Synthesis and characterization of side-chain liquid crystalline polymers and oriented elastomers containing terminal perfluorocarbon chains

Article abstract of DOI:10.1016/j.polymer.2011.09.002

Several novel chiral side-chain liquid crystalline (LC) polysiloxane resins containing epoxy groups and mesogenic components have been graft copolymerized by a one-step hydrosilylation reaction with poly(methylhydrogeno)siloxane, an epoxy monomer 2-(allyloxymethyl)oxirane, and chiral fluorinated liquid-crystalline monomers 4′-(4-(allyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate and 4′-(4-(undec-10-enoyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy) hexahydrofuro[3,2-b]furan-3-yl adipate. The synthesized epoxy resins are cured using 4,4′-diaminodiphenyl-methane in mesophase state under a magnetic field to obtain crosslinked oriented elastomers. The chemical structures, LC properties and surface morphology of the monomers, the resins and the liquid crystalline elastomers (LCEs) are characterized by use of various experimental techniques such as FTIR, ¹H NMR, EA, TGA, DSC, POM, and X-ray measurements. The mesomorphic properties of the synthesized resins and corresponding oriented elastomers are influenced by the terminal perfluorocarbon chains components effectively. The resins show chiral nematic and chiral smectic C phases (Sc*), and Sc* are frozen in their corresponding oriented elastomers. The LC phases are verified by X-ray measurements, and the orientational order parameters of the oriented LCEs are calculated as well.

Full text of DOI:10.1016/j.polymer.2011.09.002

Polymer 52 (2011) 5075e5084
Contents lists available at SciVerse ScienceDirect
Polymer
journal homepage: www.elsevier.com/locate/polymer
Synthesis and characterization of side-chain liquid crystalline polymers
and oriented elastomers containing terminal perfluorocarbon chains
*
Fan-Bao Meng , Xiao-Dong Zhang, Xiao-Zhi He, He Lu, Yue Ma, Hui-Li Han, Bao-Yan Zhang
Research Center for Molecular Science and Engineering, Northeastern University, Shenyang 110004, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Several novel chiral side-chain liquid crystalline (LC) polysiloxane resins containing epoxy groups and
mesogenic components have been graft copolymerized by a one-step hydrosilylation reaction with
poly(methylhydrogeno)siloxane, an epoxy monomer 2-(allyloxymethyl)oxirane, and chiral fluorinated
liquid-crystalline monomers 40-(4-(allyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahy-
drofuro[3,2-b]furan-3-yl adipate and 40-(4-(undec-10-enoyloxy)benzoyloxy)biphenyl-4-yl 6-(per-
fluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate. The synthesized epoxy resins are cured using
4,40-diaminodiphenyl-methane in mesophase state under a magnetic field to obtain crosslinked oriented
elastomers. The chemical structures, LC properties and surface morphology of the monomers, the resins
and the liquid crystalline elastomers (LCEs) are characterized by use of various experimental techniques
such as FTIR, 1H NMR, EA, TGA, DSC, POM, and X-ray measurements. The mesomorphic properties of the
synthesized resins and corresponding oriented elastomers are influenced by the terminal per-
fluorocarbon chains components effectively. The resins show chiral nematic and chiral smectic C phases
(Sꢀc), and Sꢀc are frozen in their corresponding oriented elastomers. The LC phases are verified by X-ray
measurements, and the orientational order parameters of the oriented LCEs are calculated as well.
Ó 2011 Elsevier Ltd. All rights reserved.
Received 22 February 2011
Received in revised form
23 July 2011
Accepted 4 September 2011
Available online 10 September 2011
Keywords:
Liquid crystalline polymers
Elastomers
Fluoropolymers
1. Introduction
macroscopically ordered) [16e20]. Chiral smectic C (Sꢀc) liquid
crystal is one of the most fantastic LC phases since it can form
Liquid crystal elastomers (LCEs) combine the orientational
ordering properties of liquid crystalline systems with the rubbery
elasticity of polymer networks, and have been developed as
promising functional materials in recent years due to their
remarkable properties such as interesting mechanical, electrical,
and optical properties [1e5]. For the rubbery elasticity of LCEs,
coupling between the polymer chain and side-groups and
restricting the relative motion of polymer chains must be consid-
ered, and the LC behaviors of LCEs can be manifested by the
mesogens and orientation. The orientation of the mesogens can be
controlled through mechanical stress [6,7], as well as by electric
and magnetic field [8e12]. Various mesogens have been introduced
into the polymer networks for different application considerations
through chemical design [13e15] and many papers recently appear
dealing with mechanical, dynamic-mechanical and rheological
properties of LCEs both on polydomain samples (in which the
mesogenic groups are macroscopically disordered) and on mono-
domain samples (in which the mesogenic groups are
helical structure. Sꢀc elastomers have attracted interest in both
industrial and scientific fields due to their additional properties
such as ferroelectricity, piezoelectricity and pyroelectricity
[21e23]. In particular, the oriented Sꢀc elastomers including mon-
odomain LCEs are ideal materials for the investigation of piezo-
electric and inverse piezoelectric effects in chiral smectic C systems
because of macroscopic ordering of mesogenic groups and non-
macroscopic flow in the polymer network matrix, because the
macroscopic flow destroys piezoelectricity in conventional low-
molar mass ferroelectric liquid crystals [24].
