Alternating side-chain liquid-crystalline copolymers with polar moieties in the backbone = Alternerende zijketen vloeibaar-kristallijne copolymeren met polaire groepen in de hoofdketen

Side-chain liquid-crystalline polymers (SCLCPs) obtained via the alternating copolymeri-zation of maleic anhydride (MA) and mesogenic 1-alkenes are an interesting class of polymers that may show good adhesion towards metal surfaces and form ordered layered structures. If these polymers contain methoxybiphenyl mesogens, they have high glass transition temperatures and exhibit highly ordered mesophases. The mesogen density of these polymers has been increased by coupling mesogen-containing alcohols onto SCLCPs with MA moieties. Depending on the structure of the mesogens of the SCLCP and the alcohols, mesophases were obtained with different degrees of interdigitation of side chains and different degrees of order. Copolymerization of MA with swallow-tailed 1-alkenes having two mesogens yielded polymers with even a higher degree of order. These polymers exhibit isotropization temperatures that were lower and glass transitions that were higher than those of polymers with half the mesogen density. The amount of MA in SCLCPs was altered by copolymerization of MA with mesogenic methacrylates. For methoxybiphenyl mesogens, the isotropization temperature increases with MA content. The temperature window of the mesophase increases with increasing spacer length.A completely new class of SCLCPs was obtained by the copolymerization of carbon monoxide and mesogenic 1-alkenes. For methoxybiphenyl mesogens, these copolymers exhibit highly ordered smectic E mesophases and high glass transition temperatures. The transition temperatures were tuned by altering the spacer length or by dilution of the mesogen content of the copolymer.Rheology showed that the loss and storage moduli and the complex viscosity strongly decrease at phase transitions. In addition, a decrease in these properties was observed in the smectic A mesophase which can probably be ascribed to rotational diffusion of the mesogens.The Langmuir-Blodgett technique showed that SCLCPs with cyano groups form multilayers on the water subphase. Transfer of SCLCPs with methoxybiphenyl mesogens results in multilayer films with a double layer periodicity, which is different from that observed in the bulk. Annealing of these films results in a more uniform d spacing.Dr.ir. R.P. NieuwhofTNO Institute of Industrial TechnologyMaterials Technology DivisionDe Wielen 6 Tel.: +31 (0)40 265 0341P.O. Box 6235 Fax: +31 (0)40 265 03025600 HE Eindhoven E-mail: [email protected] Netherlands WWW-adres: http://www.tno.nl