Side chain liquid crystal polyacrylate and polymethacrylate nickel complexes free from covalent cross-linking

Article abstract of DOI:10.1080/15421400490436412

Non-symmetrical nickel(II) complexes containing a single acrylate or methacrylate motif have been synthesised and polymerised radically in tetrahydrofuran solution using AIBN as the initiator. This results in the incorporation of the metal complexes into a polyacrylate and a polymethacrylate as freely mobile side chains, free from cross-linking. Whilst the monomers are non-liquid crystalline, the polymers show smectic A liquid crystal phases.

Full text of DOI:10.1080/15421400490436412

This article was downloaded by: [University of Kent]
On: 03 December 2014, At: 07:26
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Molecular Crystals and Liquid
Crystals
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/gmcl20
Side chain liquid crystal
polyacrylate and
polymethacrylate nickel
complexes free from covalent
cross-linking
Peter Styring a & Isabel Saez b
a Department of Chemical and Process Engineering ,
The University of Sheffield , Sheffield, UK
b Department of Chemistry , The University of Hull ,
Kingston upon Hull, UK
Published online: 18 Oct 2010.
To cite this article: Peter Styring & Isabel Saez (2004) Side chain liquid crystal
polyacrylate and polymethacrylate nickel complexes free from covalent
cross-linking, Molecular Crystals and Liquid Crystals, 411:1, 491-502, DOI:
10.1080/15421400490436412
To link to this article: http://dx.doi.org/10.1080/15421400490436412
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the
information (the “Content”) contained in the publications on our platform.
However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness,
or suitability for any purpose of the Content. Any opinions and views
expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the
Content should not be relied upon and should be independently verified with

primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages,
and other liabilities whatsoever or howsoever caused arising directly or
indirectly in connection with, in relation to or arising out of the use of the
Content.
This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden. Terms & Conditions of access and use can be found at
http://www.tandfonline.com/page/terms-and-conditions

Mol. Cryst. Liq. Cryst., Vol. 411, pp. 491=[1533]–502=[1544], 2004
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080=15421400490436412
SIDE CHAIN LIQUID CRYSTAL POLYACRYLATE
AND POLYMETHACRYLATE NICKEL COMPLEXES
FREE FROM COVALENT CROSS-LINKING
Peter Styringꢀ
Department of Chemical and Process Engineering, The University
of Sheffield, Mappin Street, Sheffield, S1 3JD, UK
Isabel M. Saez
Department of Chemistry, The University of Hull,
Kingston upon Hull, HU6 7RX, UK
Non-symmetrical nickel(II) complexes containing a single acrylate or metha-
crylate motif have been synthesised and polymerised radically in tetrahydro-
furan solution using AIBN as the initiator. This results in the incorporation
of the metal complexes into a polyacrylate and a polymethacrylate as freely
mobile side chains, free from cross-linking. Whilst the monomers are
non-liquid crystalline, the polymers show smectic A liquid crystal phases.
Keywords: acrylate; inorganic complex; liquid crystal; metacrylate
INTRODUCTION
Metal-containing liquid crystals have been the focus of considerable atten-
tion in recent years because of the possibility of incorporating the unique
properties of a metal into the conventional organic structure of a liquid
crystal [1–3]. Further attempts have been made to incorporate metal-
containing liquid crystals (metallomesogens) into polymeric structures
[3,4], however except for a few examples this has resulted in covalent
cross-linking to give non-mesomorphic networks. Deschenaux and co-
workers [5–7] have reported a number of polymeric metallomesogen based
on the organometallic ferrocene core. Serrano and co-workers have also
We thank EPSRC for financial support to IMS. We also thank The University of Hull
Analytical Services and Mrs. Julie Haley for spectroscopic and calorimetric data.
ꢀCorresponding author. Tel.: 0114 222 7571, Fax: 0114 222 7501, E-mail: p.styring@
sheffield.ac.uk
491=[1533]