Recently, the use of organo-fluorine compounds has generated
much research effort. Initial studies on fluorinated liquid crystals
focused on partly fluorinated alkanes (i.e. diblock hydrocarbon-
fluorocarbon molecules) [25]. Fluorocarbons and hydrocarbons
are poorly miscible because the conformation and electrostatic
interactions of the fluorocarbons are different from those of
hydrocarbons. The formation of liquid-crystalline mesophases is
due to the strong phase separation of fluorocarbon from hydro-
carbon chain segments and the rigid-rod-like nature of the fluo-
rocarbon chains which tend to adopt a helical conformation in the
mesophase state [26,27]. Some synthetic efforts have subsequently
resulted in the development of fluorinated liquid crystalline
* Corresponding author. Tel./fax: þ86 24 83687671.
E-mail address: mengfb@mail.neu.edu.cn (F.-B. Meng).
0032-3861/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymer.2011.09.002

5076
F.-B. Meng et al. / Polymer 52 (2011) 5075e5084
polymers in which the length of the fluorinated tail is varied. More
conventional mesogenic units have also been used in combination
with partly fluorinated tails in polymeric liquid crystals [28,29].
One can see chiral groups can form helical conformation, and some
fluorocarbon-hydrocarbon systems tend to adopt a helical confor-
mation in the mesophase state. Despite the studies reported so far,
the details of elastomers containing both fluorocarbons and chiral
groups are still unknown. In order to obtain a well-ordered and
immobilized oriented LCEs at room temperature, and to study LCE
systems bearing both fluorocarbons and chiral groups, we have
recently succeeded in obtaining oriented Sꢀc elastomers by curing
resins with isosorbide and terminal perfluorocarbon chains under
a magnetic field.
2. Experimental
2.1. Materials and methods
Poly(methylhydrogeno)siloxane (PMHS, Mn z 2300), 2-(ally-
loxymethyl)oxirane (AMO), 4,40-diaminodiphenyl-methane (DDM)
and 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoic acid are
obtained from ALDRICH without any further purification. 40-
hydroxybiphenyl-4-yl 4-(allyloxy)benzoate and 40-hydrox-
ybiphenyl-4-yl 4-(undec-10-enoyloxy)benzoate are synthesized
according to previous reported procedure [30]. Biphenyl-4,40-diol,
undec-10-enoic acid, 3-bromopropene, isosorbide, adipic acid,
hexachloroplatinic acid hydrate and reagent-grade solvents are
obtained from Jilin Chemical Industry Company and used without
any further purification. Tetrahydrofuran (THF) is dried over
sodium metal and distilled. Pyridine is purified by distillation over
KOH and NaH before using. Other reagent-grade solvents are used
as received.
Fig. 1. Synthetic routes to monomers 40-(4-(allyloxy)benzoyloxy)biphenyl-4-yl
6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate (ABPHA).
evaporator under reduced pressure. After cooling to room
temperature, the mixture is poured into 100 mL cold water and
acidified with 6 N sulfuric acid. The precipitates are isolated by
filtration and recrystallized in ethanol and dried in a vacuum oven
to obtain white crystals of 6-(40-(4-(allyloxy)benzoyloxy)biphenyl-
4-yloxy)-6-oxohexanoic acid (2). Yield: 87%. m.p.: 162 ꢁC. IR (KBr,
cmꢂ1): 3054, 2922, 2850 (CH3, ꢂCH2ꢂ and eCHe), 2648e2529
(eOH in eCOOH), 1751e1685 (C]O), 1639 (C]C on terminal
olefinic group), 1608, 1495 (Ar), 1293 (CeOeC). Anal. Calcd for
C28H26O7: C, 70.87%; H, 5.52%. Found: C, 70.78%; H, 5.59%. 1H NMR
DSC and TGA measurements are carried out with a NETZSCH
TGA 209C thermogravimetric analyzer, and a NETZSCH instruments
DSC 204 (Netzsch, Wittelbacherstrasse, Germany) at a scanning
rate of 10 ꢁC minꢂ1 under a flow of dry nitrogen. X-ray measure-
ments is performed using Cu K
a
(l
¼ 1.542 Å) radiation mono-
chromatized with a Rigaku DMAX-3A X-ray diffractometer (Rigaku,
Japan). The X-ray measurements include wide-angle X-ray
diffraction (WAXD) experiments and small-angle X-ray scattering
(SAXS) measurements. 1H NMR, FTIR and element analyses (EA) are
measured by Varian WH-90PFT NMR Spectrometer (Varian Asso-
ciates, Palo Alto, CA), PerkinElmer instruments Spectrum One
Spectrometer (PerkinElmer, Foster City, CA) and Elementar Vario EL
III (Elementar, Germany), respectively. Measurement of optical
(CDCl3, d, ppm): 1.21e1.58 [m, 4H, eOOCCH2(CH2)2CH2COOH];
2.16e2.39 [m, 4H, eOOCCH2(CH2)2CH2COOH]; 4.39e4.63 [d, 2H,
CH2]CHCH2Oe]; 4.73e5.08 (m, 2H, CH2]CHe); 5.91e6.18 (m, 1H,
CH2]CHe); 7.13e8.11 (m, 12H, AreH); 12.03e12.21 (S, 1H,
eCOOH).
The intermediate 2 (23.7 g, 0.05 mol), 50 mL thionyl chloride
and 1.0 mL of pyridine are added into a round flask equipped with
a catheter to absorb hydrogen chloride. The mixture is stirred at
room temperature for 3 h, then heated to 60 ꢁC and kept for 10 h in
a water bath to ensure that the reaction finished. The excess thionyl
chloride is distilled under reduced pressure. Then 100 mL cold THF
is added to the residue at 25 ꢁC to obtain THF solution of 40-(6-
chloro-6-oxohexanoyloxy)biphenyl-4-yl 4-(allyloxy)benzoate (3).
