Macromolecules, Vol. 36, No. 24, 2003
Liquid Crystalline Elastomers 9061
Sch em e 1. Syn th etic Rou te of Ch olester ic Mon om er
cholesteryl); 6.04 (m, 1H, CH2dCH-); 7.03-8.06 (m, 8H, Ar-
H).
4-Allyloxyben zoyl-4′-(6-a cr yloyloxyh exyloxy)ben zoyl-
p-ben zen ed iolbisa te (M2). First, 2.92 g (0.01 mol) of 4-(6-
acryloyloxyhexyloxy)benzoic acid was reacted at 40 °C with
15 mL of thionyl chloride containing a few drops of DMF and
a trace of p-hydroxyanisole for 4 h, and then the excess thionyl
chloride was removed under reduced pressure to give the acid
chloride.
The acid chloride obtained was dissolved in 5 mL of
chloroform and added dropwise to a cold solution of 2.7 g (0.01
mol) of 4-hydroxyphenyl-4′-allyloxybenzoate in 15 mL of
chloroform and 1.4 mL of triethylamine. After reacting for 14
h at room temperature, the crude product was precipitated
by adding ethanol to the filtrate and recrystallized from
ethanol. Yield 47%, mp 75 °C. IR(KBr), µ (cm-1): 3076 (dC-
H); 2938, 2863 (-CH3, -CH2-); 1736 (CdO); 1643 (CdC);
1
1610, 1513 (Ar-). H NMR (CDCl3), δ (ppm): 1.51-1.87 [m,
8H, -(CH2)4-]; 3.75 (t, 2H, -CH2CH2O-); 4.18 (t, 2H,
-COOCH2-); 4.62 (t, 2H, dCHCH2O-); 5.31-5.48 (m, 4H,
CH2dCHCH2- and CH2dCHCOO-); 6.01 (m, 1H, CH2d
CHCH2-); 6.20 (m, 1H, CH2dCHCOO-); 6.96-8.17 (m, 12H,
Ar-H).
Syn th esis of th e Ela stom er s. For the synthesis of the
elastomers P 2-P 8, the same method was adopted. The syn-
thesis of P 3 is given as an example. Monomers M1, M2, and
P MHS were dissolved in dry, freshly distilled toluene. The
mixture was heated to 65 °C under nitrogen and anhydrous
conditions, and then a proper amount of THF solution of
hexchloroplatinate hydrate catalyst was injected with a sy-
ringe. After holding the reaction mixture at 65 °C for 48 h,
the networks were obtained with methanol, and then dried
under vacuum. IR (KBr), µ (cm-1): 3000-2800 (-CH3, -CH2-
); 1735, 1711 (CdO); 1606, 1512 (Ar-); 1200-1000 (Si-O-
Si).
Sch em e 2. Syn th etic Rou te of Cr oss-Lin k in g
Mon om er
Resu lts a n d Discu ssion
Syn th eses. The synthetic routes for the target mono-
mers are shown in Schemes 1 and 2. The structural
characterization of the monomers and elastomers ob-
tained were in agreement well with the prediction.
4-Allyloxybiphenyl-4′-carboxylic acid (1), 4-hydroxyphe-
nyl-4′-allyloxybenzoate (3), and 4-(6-acryloyloxyhexy-
loxy)benzoic acid (5) were synthesized according to a
route described by Hu et al.26-28 The synthetic methods
for M1 and M2 are the same. First, activation of
compounds 1 and 5 was obtained with thionyl chloride
and then reacted, respectively, with cholesterol and 3
in chloroform to prepare cholesteric monomer M1 and
cross-linking monomer M2. IR spectra of M1 and M2
showed characteristic bands at 1741-1736, 1643-1636,
and 1610-1512 cm-1 attributed to ester CdO, olefinic
CdC, and aromatic CdC stretching band. 1H NMR
spectra of M1 and M2 showed multiplets at 0.61-4.62,
4.72-6.04, and 6.96-8.17 ppm corresponding to methyl
and methylene protons, olefinic protons, and aromatic
protons, respectively.
The elastomers were prepared by a one-step hydro-
silication reaction between Si-H groups of P MHS and
olefinic CdC of M1 and M2 in toluene, using hexchlo-
roplatinate hydrate as catalyst at 65 °C. Yields and
detailed polymerization are summarized in Table 1.
Schematic representation of the elastomers obtained is
presented in Figure 1. IR spectra of the elastomers
showed the complete disappearance of the Si-H stretch-
ing band at 2166 cm-1 and the olefinic CdC stretching
band at 1643-1636 cm-1. Characteristic Si-O-Si
stretching bands appeared at 1200-1000 cm-1. In
addition, the absorption bands of ester CdO and aro-
matic still existed.
filtered Cu KR radiation with a DMAX-3A Rigaku powder
diffractometer (Rigaku, J apan).
Syn th esis of th e Mon om er s. The synthesis of the olefinic
monomers is shown in Schemes 1 and 2. 4-Allyloxybiphenyl-
4′-carboxylic acid, 4-hydroxyphenyl-4′-allyloxybenzoate, and
4-(6-acryloyloxyhexyloxy)benzoic acid were prepared according
to the literature procedures reported.30-32
Ch olester yl 4-Allyloxybip h en yl-4′-ca r boxyla te (M1).
First, 2.54 g (0.01 mol) of 4-allyloxybiphenyl-4′-carboxylic acid
was reacted at 60 °C with 15 mL of thionyl chloride containing
a few drops of N,N-dimethylfomamide (DMF) for 3 h, and then
the excess thionyl chloride was removed under reduced pres-
sure to give the corresponding acid chloride. The acid chloride
obtained was dissolved in 5 mL of dry chloroform, and added
dropwise to a solution of 3.87 g (0.01 mol) of cholesterol in 0.8
mL of pyridine and 15 mL of chloroform. The reaction mixture
was refluxed for 10 h. The crude product was precipitated by
adding ethanol to the filtrate, and was recrystallized from ethyl
acetate/ethanol (1:1). Yield 75%, mp 111 °C. IR (KBr), µ (cm-1):
3063 (dC-H), 2930, 2852 (-CH3, -CH2-), 1741 (CdO), 1636
(CdC), 1606, 1512 (Ar-), 1152 (C-O-C). 1H NMR (CDCl3), δ
(ppm): 0.66-2.07 (m, 43H, cholesteryl-H); 4.55 (t, 2H, -OCH2-
); 4.72-5.29 (m, 2H, CH2dCH-); 5.51 (m, 1H, dCH- in