492=[1534]
P. Styring and I. M. Saez
been active in incorporating both catamitic [8] and discotic [9] metallo-
mesogens into polymeric structures. Ghedini and co-workers have also
shown that it is possible to synthesise side-chain metallomesogenic poly-
mers that are free from cross-linking using organometallic species such
as cyclopalladated complexes [10] pi-allyl complexes [11]. Some polymers
derived from non-symmetric phthalocyanine macrocycles [12] have also
been reported as have a number of siloxane materials synthesised by
ourselves [13–15].
We were interested to see if liquid crystal polymers with organic back-
bones could also be prepared with metal-containing side chains, free from
covalent cross-linking. Two examples of such polymers derived from
nickel(II) co-ordination complexes are reported here for the first time.
EXPERIMENTAL
Analysis of Materials
Confirmation of the structures of the intermediates and products was
1
obtained by H NMR spectroscopy (JEOL JNM-GX270 FT spectrometer
operating at 270 MHz), infrared spectroscopy (Perkin-Elmer 783 or 983
spectrophotometer) and mass spectrometry (Finnigan-MAT 1020 auto-
mated GC=MS). The progress of the reactions and the purity of a number
of organic products was checked using a Perkin-Elmer 8320 capillary gas
chromatography equipped with a BP1 capillary column (12 m). The tran-
sition temperatures of all mesogens were determined using an Olympus
BH-2 polarising light microscope in conjunction with a Mettler FP52
heating stage and Mettler FP5 temperature control unit. The transition
temperatures were confirmed and enthalpies determined by thermal ana-
lysis using a Perkin-Elmer DSC7-UNIX=PC differential scanning calori-
meter. Diethyl ether was dried and stored over sodium wire. THF was
dried by distillation from sodium wire and benzophenone and stored over
4A molecular sieves. Ethanol was dried by distillation from magnesium
and stored over 4A molecular sieves. Toluene was dried by distillation from
and stored over 4A molecular sieves.
Monomer Synthesis
11-Bromo-1-tetrahydropyranyloxyundecane (1)
11-Bromo-1-undecanol (50 g, 0.199 mol) (Aldrich) was dissolved in
dichloromethane (500 mL) and the mixture cooled to 0ꢁC. Dihydropyran
(22.15 mL, 0.242 mol) was added dropwise over a period of two hours.
The reaction was started by addition of a few crystals of 4-toluenesulphonic
acid at the beginning of the addition. After the addition was complete, the

Polyacrylate and Polymethacrylate Nickel Complexes
493=[1535]
reaction mixture was stirred during 15 min, and stopped by addition of
NaHCO3 (0.5 g). After evaporation of the dichloromethane, the pale yellow
syrup obtained was dissolved in ethyl acetate and purified by filtration
through silica gel. Yield ¼ 65.3 g (98%).
4-(11-Tetrahydropyranyloxyundecyloxy)phenol (2)
Potassium hydroxide (4.72 g, 65 mmol) was dissolved in absolute etha-
nol (300 mL) under an atmosphere of dry nitrogen and hydroquinone
(19.5 g, 177 mmol) was added. The reaction mixture was heated under
reflux while a solution of 11-bromo-1-tetrahydropyranyloxyundecane
(19.81 g, 59 mmol) in ethanol (50 mL) was added dropwise. The reaction
mixture was refluxed (20 h), the solvent was then evaporated off and the
residue extracted with diethyl ether (3 ꢂ 300 mL), washed with saturated
aqueous NaCl (150 mL) and dried over MgSO4. The solvents were evapo-
rated under vacuum and the residue extracted with n-heptane to afford
a first crop of pure phenol. The remaining crude material was purified by
column chromatography on flash grade silica gel (diethyl ether=hexane,
2:3; Rf ¼ 0.27). Yield ¼ 12.65 g (59%).
1H NMR (CDCl3): d 6.76 (m, 4H, aromatic); 4.90 (s, 1H, OH); 4.60
(m, 1H, CHO-CH2 THPO); 3.89 (t(J ¼ 7 Hz), 2H, CH2O); 3.74, 3.52, 3.40
(m, 4H, CH2O THPO); 1.75–1.50 (m, 4H, CH2-CH2-O); 1.30 (m, 20H,
(CH2)).
2-Hydroxy-5-(11-tetrahydropyranyloxyundecyloxy)-
benzaldehyde (3)
Anhydrous tin(IV) chloride (0.23 mL, 2.0 mmol) was added to a solution
of tetrahydropyranyloxy phenol (7.35 g, 20.0 mmol) in sodium dried,
degassed toluene (250 mL) under a nitrogen atmosphere. Tri-n-butylamine
(1.90 mL, 8.0 mmol) was added at room temperature. The solution turned
yellow and was stirred for 1 h before paraformaldehyde (BDH) (1.32 g,
44 mmol) was added and the yellow suspension heated to 105ꢁC (3 h).
The brown solution was cooled, poured onto saturated aqueous NaCl
(200 mL) and acidified to pH 2 with 10% HCl. The product was extracted
with ether (3 ꢂ 100 mL) and the combined organic layers dried over MgSO4
and evaporated. The residue was purified by column chromatography
(flash grade silica gel; petroleum ether 40–60ꢁC=diethyl ether, 1:1). The
salicylaldehyde was isolated as a yellow solid (Rf ¼ 0.45). Yield ¼ 2.79 g
(36%).
1H NMR (CDCl3): d 10.64 (s, 1H, OH); 9.85 (s, 1H, CHO); 7.20–6.80
(m, 3H, Ha, Hb, Hc); 4.60 (m, 1H, CHO-CH2 THPO); 3.93 (t(J ¼ 7 Hz),
2H, CH2O); 3.74, 3.52, 3.38 (m, 4H, CH2O THPO); 1.80–1.50 (m, 4H,
CH2-CH2-O); 1.30 (m, 20H, (CH2)).

