Syntheses and mesomorphic and luminescent properties of disubstituted polyacetylenes bearing biphenyl pendants

Article abstract of DOI:10.1021/ma049094d

Liquid-crystalline and light-emitting poly(2-alkyne)s and poly(-phenyl-1-alkyne)s containing biphenyl (Biph) cores, alkyl spacers, and alkoxy tails (-{RC=C[(CH₂)_m-OCO-Biph-OC₇H ₁₅]}_n-, where R, m = CH

Full text of DOI:10.1021/ma049094d

6408
Macromolecules 2004, 37, 6408-6417
Syntheses and Mesomorphic and Luminescent Properties of
Disubstituted Polyacetylenes Bearing Biphenyl Pendants
Yu p in g Don g,† J a ck y W. Y. La m , Ha n P en g, Kevin K. L. Ch eu k ,
Hoi Sin g Kw ok , a n d Ben Zh on g Ta n g*
Department of Chemistry and Center for Display Research, The Hong Kong University of Science &
Technology, Clear Water Bay, Kowloon, Hong Kong, China
Received May 9, 2004; Revised Manuscript Received J une 17, 2004
ABSTRACT: Liquid-crystalline and light-emitting poly(2-alkyne)s and poly(1-phenyl-1-alkyne)s containing
biphenyl (Biph) cores, alkyl spacers, and alkoxy tails (-{RC)C[(CH2)m-OCO-Biph-OC7H15]}n-, where R,
m ) CH3, 4 [P1(4)]; CH3, 9 [P1(9)]; C6H5, 4 [P2(4)]; and C6H5, 9 [P2(9)]}, were synthesized and the effects
of the spacer length and backbone structure on the properties of the polymers were investigated. The
disubstituted acetylene monomers [1(m) and 2(m) (m ) 4, 9)] were prepared by esterification of
biphenylcarboxylic acid (6) with ω-alkynyl alcohols [4(m) or 5(m)]. Polymerizations of 1(m) and 2(m) were
effected by WCl6-, MoCl5-, and NbCl5-Ph4Sn and the reactions catalyzed by WCl6-Ph4Sn under optimal
conditions produce polymers P1(m) and P2(m) with high molecular weights (Mw up to 3.1 × 105) in good
yields (up to 81%). The structures and properties of the disubstituted polyacetylenes were characterized
and evaluated by nuclear magnetic resonance (NMR), thermogravimetry (TGA), differential scanning
calorimetry (DSC), polarized optical microscope (POM), X-ray diffraction (XRD), ultraviolet spectroscopy
(UV), and photoluminescence (PL) analyses. The polymers are resistant to thermolysis (Td g 360 °C) and
all but P2(4) exhibit liquid crystallinity at elevated temperatures. The polymers with long methylene
spacers, that is, P1(9) and P2(9), form a smectic A (SmA) mesophase with a monolayer arrangement.
Upon excitation, strong UV and blue emissions peaking at 369 and 460 nm are observed in P1(m) and
P2(m), respectively, whose quantum yields are found to increase with the spacer lengths.
Ch a r t 1
In tr od u ction
Conjugated polymers containing mesogenic and chro-
mophoric units can potentially show very high carrier
mobility and emit polarized light1 and may find unique
applications and stimulate technological innovations in
the development of novel electronic and photonic devices
such as light-emitting diodes, photovoltaic cells, thin-
film transistors, and plastic lasers.2,3 Realization of
these captivating potentials requires the development
of versatile processes for the syntheses of such polymers.
Polyacetylene is an archetypal conjugated macromol-
ecule and its functionalization has attracted much
synthetic effort over the past decades.3-6 A variety of
polyacetylenes containing liquid-crystalline mesogens7-9
and light-emitting chromophores9-11 have been pre-
pared, almost all of which are, however, monosubsti-
tuted from a structural viewpoint. These monosubsti-
tuted polyacetylenes show multifaceted mesophases,
with their transition temperatures tunable by their
molecular structures.5a,8,12 The mesogenic orientations
of the polymers and their molecular arrangements can
be readily manipulated by such external stimuli as
mechanical forces13 and electrical field.14
acetylenes are known to emit strongly from their
polyene backbones.15,16 Attachment of chromophoric and
mesogenic pendants to disubstituted polyacetylene back-
bones may further enhance their emission efficiencies
through pendant-to-backbone energy transfer as well as
endowing them with liquid crystallinity. The creation
of liquid-crystalline disubstituted polyacetylenes has
been synthetically difficult. The only attempt, to our
knowledge, is a one-page report in which the authors
briefly described the polymerization of a mesogenic
disubstituted acetylene catalyzed by TaCl5-(n-C4H9)4-
Sn, which gave an oligomer with an Mn of 4600 in a
yield as low as 18%.17
We rose to the synthetic challenge and succeeded, in
our previous work, in the synthesis of a group of
disubstituted polypropiolates containing biphenyl-type
mesogens and chromophores with high molecular weights
(Mw up to 3.5 × 105) in good yields (up to ∼57%) (Chart
1).18 The polymers show mesomorphic smecticity and
emit strong UV light (λmax ) 369 nm and ΦF ) 70%
when excited at 333 nm). The color of the emission
indicates that the fluorescence is from the biphenyl
Monosubstituted polyacetylenes have, however, been
generally regarded as inefficient light emitters, with
poly(phenylacetylene) and its derivatives being particu-
larly weak fluorophores. We have previously developed
a group of poly(1-alkyne) derivatives that fluoresce
efficiently, whose emitting centers are, however, the
chromophoric pendant groups rather than the conju-
gated polyene backbones.9,11 Certain disubstituted poly-
* Corresponding author: Phone +852-2358-7375; fax +852-
2358-1594; e-mail tangbenz@ust.hk.
† On leave from College of Materials Science and Engineering
of the Beijing Institute of Technology.
10.1021/ma049094d CCC: $27.50 © 2004 American Chemical Society
Published on Web 07/27/2004

Macromolecules, Vol. 37, No. 17, 2004
Liquid-Crystalline and Light-Emitting Polyacetylenes 6409
Ta ble 1. P olym er iza tion of 7-{[(4′-Hep tyloxy-
4-bip h en ylyl)ca r bon yl]oxy}-2-h ep tyn e [1(4)]a
Sch em e 1
temp yield
b
b
no.
catalyst
solvent
(°C)
(%)
Mw
Mw/Mn
1
2
3
4
5
6
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
MoCl5-Ph4Sn toluene
NbCl5-Ph4Sn toluene
TaCl5-Ph4Sn toluene
dioxane
toluene
toluene
60
rtc
60
60
60
60
0
79.2 312 000
81.4 254 000
22.4 872 000
0
0
5.9
7.0
12.4
a
Carried out under nitrogen for 24 h; [M]0 ) 0.2 M, [cat.] )
b
[cocat.] ) 10 mM. Determined by GPC in THF on the basis of a
polystyrene calibration. c Room temperature.
