to that of PPO (Figure 11A).
The quantum yield of P1 is the same as that of PPO,
while P2 is a more efficient emitter with a higher
quantum yield (59%).
While monomer 3 emits a deep-blue light of ∼396 nm
upon excitation at 368 nm, its polymer P3x emits faintly
at ∼396 nm when excited at 368 nm, as can be seen
from the weak bump in the emission spectrum of P3x
(Figure 9B). Its spectrum is dominated by the emission
from its ODPA side chains at 491 nm. As the emission
spectrum of the unpolymerized diphenylacetylene pen-
dants of P3x overlaps with the absorption spectrum of
its ODPA side chains (cf., Figures 10 and 11), the light
emitted from its chromophoric pendants is reabsorbed
by its ODPA side chains, hence the blue-green emission
at 491 nm. The quantum yield for the emission of P3x
generated by the excitation at 368 nm is 34%, which is
Different from PPO, P3x emits a blue-green light of
491 nm, instead of a blue light of 460 nm. The energy

Macromolecules, Vol. 38, No. 8, 2005
Liquid-Crystalline and Light-Emitting Polyacetylenes 3297
mesogenic pendants (P2) exhibit nematic and smectic
mesomorphisms, respectively. In sharp contrast, the
nonlinear polymer with diphenylacetylene-cored me-
sogenic pendants and ODPA side chains (P3x) is not
liquid crystalline at all. All the polyacetylenes are
efficient light emitters with ΦF in the range of 43-59%
when excited at 355 nm. While P1 and P2 emit a blue
light from their PPA backbones, P3x emits a blue-green
light from its ODPA side chains due to the energy
transfer from its backbone to the side chains.
Of particular interest is the successful synthesis of
the soluble, cross-linked polyacetylene (P3x) under the
normal acetylene polymerization conditions from the
diyne monomer (3) with the two triple bonds in different
chemical environments and with different reactivity or
polymerizability. We have extended the utility of this
synthetic strategy to the designs and preparations of
soluble, cross-linked disubstituted polyenes with differ-
ent molecular structures and varying light-emitting
characteristics, full details of which will be reported in
our future publications in due course.
Experimental Section
General Information. Toluene (BDH) was 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. Molybdenum(V) chloride was purchased from Acros
and used as received. 4-(4-Pentylcyclohexyl)benzoic acid (5)
and 4-(4-hexyloxyphenylcarbonyl-oxy)benzoic acid (6) were
purchased from Slichem LCD Material Co., Ltd. All other
reagents and solvents were purchased from Aldrich and used
without further purification. 11-Phenyl-10-undecyn-1-ol (4)
was prepared by coupling of 10-undecyn-1-ol with iodobenzene
in the presence of PdCl2(PPh3)2 and CuI.33 4-Ethynylbenzoic
acid (7) was synthesized according to our published proce-
dures.34,35
Figure 11. Photoluminescence spectra of THF solutions
(0.05 mM) of (A) P1 (sample from Table 1, no. 2), P2 (Table 1,
no. 8), P3x (Table 1, no. 10), and poly(1-phenyl-1-octyne) (PPO)5
and (B) monomer 3, its polymer P3x, and poly(1-{p-[(1-
naphthyloxy)octyloxy]}phenyl-2-phenylacetylene) (PNOPPA)20
recorded at excitation wavelengths of (A) 355 and (B) 368 nm.
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 the solvent and tetramethylsilane (δ ) 0) or
chloroform (7.26) as the internal reference. The UV spectra
were measured on a Milton Roy Spectronic 3000 Array
spectrophotometer. The fluorescence spectra were taken in
THF on a SLM 8000C spectrofluorometer. The mass spectra
were recorded on a Finnigan TSQ 7000 triple quadrupole mass
spectrometer operating in a chemical ionization (CI) mode
using methane as the carrier gas. The average molecular
weights of the polymers were estimated by a Waters Associates
GPC system. Degassed THF was used as the eluent at a flow
rate of 1.0 mL/min. A set of monodisperse polystyrene stan-
dards covering the molecular weight range 103-107 was used
for the purpose of 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
20 °C/min. A Perkin-Elmer DSC 7 calorimeter was used to
measure the mesophase transition thermograms at a scanning
rate of 10 °C/min. An Olympus BX 60 POM equipped with a
Linkam TMS 92 hot stage was used to observe the anisotropic
optical textures. The XRD patterns were recorded on a Philips
PW1830 powder diffractometer with a graphite monochrom-
ator 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 crystalline states
by liquid nitrogen as previously reported.5,24,25
lower than that for its emission generated by the
excitation at 355 nm (57%). This is probably due to the
less efficient energy transfer from the pendants to the
ODPA chains, as evidenced by bump for the pendant
emission at ∼400 nm. With respect to the excitation
wavelength, the quantum yields for OPDA emissions
(43% and 57%) are always lower than that of PNOPPA
(98%),20 once again revealing the short effective conju-
gation length of the OPDA side chains.