494=[1536]
P. Styring and I. M. Saez
8-(3-(11-Tetrahydropyranyloxyundecyloxy)-6-hydroxy-
phenyl)-2-phenyl-4,7-diazocta-2,7-dien-1-al (5)
1,2-Diaminoethane (0.25 mL, 3.87 mmol) was added to a vigorously
stirred solution of phenylmalonaldehyde (0.573 g, 3.87 mmol) in dichloro-
methane (350 mL). A white precipitate formed immediately. 5-(Tetrahydro-
pyranyloxyundecyloxy)salicylaldehyde (1.520 g, 3.87 mmol) was added and
the resulting yellow suspension stirred at room temperature for 18 h and
refluxed using a Dean-Stark apparatus until a clear yellow solution was
obtained (approximately 6 h). The yellow solution was evaporated
in vacuo and the residue purified by column chromatography (flash grade
silica gel, Cl2CH2=THF, 4:1). The band with Rf ¼ 0.75 yielded the sym-
metrical salen derivative. The band with Rf ¼ 0.50 was collected and the
product recrystallised from hot methanol to yield yellow microcrystals of
5. Yield ¼ 0.371 g (34%).
Microanalysis: Calcd for C34H48O5N2: C 72.31; H 8.56; N 4.95. Found: C
72.33; H 8.77; N 5.03. MS (EI): m=z 565 (Mþ ); 480 (Mþ -THP).
1H NMR (CDCl3): d 12.44 (s, 1H, OH); 10.49 (m broad, 1H, NH); 9.47
=
(d, (J ¼ 4 Hz), 1H, CHO); 8.31 (s, 1H, CH N); 7.30–6.75 (m, 9H, aromatic
=
C6H5, Ha, Hb, Hc, NCH C); 4.58 (m, 1H, CHO-CH2 THP); 3.88 (t (J ¼ 7 Hz),
=
2H, CH2O); 3.87–3.34 (m, 4H, CH2-N CH and CH2-NH; 4H, CH2O THP);
1.80–1.50 (m, 4H, CH2-CH2-O); 1.30 (m, 20H, (CH2)).
[8-(3-(11-Tetrahydropyranyloxyundecyloxy)-6-hydroxy-
phenyl)-2-phenyl-4,7-diazocta-1,3,7-trienato]-
(2-) nickel(II) (6)
Nickel acetate dihydrate (110.1 mg; 0.44 mmol) was added to a solution
of the tetrahydropyranyloxy ligand 5 (0.250 g; 0.44 mmol) in methanol
(20 mL) that was at reflux. Red microcrystals formed immediately. The
suspension was heated for 1 h at reflux. After cooling to room temperature,
the red-brown needles formed were filtered off and recrystallised from
methanol. Yield ¼ 0.210 g (76%).
ꢁ
Mesomorphism: Cryst (134 SmA) 158 Iso C.
Microanalysis: Calcd for C34H46O5N2Ni: C 65.71; H 7.45; N 4.50. Found:
C 64.99; H 7.61; N 4.31. MS (EI): m=z 621 (Mþ ); 593 (Mþ -CHO); 536
(Mþ -THP). 365 (Mþ -THP-(CH2)11O).
IR (KBr disc, t cmꢃ1): 1609 (vs, sharp; C N, C O and C C-N
=
=
=
coordinated).
1
=
=
H NMR (CDCl3): d 7.45–7.10 (m, 8H; aromatic C6H5, HC N, HC O and
=
NCH C); 6.93 (s, broad, 2H, Ha, Hb); 6.52 (m, 1H, Hc); 4.67 (m, 1H,
CHO-CH2 THP); 3.88 (t, (J ¼ 7 Hz), 2H, CH2O); 3.87–3.68 (m, 2H,
=
CH2O); 3.55–3.28 (m, 4H, CH2-N CH and CH2-NH; 2H, CH2O THP);
1.80–1.50 (m, 4H, CH2-CH2-O); 1.30 (m, 20H, (CH2)).

