Convenient synthesis of a discotic side group liquid crystal polymer

Article abstract of DOI:10.1039/a705378i

The synthesis of a discotic side group liquid crystal polymer based on poly (methyl methacrylate) is reported. This involves the oxidative coupling of 3,3′,4,4′-tetrakis(hexyloxy)biphenyl with 1-hexyloxy-2-methoxybenzene to yield the unsymmetrical triphenylene nucleus, 2-methoxy-3,6,7,10,11-pentakis(hexyloxy)triphenylene. Subsequent demethylation followed by reactions first with 1,11-dibromoundecane and then with the potassium salt of methacrylic acid yielded the polymerisable monomer, 11-[3,6,7,10,11-pentakis(hexyloxy)-2-oxytriphenylene]undecyl methacrylate. This was polymerised in benzene using azoisobutyronitrile as the initiator. The thermal properties of the resulting polymer are described.

Full text of DOI:10.1039/a705378i

J O U R N A L O F
Convenient synthesis of a discotic side group liquid crystal polymer
David Stewart, Gillian S. McHattie and Corrie T. Imrie*
Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen, UK AB24 3UE
C H E M I S T R Y
The synthesis of a discotic side group liquid crystal polymer based on poly(methyl methacrylate) is reported. This involves the
oxidative coupling of 3,3∞,4,4∞-tetrakis(hexyloxy)biphenyl with 1-hexyloxy-2-methoxybenzene to yield the unsymmetrical
triphenylene nucleus, 2-methoxy-3,6,7,10,11-pentakis(hexyloxy)triphenylene. Subsequent demethylation followed by reactions first
with 1,11-dibromoundecane and then with the potassium salt of methacrylic acid yielded the polymerisable monomer, 11-
[3,6,7,10,11-pentakis(hexyloxy)-2-oxytriphenylene]undecyl methacrylate. This was polymerised in benzene using
azoisobutyronitrile as the initiator. The thermal properties of the resulting polymer are described.
OCH3
OCH3
Side group liquid crystal polymers (SGLCP) consist of three
distinct structural components: a polymer backbone, a liquid
crystal group and connecting these, a flexible spacer which is
most commonly an alkyl spacer.1–3 The role of the flexible
spacer is to decouple, to some extent, the opposing tendencies
of the polymer backbone to adopt a random coil conformation
from those of the liquid crystal groups to self-assemble into
an ordered mesophase. This decoupling endows the polymers
with a unique duality of properties; they exhibit macromolecu-
lar characteristics such as ease of processibility and glassy
behaviour combined with, for example, the electro-optic
properties of conventional low molar mass mesogens. This
combination of polymeric and low molar mass mesogenic
properties is the basis of the considerable application potential
of SGLCPs in a range of advanced electro-optic technol-
ogies.4–6 The intensive research interest in SGLCPs is not
exclusively a result of this application potential, however, but
also because they provide a demanding challenge to our
understanding of the molecular factors that promote self-
assembly in polymeric systems.
OH
i,ii
Br
Br
OH
1
iii
OC6H13
OC6H13
OC6H13
OC6H13
iv,v
(HO)2B
Br
3
2
vi
The overwhelming majority of SGLCPs reported in the
literature contain rod-like or calamitic mesogenic groups.
Indeed, there are surprisingly few reports of SGLCPs in which
discotic mesogenic moieties are attached.7–10 This situation
stems largely from the synthetic difficulties in obtaining well-
defined and monodisperse polymerisable monomers containing
a discotic mesogenic unit. Indeed, the methods reported in the
literature are based around laborious separation procedures
involving several isomers of the triphenylene-based core. In
recent years, however, there have been many advances in the
synthesis of triphenylene-based compounds and in particular
the pioneering work of Boden, Bushby, Cammidge and their
co-workers11–14 has now made it possible to obtain large
quantities of monodisperse triphenylene-containing monomers.
In this paper we describe a convenient synthetic route by
which to prepare discotic SGLCPs based on poly(methyl
methacrylate) and containing hexasubstituted triphenylene.