Concluding Remarks
In this work, a group of 1-phenyl-1-undecyne deriva-
tives with different functional substituents (1-3) are
successfully polymerized into high molecular weight
polymers (P1-P3x) in satisfactory isolation yields.
Spectroscopic characterizations reveal that P1 and P2
are linear chains while P3x possesses a nonlinear
structure. The polyacetylenes are all solution-process-
able. The excellent solubility of P3x in common solvents
is a nice surprise, because it is a cross-linked polymer.21
All the polymers are stable. No change in Mw is observed
when the polymers have been exposed to air for >4
years, although they contain double and/or triple bonds
in their molecular structures. Little weight losses are
detected when the polymers are heated to high temper-
atures (Td g 390 °C).
Monomer Preparations. 1-Phenyl-1-alkyne derivatives 1
and 2 were prepared by esterifications of 11-phenyl-10-
undecyn-1-ol (4) with 4-(4-pentylcyclohexyl)benzoic acid (5) and
4-(4-hexyloxyphenyl-carbonyloxy)benzoic acid (6), respectively,
using DCC as a dehydrating agent (cf., Scheme 1). Diyne
monomer 3 was synthesized by a multistep reaction route:
The disubstituted polyacetylenes with different pen-
dant groups or side chains show different liquid-crystal-
line and light-emitting properties. The linear polymers
with phenylcyclohexane- (P1) and phenyl benzoate-cored

3298 Lam et al.
Macromolecules, Vol. 38, No. 8, 2005
esterification of 4-ethynylbenzoic acid (7) with 11-phenyl-10-
undecyn-ol (4) in the presence of DCC, TsOH, and DMAP,
followed by coupling of the resultant intermediate 11-phenyl-
10-undecynyl 4-ethynylbenzoate (8) with 4-heptyloxyiodoben-
zene (9) using PdCl2(PPh3)2 as the catalyst. A typical example
of experimental procedures for the synthesis of 3 is given
below.
11-Phenyl-10-undecynyl 4-Ethynylbenzoate (8). 11-
Phenyl-10-undecyn-1-ol (4; 4.0 g, 16.3 mmol), 4-ethynylbenzoic
acid (7; 2.9 g, 19.6 mmol), TsOH (0.6 g, 3.3 mmol), and DMAP
(0.4 g, 3.3 mmol) were dissolved in 200 mL of dry dichloro-
methane in a 500 mL two-necked flask under nitrogen. The
solution was cooled to 0-5 °C with an ice bath, to which 5.0 g
of DCC (24.5 mmol) in 50 mL of dichloromethane was added
under stirring via a dropping funnel with a pressure-equaliza-
tion arm. The mixture was stirred at room-temperature
overnight. After the formed insoluble crystals of urea were
filtered out, the filtrate was concentrated by a rotary evapora-
tor. The crude product was purified by a silica gel column using
chloroform as the eluent. A pale yellow liquid was obtained in
78.6% yield.
11-[4-(4-Hexyloxyphenylcarbonyloxy)phenyl-
carbonyloxy]-1-phenyl-1-undecyne (2). White solid;
yield: 55.7%. IR (KBr), ν (cm-1): 2231 (CtC stretching).