Polyacrylate and Polymethacrylate Nickel Complexes
495=[1537]
[8-(3-(11-Hydroxyundecyloxy)-6-hydroxyphenyl)-2-phenyl-
4,7-diazocta-1,3,7-trienato](2-) nickel(II) (7)
The tetrahydropyranyloxy protected nickel complex
6 (0.500 g,
0.848 mmol) was dissolved in Cl2CH2=MeOH (1:1, 20 mL) and 4-toluene-
sulphonic acid monohydrate (16 mg, 0.0848 mmol) was added. The solution
was heated to reflux in air for 12 h. The reaction mixture was then cooled to
room temperature and the solvents evaporated. The residue was subjected
to column chromatography on flash grade silica gel, eluting with
Cl2CH2=THF (4:1). The alcohol-terminated nickel complex (Rf ¼ 0.33)
was isolated as golden-red needles from methanol (0.217 g). The isolated
unreacted starting nickel complex (Rf ¼ 0.66) was subjected to hydrolysis
as above, to yield a second crop of the alcohol (0.089 g). Combined
yield ¼ 0.300 g (85%).
Melting point: 210ꢁC.
Microanalysis: Calcd for C29H38O4N2Ni: C 64.83; H 7.12; N 5.21. Found:
C 64.62; H 7.05; N 4.92. MS (EI): m=z 536 (Mþ -1). IR (KBr disc, t; cmꢃ1):
=
3423 (vs, broad; OH); 1606, 1592 (vs, sharp; C N, C O and C C-N
=
=
coordinated).
1
=
=
H NMR (CDCl3): d 7.45–7.10 (m, 8H; aromatic C6H5, HC N, HC O and
=
NCH C); 6.93 (s, broad, 2H, Ha, Hb); 6.53 (m, 1H, Hc); 3.83 (t, (J ¼ 7 Hz),
2H, CH2O-Ph); 3.65 (q broad (J ¼ 6 Hz), 2H, CH2-OH); 3.40 (m, 2H, CH2-
=
N CH); 3.31 (m, 2H, CH2-NH); 1.73 (m, 2H, CH2-CH2-O); 1.30 (m, 16H,
(CH2)8).
[8-(3-(11-Acryloxyundecyloxy)-6-hydroxyphenyl)-2-phenyl-
4,7-diazocta-1,3,7-trienato](2-) nickel(II) (8)
The alcohol-terminated nickel complex 7 (0.300 g, 0.558 mmol) was
dissolved in a mixture of sodium dried toluene and dichloromethane 1=1
(30 mL) under a dry nitrogen atmosphere. Acryloyl chloride (Fluka)
(0.054 mL, 0.669 mmol) was added and the solution stirred for 5 minutes.
Triethylamine (0.093 mL, 0.669 mmol) was added and a few crystals of
hydroquinone were added to stabilise the solution. The red suspension
was stirred at room temperature (18 h). On cooling to room temperature,
the solvent was evaporated in vacuo at room temperature and the residue
purified by flash column chromatography on silica gel using Cl2CH2=THF
(9:1) as the eluent system to yield red crystals of 8. Yield ¼ 0.130 g (40%).
Melting point ¼ 185ꢁC.
Microanalysis: Calcd for C32H40O5N2Ni.1=2 CH2Cl2: C 61.59; H 6.51; N
4.41. Found: C 60.78; H 6.43; N 4.37. MS (EI): m=z 591 (Mþ ); 365 (Mþ -
=
(CH2)11OCOCH CH2).
IR (KBr disc, t cmꢃ1): 1710 (vs, sharp, COO); 1620 (sh), 1608 (vs,
=
sharp; C N, C O and C C-N coordinated).
=
=