C6H13
O
OC6H13
OC6H13
C6H13O
4
Scheme 1 Reagents and conditions: i, BBr , CH Cl ; ii, H O; iii,
C H Br, K CO , DMF; iv, BuLi; v, (PrO) B; vi, Pd(PPh ) , Na CO
3
2
2
2
6
13 3 4 3
2
3
3
2
OH
OC6H13
OCH3
i
OCH3
5
Scheme 2 Reagents and conditions: i, C H Br, K CO , DMF
13
6
2
3
Results and Discussion
approach to such compounds involves coupling a 3,3∞,4,4∞-
tetrakis(alkyloxy)biphenyl with a 1,2-dialkyloxybenzene.12,15
This general strategy was adopted here (see Scheme 3) and
hence, requires the synthesis of the appropriately substituted
biphenyl and benzene derivatives.
3,3∞,4,4∞-Tetrakis(hexyloxy)biphenyl (4 in Scheme 1) was pre-
pared by the tetrakis(triphenylphosphine)palladium(0)-cata-
lysed coupling of 3,4-bis(hexyloxy)phenylboronic acid, 3, with
3,4-bis(hexyloxy)bromobenzene, 2, according to the procedure
described by Gray et al.16 Compound 2 was obtained in two
Reaction Schemes 1–4 outline the synthetic approach used to
prepare the discotic SGLCP 10 in Scheme 4. At the heart of
this methodology lies the fact that the synthesis of a discotic
SGLCP via the polymerisation of a triphenylene-based mon-
omer necessarily involves the preparation of an unsymmetri-
cally hexasubstituted triphenylene nucleus. The preferred
* E-mail: c.t.imrie@abdn.ac.uk
J. Mater. Chem., 1998, 8(1), 47–51
47

C6H13O
OCH3
C6H13
O
OH
i
ii,iii
4 +
5
C6H13
O
OC6H13
OC6H13
C6H13
O
OC6H13
OC6H13
C6H13
O
C6H13
O
6
7
Scheme 3 Reagents and conditions: i, FeCl , CH Cl ; ii, Ph PH, BuLi; iii, HCl
3
2
2
2
O
O(CH2)11OCCCH3
CH2
C6H13
O
O(CH2)11Br
C6H13O
i
ii
7
C6H13
O
OC6H13
OC6H13
C6H13
O
OC6H13
OC6H13
C6H13
O
C6H13O
8
9
iii
CH3
C
CH2
n
C
O
O(CH2)11
O
OC6H13
C6H13
O
OC6H13
OC6H13
C6H13
O
10
Scheme 4 Reagents and conditions: i, Br(CH ) Br, K CO , acetone; ii, methacrylic acid, KHCO , DMF; iii, AIBN, benzene
2 11
2
3
3
steps (see Scheme 1): 3,4-dimethoxybromobenzene (4-bromo-
veratrole) was demethylated using boron tribromide17 followed
by the alkylation of the resulting 3,4-dihydroxybromobenzene
using bromohexane to give 2. Compound 3 was obtained via
the reaction of 2 first with butyllithium to yield the lithium
salt and subsequent conversion to the borate ester using
triisopropyl borate which was hydrolysed in situ using hydro-
chloric acid to give 3.16 1-Hexyloxy-2-methoxybenzene 5 was
obtained readily by the alkylation of 2-methoxyphenol (guai-
acol) using bromohexane (see Scheme 2).
The oxidative coupling of 4 with 5 (see Scheme 3) was
achieved using iron() chloride12,14,15 to give the unsymmetri-
cal triphenylene nucleus 6. As with previous reports, we found
no evidence that detectable quantities of the triphenylene based
on 5 were produced during the coupling reaction.