Ta ble 2. P olym er iza tion of 12-{[(4′-Hep tyloxy-
4-bip h en ylyl)ca r bon yl]oxy}-2-d od ecyn e [1(9)]a
temp yield
b
b
no.
catalyst
solvent
(°C)
(%)
Mw
Mw/Mn
1
2
3
4
5
6
7
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
MoCl5-Ph4Sn toluene
NbCl5-Ph4Sn toluene
TaCl5-Ph4Sn toluene
dioxane
toluene
toluene
toluene
60
rtc
60
80
60
60
60
trace
trace
80.7
pendant instead of the polypropiolate backbone. In other
words, the polyene backbone with the ester group in its
immediate vicinity is not luminescent. In this work, we
designed a series of new disubstituted acetylenes with-
out the ester groups in the close neighborhood of the
triple bonds [1(m) and 2(m)] to check how this structural
variation will affect the polymerization behavior of the
monomers and the material properties of their poly-
mers.19 The polymerizabilities of 1(m) and 2(m) were
found to be quite different from those of the propiolates,
but we eventually succeeded in converting them into
high molecular weight polymers via optimization of
reaction conditions. The polymer with a long alkyl
spacer (m ) 9) exhibits smecticity, irrespective of
whether it is a poly(2-alkyne) [P1(9)] or poly(1-phenyl-
1-alkyne) derivative [P2(9)]. The luminescence behav-
iors of polymers P1(m) and P2(m) are similar to and
different from those of the polypropiolates,18 respec-
tively: P1(m) emit UV light from their biphenyl pen-
dants, while P2(m) emit blue light from their polyene
backbones.
22 600
75 200
8.9
10.4
15.9
2.7
58.5
20.3 157 500d
28.3
0
4500e
a
Carried out under nitrogen for 24 h; [M]0 ) 0.2 M, [cat.] )
b
[cocat.] ) 10 mM. Determined by GPC in THF on the basis of a
polystyrene calibration. c Room temperature. Soluble fraction.
d
e Mixture of oligomer and trimer.
erization would help realize liquid crystallinity in the
polymer systems. Tungsten and molybdenum chlorides
are the most commonly used catalysts for acetylene
polymerizations.9,21 These chlorides have, however, often
been found to be incapable of initiating the polymeriza-
tions of acetylene monomers containing polar functional
groups.22 Polymerizations of monomers 1(m) and 2(m)
may thus be difficult because they contain the polar
ester and ether units.
We first attempted to polymerize 1(4) using WCl6-
Ph4Sn as catalyst. Stirring a dioxane solution of 1(4)
under nitrogen in the presence of the W mixture at 60
°C for 24 h, however, gives no polymeric product (Table
1, no. 1). The reaction carried out in toluene with the
same W mixture at room temperature, delightfully,
produces a gray powdery solid in ∼79% yield. Analysis
by gel-permeation chromatography (GPC) gives an Mw
of 3.1 × 105 and a polydispersity index (Mw/Mn) of 5.9,
confirming the polymeric nature of the reaction product.
Raising the temperature to 60 °C did not affect the
reaction output much. MoCl5-Ph4Sn can also initiate
the polymerization of 1(4), giving a polymer with a very
high molecular weight (8.7 × 105) in a moderate yield
(Table 1, no. 4). Generally speaking, the W mixture is
a better catalyst than the Mo one in the polymerization
of 1(4), which is different from what we observed in the
polymerization of its propiolate counterpart, where the
Mo catalyst performed much better than the W one.18
This clearly demonstrates how variation in the molec-
ular structure changes polymerization behavior of an
acetylene monomer. Our attempts in using NbCl5- and
TaCl5-Ph4Sn as catalysts for polymerization of 1(4)
failed, possibly owing to the “toxic” interactions of the
ester and ether functional groups with the transition-
metal mixtures or to the formation of oligomeric species
that were soluble in the precipitating solvent.
Resu lts a n d Discu ssion
Mon om er Syn th eses. Four disubstituted acetylene
monomers were prepared by esterification of 4′-heptyl-
oxy-4-biphenylcarboxylic acid (6) with ω-alkynyl alco-
hols [4(m) or 5(m)] in the presence of 1,3-dicyclohexyl-
carbodiimine (DCC), p-toluenesulfonic acid (TsOH), and
4-(dimethylamino)pyridine (DMAP; Scheme 1). All the
reactions went smoothly and the monomers were iso-
lated in high yields (72-88%). All the monomers were
characterized by standard spectroscopic methods, from
which satisfactory analysis data were obtained (see
Experimental Section for details).
The disubstituted acetylene monomers are white
solids at room temperature. None of them exhibits liquid
crystallinity at elevated temperatures. In our search for
liquid-crystalline acetylene monomers and polymers, we
have found that most monosubstituted acetylene mono-
mers containing the biphenylester groups are meso-
morphic.8,9 The nonmesomorphism of the disubstituted
acetylene monomers 1(m) and 2(m) suggests that the
acetylenic proton plays an important role in the forma-
tion of mesophases in the monosubstituted acetylene
monomers.
P olym er iza tion Beh a vior s. Many nonmesomorphic
calamitic monomers become liquid crystalline after
polymerization due to the involved “polymer effect”.20
We tried to polymerize the disubstituted acetylene
monomers 1(m) and 2(m) in the hope that the polym-
Table 2 lists the polymerization results of 1(9). Like
1(4), 1(9) cannot be effectively polymerized by WCl6-
Ph4Sn in dioxane. Surprisingly, the polymerization

6410 Dong et al.
Macromolecules, Vol. 37, No. 17, 2004
Ta ble 3. P olym er iza tion of 6-{[(4′-Hep tyloxy-4-
bip h en ylyl)ca r bon yl]oxy}-1-p h en yl-1-h exyn e [2(4)]a
temp yield
b
b
no.
catalyst
solvent
(°C)
(%)
Mw
Mw/Mn
1
2
3
4
5
6
7
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
MoCl5-Ph4Sn toluene
NbCl5-Ph4Sn toluene
TaCl5-Ph4Sn toluene
dioxane
toluene
toluene
toluene
60
rtc
60
80
60
60
60
trace
trace
63.2
78.0
0
63 000
62 000
1.9
1.9
0
0
a
Carried out under nitrogen for 24 h; [M]0 ) 0.2 M, [cat.] )
b
[cocat.] ) 10 mM. Determined by GPC in THF on the basis of a
polystyrene calibration. c Room temperature.