496=[1538]
P. Styring and I. M. Saez
1
=
H NMR (CDCl3; 400 MHz): d 7.45–7.10 (m, 8H; aromatic C6H5, HC N,
=
=
HC O and NCH C); 6.93 (s, broad, 2H, Ha, Hb); 6.53 (m, 1H, Hc); 6.39
(d, (Jtrans ¼ 17Hz)d(Jde ¼ 1Hz), 1H, He); 6.12 (d, (Jtrans ¼ 17Hz), d,
(Jcis ¼ 10Hz), 1H, Hf); 5.81 (d, (Jcis ¼ 10Hz), d, (Jde ¼ 1Hz), 1H, Hd);
4.15 (t, (J ¼ 7 Hz), 2H, CH2-OCO); 3.82 (t, (J ¼ 7Hz), 2H, CH2O-Ph);
=
3.39 (t, (J ¼ 6 Hz), 2H, CH2-N CH); 3.30 (t, (J ¼ 6 Hz), 2H, CH2-NH);
1.95 (s, 3H, CH3-CH ¼); 1.69 (m, 2H, CH2-CH2-O); 1.33 (m, 16H,
(CH2)8).
[8-(3-(11-Methacryloxyundecyloxy)-6-hydroxyphenyl)-
2-phenyl-4,7-diazocta-1,3,7-trienato](2-) nickel(II) (9)
The alcohol-terminated nickel complex 7 (0.185 g, 0.345 mmol) was
dissolved in sodium dried toluene (30 mL) under nitrogen atmosphere.
Methacryloyl chloride (0.033 mL, 0.345 mmol) was added and the solution
stirred for 5 minutes. A few crystals of hydroquinone were added to stabi-
lise the solution then triethylamine (0.048 mL, 0.345 mmol) was added and
the red suspension stirred at room temperature (18 h). The solvent was
evaporated in vacuo at room temperature and the residue purified by flash
column chromatography on silica gel using Cl2CH2=THF (9:1) as the eluent
system to yield red crystals of 9. Yield ¼ 0.124 g (60%).
Melting point ¼ 185ꢁC.
Microanalysis: Calcd for C33H42O5N2Ni: C 65.47; H 6.98; N 4.62. Found:
C 65.31; H 7.03; N 4.53. MS (EI): m=z 605 (Mþ ); 368 (Mþ -(CH2)11OCO-
MeCH CH2). IR (KBr disc, t; cmꢃ1): 1710 (vs, sharp, COO); 1620 (sh),
=
=
=
=
1608 (vs, sharp; C N, C O and C C-N coordinated).
1
=
=
H NMR (CDCl3): d 7.45–7.10 (m, 8H; aromatic C6H5, HC N, HC O and
=
NCH C); 6.93 (s, broad, 2H, Ha, Hb); 6.53 (m, 1H, Hc); 6.10 (s, 1H,
=
=
cis-CH C(COO)); 5.55 (m, 1H, trans-CH C(COO)); 4.14 (t, (J ¼ 7 Hz),
2H, CH2-OCO); 3.82 (t, (J ¼ 7 Hz), 2H, CH2O-Ph); 3.40 (m, 2H, CH2-
=
N CH); 3.32 (m, 2H, CH2-NH); 1.95 (s, 3H, CH3-CH ); 1.70 (m, 2H,
=
CH2-CH2-O); 1.30 (m, 16H, (CH2)8).
Polymerisation Reactions
Polymerisation reactions were carried out in sodium=benzophenone-dried
THF, using AIBN as radical initiator, under nitrogen atmosphere. In both
cases, the final polymer was precipitated from dichloromethane into a large
volume of methanol with vigorous stirring. Absence of initial monomer was
checked at this stage by thin layer chromatography. The polymers were
recovered by filtration and dried under vacuum for several hours. The
1H NMR spectra of the polymers showed broad resonances, typical of
polymers, however resolution was sufficient to allow relative integrations