1H NMR (300 MHz, CDCl3), δ (ppm): 8.12 (m, 4H, Ar-H ortho
to CO2CH2 and meta to OC6H13), 7.39 (m, 2H, Ar-H ortho to
CtC), 7.27 (m, 5H, Ar-H para and meta to CtC and meta to
CO2CH2), 6.97 (d, Ar-H ortho to OC6H13), 4.31 (t, 2H,
ArCO2CH2), 4.03 (t, 2H, OCH2), 2.40 (t, 2H, tC-CH2), 1.80
(m, 4H, ArCO2CH2CH2 and tC-CH2CH2), 1.47 (m, 2H,
OCH2CH2), 1.38-1.32 [m, 16H, (CH2)8], 0.93 (t, 3H, CH3). 13
C
NMR (75 MHz, CDCl3), δ (ppm): 165.6 (CH2OCO), 164.0
(ArOCO), 163.5 (aromatic carbon linked to OC6H13), 154.5
(aromatic carbon para to CO2CH2), 132.1 (aromatic carbons
meta to OC6H13), 131.3 (aromatic carbons ortho to CtC), 130.8
(aromatic carbons ortho to CO2CH2), 127.9 (aromatic carbon
linked to CO2CH2), 127.7 (aromatic carbons meta to CtC),
127.2 (aromatic carbons para to CtC), 123.9 (aromatic carbon
linked to CtC), 121.6 (aromatic carbons meta to CO2CH2),
120.8 (aromatic carbon para to OC6H13), 114.1 (aromatic
carbons ortho to OC6H13), 90.2 (ArC≡), 80.4 (tCCH2), 68.0
(OCH2), 64.9 (ArCO2CH2), 31.3, 29.2, 29.0, 28.9, 28.8, 28.7,
28.54, 28.51, 25.8, 25.4, 22.4, 19.2, 13.9. MS(CI): m/e 569.4
[(M + 1)+, calcd 569.4].
Polymer Syntheses. All of 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 polym-
erization of 3 or for the synthesis of P3x is given below:
Into a baked 20 mL Schlenk tube with a stopcock in the
sidearm was added 440.5 mg (0.78 mmol) of 3. The tube was
evacuated under vacuum and then flushed with nitrogen three
times through the sidearm. Freshly distilled toluene (2 mL)
was injected into the tube to dissolve the monomer. The
catalyst solution was prepared in another tube by dissolving
15.9 mg of tungsten(VI) chloride and 17.2 mg of tetraphenyltin
in 2 mL of toluene. The two tubes were aged at 60 °C for
15 min and then 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 and then filtered
with a Gooch crucible. The polymer was washed with acetone
and dried in a vacuum oven to a constant weight.
11-[4-(4-Heptyloxyphenylethynyl)phenylcarbonyloxy]-
1-phenyl-1-undecyne (3). Into a 500 mL two-necked flask
were added 0.1 g (0.14 mmol) of PdCl2(PPh3)2, 0.1 mg
(5 × 10-4 mmol) of CuI, and 150 mL of a triethylamine solution
of 9 (2.1 g, 10.5 mmol) under nitrogen. After all the catalysts
were dissolved, 3.2 g of 8 (8.7 mmol) in 50 mL of triethylamine
was injected into the flask. The mixture was stirred at 60 °C
for 24 h. After the formed salt was filtered out, the solution
was concentrated by a rotary evaporator. The product was
purified by a silica gel column using chloroform/hexane
(3:2 by volume) as the eluent. Recrystallization in ethanol/
water mixture (3:1 by volume) gave 3.0 g of product 3 as a
white solid in 61.5% yield. IR (KBr), ν (cm-1): 2217 (CtC
stretching). 1H NMR (300 MHz, CDCl3), δ (ppm): 8.00 (d, 2H,
Ar-H ortho to CO2), 7.56 (d, 2H, Ar-H meta to CO2), 7.48
(d, 2H, Ar-H meta to OC7H15), 7.39 (m, 2H, Ar-H ortho to
CtCCH2), 7.25 (m, 3H, Ar-H para and meta to CtCCH2),
6.98 (d, 2H, Ar-H ortho to OC7H15), 4.30 (t, 2H, ArCO2CH2),
3.97 (t, 2H, OCH2), 2.40 (m, 2H, tC-CH2), 1.74 (m, 4H, ArCO2-
CH2CH2 and tCCH2CH2), 1.62 (m, 2H, OCH2CH2), 1.45-1.31
[m, 18H, (CH2)9], 0.90 (t, 3H, CH3). 13C NMR (75 MHz, CDCl3),
δ (ppm): 166.0 (ArCO2), 159.2 (aromatic carbon linked to
OC7H15), 133.1 (aromatic carbons meta to OC7H15), 131.5
(aromatic carbons ortho to CtC), 131.1 (aromatic carbons
ortho to CO2), 129.4 (aromatic carbons meta and para to CO2),
128.2 (aromatic carbon linked to CO2), 128.1 (aromatic carbons
meta to CtC), 127.4 (aromatic carbons para to CtC), 124.0
(aromatic carbon linked to CtC), 114.5 (aromatic carbon para
to OC7H15), 114.4 (aromatic carbons ortho to OC7H15), 92.6
(OCOArCt), 90.3 (tCCH2), 87.4 (tCArOC7H15), 80.6 (ArCt
CCH2), 68.0 (OCH2), 65.1 (ArCO2CH2), 31.7, 29.3, 29.2, 29.1,
29.0, 28.8, 28.7, 28.6, 25.94, 25.90, 22.5, 19.3 (tC-CH2), 14.0.