Isosorbide (43.8 g, 0.3 mol) and 18 mL pyridine are dissolved in
300 mL dry THF. To the solution, it is added dropwise with THF
solution of 3. The reaction mixture is stirred at 65 ꢁC for 36 h. The
solvent is distilled out partly under reduced pressure. After cooling
to room temperature, the residue is poured into 500 mL cold water.
The precipitates are isolated by filtration, washed by hot water and
dried in a vaccum oven. Recrystallization in alcohol results in white
crystals of 40-(4-(allyloxy)benzoyloxy)biphenyl-4-yl 6-hydroxyhex-
ahydrofuro[3,2-b]furan-3-yl adipate (4). Yield: 63%. m.p.: 93 ꢁC. IR
(KBr, cmꢂ1): 3405 (eOH), 3076, 2935, 2871 (CH3, eCH2e, eCHe
and AreH), 1756e1722 (C]O), 1605, 1494 (Ar), 1292, 1256, 1167
(CeO). Anal. Calcd for C34H34O10: C, 67.76%; H, 5.69%. Found: C,
rotation (
a) is carried out with a PerkinElmer instrument Model 341
Polarimeter at room temperatures using sodium light source
(
l
¼ 589 nm). The polarized optical microscopy (POM) study is
performed using a Leica DMRX (Leica, Wetzlar, Germany) equipped
with a Linkam THMSE-600 (Linkam, Surrey, England) heating stage.
The magnetic fields for curing samples are carried out with a SA-
4602 type electromagnet provided by Shenyang Changcheng
Electromagnet Manufacture Co (Yuhong, Shenyang, China).
2.2. Synthesis of the liquid crystalline monomers
Fig. 1 shows the synthesis routes of chiral liquid crystal-
line monomers 40-(4-(allyloxy)benzoyloxy)biphenyl-4-yl 6-(per-
fluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate (ABPHA).
Adipoyl dichloride (18.3 g, 0.1 mol), 200 mL chloroform are
added into a round flask. It is added dropwise with solution of
compound 40-hydroxybiphenyl-4-yl 4-(allyloxy)benzoate (1)
(6.93 g, 0.02 mol, dissolved in 150 mL dry chloroform) and 10 mL
pyridine. The reaction mixture is stirred at 65 ꢁC for 24 h. The
solvent and excess adipoyl dichloride is distilled using a rotatory
67.83%; H, 5.62%. 1H NMR (CDCl3,
d, ppm): 1.27e1.59 [m, 4H,
eOOCCH2(CH2)2CH2COOe]; 2.21e2.38 [m, 4H, eOOCCH2(CH2)2
CH2COOe]; 3.69e4.68 [m, 10H, CH2]CHCH2Oe, and eCH2eOe or

F.-B. Meng et al. / Polymer 52 (2011) 5075e5084
5077
Fig. 2. Synthetic route to resins and elastomers.
eCHeOe in isosorbide group]; 4.93e5.16 (m, 2H, CH2]CHe);
5.90e6.17 (m, 1H, CH2]CHe); 7.11e8.14 (m, 12H, AreH); 9.45e9.69
(S, 1H, eOH).
2.51e2.61 [m, 4H, eOOCCH2(CH2)2CH2COOe]; 3.68e4.47 [m, 8H,
eCH2eOe andeCHeOe in isosorbide group]; 4.59e4.65 [d, 2H,
CH2]CHCH2Oe]; 5.26e5.51 (m, 2H, CH2]CHe); 6.05e6.18 (m, 1H,
CH2]CHe); 7.05e8.17 (m, 12H, AreH).
Compound 4 (30.1 g, 0.05 mol) and 10.0 mL dry pyridine are
dissolved in 250 mL dry THF to form a solution. Perfluorooctanoyl
chloride (21.6 g, 0.05 mol) is added dropwise to the solution and
reacted at 63 ꢁC for 48 h; then some solvent is distilled out. The
mixture is cooled, poured in 600 mL cold water. The precipitated
crude product is filtered, washed with hot water, recrystallized with
alcohol and dried overnight under vacuum to obtain a white powder
The synthesis scheme of 40-(4-(undec-10-enoyloxy)benzoy-
loxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]
furan-3-yl adipate (UBPHA) is identical to the one of ABPHA.
6-Oxo-6-(40-(4-(undec-10-enoyloxy)benzoyloxy)biphenyl-4-
yloxy)hexanoic acid is prepared by use of 40-hydroxybiphenyl-4-yl 4-
(undec-10-enoyloxy)benzoate and adipoyl dichloride. Yield: 81%.
m.p.: 162 ꢁC. IR (KBr, cmꢂ1): 3075, 2925, 2852 (CH3, eCH2e and
eCHe), 2640e2530 (eOH in eCOOH), 1755, 1717, 1686 (C]O), 1641
(C]C on terminal olefinic group), 1608, 1493 (Ar), 1278 (CeO). Anal.
