Dynamic mechanical behaviour of random copolymers of a LC-methacrylate and octyl methacrylate |
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Authors: | Helena Valentová Miroslav Ka?par Věra Hamplová Karel Bouchal Michal Ilavský Antonín Sikora Daniel Froelich René Muller |
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Affiliation: | (1) Faculty of Mathematics and Physics, Charles University, 180 00 Prague 8, Czech Republic, CS;(2) Institute of Physics, Academy of Sciences of the Czech Republic, 180 40 Prague 8, Czech Republic, CS;(3) Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic, CS;(4) Ecole d'Application des Hauts Polymères, Université Louis Pasteur, F-67000 Strasbourg, France, FR |
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Abstract: | The dynamic mechanical behaviour of random copolymers of LC monomer-1-(hexyloxycarbonyl)ethyl 4-4-(methacryloyloxy)benzoyloxy]benzoate
(HB) and octyl methacrylate (OMA) was studied in the main transition and flow regions. Even though the aliphatic end groups
of the side chain of HB and OMA are roughly the same, the T
g temperature of poly(HB) is ∼ 80 K higher than that of poly(OMA); this fact is due to the presence of the stiff phenyl benzoate
mesogenic group in the side chain of HB. With increasing content of OMA in the copolymer the superimposed curves of the storage
G′
p and loss G′′
p moduli at a constant temperature shift towards shorter frequencies. It has been shown that this shift is mainly due to an
increase of the free volume in the copolymers with increasing content of OMA. While HB monomer shows liquid crystalline (LC)
properties, its polymer (poly(HB)) and random copolymers with OMA show only isotropic thermal behaviour because no flexible
spacer is present in the side chain of HB which would decouple the main chain and mesogenic group motions. This means that
neither the homopolymer of HB, nor its copolymers with a flexible comonomer retain the LC properties of the starting LC monomer,
HB.
Received: 26 September 1996/Revised: 7 November 1996/Accepted: 7 November 1996 |
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