Ta ble 4. P olym er iza tion of 11-{[(4′-Hep tyloxy-4-
bip h en ylyl)ca r bon yl]oxy}-1-p h en yl-1-u n d ecyn e [2(9)]a
F igu r e 1. IR spectra of (A) monomer 2(9) and (B) its polymer
P2(9) (sample taken from Table 4, no. 3).
temp yield
b
b
no.
catalyst
solvent
(°C)
(%)
Mw
Mw/Mn
1
2
3
4
5
6
7
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
WCl6-Ph4Sn
MoCl5-Ph4Sn toluene
NbCl5-Ph4Sn toluene
TaCl5-Ph4Sn toluene
dioxane
toluene
toluene
toluene
60
rtc
60
80
60
60
60
trace
45.1
48.7
66.4
0
13 100
43 900
53 400
2.0
2.1
1.8
trace
0
a
Carried out under nitrogen for 24 h; [M]0 ) 0.2 M, [cat.] )
b
[cocat.] ) 10 mM. Determined by GPC in THF on the basis of a
polystyrene calibration. c Room temperature.
catalyzed by the same catalyst in toluene at room
temperature yields almost no polymer (Table 2, no. 2),
which is in sharp contrast to the fact that the polym-
erization of 1(4) under similar conditions gives a high
molecular weight polymer in a high yield (cf., Table 1,
no. 2). Fortunately, the polymerization of 1(9) proceeds
well at 60 °C and produces a polymer in a high yield.
Further raising the temperature to 80 °C decreases the
yield but increases the Mw by more than 3-fold. MoCl5-
Ph4Sn can polymerize 1(9) but the resultant polymer is
only partially soluble. NbCl5-Ph4Sn can oligomerize
1(9) but its Ta counterpart is totally ineffective.
While WCl6-Ph4Sn is ineffective in polymerizing 2(4)
in dioxane, it can initiate the polymerization of this
monomer in toluene at elevated temperatures, yielding
polymers with high molecular weights (Table 3). The
attempted polymerizations of 2(4) by MoCl5-, NbCl5-,
and TaCl5-Ph4Sn all end up in dismay. The effects of
catalyst, solvent, and temperature on the polymerization
of 2(9) are summarized in Table 4. Dioxane again is a
poor solvent for the polymerization. While almost no
polymer is obtained when the polymerization of 2(4) is
catalyzed by WCl6-Ph4Sn in toluene at room temper-
ature, under similar conditions 2(9) is polymerized into
a polymer with an Mw of 13 100 in a moderate yield.
Increasing the polymerization temperature leads to
increments in both molecular weight and polymer yield.
Similar to 2(4), the polymerization of 2(9) is hard to
initiate by the MoCl5-, NbCl5-, and TaCl5-Ph4Sn
mixtures.
F igu r e 2. 1H NMR spectra of chloroform-d solutions of (A)
2(9) and (B) its polymer P2(9) (sample taken from Table 4,
no. 3). The solvent peak is marked by an asterisk.
which completely disappears in the spectrum of its
polymer (Figure 1B). The strong C)O band at 1715
cm-1, however, experiences little change, proving that
the acetylene polymerization is harmless to the carbonyl
functional group.
1
The H NMR spectra of P2(9) and its monomer 2(9)
are shown in Figure 2. The protons of the phenyl ring
next to the triple bond of 2(9) resonate at δ 7.40 and
7.28, which are upfield-shifted after the monomer is
polymerized. No unexpected signals are observed in the
spectrum of the polymer and all the resonance peaks
can be assigned to appropriate protons as marked in
Figure 2B. The NMR as well as the IR analyses confirm
that the acetylene triple bond has been consumed by
the polymerization reaction and that the molecular
structure of the polymeric product is indeed P2(9), as
given in Chart 1.
Str u ctu r a l Ch a r a cter iza tion . The polymeric prod-
ucts were characterized by spectroscopic methods and
all the polymers gave satisfactory data corresponding
to their expected molecular structures (see Experimen-
tal Section for details). An example of the IR spectrum
of P2(9) is shown in Figure 1; the spectrum of its
monomer 2(9) is also given in the same figure for
comparison. The monomer shows a weak band at 2230
cm-1 associated with the C≡C stretch (Figure 1A),

Macromolecules, Vol. 37, No. 17, 2004
Liquid-Crystalline and Light-Emitting Polyacetylenes 6411
F igu r e 4. TGA thermograms of P1(4) (sample taken from
Table 1, no. 3), P1(9) (Table 2, no. 3), P2(4) (Table 3, no. 3),
P2(9) (Table 4, no. 3), and poly(1-hexyne) (PH),23 recorded
under nitrogen at a heating rate of 20 °C/min.
F igu r e 3. 13C NMR spectra of chloroform-d solutions of (A)
2(9) and (B) its polymer P2(9) (sample taken from Table 4,
no. 3). The solvent peaks are marked by asterisks.
Figure 3 shows the 13C NMR spectrum of 2(9) along
with that of its polymer P2(9). The acetylenic carbon
atoms of 2(9) resonate at δ 90.4 and 80.6. These
absorptions are absent in the spectrum of P2(9). The
resonance peaks of the acetylenic phenyl carbons at δ
131.5, 128.1, 127.4, and 124.1 and the propargyl carbon
at δ 19.4 all disappear owing to the transformation of
the acetylenic triple bonds to the olefinic double bonds
by the acetylene polymerization. However, the absorp-
tions of the olefinic carbons of the polyene backbone
cannot be easily identified due to their overlapping with
those of the pendant biphenyl carbons.
Th er m a l Sta bility a n d Liqu id Cr ysta llin ity. Be-
fore investigating the mesomorphic properties of the
polymers, we first examined their thermal stability.
Poly(1-hexyne) (PH), a poly(1-alkyne), is so unstable
that it starts to lose its weight when it is heated to a
temperature as low as ∼150 °C (Figure 4).23 Polymers
P1(m) and P2(m) are, however, thermally stable and
lose almost no weight when they are heated to 360 °C
in the thermogravimetric analysis (TGA). Clearly the
incorporation of the stable biphenyl pendants into the
polyacetylene structure has dramatically enhanced the
thermal stability of the polymers, due to the protective
“jacket effect” of the mesogenic groups9 plus the ad-
ditional shielding effect contributed by the methyl or
phenyl group directly attached to the polyene backbone.
Polymers P1(4), P1(9), and P2(9) exhibit optical
anisotropy when heated or cooled but P2(4) does not,
which suggests that the first three polymers are liquid
crystalline but the fourth one is not. To know more
about the thermal transitions of P1(m) and P2(9), their
thermograms were measured under nitrogen on a
differential scanning calorimeter (DSC). As can be seen
from Figure 5A, P1(4) shows several transition peaks
in the temperature range of 186.2-116.8 °C in the first
cooling cycle. These thermal transitions are enantiotro-
pic but their exact nature is difficult to identify. Their
possible associations with cis-trans isomerization24 and
thermal degradation23 can be ruled out. The molecular
F igu r e 5. DSC thermograms of mesomorphic polyacetylenes
P1(4) (sample taken from Table 1, no. 3), P1(9) (Table 2, no.