Polyacrylate and Polymethacrylate Nickel Complexes
497=[1539]
to be calculated: the absence of unreacted monomer was confirmed in both
cases.
Poly[8-(3-(11-acryloxyundecyloxy)-6-hydroxyphenyl)-
2-phenyl-4,7-diazocta-1,3,7-trienato](2-) nickel(II)] (10)
The acrylate monomer 8 (84 mg, 0.142 mmol) and 66 mL of a solution of
AIBN (0.1 g) in dry THF (10 mL) [inititor=monomer ratio ¼ 3 mol%] were
placed in a Schlenck tube that was evacuated then filled with nitrogen sev-
eral times. Freshly distilled dry THF (6 mL) was added and the solution
subjected to three freeze-thaw cycles, then flushed with nitrogen. The tube
was placed in an oil bath at 70ꢁC to initiate the polymerisation. After 48 h
the reaction solution was cooled to room temperature, whereupon a fine
ochre coloured solid precipitated out. The whole mixture was evaporated
to dryness, the residue dissolved in CH2Cl2 (3 mL) and precipitated into
methanol (200 mL) with vigorous stirring. This procedure was repeated
once more, until the solid showed no trace of acrylate monomer by TLC.
The red-ochre solid was filtered off and dried under vacuum. Yield ¼
44 mg (53%).
ꢁ
Mesomorphism: Cryst 167 SmA 260 dec C.
Microanalysis: Calcd for C32H40O5N2Ni: C 64.99; H 6.81; N 4.73. Found:
C 64.24; H 6.96; N 4.45. IR (KBr disc, t; cmꢃ1): 1710 (vs, sharp, COO); 1620
=
=
=
(sh), 1608 (vs, sharp; C N, C O and C C-N coordinated).
1
=
H NMR (CDCl3; 400 MHz): d 7.45–7.10 (m, 8H; aromatic C6H5, HC N,
=
HC O and NCH C); 6.89 (s, broad, 2H, Ha, Hb); 6.40 (broad, 1H, Hc);
=
4.05 (s, 2H, CH2-OCO); 3.76 (s, br, 2H, CH2O-Ph); 3.34 (s, br, 4H, CH2-
=
N CH, CH2-NH); 2.51–2.00 (br, CH2-CH-OCO); 1.84 (br, CH2-CH-OCO);
1.69 (m, br, 2H, CH2-CH2-O); 1.60 (m, br, 2H, CH2-CH2-O); 1.33
(m, 16H, (CH2)8).
Poly[8-(3-(11-methacryloxyundecyloxy)-6-hydroxyphenyl)-
2-phenyl-4,7-diazocta-1,3,7-trienato](2-) nickel(II)] (11)
Polymer 11 was prepared following the procedure described above from
the methacryloxy nickel complex (80 mg, 0.132 mmol) and AIBN (0.2 mg, 1
mol%) in THF (6 mL). Yield ¼ 50 mg (62%).
ꢁ
Mesomorphism: g 129 E=B 189 SmA 195 Iso C.
Microanalysis: Calcd for C33H42O5N2Ni: C 65.47; H 6.98; N 4.62. Found:
C 65.11; H 6.83; N 4.61. IR (KBr disc, t; cmꢃ1): 1710 (vs, sharp, COO); 1620
=
=
(sh), 1608 (vs, sharp; C N, C O and C C-N coordinated).
=
1
=
=
H NMR (CDCl3): d 7.45–6.50 (m, 11H; aromatic C6H5, HC N, HC O,
=
NCH C, Ha, Hb, Hc); 4.05 (s, br, 2H, CH2-OCO); 3.76 (s, br, 2H, CH2O-
=
Ph); 3.34 (s, br, 4H, CH2-N CH, CH2-NH); 2.51–1.50 (br, several signals,
CH2-CH-OCO, CH2-CH-OCO); CH2-CH2-O, CH2-CH2-O); 1.33 (m, 16H,
(CH2)8).

498=[1540]
P. Styring and I. M. Saez
RESULTS AND DISCUSSION
Synthesis
The synthesis of the nickel-containing monomers proved more difficult
than the analogous monomers used in the siloxane syntheses [13–15],
requiring the use of a tetrahydropyranyl (THP) protecting group from an
early stage of a linear synthesis as shown in Scheme 1. 11-Bromodecanol
was protected with dihydropyran to give the THP intermediate 1 which
was used to alkylate hydroquinone to 2 in good yield. This was then formy-
lated, again in good yield, using paraformaldehyde and tin(IV) chloride to
give the substituted salicylaldehyde 3 which was condensed with equimolar
quantities of 2-phenylmalonaldehyde (4) and 1,2-diaminoethane to give 5
in reproducible yields of up to 30%. Complex 6 was formed in 80% yield
and then deprotected to give the hydroxy-terminated complex 7 in 85%
yield. The acrylate (8) and methacrylate (9) monomers were prepared
by reacting 7 with acryloyl chloride or methacryloyl chloride respectively
SCHEME Synthetic pathway to the nickel(II)-containing monomers and polymers.