MS(CI): m/e 563.4 [(M + 1)+, calcd 563.4].
11-[4-(4-Pentylcyclohexyl)phenylcarbonyloxy]-1-phen-
yl-1-undecyne (1). It was prepared by the esterification of 4
with 5 using DCC as the dehydrating agent. A colorless liquid
was obtained in 89.8% yield. (The absorption band of the
1-phenyl-1-alkyne triple bond in 1 was too weak to be identi-
fied in the IR spectrum.) 1H NMR (300 MHz, CDCl3), δ (ppm):
7.96 (d, 2H, Ar-H ortho to CO2), 7.39 (m, 2H, Ar-H ortho to
CtC), 7.25 (m, 5H, Ar-H para and meta to CtC and meta to
CO2), 4.28 (t, 2H, ArCO2CH2), 2.38 (m, 3H, tC-CH2 and C-H
para to C5H11), 1.85 (d, C-H meta to C5H11), 1.73 (m, 2H,
ArCO2CH2CH2), 1.59 (m, 2H, tCCH2CH2), 1.48-1.22 [m, 17H,
C-H linked to C5H11 and (CH2)8], 0.90 [m, 5H, CH2(CH2)3CH3
and CH3)] 13C NMR (75 MHz, CDCl3), δ (ppm): 166.5 (ArCO2),
153.0 (aromatic carbon para to CO2), 131.4 (aromatic carbons
ortho to CtC), 129.5 (aromatic carbons ortho to CO2), 128.0
(aromatic carbons para to CO2), 127.2 (aromatic carbons meta
and para to CtC), 126.7 (aromatic carbons meta to CO2), 124.0
(aromatic carbon linked to CtC), 90.2 (ArCt), 80.5 (tCCH2),
64.7 (ArCO2CH2), 44.6, 37.2, 37.1, 33.9, 33.3, 32.1, 29.3, 29.1,
29.0, 28.8, 28.7, 26.5, 25.9, 22.6, 19.3, 14.0. MS(CI): m/e 501.4
[(M + 1)+, calcd 501.4].
Characterization Data. P1. Yellow powder: yield 68.5%.
Mw 62400; Mw/Mn 2.3 (GPC; Table 1, no. 2). 1H NMR (300 MHz,
CDCl3), δ (ppm): 7.94 (Ar-H ortho to CO2), 7.23 (Ar-H meta
to CO2), 4.26 (ArCO2CH2), 2.50 (C-H para to C5H11), 1.87
(C-H meta to C5H11), 1.72 (ArCO2CH2CH2 and dCCH2CH2),
1.32 [(CH2)8], 0.93 [CH2(CH2)3CH3], 0.91 (CH3). 13C NMR
(75 MHz, CDCl3), δ (ppm): 166.3 (ArCO2), 152.8 (aromatic
carbon para to CO2), 129.4 (aromatic carbons ortho to CO2),
127.9 (aromatic carbons para to CO2), 126.6 (aromatic carbons
meta to CO2), 64.8 (ArCO2CH2), 44.8, 37.4, 37.3, 34.1, 33.5,
32.3, 29.5, 28.9, 26.8, 26.2, 22.8, 14.3. UV (THF, 8.0 × 10-5
mol/L), λmax (nm)/ꢀmax (mol-1 L cm-1): 240/1.86 × 104,
332/2.55 × 103. PL (THF, 5.0 × 10-5 mol/L), λmax: 460 nm;
ΦF: 43%.
P2. Yellow powder: yield 86.2%. Mw 36100; Mw/Mn 1.6
1
(GPC; Table 1, no. 9). H NMR (300 MHz, CDCl3), δ (ppm):
8.06 (Ar-H ortho to CO2CH2 and meta to OC6H13), 7.22 (Ar-H
meta to CO2CH2), 6.92 (Ar-H ortho to OC6H13), 4.26
(ArCO2CH2), 3.99 (OCH2), 1.79 (ArCO2CH2CH2 and dC-
CH2CH2), 1.45 (OCH2CH2), 1.34 [(CH2)8], 0.90 (t, 3H, CH3).