3), and P2(9) (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.
weight of P1(4) does not change when it is heated to
200 °C, further proving that the chain scission and/or
cross-linking reactions are not involved in the thermal
transition processes. We are now working with our
physicist colleagues in an effort to decipher the myths
of these thermal transitions.
The polymer with nine methylene units, P1(9), readily
forms the SmA mesophase enantiotropically. The melt-
ing and isotropization transitions of its biphenyl me-
sogens are well-defined. Its long alkyl spacer decouples
the motions of the mesogenic pendant from the polyene
backbone, enabling the mesogens to undergo thermal
transitions in a relatively independent fashion. Simi-
larly, P2(9) shows an enantiotropic smecticity. The

6412 Dong et al.
Macromolecules, Vol. 37, No. 17, 2004
F igu r e 6. POM textures observed on cooling P1(4) (sample taken from Table 1, no. 3) to 128 °C (A), P2(9) (Table 2, no. 3) to 155
°C (B) and 135 °C (C), and P2(9) (Table 4, no. 3) to 168 °C (D) 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 P 1(9) a n d P 2(9)a
T (∆H, ∆S)b
polymer
cooling
heating
P1(9)
P2(9)
i 157.3 (-7.95, -18.48) SmA 96.1 (-1.85; -5.24) g
i 172.0 (-) SmA 158.6 (-10.21, -23.05)c g
g 99.0 (1.82, 4.89) SmA 163.6 (4.59, 10.51) i
g 167.0 (11.35, 25.8)c SmA 188.3 (-) i
a
Data were taken from the DSC thermograms recorded under nitrogen in the first cooling and second heating scans. Abbreviations:
b
n ) nematic phase, SmA ) smectic A phase, g ) glassy state, i ) isotropic melt. T is given in degrees Celsius; ∆H is given in kilojoules
per monomer repeating unit; ∆S is given in joules per monomer repeating unit per kelvin. c Sum of overlapping transitions.
temperature range for the smectic transition is, how-
ever, rather narrow, due to the high rigidity of its poly-
(1-phenyl-1-alkyne) backbone. Indeed, this backbone is
so stiff that it prevents P2(4), the congener of P2(9) with
a shorter methylene spacer, from showing any meso-
morphism.
may have partially distorted the order of the mesogenic
pendant groups and impeded them from growing into a
characteristic SmA texture.
The thermal transitions of P1(9) and P2(9) and their
corresponding enthalpy and entropy changes are sum-
marized in Table 5.25 The ∆H and ∆S for the i-SmA
and SmA-i transitions of P1(9) are large, in agreement
with the good packing order of its mesogens revealed
by the POM observation (cf. Figure 6). Its mesomorphic
temperature range is ∼61 (i-g) or ∼65 °C (g-i), which
is much wider than that of P2(9) [∼13 (i-g) or ∼21 °C
(g-i)]. It is known that an increase in the backbone
rigidity of a polymer leads to a decrease in the stability
of its liquid crystalline phase.26 The observed difference
in the mesomorphic temperature ranges between P1(9)
and P2(9) agrees with the early observation that a poly-
(2-alkyne) backbone is less stiff than a poly(1-phenyl-
1-alkyne) one.27
To gain more information on the mesomorphic struc-
tures of the polymers and their molecular packing
arrangements in the mesomorphic phases, we measured
their XRD data using the quenching technique devel-
oped in our early work.9 The diffractogram of P1(4)
quenched from 128 °C shows a broad peak at 2θ )
20.35° (Figure 7), from which a d spacing of 4.36 Å is
derived from Bragg’s law (Table 6). No reflections are
observed at low angles, indicating that there exists no
Figure 6 shows microphotographs of the mesomorphic
textures of P1(m) and P2(9) taken under a polarized
optical microscope (POM). Upon cooling the isotropic
liquid of P1(4), a birefringent texture is formed (Figure
6A), the mesophasic nature of which is, however,
difficult to specify. We repeatedly grew the liquid
crystals with care but still failed to obtain any charac-
teristic mesomorphic texture. The polymer with nine
methylene units [P1(9)], however, readily forms the
typical focal conic texture of SmA phase. Panels B and
C of Figure 6 show the dynamic process of the texture
formation. Many baˆtonnets emerge from the dark
background when P1(9) is cooled from its isotropic melt,
which grow to bigger domains when the sample is
further cooled. Further lowering the temperature en-
courages further growth of the domains, leading to the
formation of the focal conic texture characteristic of the
SmA phase. When P2(9) is cooled from its isotropic
state, many anisotropic entities are formed but their
development into the focal conic texture of SmA phase
is difficult. The rigid poly(1-phenyl-1-alkyne) backbone

Macromolecules, Vol. 37, No. 17, 2004
Ta ble 6. X-r a y Diffr a ction An a lysis Da ta of P 1(4), P 1(9), a n d P 2(9)a
mesogenic
Liquid-Crystalline and Light-Emitting Polyacetylenes 6413
ratio
d1/l
polymer
T (°C)
d1 (Å)
d2 (Å)
d3 (Å)
d4 (Å)
lengthb (l, Å)
phase
P1(4)
P1(9)
P2(9)
128
140
170
4.36
4.40
4.33
25.16
31.38
31.38
n (?)29
SmA
SmA
32.10
32.70
1.02
1.04
16.51
11.11
a
The mesophases in the liquid crystalline states at given temperatures were frozen by rapid quenching with liquid nitrogen. b Calculated
from monomer repeating units of the polymers in their fully extended conformations.
F igu r e 8. UV spectra of THF solutions of P1(4) (sample taken
from Table 1, no. 3), P1(9) (Table 2, no. 3), P2(4) (Table 3, no.
3), and P2(9) (Table 4, no. 3).
F igu r e 7. XRD patterns of the mesomorphic polyacetylenes
quenched with liquid nitrogen from their liquid crystalline
states: P1(4) (sample taken from Table 1, no. 3) at 128 °C,
P2(9) (Table 2, no. 3) at 140 °C, and P2(9) (Table 4, no. 3) at
170 °C.
layer order. It is known that a nematic phase shows only
a diffuse halo in a high angle region.28 The optical
anisotropy observed at 128 °C by POM may thus be
associated with a nematic arrangement of the mesogens
in P1(4).29 The diffractogram of P1(9) displays a Bragg
reflection at a low angle of 2θ ) 2.75° and a large peak
at a high angle of 2θ ) 20.15°. The d spacing derived
from the low-angle peak is 32.10 Å, which is close to
the calculated mesogenic length for the repeat unit of
P1(9) at its most extended conformation (31.38 Å), thus
proving the monolayer nature of the SmA phase.