Polyacrylate and Polymethacrylate Nickel Complexes
499=[1541]
in quantitative yields. Polymerisation was achieved using AIBN as the
radical initiator in THF solvent at 60ꢁC. The polymers were obtained pure in
approximately 50% yield as dark brown waxy solids by repeated precipita-
tions from dichloromethane=methanol. The average degree of polymeris-
ation for both the methacrylate and acrylate was determined to be 5 by
1H NMR (270 MHz) using end group analysis based on the relative integra-
tions of the signals. This was disappointing but can be attributed to the low
solubilities of the products in THF at 60ꢁC, resulting in premature precipi-
tation and therefore termination of the reaction. Alternatively, it could be
that the metal plays a key role in the polymerisation process by hindering
the radical process and so either terminating the reaction or retarding it to
an extent where only short chains are formed [9,10]. The average molecular
weights (Mn) of the polymethacrylate and polyacrylate are 3027.6 and
2957.5 daltons respectively. Alternatively, intermolecular metal–metal
interactions of the type reported previously for the siloxane systems [8]
may also result in non-covalent networks that cause premature precipi-
tation, although this might not be such an important factor bearing in mind
the relatively low concentration of the reaction solution. Efforts are now
being focussed on to the feasibility of performing solid-state polymer
synthesis from a monomer melt under UV irradiation.
Mesomorphic Properties
The melting behaviour of the materials prepared was investigated by hot-
stage polarising light microscopy and transitions confirmed by differential
scanning calorimetry. All intermediates and the ligand were found to exhi-
bit simple melting behaviour, with the exception of the THP protected
nickel complex (6), which exhibited a monotropic smectic A phase on
cooling from the isotropic liquid as shown in Table 1. Removal of the
THP protecting group gave the terminal hydroxy-substituted complex
which was non-mesomorphic, undergoing simple melting at 210ꢁC. Esteri-
fication gave either the methacrylate (8) or acrylate (9) monomers, which
again underwent simple melting at 185 and 154ꢁC respectively.
On polymerisation we were surprised to discover that the materials were
liquid crystalline despite the simple melting behaviour of the monomers.
The polymethacrylate (10) was a waxy solid at room temperature which
underwent a glass transition, characterised by a second order thermal
event of the DSC thermogram, at 167ꢁC, only 13ꢁC higher than the melting
point of the monomer. Observation of the optical texture by polarised light
microscopy revealed a smectic A phase characterised by small focal conic
defects. A good cooling texture could not be obtained because the sample
rapidly decomposed at 260ꢁC and consequently a value for the enthalpy
could not be determined. It is recognised that the increased flexibility of

500=[1542]
P. Styring and I. M. Saez
TABLE 1 Transition Temperatures of the Nickel(II)-Containing Intermediates,
Monomers and Polymers (ꢁC) with Transition Enthalpies (kJ molꢃ1) Given in
Parentheses
Material
Cryst
g
E=B
SmA
Iso
6
7
.
.
.
.
–
–
–
–
–
.
–
–
–
–
–
(134
.)
–
158
210
185
154
260
*
.
.
.
.
dec
8
–
9
10
–
167
Tg
.
11
–
.
129
Tg
.
189
(9.1)
.
195
(0.1)
.
ꢀPeak not observed due to broad decomposition.
the polyacrylate backbone relative to the polymethacrylate results in a
decrease in the glass transition and liquid crystalline phase transition
temperatures [16]. Consequently the polyacrylate (11) exhibited a glass
transition temperature at 129ꢁC to give an anisotropic plastic crystal phase.
A first order endothermic transition to a smectic Aꢁphase was observed at
189ꢁC (9.1 kJ molꢃ1), which was stable up to 195 C (9.1 kJ molꢃ1) when
the isotropic liquid phase formed without decomposition. This allowed us
to achieve some good optical textures by slowly annealing from the
isotropic liquid over a period of several hours. The focal conic texture
confirmed the smectic A phase, while the lower temperature ordered phase
FIGURE 1 Schematic representation of self-organisation of the mesogenic com-
plexes on polymerisation.