Demethylation of 6 using lithium diphenylphosphide18
yielded the phenol 7 (see Scheme 3) which was reacted with a
tenfold excess of 1,11-dibromoundecane19 to give the mono-
functionalised triphenylene nucleus 8 (see Scheme 4). This in
turn was reacted with the potassium salt of methacrylic acid20
yielding the methyl methacrylate-based monomer 9. The
polymerisation of 9 was performed in benzene using azoiso-
butyronitrile (AIBN) as the initiator.
The estimated weight average molar mass derived from gel
permeation chromatography (GPC) for 10 is 61 000 g mol−1
and the number average molar mass is 9000 g mol−1; the
polydispersity of 10 is, therefore, high, 6.8. This can be attri-
buted to the presence of a significant high molar mass fraction.
We should note that these values for the molecular masses are
at best approximations given the large differences in the
hydrodynamic volumes of 10 and the polystyrene standards
used to calibrate the GPC. For calamitic SGLCPs, however,
these molar masses would ensure that not only does the
polymer’s thermal properties lie outside the molar mass depen-
dent regime21 but also that polydispersity did not influence
the transitional behaviour.22 It is not known whether the molar
mass dependence of the thermal properties of discotic SGLCPs
mirror those of calamitic systems and hence, it is unclear if the
thermal behaviour of 10 is still molar mass dependent. We will
return to this issue below.
The DSC trace obtained on the initial heating of 10 contains
two transitions (see Fig. 1): a weak step in the baseline is
observed at 2 °C and an endothermic peak is seen at 45 °C.
On cooling from the isotropic phase, a birefringent texture
begins to develop at ca. 45 °C and the phase is fluid albeit
highly viscous. In consequence this is identified as a liquid
crystal phase. The optical texture, however, is rather poorly
defined and even after annealing for several days does not
develop into a clear, characteristic texture in which a phase
assignment is possible. The texture remains unchanged to
below the second transition and thus, this is assigned as the
glass transition. The entropy change associated with the
48
J. Mater. Chem., 1998, 8(1), 47–51

ology described, however, will allow for the synthesis of a
wider range of materials to test these initial findings.
Experimental
3,4-Dihydroxybromobenzene, 1
Compound 1 was prepared using the method described by
McOmie et al.17 Boron tribromide (20 ml, 0.2115 mol) was
dissolved in dried dichloromethane (DCM) (100 ml) at
−80 °C. A solution of 4-bromoveratrole (14 g, 0.0645 mol) in
DCM (100 ml) was added dropwise. The resulting mixture
was allowed to warm slowly to room temp. and stirred under
a positive pressure of argon for 96 h. Water (50 ml) was added
very slowly and the reaction mixture extracted using diethyl
ether. The organic extract was washed twice with water and
dried over magnesium sulfate. The diethyl ether was removed
under reduced pressure to yield a crystalline solid which did
not require purification. Yield 85%. d (CDCl ) 6.8–7.0 (m,
Fig. 1 DSC trace obtained on heating 10
H
3
aromatic, 3H); 4.4–5.8 (brs, OH, 2H). Mp 85–86 °C.
clearing transition expressed as the dimensionless quantity
DS/R is 3.55. This relatively high value indicates that the phase
possesses at least medium range ordering and given the struc-
ture of the polymer, is presumably columnar in nature. On
cooling at 10 °C min−1 the isotropic phase is quenched into
the glassy state and only on reheating is the mesophase
observed. Similar behaviour has been observed for other
discotic SGLCPs containing relatively rigid backbones.9
The monomeric analogue of the side-chain attached in
polymer 10, i.e. 2-undecyloxy-3,6,7,10,11-pentakis(hexyloxy)-
triphenylene, has not been reported in the literature. The
symmetric hexakis(hexyloxy)triphenylene has a clearing trans-
ition at 97 °C23 and by analogy with other unsymmetrically
substituted triphenylenes15 this may be expected to fall by ca.
30 °C on replacing one hexyloxy chain by an undecyloxy chain.
Thus it would appear that attaching the discotic monomer to
the polymer backbone has reduced its clearing temperature.