Similarly, P2(9) shows a reflection in the low-angle
region, from which a d spacing of a monolayer SmA
structure is derived. Interestingly, its secondary reflec-
tion at a middle angle of 2θ ) 5.35° (16.51 Å) is also
detected by the diffractometer. The peaks are, however,
quite broad, suggesting that the mesogenic pendants are
not well packed. The broad peak at 2θ ) 7.95° may be
associated with the ordering of the biphenyl cores.9
F igu r e 9. Photoluminescence spectra of THF solutions of
P1(4) (sample taken from Table 1, no. 3), P1(9) (Table 2, no.
3), and poly(1-phenyl-1-octyne) (PPO). Polymer concentration
was 0.05 mM. Excitation wavelengths were 335 nm [for P1(m)]
and 355 nm (for PPO).
Electr on ic Absor p tion a n d Ligh t Em ission . The
absorption spectra of the tetrahydrofuran (THF) solu-
tions of the polymers are given in Figure 8. Polymers
P1(m) absorb strongly at 295 nm, which are assignable
to the K bands of their biphenyl pendants, because their
monomer absorptions peak at similar wavelengths. The
polyene backbone absorptions of the polymers are,
however, very weak. The low absorptivity of the poly-
(2-alkyne) main chain may be due to the steric effect of
the methyl group directly attached to the polyene
backbone, which twists the double bonds and reduces
the effective conjugation length along the main chain.
The absorptions of the poly(1-phenyl-1-alkyne) backbone
of P2(m) are, however, observed at wavelengths longer
than 340 nm and extend up to ∼425 nm. This suggests
that the polymer backbone exists in a more planar
conformation with a better conjugation.30
A polymer with both liquid-crystalline and light-
emitting properties may find unique technological
applications,1-3,12 and we thus investigated the fluores-
cence properties of the polymers. When P1(4) is photo-
excited at 335 nm, it emits a strong UV light of 369 nm
(Figure 9). This UV emission is due to the photolumi-
nescence (PL) of its biphenyl pendant, because the
emission spectrum of its monomer 1(4) peaks at 366 nm.
By use of 9,10-diphenylanthracene as reference, the
fluorescence quantum yield (ΦF) of P1(4) is calculated
to be 69%. The PL of P1(9) is observed in the same
spectral region with a higher emission efficiency (81%),
in agreement with the previous observation that a

6414 Dong et al.
Macromolecules, Vol. 37, No. 17, 2004
to that of PPO (43%). While the 335-nm photons mainly
excite the biphenyl pendant, the 355-nm photons can
excite both the biphenyl pendant and the polyene
backbone. The direct excitation plus the energy trans-
ferred from the pendant may be the cause for the more
efficient emission of P2(4) induced by the longer wave-
length excitation. The PL quantum yield of P2(9) is even
higher (59%), once again demonstrating that the longer
alkyl spacer promotes more efficient light emission.11,12,15
Con clu d in g Rem a r k s
Following our previous success in polymerizing a
special group of functional disubstituted acetylene
monomers (namely, propiolates),18 in this work we
succeeded in polymerizing two groups of “common”
disubstituted acetylene monomers with no ester groups
in the close neighborhood of the triple bonds, that is,
the functional 2-alkynes [1(m)] and 1-phenyl-1-alkynes
[2(m)]. This structural difference makes the new mono-
mers behave quite differently from the propiolates: the
former are polymerized by the tungsten catalyst; the
latter, by the molybdenum one. The liquid crystallinity
and light emission are realized in the new polymers with
“right” molecular structures. The polymers with long
alkyl spacers, viz., P1(9) and P2(9), exhibit thermotropic
smecticity enantiotropically. Similar to the polypropi-
olates, the functional poly(2-alkyne) derivatives [P1(m)]
emit UV light with high efficiency upon excitation of
their biphenyl pendants. Backbone emission is achieved
in the functional poly(1-phenyl-1-alkyne) system: P2(m)
emit blue light when their pendants and/or backbones
are excited. The long alkyl spacer is found to be good
for both mesomorphism and luminescence. Its decou-
pling effect minimizes the influence of the rigid back-
bone on the packing of the mesogenic pendants7-9,12 and
reduces the electronic interactions of the main and side
chains, hence enabling efficient light emission.9-11,15,16
F igu r e 10. Photoluminescence spectra of THF solutions of
P2(4) (sample taken from Table 3, no. 3), P2(9) (Table 4, no.
3), and PPO. Polymer concentration was 0.05 mM. Excitation
wavelengths were (A) 335 and (B) 355 nm.
longer alkyl spacer favors stronger light emission.11,15
Poly(1-phenyl-1-octyne) {PPO; -[(C6H5)C)C(C6H13)]n-}
is a well-known luminescent disubstituted polyacety-
lene, which emits a blue light of 460 nm with a quantum
efficiency of 43% when its polyene backbone is photo-
excited at 355 nm.15 Comparison with the PPO data
reveals that the poly(2-alkyne) backbone of P1(m) does
not emit in the visible region although their biphenyl
pendants radiate efficiently in the UV region.
Polymers P2(m) are PPO derivatives bearing biphenyl
pendants, and it is of interest to see how they emit upon
photoexcitation. When excited at 335 nm, the biphenyl
pendant of P2(4) emits weakly at 369 nm, with its PL
spectrum dominated by a blue emission peaking at 460
nm (Figure 10A). As can be seen from the spectrum
shown in Figure 8, the polyene backbone of P2(4)
absorbs in a spectral region where its biphenyl pendant
emits. Therefore, although the 335-nm excitation pumps
its biphenyl pendant to the excited state, the UV light
emitted from the pendant is reabsorbed by the polyene
chromophore, hence explaining why the PL of the
polymer is dominated by the blue emission of its
backbone. The fluorescence spectrum of P2(9) is analo-
gous to that of P2(4), suggesting that a similar energy
transfer path is involved in the PL process of this
polymer.
Exp er im en ta l Section
Ma ter ia ls. Dioxane (Nacalai Tesque) and toluene (BDH)
were predried over 4 Å molecular sieves and distilled from
sodium benzophenone ketyl immediately prior to use. Dichlo-
romethane (Lab-Scan) was dried over molecular sieves and
distilled over calcium hydride. 4′-Heptyloxy-4-biphenylcar-
boxylic acid (6) was prepared according to our previously
published procedures.9 Except for molybdenum(V) chloride
(Acros), all other reagents and solvents were purchased from
Aldrich and used without further purification.
