A series of five nonaligned comblike polyUV-maleimides) have been studied by frequency (200 Hz-100 kHz) and temperature (from 123 to 423 K) dependent dielectric measurements. Three of them are smectic side-chain liquid crystal polymers (SCLCPs) and the other two are amorphous materials. These samples also allow us to study the possible influence of the smectic field. By a change of the chemical nature of the structure of mesogens, a self-consistent assignment of the different relaxational processes has been possible. Six main relaxation processes have been found and assigned: (i) Two relaxations, ft and ft, are produced at temperatures below T" due to rotational motions and torsional oscillations of the mesogens, respectively. They can be attributed to the reorientation of the perpendicular component to the major axis of the permanent dipolar moment located at the center of the mesogenic groups. In polymer V, these two relaxations are reduced to one ft. Here the second type of motion is no longer possible because of the absence of an oblong moiety with interphenylenic ester groups and because of the presence of a tetramethylbutane group as a substituent in the phenylene group, (ii) Two relaxations, 72 and 71, are located at the lower temperature and attributed to localized motions of n-alkoxy pendant groups linked to mesogens in para position and to the spacer with its interconnecting functional groups which link it to the main chain and the mesogen, respectively, (iii) Two relaxations, a and 5, respectively, are produced at temperatures above T, which are assigned respectively to dipole reorientation of the main chain motions and to displacements of the mesogens which are able to reorientate the dipolar moment component parallel to the long axis of the mesogens. The absence of a ¿-process in polymers I and II may be due to the absence of orientational rotation of the anisodiametrical mesogenic group; as a result, the orientation of the parallel component µ; of the dipole moment of the mesogen does not take place. It is possible that topological constraints imposed by a strong smectic field due to the existence of a long range order in the smectic layer of these two highly ordered polymers may be responsible for this behavior by hindering such a motion. The structure and phase transitions of the five polymers were studied by optical polarizing microscopy, small and wide-angle X-ray diffraction on aligned and unaligned samples, and differential scanning calorimetry.

A homologous series of side‐chain liquid crystalline (SCLC) poly{[N‐[10‐((4‐(((4′‐n‐hexyloxy)benzoyl)oxy)phenoxy)carbonyl)‐n‐decyl]maleimide]‐co‐[N‐(n‐octadecyl)maleimide]} [(ME6)‐co‐(MI‐18)] random copolymers with various MI‐18 contents have been synthesized and their properties studied. The high content in threo‐disyndiotactic sequences of the maleimide main chain seems responsible for the stability of the highly ordered smectic mesophase. The relationship between structure and composition on thermotropic mesophase was investigated by polarizing optical microscopy, differential scanning calorimetry, and X‐ray diffraction. For copolymers with mesogenic unit contents less than ∼0.655 molar fraction the transition from (SA) texture to isotropic (I) is maintained, as shown by the TCl, ΔHCl and ΔSCl amounts and intermolecular spacing 4.42–4.53 Å and intralayer correlation lengths of 44.2–45.2 Å. The layer thickness does not appreciably depend on copolymer composition. However, copolymers with non‐mesogenic comonomer MI‐18 molar contents larger than >0.655 molar fraction X(M), are no longer liquid crystalline materials, despite its packing is preserved without any detectable appearance of birefringence. Thermodynamic boundaries of the liquid crystalline state have been established through a phase diagram. The properties of this n‐hexyloxy pendant group‐based series are compared to those of the analogous materials containing methoxy pendant groups (ME1), and differences are accounted for in terms of the local side‐chain packing within the mesophase. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011