Calcd for C36H40O8: C, 71.98%; H, 6.71%. Found: C, 71.92%; H, 6.69%. 1H
of liquid-crystalline monomer ABPHA. Yield: 53%. ½a D20
ꢃ
¼ þ 41.1ꢁ,
c ¼ 1, chloroform; m.p.: 64.4 ꢁC. IR (KBr, cmꢂ1): 3074, 2926, 2851
(CH3ꢂ , ꢂCH2ꢂ , eCHe and AreH), 1755e1724 (C]O), 1608, 1510 (Ar),
1293, 1259, 1213, 1170 (CeO), 1149 (CeF). Anal. Calcd for
C42H33F15O11: C, 50.51%; H, 3.33%. Found: C, 50.63%; H, 3.29%.1H NMR
NMR (CDCl3,
d, ppm):1.11e1.69[m,16H, CH2]CHCH2(CH2)6CH2COOe
(CDCl3,
d, ppm): 1.32e1.70 [m, 4H, eOOCCH2(CH2)2CH2COOe];
and eOOCCH2(CH2)2CH2COOe]; 2.01e2.16 [m, 2H, CH2]

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F.-B. Meng et al. / Polymer 52 (2011) 5075e5084
CHCH2(CH2)6CH2COOe]; 2.30e2.56 [m, 6H, CH2]CHCH2(CH2)6
CH2COOe and eOOCCH2(CH2)2CH2COOe]; 4.91e5.14 (m, 2H, CH2]
CHe); 5.93e6.11 (m, 1H, CH2]CHe); 7.07e8.14 (m, 12H, AreH);
12.11e12.22 (S, 1H, -COOH).
residue is cooled to room temperature and poured into 100 mL
methanol. The product is filtered off, dissolved in chloroform and
precipitated in methanol (3 times), and dried at 80 ꢁC under
vacuum for 24 h to obtain 2.49 g of liquid crystalline resin PI-2.
6-Hydroxyhexahydrofuro[3,2-b]furan-3-yl 40-(4-(undec-10-enoy-
loxy)benzoyloxy)biphenyl-4-yl adipate is synthesized using 40-
(6-chloro-6-oxohexanoyloxy)biphenyl-4-yl 4-(undec-10-enoyloxy)
benzoate and isosorbide. Yield: 61%. m.p.: 82 ꢁC. IR (KBr, cmꢂ1): 3441
(eOH), 3075, 2925, 2852 (CH3, ꢂCH2ꢂ , eCHe and AreH), 1758-1721
(C]O), 1602, 1494 (Ar) 1274, 1206, 1164 (CeO). Anal. Calcd for
C42H48O11: C, 69.21%; H, 6.64%. Found: C, 69.73%; H, 6.62%. 1H NMR
Yield: 93%. The specific rotation (½a D
ꢃ
20) and the epoxy value are
listed in Table 1. IR (KBr, cmꢂ1): 2928, 2852 (CeH aliphatic),
1785e1716 (C]O in different ester linkages), 1607, 1510 (Ar), 1273,
1169 (CeOeC), 1146 (CeF), 1023 (SieO). 1H NMR (CDCl3,
d, ppm):
0e0.20 (s, 1.14H, SieCH3); 0.41e0.53 (m, 0.69H, SieCH2e);
1.22e2.58 (m, 3.28H, alkyl-H); 3.78e4.47 [m, 3.13H, eCH2eOe
andeCHeOe]; 7.08e8.16 (m, 2.76H, AreH).
(CDCl3, d, ppm): 1.14e1.73 [m,16H, CH2]CHCH2(CH2)6CH2COOe and
eOOCCH2(CH2)2CH2COOe]; 2.10e2.19 [m, 2H, CH2]CHCH2
(CH2)6CH2COOe]; 2.29e2.58 [m, 6H, CH2]CHCH2(CH2)6CH2COOe
and eOOCCH2(CH2)2CH2COOe]; 3.64e4.69 [m, 8H, eCH2eOe and
eCHeOe in isosorbide group]; 4.90e5.12 (m, 2H, CH2]CHe);
6.03e6.18 (m, 1H, CH2]CHe); 7.15e8.11 (m, 12H, AreH); 9.37e9.49
(S, 1H, eOH).
2.4. Preparation of the orientated liquid crystalline elastomers
Liquid crystalline resins are cured by mechanically mixing the
epoxy resins and curing agent DDM without any solvent, taken in
a stoichiometric ratio (2:1) according to the epoxy value of the
resins in Table 1. Each mixture is heated to 98 ꢁC and stirred for
10 min at this temperature, to make it homogeneous. The epoxy
resins and the curing agent are miscible when they were
mechanical mixed, and the mixture turn white during the mixing.
Successively, it is poured between two glass slides and cured under
magnetic fields of 10 T at 98 ꢁC, and the crosslinking reaction is
monitored by measuring the FTIR spectra. The FTIR spectroscopy is
used to detect the curing process previously [31].
Liquid crystalline monomer UBPHA is prepared from 6-
hydroxyhexahydrofuro[3,2-b]furan-3-yl 40-(4-(undec-10-enoyloxy)
benzoyloxy)biphenyl-4-yl adipate and perfluorooctanoyl chloride.
a 20
Yield: 51%. ½ ꢃD ¼ þ 40.2ꢁ,c ¼ 1, chloroform; m.p.: 61.0 ꢁC. IR (KBr,
cmꢂ1): 3075, 2928, 2854 (ꢂCH3ꢂ , ꢂCH2ꢂ , eCHe and AreH),
1760e1724 (C]O), 1603, 1495 (Ar), 1272, 1258, 1207, 1166 (CeOeC),
1146 (CeF). Anal. Calcd for C50H47F15O12: C, 53.39%; H, 4.21%.