In st r u m en t a t ion s. The IR spectra were measured on a
Perkin-Elmer 16 PC Fourier transform infrared spectropho-
tometer. The NMR spectra were recorded on a Bruker ARX
300 NMR spectrometer with 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 and the molar
absorptivities (ꢀ) of the polymers were calculated on the basis
of their monomer repeating units. The mass spectra were
recorded on a Finnigan TSQ 7000 triple-quadrupole mass
spectrometer operating in a chemical ionization (CI) mode with
methane as the carrier gas. The 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 standards covering
a molecular weight range of 103-107 was used for the molecular
weight calibration.
When excited by the photons of a longer wavelength
(355 nm), P2(4) emits a blue light with a spectral profile
similar to that given by the polymer when it is excited
at the shorter wavelength (335 nm; cf. panels B and A
of Figure 10). The quantum yield of the PL induced by
the 355-nm excitation is 44%, which is much higher
than that by the 335-nm excitation (9%) and comparable
The thermal stability of the polymers was evaluated by
measuring their weight loss thermograms on a Perkin-Elmer
TGA 7 under nitrogen at a heating rate of 20 °C/min. A Perkin-
Elmer DSC 7 was used to measure the phase transition
thermograms at a heating or cooling rate of 10 °C/min. An

Macromolecules, Vol. 37, No. 17, 2004
Liquid-Crystalline and Light-Emitting Polyacetylenes 6415
Olympus BX 60 POM equipped 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 with 1.5406 Å
Cu KR wavelength at room temperature (scanning rate 0.05
deg/s, scan range 2-30°). The polymer samples for the XRD
measurements were prepared by freezing the molecular ar-
rangements in the liquid crystalline states by liquid nitrogen
as reported in our previous papers.9
carbons para to CO2), 132.1 (aromatic carbons para to OC7H15),
130.0 (aromatic carbons ortho to CO2), 128.4 (aromatic carbons
meta to OC7H15), 128.2 (aromatic carbon linked to CO2), 126.3
(aromatic carbons meta to CO2), 114.8 (aromatic carbons ortho
to OC7H15), 78.6 (≡CCH2), 76.0 (CH3C≡), 68.1 (OCH2), 64.5
(ArCO2CH2), 31.7, 29.2, 29.0, 27.9, 26.0, 25.6, 22.6, 18.4 (≡C-
CH2), 14.1, 3.4 (CH3C≡). MS (CI): m/e 407.1 [(M + 1)+, calcd
407.1].
All other monomers used in this work were synthesized by
procedures similar to that described above for the preparation
of 1(4). The characterization data for these monomers are given
below:
Mon om er Syn th esis. The 2-alkyne derivatives 1(m) were
synthesized by esterification of 4′-heptyloxy-4-biphenylcar-
boxylic acid (6) with ω-alkyn-1-ol [4(m)] in the presence of 1,3-
dicyclohexylcarbodiimine (DCC), p-toluenesulfonic acid (TsOH),
and 4-(dimethylamino)pyridine (DMAP) (Scheme 1). The
1-phenyl-1-alkyne derivatives 2(m) were prepared by esteri-
fication of the same acid with 1-phenyl-1-alkyn-ω-ol [5(m)],
again with DCC as a dehydrating agent. Typical synthetic
procedures are given below. (While all the compounds prepared
in this work have been characterized spectroscopically, only
the analysis data for the final products, i.e., the new mono-
mers, are given below due to space limitations. The spectro-
scopic data for some of the intermediates can be found in
12-{[(4′-Hep tyloxy-4-bip h en ylyl)ca r bon yl]oxy}-2-d od e-
1
cyn e [1(9)]. Yield: 85.2%. White solid; mp 62.0 °C. H NMR
(300 MHz, CDCl3), δ (ppm): 8.07 (d, 2H, Ar-H ortho to CO2),
7.61 (d, 2H, Ar-H meta to CO2), 7.55 (d, 2H, Ar-H meta to
OC7H15), 6.97 (d, 2H, Ar-H ortho to OC7H15), 4.32 (t, 2H,
ArCO2CH2), 3.99 (t, 2H, OCH2), 2.11 (m, 2H, ≡C-CH2),
1.83-1.76 (m, 9H, CH3C≡, ArCO2CH2CH2, ≡CCH2CH2, and
OCH2CH2), 1.47-1.32 [m, 18H, (CH2)9], 0.90 (t, 3H, CH3). 13C
NMR (75 MHz, CDCl3), δ (ppm): 166.6 (ArCO2), 159.4 (aro-
matic carbon linked to OC7H15), 145.1 (aromatic carbons para
to CO2), 132.1 (aromatic carbons para to OC7H15), 130.0
(aromatic carbons ortho to CO2), 128.5 (aromatic carbons meta
to OC7H15), 128.2 (aromatic carbon linked to CO2), 126.3
(aromatic carbons meta to CO2), 114.9 (aromatic carbons ortho
to OC7H15), 79.3 (≡CCH2), 75.3 (CH3C≡), 68.1 (OCH2), 65.0
(ArCO2CH2), 31.7, 29.4, 29.23, 29.22, 29.1, 29.0, 28.8, 28.7,
26.0, 22.6, 18.7 (≡C-CH2), 14.1, 3.4 (CH3C≡). MS (CI): m/e
477.2 [(M + 1)+, calcd 477.2].
handbooks, databases, etc.31
)
5-Hep tyn -1-ol [4(4)]. Into a two-necked 500-mL round-
bottom flask equipped with a nitrogen inlet, a pressure-
equalized dropping funnel, and a magnet stirrer were added
100 mL of anhydrous THF and 3.6 g (37 mmol) of 5-hexyn-1-
ol [3(4)]. To this solution was added 35 mL (87.5 mmol) of 2.5
M solution of n-BuLi in pentane at -78 °C. The reaction was
allowed to stay overnight and the mixture was then trans-
ferred into a separating funnel containing 200 mL of water
and 100 mL of chloroform. The organic layer was separated
and the aqueous phase was extracted with chloroform several
times. The combined organic phase was washed with water
and dried over anhydrous MgSO4. The crude product was
purified by vacuum distillation at 98 °C/21 mbar, and 5-hep-
tyn-1-ol [4(4)] was obtained in 43.0% yield as a colorless liquid.
10-Dod ecyn -1-ol [4(9)]. This compound was prepared by
a procedure similar to that used for the synthesis of 4(4) and
was purified by vacuum distillation at 95 °C/1 mbar. Colorless
liquid; yield 37.5%.