13C NMR (75 MHz, CDCl3), δ (ppm): 165.7 (CH2OCO), 164.2
(ArOCO), 163.6 (aromatic carbon linked to OC6H13), 154.6
(aromatic carbon para to CO2CH2), 132.2 (aromatic carbons
meta to OC6H13), 131.0 (aromatic carbons ortho to CO2CH2),
127.8 (aromatic carbon linked to CO2CH2), 127.7 (aromatic
carbons meta to CtC), 121.6 (aromatic carbons meta to
CO2CH2), 121.0 (aromatic carbon para to OC6H13), 114.1
(aromatic carbons ortho to OC6H13), 68.2 (OCH2), 65.1

Macromolecules, Vol. 38, No. 8, 2005
Liquid-Crystalline and Light-Emitting Polyacetylenes 3299
(8) (a) Sanda, F.; Nakai, T.; Kobayashi, N.; Masuda, T. Macro-
molecules 2004, 37, 2703-2708. (b) Yu, G.; Liu, Y. Q.; Zhan,
X. W.; Li, H. Y.; Yang, M. J.; Zhu, D. B. Thin Solid Films
2000, 363, 126-129. (c) Wang, Y. Z.; Sun, R. G.; Wang, D.
K.; Swager, T. M.; Epstein, A. J. Appl. Phys. Lett. 1999, 74,
2593-2595. (d) Hidayat, R.; Hirohata, M.; Fujii, A.; Teragu-
chi, M.; Masuda, T.; Yoshino, K. Jpn. J. Appl. Phys. 1999,
38, 931-935.
(9) (a) Chen, J.; Xie, Z. Lam, J. W. Y.; Law, C. C. W.; Tang, B. Z.
Macromolecules 2003, 36, 1108-1117. (b) Lam, J. W. Y.; Law,
C. K.; Dong, Y.; Wang, J.; Ge, W.; Tang, B. Z. Opt. Mater.
2002, 21, 321-324. (c) Lam, J. W. Y.; Dong, Y.; Luo, J. Cheuk,
K. K. L.; Xie, Z.; Tang, B. Z. Thin Solid Films 2002, 417,
143-146. (d) Lam, J. W. Y.; Dong, Y.; Cheuk, K. K. L.; Luo,
J.; Xie, Z.; Kwok, H. S.; Mo, Z.; Tang, B. Z. Macromolecules
2002, 35, 1229-1240. (e) Lee, P. P. S.; Geng, Y.; Kwok, H.
S.; Tang, B. Z. Thin Solid Films 2000, 363, 149-151.
(f) Huang, Y. M.; Lam, J. W. Y.; Cheuk, K. K. L.; Ge, W.;
Tang, B. Z. Macromolecules 1999, 32, 5976-5978. (g) Huang,
Y. M.; Ge, W.; Lam, J. W. Y.; Tang, B. Z. Appl. Phys. Lett.
1999, 75, 4094-4096.
(10) (a) Ting, C. H.; Hsu, C. S. Jpn. J. Appl. Phys. 2001, 40, 5342-
5345. (b) Sun, R. G.; Wang, Y. Z.; Wang, D. K.; Zheng, Q. B.;
Epstein, A. J. Synth. Met. 2000, 111, 403-408. (c) Hidayat,
R.; Tatsuhara, S.; Kim, D. W.; Ozaki, M.; Yoshino, K.;
Teraguchi, M.; Masuda, T. Phys. Rev. B 2000, 61, 10167-
10173. (d) Frolov, S. V.; Fujii, A.; Chinn, D.; Hirohata, M.;
Hidayat, R.; Taraguchi, M.; Masuda, T.; Yoshino, K.; Vard-
eny, Z. V. Adv, Mater. 1998, 10, 869-872. (e) Sun, R. G.;
Masuda, T.; Kobayashi, T. Synth. Met. 1997, 91, 301-303.
(11) (a) Xie, Z.; Lam, J. W. Y.; Dong, Y.; Qiu, C.; Kwok, H. S.;
Tang, B. Z. Opt. Mater. 2002, 21, 231-234. (b) Tang, B. Z.
Xu, H.; Lam, J. W. Y.; Lee, P. P. S.; Xu, K.; Sun, Q.; Cheuk,
K. K. L. Chem. Mater. 2000, 12, 1446-1455.
(12) (a) Sun, R. G.; Zheng, Q. B.; Zhang, X. M.; Masuda, T.;
Kobayashi, T. Jpn. J. Appl. Phys. 1999, 38, 2017-2023. (b)
Tada, K.; Hidayat, R.; Hirohata, M.; Teraguchi, M.; Masuda,
T.; Yoshino, K. Jpn. J. Appl. Phys. 1996, 35, 1138-1141.