Found: C, 53.33%; H, 4.17%. 1H NMR (CDCl3,
d, ppm): 1.21e1.75 [m,
16H, CH2]CHCH2(CH2)6CH2COOe and eOOCCH2(CH2)2CH2COOe];
2.05e2.18 [m, 2H, CH2]CHCH2(CH2)6CH2COOe]; 2.48e2.62 [m,
6H, CH2]CHCH2(CH2)6CH2COOe and eOOCCH2(CH2)2CH2COOe];
3.69e4.21 [m, 8H, eCH2eOe and eCHeOe in isosorbide group];
4.91e5.13 (m, 2H, CH2]CHe); 5.79e5.93 (m, 1H, CH2]CHe);
6.98e8.16 (m, 12H, AreH).
3. Results and discussion
3.1. Preparation and characterization
The chemical structures of ABPHA, UBPHA and the liquid
crystalline resins are characterized by FTIR and 1H NMR spectra.
The liquid-crystalline monomers ABPHA and UBPHA are prepared
by etherification of perfluorooctanoyl chloride and hydroxyl
compound. In the 1H NMR spectra attribute analysis of ABPHA and
UBPHA, the chemical shift values nearby 1.2e2.9, 4.8e5.6, 5.8e6.2
and 7.0e8.2 ppm correspond to the characteristic protons in the
monomers such as methylene protons, olefinic protons, and
aromatic protons, respectively. IR spectra of ABPHA and UBPHA
display characteristic weak peaks near 3060 and 1640 cmꢂ1
attributable to CeH and C]C stretching on terminal olefinic
groups, and strong peaks near 1760e1724, 1608e1495,
1145e1149 cmꢂ1 corresponding to C]O, aromatic C]C and CeF
stretching bands respectively. The structure characterization and
elemental analysis of the monomers are in good agreement with
the prediction.
2.3. Synthesis of the liquid crystalline resins
The side-chain liquid crystalline resins are prepared from LC
monomers ABPHA and UBPHA, epoxy compound AMO and
commercially available PMHS with an averaged degree of poly-
merization of 35. Fig. 2 shows the synthesis of the resins and
elastomers, and the polymerization experiments are summarized
in Table 1. The synthesis of polymer PI-2 is given as an example.
Liquid-crystalline monomer ABPHA (2.31 g, 2.31 mmol) and the
epoxy compound AMO (0.14 g, 1.19 mmol) is dissolved in 30 mL of
dry, fresh distilled toluene. To the stirred solution, PMHS (0.23 g,
0.10 mmol) and 2 mL of a 0.5% hexachloroplatinic (THF solution) are
added and heated under nitrogen and anhydrous conditions at
65e68 ꢁC for 30 h. Then 20 mL of the solvent is distilled out, and the
Table 1
Polymerization, specific rotation analyses, WAXD data, and order parameter of the samples.
sample
monomer composition in feeda
ab
Epoxy valuec
(mmol/g)
WAXD Data
(deg) [intensity (a.u.)]/D
-spacing (Å)d
order
parameter S
ABPHA (mmol)
UBPHA (mmol)
AMO (mmol)
(ꢁ)
2
q
PIL1
PIL2
PIIL1
PII-2
EIL1
EIL2
EIIL1
EII-2
2.91
2.31
0
0
0
2.91
2.31
0.59
1.19
0.59
1.19
þ 38.8
þ 35.2
þ 37.6
þ 34.7
0.197
0.485
0.175
0.434
2.70s[6200]/32.7, 4.98s[1800]/17.7, 16.42b[4100]/5.4
2.74s[5900]/32.2, 5.12s[1800]/17.3, 16.84b[3600]/5.3
2.49s[6500]/35.5, 4.73s[1250]/18.7, 16.49b[1950]/5.4
2.84s[9100]/31.1, 5.22s[2200]/16.9, 16.94b[4200]/5.2
2.61s[13,100]/33.8, 4.98s[1800]/17.7, 16.70b[3000]/5.3
2.74s[27,500]/32.2, 5.07s[2200]/17.4, 16.41b[4100]/5.4
2.63s[21,000]/33.6, 5.21s[1600]/17.0, 17.72b[4100]/5.0
2.70s[31,000]/32.7, 5.11s[2900]/17.3, 16.89b[3100]/5.2
0
0.84
0.76
0.87
0.78
a
based on 0.1 mmol of the starting poly(methylhydrogeno)siloxane (PMHS) for each sample.
specific rotation of resins, 0.1 g in 10 mL CHCl3.
the epoxy value is measured via hydrogen bromide-acetic acid titrimetric analysis.
WAXD peak shape: s, sharp; b, broad; intensity, the maximum peak height. All the samples are measured at 80 ꢁC.
b
c
d

F.-B. Meng et al. / Polymer 52 (2011) 5075e5084
5079
3.2. Liquid crystalline monomers
The olefin compound ABPHA and UBPHA containing chiral and
terminal perfluorocarbon-chain units display enantiotropic meso-
phases including Sꢀc and N* phases. The transition temperatures and
corresponding enthalpy changes (DH) are displayed in Fig. 4.
The DSC curves of LC monomer ABPHA show a crystalline
melting endotherm at 64.4 ꢁC (
D
H ¼ 14.48 J gꢂ1), a SꢀceN* transition
at 126.4 ꢁC (0.09 J gꢂ1) and mesogenic-isotropic phase transition at
209.4 ꢁC (16.59 J gꢂ1) on heating, as well as a isotropicemesogenic
transition at 198.5 ꢁC (ꢂ8.49 J gꢂ1), a N*eSꢀc transition at 139.5 ꢁC
(ꢂ0.73 J gꢂ1) and crystallization at 55.5 ꢁC (ꢂ2.37 J gꢂ1) on cooling.
