Nematic Polymers and Related Structures

Abstract

RBsumB. -Avec des polymtres A chaine rigide ou structure helicoidale, des proprietts anisotropes apparaissent. Si les polymeres sont obtenus par la polymtrisation d'un monomtre chiral, l'examen de leurs solutions montre une structure cholesterique. Dans le cas d'une miscibilitt illimitte du polymere, en examinant les solutions, on peut inferer les propriktes anisotropes du polymere en masse.En intkgrant dans la chaine de polymeres des segments anisotropes et rigides, il est possible de synthktiser des polymkres ntmatiques en masse. Dans la littkrature, les proprittks mksomorphes de tels polymkres ne sont pas encore dkcrites en dktail.L'objet du present travail est l'examen du poly-(phknyl-p-acryloyloxybenzoate) et aussi de quatre poly-(p-alcoxy-phenyl-p-acryloylbenzoates). Nous avons utilise les methodes suivantes : d6termination de la texture A I'aide d'un microscope polarisant, de la densite, ainsi que la diffraction de rayons X ( A petit et grand angle) et de lumikre laser, mesures de calorimktrie differentielle et de microscopie 6lectronique. Les rtsultats ont kte compares aux resultats de mesures par la chromatographie sur gels des dimensions molkculaires des polymeres plastifies et aux spectres RMN et de diffraction de rayons X en champs magnktiques.En conclusion, nous avons donne un modele du polymere nkmatique. Ce modele permet de montrer que le polymere nematique ne peut pas dtre isomorphe par rapport a la phase nematique de son monomere. La polymkrisation effectuee dans la phase monomere nkmatique orientke conduit A un polymere orient6 smectique dont la chaine est perpendiculaire au champ magnktique.

Polymerization in liquid crystals. XIII. Copolymerization of mesogenic monomers

“…-CH2CH20-) above their smectic structure (15). Only polymers with conventional smectic, nematic, or cholesteric (N*) states may be isomorphous with small molecular compounds, which is in agreement with the experiments (9,12). Polymers with aperiodic helical structures are precipitated as new phases in the course of the polymerization.…”

“…If polymerization is carried out with such monomer which has high molecular size and, correspondingly, high Eu value, the structure of the resulting polymer will be much more fixed than that obtained from small size monomer molecules. The macromolecules produced will not simply exhibit random coil configuration (9). The structure of the monomer liquid surrounding the propagating radical in such cases, will be determined by the last monomer units in the chain.…”

“…Different smectic states corresponding to folded chains as well as nematic and cholesteric structures of polymers prepared from mesogenic compounds connected with flexible chain segments were identified by miscibility investigations (24,37). The results of miscibility investigations were negative for polymers containing mesogenic groups in the side chains connected directly to the main chain (9)(10)(11)16). With mesogenic side chains connected to the main chain by flexible chains, called a "spacer" (6,14^1-23,44,46,47pi), smectic state polymers were observed.…”

Supermolecular organization in liquid crystalline polymers

“…Thus, a characteristic "mosaic" morphology was revealed in thin polymer films with the dimensions of microregions on the microphotographs were in agreement with value determined from SAXS data [II,961. In the study of block samples of smectic polymers by a scanning electron microscope [55,88,92] a well pronounced lamellar morphology with supermolecular formations measuring several microns was found. Thus, a characteristic "mosaic" morphology was revealed in thin polymer films with the dimensions of microregions on the microphotographs were in agreement with value determined from SAXS data [II,961. In the study of block samples of smectic polymers by a scanning electron microscope [55,88,92] a well pronounced lamellar morphology with supermolecular formations measuring several microns was found.…”