This is in stark contrast to the behaviour observed for calamitic
SGLCPs for which attachment of the monomer significantly
increases its clearing temperature.1–3 This latter observation
reflects that the attachment of the mesogenic units to the
polymer chain increases the orientational correlations between
the groups and hence, enhances the clearing temperature.24
The decrease in the clearing temperature of discotic mon-
omers on attachment to a polymer backbone has also been
observed for other systems and has been interpreted in terms
of the polymer backbone acting as a diluent which reduces the
ability of the columns to pack efficiently so reducing the
clearing temperature.9 The backbones must also traverse
differing columns which again will have a destabilising effect
on the arrangement of the columns. In addition, the attachment
of the discs to the backbone hinders the axial motions of the
discs within a column, which are known to occur in low molar
systems,8,25 so reducing the intra-column orientational corre-
lations between the mesogenic groups. The possible effect of
the end-groups on the thermal behaviour of 10 should not be
neglected. A columnar arrangement will clearly be destabilised
by the presence of bulky end-groups to a greater extent than
a calamitic smectic phase in which the backbone is accommo-
dated, at least to some extent, between the smectic layers.26
Thus, the properties of discotic SGLCPs may remain molar
mass dependent to higher degrees of polymerisation than
calamitic SGLCPs and this now requires further investigation.
3,4-Bis(hexyloxy)bromobenzene, 2
A mixture of 1 (10.1 g, 53.4 mmol), bromohexane (36.3 g,
220 mmol) and potassium carbonate (41.2 g, 299 mmol) in
dimethylformamide (DMF; 200 ml) was heated with stirring
at 120 °C overnight. The mixture was allowed to cool and
poured into cold water (ca. 1 l). This was extracted using
chloroform and the organic extracts washed several times using
water, twice using sodium hydroxide solution (5% w/v) and
twice using water. The organic layer was dried over magnesium
sulfate and the chloroform removed under reduced pressure.
The oily residue was distilled from calcium hydride using a
Kugelrohr apparatus. Yield 63%. d (CDCl ) 6.7–7.1 (m,
¨
aromatic, 3H); 4.0 (m, OCH , 4H); 1.8 (m, OCH CH , 4H);
0.9–1.7 [m, O(CH ) (CH ) CH , 18H].
H
3
2
2
2
2 2 2 3
3
3,4-Bis(hexyloxy)phenylboronic acid, 3
The acid 3 was prepared using the method described by Gray
et al.16 Thus, 2 (4 g, 11.2 mmol) was degassed under high
vacuum using the freeze–pump–thaw method and tetrahydro-
furan (40 ml) was distilled into the flask from sodium–benzo-
phenone. This was stirred under a positive over pressure of
argon for ca. 15 min and cooled to ca. −80 °C. A 10.0 
solution of n-butyllithium (1.5 ml) was injected into the flask
and the resulting mixture stirred for a further ca. 2.5 h.
Triisopropyl borate (8 ml) was added and the mixture allowed
to warm to room temp. with stirring overnight. 3.0 
Hydrochloric acid (80 ml) was added, the mixture stirred for
ca. 1 h and then extracted twice using diethyl ether. The
combined organic extracts were washed several times using
water and dried over magnesium sulfate. The diethyl ether was
removed under reduced pressure and the crude product recrys-
tallised from aqueous ethanol. Mp 96–97 °C. Yield 93%. d
(CDCl ) 6.7–7.9 (m, aromatic, 3H); 3.9–4.2 (m, OCH , 4H);
H
3
2
0.8–2.0 [m, OCH (CH ) CH , 22H]. The location of the acidic
H is uncertain due to rapid exchange with small amounts of
H O in the solvent.