Comparing with the enthalpy changes of melting and SꢀceN* tran-
sition, enthalpy change of the mesogenic-isotropic phase transition
is the greatest, suggesting influence of terminal perfluorocarbon
chains unit. The strong self-segregation of fluorinated segments
and the rigid-rod-like nature of fluorocarbon chains tend to adopt
a stabilized conformation in the mesophase state. Thus the phase
transition from mesophase to isotropic phase in the hydrocarbon-
perfluorocarbon systems needs more energy. Observed by POM,
ABPHA exhibited Sꢀc and N* textures upon heating and cooling
circles, as illustrated in Fig. 5. Oily streak texture is one of the most
commonly observed textures of the chiral nematic phase prepared
between two untreated glass substrates. These oily streaks can be
seen as a network of defect lines dispersed in uniformly helical
regions. Influenced by self-segregation of fluorinated segments,
these actual oily streaks appeared in large bundles as shown in
Fig. 5a. When the isotropic state is cooled, cholesteric droplets of N*
phase separated from the isotropic melt, and different colors
correspond to different twist states as displayed in Fig. 5b. On
further cooling, a fan-shaped texture of Sꢀc phase with an equidis-
tant line pattern is displayed in Fig. 5c, which is due to the helical
superstructure.
Compared with ABPHA, the monomer UBPHA possesses longer
hydrocarbon chain on the other terminal side of the molecules. The
DSC curves and the enthalpy changes of UBPHA are similar to those
of ABPHA, as illustrated in Fig. 4. These results suggest that the
length of the terminal hydrocarbon chain can’t influence greatly to
the liquid crystalline systems with another terminal per-
fluorocarbon chains. However, UBPHA shows a little different from
ABPHA when it is observed by POM. Fig. 5d displays cholesteric
droplets from the isotropic melt. As the droplets grow larger, they
are superimposed by the equidistant line pattern due to the Scꢀ
helix, showing a focal conic texture as seen in Fig. 5e. This suggests
Fig. 3. FTIR spectra of representative polymers PI-1, PII-1, EI-1 and EII-1.
The side-chain liquid crystalline resins PI-1, PI-2, PII-1 and PII-2
are prepared by a one-step hydrosilylation reaction between SieH
groups of PMHS and terminal olefinic CH2]CHe of LC monomers
ABPHA and UBPHA, epoxy compound AMO in anhydrous toluene,
using hexachloroplatinic acid as catalyst. The specific rotations of
the liquid crystalline resins PI-1, PI-2, PII-1 and PII-2 are given in
Table 1, indicating that the polysiloxanes show lower specific
rotation absolute values in comparison with monomers. It suggests
that cleavage of the terminal olefinic bond and the binding of
monomers to the polysiloxane main chains affect the chirality of
the polysiloxanes.
The orientated liquid crystalline elastomers EI-1, EI-2, EII-1 and
EII-2 are prepared by curing of the corresponding liquid crystalline
resins PI-1, PI-2, PII-1 and PII-2 with a curing agent under
magnetic fields. The crosslinking reaction is monitored by
measuring the FTIR spectra of the film, as shown in Fig. 3. A
reduction of the epoxide group concentration is verified for all
samples by observing the infrared absorption peak at 920 cmꢂ1
which is due to the asymmetric stretch of the oxirane ring. Absence
of characteristic epoxy peak peaks for EI-1, EI-2, EII-1 and EII-2
suggests that the crosslinking reaction is thoroughly finished.
,
Fig. 4. DSC thermograms for (a) 40-(4-(allyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate (ABPHA); and (b) 40-(4-(undec-10-
enoyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate (UBPHA).

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F.-B. Meng et al. / Polymer 52 (2011) 5075e5084
Fig. 5. Optical texture of the monomers (200 ꢄ ): (a) oily-streak texture (N*) of 40-(4-(allyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl
adipate (ABPHA) on heating to 194 ꢁC; (b) cholesteric droplets of ABPHA on cooling to 193 ꢁC; (c) striped fan-shape texture (Scꢀ) for ABPHA on cooling to 118 ꢁC; (d) cholesteric
droplets of 40-(4-(undec-10-enoyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate (UBPHA) on cooling to 181 ꢁC; (e) focal conic
texture of UBPHA on cooling to 141 ꢁC; (f) striped fan-shape texture (Sꢀc) for UBPHA on cooling to 128 ꢁC.
that the helix axes of the cholesteric and the Sꢀc phases are
perpendicular to each other. On further cooling, a striped fan-shape
texture of Sꢀc phase is also displayed for UBPHA in Fig. 5f.
and PII-2, the isotropization temperatures and mesophasic ranges
are reduced as the perfluorocarbon chains decreased. The glass
transition temperature (Tg) of all epoxy resins are showed near
50 ꢁC, but the mesophase-isotropic phase transition temperature
(Ti) of the PI and PII series of resins decreased slightly with increase
of epoxy compound AMO component in the polymer systems,
suggesting reduced mesophasic ranges for PI-2 and PII-2 in
comparison with PI-1 and PII-1. The enthalpy changes of SꢀceN*
transition for PI-1, PI-2, PII-1 and PII-2 are higher than those of
corresponding monomers ABPHA and UBPHA. This can be
explained by the bound state of mesogens in the polymer systems.