(13) Fujii, A.; Hidayat. R.; Sonoda, T.; Fujisawa, T.; Ozaki, M.;
Vardeny, Z. V.; Teraguchi, M.; Masuda, T.; Yoshino, K. Synth.
Met. 2001, 116, 95-99.
(14) (a) Tang, B. Z.; Lam, J. W. Y.; Lai, L. M.; Xie, Z.; Kwok, H.
S. Proc. SPIE 2003, 5213, 15-25. (b) Tang, B. Z.; Lam, J. W.
Y.; Luo, J.; Dong, Y.; Cheuk, K. K. L.; Xie, Z.; Kwok, H. S.
Proc. SPIE 2001, 4463, 132-138.
(15) Dong, Y. P.; Lam, J. W. Y.; Peng, H.; Cheuk, K. K. L.; Kwok,
H. S.; Tang, B. Z. Macromolecules 2004, 37, 6408-6417.
(16) (a) McArdle, C. B. Side Chain Liquid Crystal Polymers;
Blackie: London, 1989. (b) Handbook of Liquid Crystal
Research, Collings, P. J., Patel, J. S., Eds.; Oxford University
Press: New York, 1997.
(17) (a) Kong, X.; Tang, B. Z. Chem. Mater. 1998, 10, 3352-3363.
(b) Tang, B. Z.; Kong, X.; Wan, X.; Peng, H.; Lam, W. Y.; Feng,
X.; Kwok, H. S. Macromolecules 1998, 31, 2419-2432.
(18) Shirakawa, H.; Masuda, T.; Takeda, K. In The Chemistry of
Triple-Bonded Functional Groups; Patai, S., Ed.; Wiley: New
York, 1994. Supplement C2; Vol. 2; Chapter 17, pp 945-1016.
(19) (a) Tsuchihara, K.; Masuda, T.; Higashimura, T. Macromol-
ecules 1992, 25, 5816-5820. (b) Tachimori, H.; Masuda, T.;
Kouzai, H.; Higashimura, T. Polym. Bull. (Berlin) 1994, 32,
133-140. (c) Kouzai, H.; Masuda, T.; Higashimura, T.
Polymer 1994, 35, 4920-4923.
(ArCO2CH2), 31.4, 28.9, 28.7, 25.9, 25.5, 22.5, 13.9. UV (THF,
7.0 × 10-5 mol/L), λmax (nm)/ꢀmax (mol-1 L cm-1): 264/2.22 ×
104, 330/2.10 × 103. PL (THF, 5.0 × 10-5 mol/L), λmax
460 nm; ΦF: 59%.
:
P3x. Yellow-green powder: yield 32.4%. Mw 50500; Mw/Mn
1.7 [GPC (for the main GPC peak in the “normal” molecular
weight region); Table 1, no. 10). IR (KBr), ν (cm-1): 2214
1
(CtC stretching). H NMR (300 MHz, CDCl3), δ (ppm): 7.96
(Ar-H ortho to CO2), 7.50 (Ar-H meta to CO2 and OC7H15),
6.84 (Ar-H ortho to OC7H15), 4.26 (ArCO2CH2), 3.94 (OCH2),
2.34 (dC-CH2), 1.78 (ArCO2CH2CH2 and dCCH2CH2), 1.32
[OCH2CH2 and (CH2)9], 0.89 (CH3). 13C NMR (75 MHz, CDCl3),
δ (ppm): 165.9 (ArCO2), 159.4 (aromatic carbon linked to
OC7H15), 133.1 (aromatic carbons meta to OC7H15), 31.1
(aromatic carbons ortho to CO2), 129.3 (aromatic carbons meta
and para to CO2), 128.1 (aromatic carbon linked to CO2), 114.5
(aromatic carbons para and meta to OC7H15), 92.5 (OCOArCt
), 87.5 (tCArOC7H15), 68.1 (OCH2), 65.2 (ArCO2CH2), 31.8,
29.2, 29.1, 28.8, 26.0, 22.7, 14.0. UV (THF, 8.5 × 10-5 mol/L),
λmax (nm)/ꢀmax (mol-1 L cm-1): 316/2.51 × 104. PL (THF,
5.0 × 10-5 mol/L), λmax: 491 nm; ΦF: 57%.