2
2 4
3
2
3,3∞,4,4∞-Tetrakis(hexyloxy)biphenyl, 4
The biphenyl 4 was prepared using the method described by
Gray et al.16 A solution of 3 (2.7 g, 8.4 mmol) in ethanol
(30 ml) was added to a stirred mixture of 2 (2.6 g, 7.3 mmol)
and sodium carbonate (3.5 g, 33 mmol) in water (30 ml) under
a positive over pressure of argon. A solution of tetrakis(triphen-
ylphosphine)palladium(0) (0.25 g, 0.216 mmol) in benzene
(30 ml) was added and the resulting mixture stirred under
argon for ca. 24 h. This was allowed to cool and extracted
using diethyl ether. The organic extracts were washed twice
using brine and dried over magnesium sulfate. The solvent was
Conclusions
A convenient route for the preparation of discotic SGLCPs
has been described. Structure–property relationships in discotic
SGLCPs appear to be quite different to those established for
calamitic systems although only a very limited number of
discotic materials have been studied. The synthetic method-
J. Mater. Chem., 1998, 8(1), 47–51
49

removed under reduced pressure and the crude product recrys-
tallised with hot filtration from ethanol. Yield 62%. d (CDCl )
2-(11-bromoundecyloxy)-3,6,7,10,11-pentakis(hexyloxy)-
triphenylene, 8
H
3
6.9–7.1 (m, aromatic, 6H); 4.0 (m, OCH , 8H); 1.8 (m,
OCH CH , 8H); 1.4, 1.6 (m, CH , 24H); 0.9 (t, CH , 12H, J
2
Compound 8 was prepared using the method described by
Attard et al.19 Thus, a mixture of 7 (2 g, 2.69 mmol), 1,11-
dibromoundecane (8.5 g, 27 mmol), potassium carbonate (4 g,
28 mmol) and acetone (200 ml) was refluxed with stirring
overnight. The reaction mixture was filtered hot to remove the
insoluble inorganic material and the acetone removed under
reduced pressure. The excess 1,11-dibromoundecane was
2
2
2
3
7.0) (J values in H throughout). Mp 75–76 °C.
z
1-Hexyloxy-2-methoxybenzene, 5
A mixture of 2-methoxyphenol (guaiacol, 20.8 g, 168 mmol),
bromohexane (29.4 g, 178 mmol), potassium carbonate (35.2 g,
255 mmol) and DMF (200 ml) was heated at 120 °C with
stirring overnight. The reaction mixture was allowed to cool
and poured into cold water (ca. 1 l). The isolation and purifi-
cation of the product was identical to that described for 2.
Yield 55%. d (CDCl ) 6.8 (m, aromatic, 6H); 4.1 (t, ArOCH ,
removed using a Kugelrohr apparatus. The residue was recrys-
¨
tallised from ethanol with hot filtration and dried under
vacuum. Yield 2.1 g (80%). d (CDCl ) 7.8 (s, aromatic, 6H);
4.2 (t, ArOCH , 12H, J 6.4); 3.4 (t, CH Br, 2H, J 6.7); 0.9–2.0
H
3
2
3
2
[m, (CH ) CH , (CH ) CH Br, 73H]. Mp 46 °C.
2 4 2 9
2
H
3
2
11-[3,6,7,10,11-Pentakis(hexyloxy)triphenylen-2-yloxy]-
undecyl methacrylate, 9
2H, J 6.9); 4.0 (s, ArOCH , 3H); 1.9 (m, OCH CH , 2H);
1.3–1.6 [m, O(CH ) (CH ) , 4H]; 1.0 (t, CH , 3H, J 7.0).
3
2
2
2 2 2 2
3
The methacrylate 9 was prepared using the method described
by Craig and Imrie.20 Methacrylic acid (1.1 g, 12.8 mmol) was
dropped onto potassium hydrogen carbonate (1.0 g,
10.0 mmol) to form the potassium salt of methacrylic acid.