In contrast to the monomers, the mesogenic units bearing terminal
fluorocarbon chains are surrounded by the polymer matrix in Scꢀ
mesophase, resulting in increase of enthalpy changes.
3.3. Liquid crystalline resins
Thermal analysis of resins has been employed by TGA and DSC. It
suggests high thermal stability in consideration of greater than
300 ꢁC of onset weight loss temperatures (Td) for PI-1, PI-2, PII-1
and PII-2. DSC thermograms of the resins on heating cycles are
displayed in Fig. 6a. All the epoxy resins PI and PII series display
glass transition, SꢀceN* mesophase transition and N*-isotropic
phase transition on heating. With regard to the variation of mes-
ophasic transition temperatures of epoxy resins PI-1, PI-2, PII-1

F.-B. Meng et al. / Polymer 52 (2011) 5075e5084
5081
Fig. 6. DSC thermograms of (a) resins upon second heating and (b) elastomers upon first heating, and phase diagrams of (c) EI elastomers (including originated monomer ABPHA
and the resins) and (d) EII elastomers (including originated monomer UBPHA and the resins).
The optical textures of the epoxy resins are studied by use of
POM with hot stage, and some representative optical textures are
shown in Fig. 7. Fig. 7a shows a oily-streak texture of chiral nematic
(N*) phase of PI-1 at 165 ꢁC in heating process, and the oily-streak
texture is due to horizontal (homeotropic) alignment of mesogenic
core in N* phase. Fig. 7b displays a line texture of chiral smectic C
(Sꢀc) phase of PI-2 at 95 ꢁC in heating process. The helix lines are
parallel to the smectic layer planes and the helix axis is perpen-
dicular to the lines, i.e. the smectic layer plane. For PII-1, it shows
a striped fan-shape texture (Sꢀc) on heating to 105 ꢁC Fig. 7c, which
is superimposed by an equidistant line pattern due to the helical
superstructure when passing into Sꢀc phase. Fig. 7d displays
a parabolic texture (Sꢀc) of PII-2 on cooling to 92 ꢁC, and a little lines
appeared in the textures suggest the helix structure of the polymer.
In these epoxy resins, the Sꢀc phase can be detected from DSC and
optical microscopic methods, but it is more definitely detected from
an estimation of layer spacing by X-ray measurements. X-ray
studies are carried out to obtain some detailed information on LC
phase structure, and some WAXD data of all the samples are
summarized in Table 1. A broad reflection at wide angles (associ-
ated with the lateral packings) and sharp reflection at small angles
(associated with the smectic layers) are separately shown by all the
profile curves of resins PI-1, PI-2, PII-1 and PII-2 when the samples
are heated above glass transition temperature. Fig. 8a shows a one-
dimensional WAXD powder pattern of PII-1, providing structural
information on two length scales. One is on the nanometer scale in
these polysiloxanes to give smectic layers can be calculated, and for
PII-1 it is approximately 46.4 Å. The X-ray diffraction data show the
layer periodicity is nearly 35.5 Å and the ratio of the observed layer
spacing (d) to the calculated lengths (L) is 0.765, showing that the
side chains are located on one side of the main chain. Because the
measured d is relatively smaller than the calculated L, the LC side
chains should be tilted to the layer to form a Sꢀc phase. The tilt angle
is estimated nearly 40ꢁ, which can be calculated from a relative
ratio of d and L. This result indicates synergistic effect between
chiarl isosorbide groups and helical conformation of the rigid-rod-
like nature of fluorocarbon chains. On further heating, the sharp
reflection of d-spacing 35.5 Å became diffuse and weakly, verifying
the SꢀceN* transition of the samples.
3.4. Oriented liquid crystalline elastomers
TGA thermograms of the oriented elastomers show high
thermal stability in consideration of greater than 300 ꢁC of onset
weight loss temperatures (Td) for EI-1, EI-2, EII-1 and EII-2. Fig. 6b
shows DSC thermograms of the oriented elastomers on heating
cycles. All the elastomers EI-1, EI-2, EII-1 and EII-2 display glass
transition and Sꢀc phase, but isotropic transition is not shown
distinctly for EI-2 and EII-2 on heating. In comparison with cor-
responding epoxy resins, ScꢀeN* transition disappeared for the
elastomers because of orientation and crosslinking process. The Scꢀ
mesophasic ranges for the oriented elastomers became greater
than those for corresponding epoxy resins, as shown in Fig. 6c and
d. The optical textures of the elastomers didn’t change almost when
the samples are heated from room temperature to decomposition
temperature, as shown in Fig. 7e and f. For all the oriented elasto-
mers, the formation of a periodic stripe pattern by application of
the low 2
q
angle region at 2.49ꢁ (d-spacing ¼ 3.55 nm), and the
other is on the subnanometer scale at 16.49ꢁ (d-spacing ¼ 0.54 nm).