Acknowledgment. The work described in this paper
was partially supported by the Research Grants Council
of Hong Kong (603304, 604903, N_HKUSR606_03,
HKUST6085/02P and 6121/01P), the University Grants
Committee of Hong Kong through an Area of Excellence
(AoE) Scheme (AoE/P-10/01-1A), and High Impact Area
(HIA) Grants of our University (HIA02/03.SC06). We
also thank the financial support from the National
Science Foundation of China and the Cao Guangbiao
Foundation of Zhejiang University.
References and Notes
(1) Nobel lectures: (a) Shirakawa, H. Angew. Chem., Int. Ed.
2001, 40, 2575-2580. (b) MacDiarmid, A. G. Angew. Chem.,
Int. Ed. 2001, 40, 2581-2590. (c) Heeger, A. J. Angew. Chem.,
Int. Ed. 2001, 40, 2591-2611.
(2) (a) Chien, J. C. W. Polyacetylene: Chemistry, Physics, and
Material Science; Academic Press: New York, 1984.
(b) Conjugated Oligomers, Polymers, and Dendrimers; Bre´das,
J. L., Ed.; De Boeck Universite´: Paris, France, 1999.
(3) For reviews, see: (a) Yashima, E.; Maeda, K.; Nishimura, T.
Chem.sEur. J. 2004, 10, 43-51. (b) Sedlacek, J.; Vohlidal,
J. Collect. Czech. Chem. Commun. 2003, 68, 1745-1790. (c)
Nagai, K.; Masuda, T.; Nakagawa, T.; Freeman, B. D.;
Pinnau, Z. Prog. Polym. Sci. 2001, 26, 721-798. (d) Choi, S.
K.; Gal, Y. S.; Jin, S. H.; Kim, H. K. Chem. Rev. 2000, 100,
1645-1681. (e) Ginsburg, E. J.; Gorman, C. B.; Grubbs, R.
H. In Modern Acetylene Chemistry; Stang, P. J.; Diederich,
F., Eds.; VCH: Weinheim, Germany, 1995; Chapter 10. (f)
Saunders, R. S.; Cohen, R. E.; Schrock, R. R. Acta Polym.
1994, 45, 301-307.
(4) For reviews, see: (a) Cheuk, K. K. L.; Li, B. S.; Tang, B. Z.
In Encyclopedia of Nanoscience and Nanotechnology; Nalwa,
H. S., Ed.; American Scientific Publishers: Stevenson Ranch,
CA, 2004; Vol. 8, pp 703-713. (b) Lam, J. W. Y.; Chen, J.;
Law, C. C. W.; Peng, H.; Xie, Z.; Cheuk, K. K. L.; Kwok, H.
S.; Tang, B. Z. Macromol. Symp. 2003, 196, 289-300. (c) Xie,
Z.; Peng, H.; Lam, J. W. Y.; Chen, J.; Zheng, Y.; Qiu, C.;
Kwok, H. S.; Tang, B. Z. Macromol. Symp. 2003, 195, 179-
184. (d) Cheuk, K. K. L.; Li, B. S.; Tang, B. Z. Curr. Trends
Polym. Sci. 2002, 7, 41-55. (e) Tang, B. Z. Polym. News 2001,
26, 262-272.
(20) (a) Law, C. C. W.; Lam, J. W. Y.; Dong, Y. P.; Tang, B. Z.
Polym. Prepr. 2004, 45 (2), 839-840. (b) Law, C. C. W.
M.Philos. Thesis, The Hong Kong University of Science &
Technology, Aug 2004.
(21) (a) Li, F. X.; Lu, Z. F.; Qian, H. T.; Rui, J. M.; Chen, S. N.;
Jiang, P.; An, Y. L.; Mi, H. F. Macromolecules 2004, 37, 764-
768. (b) Schmitz, K. S.; Wang, B.; Kokufuta, E. Macromol-
ecules 2001, 34, 8370-8377. (c) Downey, J. S.; McIsaac, G.;
Frank, R. S.; Sto¨ver, H. D. H. Macromolecules 2001, 34,
4534-4541 (d) Lindenblatt, G.; Schartl, W.; Pakula, T.;
Schmidt, M. Macromolecules 2000, 33, 9340-9347. (e) Okay,
O.; Durmaz, S.; Erman, B. Macromolecules 2000, 33, 4822-
4827. (f) Szuromi, E.; Berka, M.; Borbely, J. Macromolecules
2000, 33, 3993-3998. (g) Ferna´ndez-Nieves, A.; Ferna´ndez-
Barbero, A.; Vncent, B.; de las Nieves, F. J. Macromolecules
2000, 33, 2114-2118.