6-P h en yl-5-h exyn -1-ol [5(4)]. Into a 250-mL two-necked
flask were added 0.6 g (0.9 mmol) of PdCl2(PPh3)2, 0.2 mg (0.2
mmol) of CuI, and 180 mL of a triethylamine solution of
iodobenzene (12.5 g, 61 mmol) under nitrogen. After all the
catalysts were dissolved, 5-hexyn-1-ol [3(4); 4.5 g, 45 mmol]
was injected into the flask and the mixture was stirred at room
temperature for 24 h. After the formed salt was filtered out,
the solution was concentrated by a rotary evaporator. The
reaction product [5(4)] was purified on a silica gel column with
chloroform/acetone (10:1 by volume) as the eluent. Yellow
liquid; yield 92.0%.
11-P h en yl-10-u n d ecyn -1-ol [5(9)]. This compound was
prepared by a similar procedure. Yellow liquid; yield 90.7%.
7-{[(4′-H ep t yloxy-4-b ip h en ylyl)ca r b on yl]oxy}-2-h ep -
tyn e [1(4)]. In a typical run, 4(4) (0.5 g, 4.9 mmol), DCC (1.5
g, 7.1 mmol), TsOH (0.2 g, 1.1 mmol), and DMAP (0.1 g, 0.8
mmol) were dissolved in 250 mL of dry dichloromethane in a
500-mL two-necked flask under nitrogen. The solution was
cooled to 0-5 °C, to which 1.5 g of 6 (4.7 mmol) dissolved in
50 mL of dichloromethane 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
on a silica gel column with chloroform as the eluent. Recrys-
tallization in an ethanol/H2O mixture (4:1 by volume) gave
monomer 1(4) as a white solid in 72.0% yield. Mp: 71.5 °C.
1H NMR (300 MHz, CDCl3), δ (ppm): 8.07 (d, 2H, Ar-H ortho
to CO2), 7.61 (d, 2H, Ar-H meta to CO2), 7.55 (d, 2H, Ar-H
meta to OC7H15), 6.99 (d, 2H, Ar-H ortho to OC7H15), 4.35 (t,
2H, ArCO2CH2), 4.00 (t, 2H, OCH2), 2.23 (m, 2H, ≡C-CH2),
1.89-1.78 (m, 7H, CH3C≡, ArCO2CH2CH2, and ≡CCH2CH2),
1.67 (m, 2 H, OCH2CH2), 1.36-1.32 [m, 8H, (CH2)4], 0.90 (t,
3H, CH3). 13C NMR (75 MHz, CDCl3), δ (ppm): 166.5 (ArCO2),
159.4 (aromatic carbon linked with OC7H15), 145.2 (aromatic
6-{[(4′-Hep tyloxy-4-bip h en ylyl)ca r bon yl]oxy}-1-p h en -
yl-1-h exyn e [2(4)]. Yield: 85.7%. White solid; mp 75.0 °C.
1H NMR (300 MHz, CDCl3), δ (ppm): 8.08 (d, 2H, Ar-H ortho
to CO2), 7.61 (d, 2H, Ar-H meta to CO2), 7.54 (d, 2H, Ar-H
meta to OC7H15), 7.40 (m, 2H, Ar-H ortho to C≡C), 7.26 (m,
3H, Ar-H para and meta to C≡C), 6.97 (d, 2H, Ar-H ortho
to OC7H15), 4.39 (t, 2H, ArCO2CH2), 3.99 (t, 2H, OCH2), 2.51
(m, 2H, ≡C-CH2), 1.98 (m, 2H, ArCO2CH2CH2), 1.80 (m, 4H,
≡CCH2CH2 and OCH2CH2), 1.49-1.32 [m, 8H, (CH2)4], 0.90
(t, 3H, CH3). 13C NMR (75 MHz, CDCl3), δ (ppm): 166.5
(ArCO2), 159.4 (aromatic carbon linked to OC7H15), 145.2
(aromatic carbons para to CO2), 132.0 (aromatic carbons para
to OC7H15), 131.5 (aromatic carbons ortho to C≡C), 130.0
(aromatic carbons ortho to CO2), 128.3 (aromatic carbons meta
to OC7H15), 128.2 (aromatic carbon linked to CO2), 128.1
(aromatic carbons meta to C≡C), 127.5 (aromatic carbons para
to C≡C), 126.3 (aromatic carbons meta to CO2), 123.8 (aromatic
carbon linked to C≡C), 114.8 (aromatic carbons ortho to
OC7H15), 89.5 (≡CCH2), 81.1 (ArC≡), 68.0 (OCH2), 64.4
(ArCO2CH2), 31.7, 29.2, 29.0, 27.9, 25.9, 25.3, 22.5, 19.1 (≡C-
CH2), 14.0. MS (CI): m/e 469.1 [(M + 1)+, calcd 469.1].
11-{[(4′-Hep tyloxy-4-bip h en ylyl)ca r bon yl]oxy}-1-p h en -
yl-1-u n d ecyn e [2(9)]. Yield: 88.1%. White solid; mp 55.0 °C.
1H NMR (300 MHz, CDCl3), δ (ppm): 8.09 (d, 2H, Ar-H ortho
to CO2), 7.63 (d, 2H, Ar-H meta to CO2), 7.57 (d, 2H, Ar-H
meta to OC7H15), 7.40 (m, 2H, Ar-H ortho to C≡C), 7.28
(m, 3H, Ar-H para and meta to C≡C), 7.00 (d, 2H, Ar-H ortho
to OC7H15), 4.37 (t, 2H, ArCO2CH2), 4.01 (t, 2H, OCH2),
2.42 (m, 2H, ≡C-CH2), 1.81 (m, 4H, ArCO2CH2CH2 and
≡CCH2CH2), 1.68 (m, 2H, OCH2CH2), 1.48-1.34 [m, 18H,
(CH2)9], 0.92 (t, 3H, CH3). 13C NMR (75 MHz, CDCl3), δ
(ppm): 166.6 (ArCO2), 159.4 (aromatic carbon linked to
OC7H15), 145.1 (aromatic carbons para to CO2), 132.2 (aromatic
carbons para to OC7H15), 131.5 (aromatic carbons ortho to
C≡C), 130.0 (aromatic carbons ortho to CO2), 128.5 (aromatic
carbons meta to OC7H15), 128.3 (aromatic carbon linked to
CO2), 128.1 (aromatic carbons meta to C≡C), 127.4 (aromatic
carbons para to C≡C), 126.3 (aromatic carbons meta to CO2),
124.1 (aromatic carbon linked to C≡C), 114.9 (aromatic
carbons ortho to OC7H15), 90.4 (≡CCH2), 80.6 (ArC≡), 68.1
(OCH2), 65.0 (ArCO2CH2), 31.8, 29.4, 29.25, 29.23, 29.1, 28.8,
28.7, 26.02, 26.00, 22.6, 19.4 (≡C-CH2), 14.1. MS (CI): m/e
539.3 [(M + 1)+, calcd 539.3].
