Structure et proprietes thermodynamiques de polyamides rigides portant ces groupes lateraux flexibles

Combined main chain/side chain polymers. A new class of liquid crystalline polymers with unusual structural, thermodynamic and dynamic properties

Abstract Combined main chain/side chain polymers carry rigid rod-like mesogenic units both in the side chain and along the chain backbone. The properties of such combined systems are expected to be controlled by the competition of the interactions between the mesogenic units in the side and main chains as well as the tendency of the chain backbones to maximize their entropy. The thermodynamic, structural and dynamic properties of such combined main chain/side chain liquid-crystalline polymers were investigated for various chain architectures. The combined systems were found to display properties corresponding in many cases to a favourable superposition of properties characteristic of both m…

Sanidics: A new class of mesophases, displayed by highly substituted rigid-rod polyesters and polyamides

Abstract The structure of rigid-chain polyesters and polyamides which possess flexible side chains consisting of methylene or 1,4,7-trioxaoctyl oxide units have been investigated by means of X-ray scattering. The X-ray studies were performed on fibres and monodomains. Additional information was gained from calorimetric, dilatometric and microscopic studies. The investigations revealed that these polymers display mesophases and that the structures of the mesophases differ from those observed for discotic and calamitic phases. They are characterized by the fact that in the ordered and disordered phases board-like molecules are stacked parallel on top of each other and that these stacks of mol…

Structural variations of liquid crystalline polymers with phasmidic-type mesogens

Abstract The fixation of phasmidic-type mesogens through spacer groups to polysiloxane backbones provided a method of obtaining liquid crystalline polymers with phasmidic mesogens as side groups. The polymer 6b showed a bilayer structure in the mesophase range. The tendency to form liquid-crystalline phase depends on the number and the length of alkoxy substituents.

Structure formation in doped discotic polymers and low molar mass model systems

Abstract Doping of low molar mass materials or polymers, possessing disc-like units, with electron acceptors leads to the stabilization of columnar discotic phases or even to the induction of such phases in compounds which either display a nematic discotic phase or only an amorphous phase in the absence of the electron acceptor. The induced columnar phase corresponds frequently to a hexagonally ordered one. We have observed, however, in addition the induction of new columnar phases such as the rectangularly ordered (Dro) and the columnar nematic phase (Nc). The enhancement of the tendency towards the formation of columnar phases is a consequence of electron acceptor—electron donor complex f…

Modes of Structure Formation in Doped Discotic Polymers and Low Molar Mass Model Systems

By doping low molar mass or polymeric liquid crystals containing flat disc-like units with electron acceptors one achieves a stabilization of columnar phases, the induction of a columnar phases in otherwise discotic nematic or even in amorphous systems. Theoretical models based on the assumption of strong electron donator-acceptor (EDA) complex formation are able to account for the structure formation on a molecular level and the thermodynamic properties of the mixtures and the model of diffusion limited aggregation (DLA) for the structure formation on a supermolecular structure.

Liquid crystal polymers from swallow-tailed mesogens

Abstract Swallow-tailed compounds containing an acetylenic unit have been synthesized. Only those compounds with a three ring structure exhibited liquid-crystalline phases. The platinum catalysed addition of these monomers to compounds containing Si-H groups was used to synthesize polymeric materials. Only those polymers with the tetramethyldisiloxane unit showed mesophases. The synthesis, characterization, and phase behaviour are described.

The synthesis of a new type of combined polymers containing both disc- and rod-like mesogens is reported. The polyesters, having a triphenylene derivative as a discotic mesogen in the side group and azobenzene or biphenyl derivatives as rod-like mesogens in the main chain were characterized by polarizing microscopy, differential scanning calorimetry, and X-ray scattering studies. The homopolymer 7 is highly crystalline, while the copolymer 8 is amorphous, both, however, do not form liquid-crystalline phases.

It is shown that the acceptor polyesters [(CH 2 ) x OCOC(=R) COO(CH 2 ) x ] n (R=9-[2,4,7-trinitrofluorenylidene]) x=3, 6, 8) influence the chain behaviour of the discotic hexapentyloxytriphenylene without changing the phase type (D ho ). The clearing temperature of the complexes has a maximum value when x=G. Both intra- and intercolumnar distance are smaller than in the pure discotic compound and independant of the spacer