(5) For a review, see: Lam, J. W. Y.; Tang, B. Z. J. Polym. Sci.,
Part A: Polym. Chem. 2003, 41, 2607-2629.
(6) (a) Masuda, T.; Tang, B. Z.; Higashimura, T.; Yamaoka, H.
Macromolecules 1985, 18, 2369-2373. (b) Masuda, T.; Tang,
B. Z.; Tanaka, T.; Higashimura, T. Macromolecules 1986, 19,
1459-1464.
(7) For reviews, see: (a) Friend, R. H.; Gymer, R. W.; Holmes,
A. B.; Burroughes, J. H.; Marks, R. N.; Taliani, C.; Bradley,
D. D. C.; Dos Santos, D. A.; Bredas, J. L.; Logdlund, M.;
Salaneck, W. R. Nature (London) 1999, 397, 121-128.
(b) Soos, Z. G.; Galvao, D. S.; Etemad, S. Adv. Mater. 1994,
6, 280-287.
(22) Silverstein, R. M.; Webster, F. X. Spectrometric Identification
of Organic Compounds, 6th ed.; Wiley: New York, 1998.
(23) Sun, Q.; Xu, K.; Peng, H.; Zheng, R.; Ha¨ussler, M.; Tang, B.
Z. Macromolecules 2003, 36, 2309-2320.

3300 Lam et al.
Macromolecules, Vol. 38, No. 8, 2005
(24) (a) Lam, J. W. Y.; Dong, Y.; Cheuk, K. K. L.; Luo, J.; Xie, Z.;
Kwok, H. S.; Mo, Z.; Tang, B. Z. Macromolecules 2002, 35,
1229-1240. (b) Lam, J. W. Y.; Kong, X.; Dong, Y.; Cheuk, K.
K. L.; Xu, K.; Tang, B. Z. Macromolecules 2000, 33, 5027-
5040.
(30) Lam, J. W. Y. M.Philos. Thesis, The Hong Kong University
of Science & Technology, Aug 1998.
(31) (a) Liquid Crystalline Order in Polymers; Blumstein, A., Hsu,
E. C., Eds.; Academic Press: New York, 1978. (b) Mariani,
P.; Rustichelli, F.; Torquati, G. In Physics of Liquid Crystal-
line Materials; Khoo, I.-C., Simoni, F., Eds.; Gordon & Breach
Science: New York, 1991; Chapter 1.
(32) Masuda, T.; Takahashi, T.; Higashimura; T. Macromolecules
1985, 18, 311-317.
(33) Lam, J. W. Y. Ph.D. Dissertation, The Hong Kong University
of Science & Technology, Jan 2003.
(25) Kong, X.; Lam, J. W. Y.; Tang, B. Z. Macromolecules 1999,
32, 1722-1730.
(26) Ha¨ussler, M.; Zheng, R.; Lam, J. W. Y.; Tong, H.; Dong, H.;
Tang, B. Z. J. Phys. Chem. B 2004, 108, 10645-10650.
(27) (a) Demus, D.; Richter, L. Textures of Liquid Crystals; Verlag
Chemie: Weinheim, Germany, 1978. (b) Gray, G. W.; Goodby,
J. W. G. Smectic Liquid Crystals: Texture and Structures;
Leonard Hill: London, 1984.
(28) (a) Goto, H.; Akagi, K.; Shirakawa, H.; Oh, S.-Y.; Araya, K.
Synth. Met. 1995, 71, 1899-1900. (b) Akagi, K.; Goto, H.;
Shirakawa, H.; Oh, S.-Y, Araya, K. Synth. Met. 1995, 69, 13-
16. (c) Oh, S.-Y.; Akagi, K.; Shirakawa, H.; Araya, K.
Macromolecules 1993, 26, 6203-6206.
(29) Lam, W. Y.; Kong, X.; Tang, B. Z. Polym. Mater. Sci. Eng.
1999, 80, 159-160.
(34) Tang, B. Z.; Kong, X.; Wan, X.; Feng, X.-D. Macromolecules
1997, 30, 0, 5620-5628.
(35) Cheuk, K. K. L.; Lam, J. W. Y.; Chen, J.; Lai, L. M.; Tang, B.
Z. Macromolecules 2003, 36, 5947-5959.
MA048076T