P olym er iza tion . All the polymerization reactions and
manipulations were carried out under nitrogen by Schlenk

6416 Dong et al.
Macromolecules, Vol. 37, No. 17, 2004
techniques in a vacuum line system or a Vacuum Atmospheres
inert-atmosphere glovebox, except for the purification of the
polymers, which was done in an open atmosphere. A typical
experimental procedure for the polymerization of 1(4) is given
below as an example.
Ack n ow led gm en t. The work described in this paper
was partially supported by the Research Grants Council
(Projects N_HKUSR606_03, 604903, HKUST6085/02P,
6121/01P, and 6187/99P) and the University Grants
Committee of Hong Kong through an Area of Excellence
(AoE) Scheme (Project AoE/P-10/01-1A).
Into a baked 20-mL Schlenk tube with a stopcock in the
sidearm was added 257.0 mg (0.63 mmol) of 1(4). The tube
was evacuated under vacuum and then flushed with dry
nitrogen three times through the sidearm. Freshly distilled
toluene (1.5 mL) was injected into the tube to dissolve the
monomer. The catalyst solution was prepared in another tube
by dissolving 12.0 mg of tungsten(VI) chloride and 13.0 mg of
tetraphenyltin in 1.5 mL of toluene. The catalyst solution was
aged at 60 °C for 15 min, to which the monomer solution was
added by use of 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 was then filtered with a Gooch
crucible. The polymer [P1(4)] was washed with acetone and
dried in a vacuum oven to a constant weight.
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Ch a r a ct er iza t ion Da t a : P 1(4). Grey powder; yield
81.4%. Mw 254 200; Mw/Mn 2.0 (GPC; Table 1, no. 3). 1H
NMR (300 MHz, CDCl3), δ (ppm): 7.94, 7.41, 6.97 (Ar-H),
4.34 (ArCO2CH2), 3.86 (OCH2), 1.74 (ArCO2CH2CH2 and
dCCH2CH2), 1.31 [(CH2)5], 0.90 (CH3). 13C NMR (75 MHz,
CDCl3), δ (ppm): 166.3 (ArCO2), 159.3 (aromatic carbon linked
to OC7H15), 144.8 (aromatic carbons para to CO2), 131.9
(aromatic carbons para to OC7H15), 130.0 (aromatic carbons
ortho to CO2), 128.1 (aromatic carbons meta to OC7H15 and
linked to CO2), 126.1 (aromatic carbons meta to CO2), 114.7
(aromatic carbons ortho to OC7H15), 68.0 (OCH2), 64.8
(ArCO2CH2), 31.8, 29.3, 29.1, 26.0, 22.6, 14.1. UV (THF, 7.4 ×
10-5 mol/L): λmax 295 nm, ꢀmax 2.02 × 104 mol-1 L cm-1
.
P 1(9). Grey powder; yield 80.7%. Mw 22 600; Mw/Mn 8.9
(GPC; Table 2, no. 3). 1H NMR (300 MHz, CDCl3), δ (ppm):
7.99, 7.48, 6.88 (Ar-H), 4.25 (ArCO2CH2), 3.90 (OCH2), 1.92
(ArCO2CH2CH2, dCCH2CH2, and OCH2CH2), 1.30 [(CH2)9],
0.88 (CH3). 13C NMR (75 MHz, CDCl3), δ (ppm): 166.4 (ArCO2),
159.3 (aromatic carbon linked to OC7H15), 144.9 (aromatic
carbons para to CO2), 131.9 (aromatic carbons para to OC7H15),
129.9 (aromatic carbons ortho to CO2), 128.4 (aromatic carbons
meta to OC7H15), 1278.1 (aromatic carbon linked to CO2), 126.2
(aromatic carbons meta to CO2), 114.7 (aromatic carbons ortho
to OC7H15), 67.9 (OCH2), 64.9 (ArCO2CH2), 31.7, 29.2, 29.0,
28.7, 25.9, 22.5, 14.0. UV (THF, 5.9 × 10-5 mol/L): λmax 295
nm, ꢀmax 1.99 × 104 mol-1 L cm-1
.
P 2(4). Grey powder; yield 63.2%. Mw 63 000; Mw/Mn 1.9
(GPC; Table 3, no. 3). 1H NMR (300 MHz, CDCl3), δ (ppm):
7.84, 7.41, 6.84 (Ar-H), 3.88 (ArCO2CH2 and OCH2), 1.74
(ArCO2CH2CH2, dCCH2CH2, and OCH2CH2), 1.31 [(CH2)4],
0.89 (CH3). 13C NMR (75 MHz, CDCl3), δ (ppm): 166.1 (ArCO2),
159.2 (aromatic carbon linked to OC7H15), 144.6 (aromatic
carbons para to CO2), 131.9 (aromatic carbons para to OC7H15),
129.9 (aromatic carbons ortho to CO2), 128.1 (aromatic carbons
meta to OC7H15 and linked to CO2), 126.1 (aromatic carbons
meta to CO2), 114.7 (aromatic carbons ortho to OC7H15), 67.9
(OCH2), 64.3 (ArCO2CH2), 31.8, 29.2, 29.1, 26.0, 22.6, 14.1. UV
(THF, 7.3 × 10-5 mol/L): λmax 295 nm, ꢀmax 2.44 × 104 mol-1
L
cm-1
.
P 2(9). Yellow powder; yield 48.7%. Mw 43 900; Mw/Mn 2.1
(GPC; Table 4, no. 3). 1H NMR (300 MHz, CDCl3), δ (ppm):
8.00, 7.50, 6.90 (Ar-H), 4.26 (ArCO2CH2), 3.93(OCH2), 1.76
(ArCO2CH2CH2 and dCCH2CH2), 1.31 [(CH2)10], 0.89 (CH3).
13C NMR (75 MHz, CDCl3), δ (ppm): 166.4 (ArCO2), 159.3
(aromatic carbon linked to OC7H15), 144.9 (aromatic carbons
para to CO2), 132.0 (aromatic carbons para to OC7H15), 129.9
(aromatic carbons ortho to CO2), 128.4 (aromatic carbons meta
to OC7H15), 128.1 (aromatic carbon linked to CO2), 126.2
(aromatic carbons meta to CO2), 114.8 (aromatic carbons ortho
to OC7H15), 68.0 (OCH2), 64.9 (ArCO2CH2), 31.7, 29.2, 29.0,
28.8, 25.9, 22.5, 14.0. UV (THF, 7.1 × 10-5 mol/L): λmax 295
nm, ꢀmax 2.28 × 104 mol-1 L cm-1
.

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