They can be assigned as the average lateral distance (5.4 Å) between
molecules and the average length (35.5 Å) of the repeat units with
short-range order. From molecular models the side-chain length of

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F.-B. Meng et al. / Polymer 52 (2011) 5075e5084
Fig. 7. Optical texture of the liquid crystalline resins (200 ꢄ ): (a) oily-streak texture (N*) of PI-1 at 165 ꢁC in heating process, (b) line texture of chiral smectic C (Scꢀ) phase of PI-2 at
95 ꢁC in heating process, (c) striped fan-shape texture (Scꢀ) of PII-1 on heating to 105 ꢁC, (d) parabolic texture (Scꢀ) of PII-2 on cooling to 92 ꢁC, (e) magnetic field induced striped
domain texture (Sꢀc) of EI-1, (f) magnetic field induced striped domain texture (Sꢀc) of EII-2.
a magnetic field can be observed by POM, and the periodic stripe
texture can be frozen via crosslinking reaction. These results indi-
cate that the perfluorocarbon chains stabilize the Sꢀc mesophase
owing to the strong self-segregation of fluorinated segments and
the rigid-rod-like nature of fluorocarbon chains in the crosslinking
polymer systems. These can also be verified by X-ray method, and
some WAXD data of all the oriented elastomers are listed in Table 1.
Fig. 8b illustrates a WAXD curve of EII-1. A broad reflection at wide
distances, the larger intensity of these peaks suggests the stronger
regularity between the layer spacing. Because the measured layer
spacing d is relatively smaller than the calculated lengths L, the LC
side chains should be tilted to the layer to form a Sꢀc phase for all the
elastomers, indicating nearly 40ꢁ of a tilt angle calculated from
a relative ratio of d and L.
For the oriented elastomers EI-1, EI-2, EII-1 and EII-2, the
average degree of orientation of the LC domains can be represented
by the orientation parameter, S, which is defined according to eq:
angles (2
q
z 17ꢁ) and a strong sharp reflection at small angles
(2
q
z 2.7ꢁ) are shown in the profile curves of EI-1, EI-2, EII-1 and
ꢀ
ꢁ.
S ¼ 3 < cos2
4
> ꢂ 1
2
(1)
EII-2, and are similar to those of corresponding epoxy resins PI-1,
PI-2, PII-1 and PII-2, as displayed in Table 1. But the maximum peak
heights at small angles (near 2.7ꢁ) of the elastomers are much
greater than those of corresponding epoxy resins (see Fig. 8c).
Because the reflections near 2.7ꢁ corresponds to the interlayer
where
f
is the angle between the individual domain directors and
the orientation direction, and < > denotes an average of cos2
all the LC domains. The order parameters of the LCEs are
4 over

F.-B. Meng et al. / Polymer 52 (2011) 5075e5084
5083
Fig. 8. WAXD curves of (a) epoxy resin PII-1 and (b) crosllinked oriented elastomers EII-1, and (c) the maximum peak heights of the resins and elastomers at small angles.
determined by X-ray measurements, which are listed in Table 1.
Fig. 9a shows a two-dimensional SAXS pattern of the sample EII-1
at room temperature. The macroscopic layer thickness can be
determined by use of SAXS measurements. The two-dimensional
SAXS patterns of the oriented LCEs display quadrants, providing
structural information on two aspects. On the one hand, the scat-
tering patterns confirm the smectic mesophase. As a rule, nematic
liquid crystalline polymers show no scattering information in SAXS
pattern, but smectic liquid crystalline polymers display scattering
patterns. In addition, the greater scattering angles suggest that
layer thickness is minor, indicating the tilted structure for the Scꢀ
phase. On the other hand, the quadrant patterns should be origi-
nated from orientation of the elastomers. For the LCEs, the rigid-
rod-like fluorocarbon chains tend to form layers due to poor
miscible between fluorocarbons and hydrocarbons. Thus both the
terminal fluorocarbon chains and the mesogenic groups constitute
rigid units in the LCEs. As a result, the tilted rigid units cause tilted
scattering patterns. The schematic of the macroscopic orientation is
shown in Fig. 9b.
The four-spot small-angle pattern in Fig. 9 suggests that the
oriented elastomers have a conical distribution of smectic layer
normals around the director similar to some reported chiral and
achiral smectic C main-chain LCEs [32,33]. The conical distribution
of the layer normals is reflected in the splitting into 4 peaks with
layer normals for chiral smectic C LCEs [32]. In these chiral smectic
C LCEs, the smectic layer normal is not oriented parallel to the
director but tilted by a tilt angle. As the samples were orientated
and crosslinked under a magnetic field, a uniaxial deformation
couples to the director orientation, resulting in a uniform director
alignment parallel to the deformation axis and a conical distribu-
tion of the smectic layer normals around the director.
Fig. 9. Two-dimensional SAXS pattern of the sample EII-1 at room temperature (a) and
the schematic of the macroscopic orientation (b).

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F.-B. Meng et al. / Polymer 52 (2011) 5075e5084
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Several novel side-chain liquid crystalline polysiloxane epoxy
resins with various molar ratio of epoxy groups and mesogenic
components are synthesized using liquid crystals bearing both
chiral isosorbide units and terminal perfluorocarbon chains, and
the epoxy resins are cured at mesophase state under a magnetic
field to obtain crosslinked oriented elastomers. The mesomorphic
properties in the side-chain comb-shaped liquid crystalline resins
and their corresponding oriented elastomers are influenced by the
terminal perfluorocarbon chains components effectively. Several
kinds of chiral nematic and tilted smectic phases are obtained in
the side-chain epoxy resins, and tilted smectic phases are frozen in
their corresponding oriented elastomers. The LC phases are verified
by X-ray measurements, and the orientational order parameters of
the oriented LCEs are calculated.
Acknowledgments
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The authors are supported by the Fundamental Research Funds
for the Central Universities (N090405003 and N090105001),
Program for New Century Excellent Talents in University and
Project 50873018 supported by NSFC.
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