This was stirred for ca. 10 min prior to the addition of a
solution of 8 (2.1 g, 2.15 mmol) in DMF (30 ml) and a trace
amount of hydroquinone. The resulting mixture was stirred at
120 °C for 24 h. After cooling, the mixture was poured into ice
cold water (1 l) and the resulting precipitate collected by
filtration and dissolved in chloroform. This solution was
washed twice with 5% sodium hydroxide solution and twice
with water. The organic extracts were dried over anhydrous
magnesium sulfate and the chloroform removed under reduced
pressure. The product was purified by recrystallisation twice
from ethanol. Yield 80%. d (CDCl ) 7.8 (s, aromatic, 6H);
2-Methoxy-3,6,7,10,11-pentakis(hexyloxy)triphenylene, 6
Iron() chloride (0.89 g, 5.5 mmol) was added to a stirred
solution of 4 (2.92 g, 5.27 mmol) in dichloromethane (70 ml)
at 0 °C. The resulting mixture was stirred for a further ca.
10 min at 0 °C and 5 (1.65 g, 7.93 mmol) was added. This was
stirred for ca. 15 min at 0 °C and a second portion of iron()
chloride (1.32 g, 8.14 mmol) added. The reaction mixture was
allowed to stir at 0 °C for 3 h and a second batch of 5 added
(1.65 g, 7.93 mmol). After a further 10 min additional iron()
chloride was added (0.89 g, 5.5 mmol). The resulting mixture
was stirred at 0 °C for 1 h and subsequently allowed to warm
to room temp. (ca. 30 min). The reaction mixture was poured
into methanol at 0 °C and stored at ca. −20 °C overnight. The
resulting precipitate was collected by filtration and this crude
product was found to be a mixture of 4 and 6. 6 was obtained
by column chromatography using silica as the stationary phase
and a 10% v/v diethyl ether–light petroleum (bp 40–60 °C)
mixture as the eluent. The unreacted 4 eluted first from the
column and was recovered. 6 was recrystallised from ethanol
and dried under vacuum. The transitional behaviour of 6 is in
good agreement with that reported in the literature.23 Yield
55%. d (CDCl ) 7.8 (m, aromatic, 6H); 4.2 (t, ArOCH , 10H,
H
3
5.5, 6.1 (m, CNCH , 2H); 4.2 (t, ArOCH , 12H, J 6.4); 4.1 [t,
CH OC(O), 2H, J 6.6]; 1.81 (m, OCH CH , 14H); 1.2–1.7 (m,
2
2
2
2
2
CH2, 44H); 0.9 (m, CH , 18H). Mp 35 °C.
3
Polymerisation of 9
Monomer 9 (0.7 g, 0.86 mmol) was dissolved in dry benzene
(25 ml), and AIBN (5.74 mg, 0.034 mmol) was added as
initiator. The reaction mixture was degassed twice using the
freeze–pump–thaw method and subsequently flushed with
argon for 15 min. The polymerisation flask was placed in a
water bath at 60 °C to initiate polymerisation. After 72 h the
polymer was precipitated in a large amount of methanol. The
polymer was then redissolved in chloroform and reprecipitated
into methanol. The removal of 9 from the polymer was
monitored spectroscopically; specifically, the alkene stretch at
1637 cm−1 in the IR spectra of the monomer and the peaks
associated with the alkene protons at 5.5 and 6.1 ppm in the
1H NMR spectra. Repeated precipitations failed to completely
remove traces of monomer, however, and instead, the polymer
was purified by Soxhlet extraction using methanol for up to
72 h. Spectroscopic analysis confirmed the removal of mon-
omer within the detection limits. d (CDCl ) 7.2, 7.8 m, aro-
H
3
2
J 6.4); 4.1 (s, ArOCH , 3H); 1.1–2.1 [m, OCH (CH ) , 40H];
1.0 (t, CH , 15H, J 6.9). Crystal–crystal 53 °C; crystal–meso-
3
2
2 4
3
phase 69 °C; mesophase–isotropic 78 °C.
2-Hydroxy-3,6,7,10,11-pentakis(hexyloxy)triphenylene, 7
Compound 7 was prepared using a method described by
Ireland and Walba.18 Thus, tetrahydrofuran (20 ml) was dis-
tilled from Na–benzophenone into a two-necked round bot-
tomed flask on a high vacuum line. This was cooled to 0 °C
and while stirring with an argon over pressure, diphenylphos-
phine (1.5 ml, 8.7 mmol) followed by n-butyllithium (1 ml of a
10  solution) were injected into the flask. This mixture was
allowed to warm to room temp. (ca. 30 min) and a solution of
6 (2.1 g, 2.77 mmol) in THF (30 ml) was injected into the flask.