Polyacrylate and Polymethacrylate Nickel Complexes
501=[1543]
was most likely an E or B phase based on the fine mosaic texture observed,
however without X-ray diffraction data we were unable to differentiate
between the two. Studies are currently in progress to characterise the
liquid crystalline phases of the polymers by small angle X-ray scattering
(SAXS) studies as a function of temperature over the range of mesophase
existence. Preliminary results have been obtained using unaligned samples,
however the SAXS patterns are poor; giving in the case of the methacrylate
at 140ꢁC a broad, diffuse reflection corresponding to a layer spacing of
˚
approximately 28 A consistent with molecular dimensions. No lateral
spacings could be assigned. It was not possible to obtain good data for
the acrylate because of decomposition.
The fact that only orthogonal smectic phases are observed is consistent
with results obtained for polymeric siloxane materials derived from struc-
turally similar nickel [13,14] and copper [15] complexes. Although not cova-
lently bonded, we have shown by single crystal and small angle X-ray
scattering [14] that intermolecular metal–metal or metal–ligand interac-
tions promote layer formation and stabilise orthogonal liquid crystal
phases. In the case of the materials reported here, immobilisation of the
non-liquid crystalline monomer complexes on a short polymer backbone
serves to bring the cores into close proximity. This allows for intermolecu-
lar interactions and so promotes smectic phase formation (Figure 1). As
the monomers are themselves non-liquid crystalline, the polymer backbone
may be regarded as acting as a template self-organisation and hence
mesophase stabilisation. A similar effect has been noted by Bazuin and
co-workers [17] in the case non-covalent, but ionic complexation of non-
liquid crystalline monomers to a poly(sulfonate) backbone.
CONCLUSIONS
Two polymers based on organic (meth)acrylate backbones have been
synthesised and have been shown to exhibit liquid crystalline phases.
Whilst the degree of polymerisation is low (DP ¼ 5) we have demonstrated
a proof of principle in that we have shown that anisotropic inorganic mono-
mers can be polymerised using conventional chemistries to produce assem-
blies in which the complex is immobilised at one point whilst the remainder
of the molecule is not covalently cross-linked. Furthermore, we have shown
that immobilisation of the complexes onto a backbone actually promotes
liquid crystalline phase behaviour through self-assembly of the non-
mesomorphic monomers. This has now opened up a number of possibilities
for future work including co-polymerisation with organic monomers and
investigations into the application of such polymers as immobilised cata-
lysts in organic chemistry.

502=[1544]
P. Styring and I. M. Saez
REFERENCES
[1] Serrano, J. L. (1996). (Ed.), Metallomesogens: Synthesis, Properties and Applications,
Wiley: Weinheim.
[2] Giroud, A. M. & Maitlis, P. M. (1991). Angew. Chem. Int. Ed. Engl., 30, 375.
[3] Hudson, S. A. & Maitlis, P. M. (1993). Chem. Rev., 93, 861.
[4] Oriol, L. & Serrano, J. L. (1995). Adv. Mater., 7, 348.
[5] Deschenaux, R., Kosztics, I., Scholten, U., Guillon, D., & Ibn-Elhaj, M. (1994). J. Mater.
Chem., 4, 1351.
[6] Deschenaux, R., Jauslin, I., Scholten, U., Turpin, F., Guillon, D., & Heinrich, B. (1998).
Macromolecules, 31, 5647.
[7] Turpin, F., Guillon, D., & Deschenaux, R. (2001). Mol. Cryst., Liq. Cryst., 362, 171.
[8] Valdebenito, N., Oriol, L., Barbera, J., Diaz, F., & Serrano, J. L. (2000). Macromol. Chem.
Phys., 201, 2573.
[9] Oriol, L., Pinol, M., Poelsma, S., Serrano, J. L., & Vinuales, A. (2000). J. Polym. Sci. Part
A-Polym. Chem., 38, 4466.
[10] Ghedini, M., Aiello, I., & Roviello, A. (1997). Acta Polym., 48, 400.
[11] Ghedini, M., Panunzi, B., & Roviello, A. (1998). Liq. Cryst., 25, 225.
[12] van der Pol, J. F., Neeleman, E., Nolte, R. J. M., Zwikker, J. W., & Drenth, W. (1989).
Makromol. Chem., 190, 2727.
[13] Saez, I. M. & Styring, P. (1996). Adv. Mater., 8, 1001.
[14] Saez, I. M., Styring, P., Mehl, G. H., & Sinn, E. (1998). J. Organomet. Chem., 551, 299.
[15] Saez, I. M. & Styring, P. (1997). Mol. Cryst. Liq. Cryst., 299, 163.
[16] Percec, V. & Pugh, C. (1989). Side chain liquid crystal polymers. In: McArdle, C. B., (Ed.)
Blackie: Glasgow, London.
[17] Bazuin, C. G. & Tork, A. (1995). Macromolecules, 28, 8877.