The resulting solution was allowed to stir at room temp. under
a positive argon pressure overnight. 3  Hydrochloric acid
was added (100 ml) and after stirring for a further 30 min, the
reaction mixture was extracted using chloroform. The organic
layer was washed several times with water, once with 5%
sodium hydroxide solution and finally twice more with water.
The organic extracts were dried over anhydrous magnesium
sulfate and the solvent removed under reduced pressure. The
crude product was recrystallised from ethanol with hot fil-
H
3
matic, 6H); 4.2 [m, ArOCH , CH OC(O), 14H]; 1.9, 1.6, 1.3
(m, CH , 60H); 0.9 (m, CH , 18H).
2
2
2
3
Characterisation
The proposed structures of all the compounds were verified
using 1H NMR and IR spectroscopy. 1H NMR spectra were
measured in CDCl on a Bruker AC-F 250 MHz NMR
spectrometer. IR spectra were recorded using a Nicolet 205
3
FTIR spectrometer. The purities of all the intermediates were
verified using thin layer chromatography. The molar masses
of the polymers were measured by gel permeation chromatog-
raphy (GPC) using a Knauer Instruments chromatograph
equipped with two PL gel 10 mm mixed columns and con-
trolled by Polymer Laboratories GPC SEC V5.1 Software.
tration and dried under vacuum. Yield 1.85 g (90%). d
(CDCl ) 7.6–8.0 (m, aromatic, 6H); 4.2 (m, ArOCH , 10H);
H
3
2
0.9–2.0 [m, O(CH ) (CH ) CH , 55H]. Mp 45–46 °C.
2 2 2 2
3
50
J. Mater. Chem., 1998, 8(1), 47–51

9
M. Werth and H. W. Spiess, Makromol. Chem., Rapid Commun.,
1993, 14, 329.
THF was used as the eluent. A calibration curve was obtained
using polystyrene standards.
10 C. D. Favre-Nicolin and J. Lub, Macromolecules, 1996, 29, 6143.
11 N. Boden, R. C. Borner, R. J. Bushby, A. N. Cammidge and
M. V. Jesudason, L iq. Cryst., 1993, 15, 851.
12 N. Boden, R. J. Bushby and A. N. Cammidge, J. Chem. Soc., Chem.
Commun., 1994, 465.
13 N. Boden, R. J. Bushby and A. N. Cammidge, J. Am. Chem. Soc.,
1995, 117, 924.
14 N. Boden, R. J. Bushby, A. N. Cammidge and G. Headdock,
J. Mater. Chem., 1995, 5, 2275.
Thermal properties were determined by differential scanning
calorimetry (DSC) using a Mettler-Toledo DSC 820 system
equipped with an intracooler accessory and calibrated using
an indium standard. The heating and cooling rates in all cases
were 10 °C min−1. Phase identification was performed by
polarised light microscopy using an Olympus BH-2 optical
microscope equipped with a Linkam THMS 600 heating stage
and TMS 91 control unit.
15 J. W. Goodby, M. Hird, K. J. Toyne and T. Watson, J. Chem. Soc.,
Chem. Commun., 1994, 1701.
16 G. W. Gray, M. Hird, D. Lacey and K. J. Toyne, J. Chem. Soc.
Perkin T rans. 2, 1989, 2041.
17 J. F. W. McOmie, M. L. Watts and D. E. West, T etrahedron, 1968,
24, 2289.
We gratefully acknowledge the EPSRC, grant number
GR/J32701, for supporting this work.
18 R. E. Ireland and D. M. Walba, Org. Synth., 1977, 56, 44.
19 G. S. Attard, S. Garnett, C. G. Hickman, C. T. Imrie and L. Taylor,
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