S. S. Skorokhodov

The Effect of External Orienting Electric Field on Dielectric Relaxation of Segmented Polyesters in Dilute Solution

A comparative study of dipole polarization relaxation in the absence and in the presence of an external orienting electric field was performed for linear segmented polyesters with alternating rigid (oxyfumaroylbis-4-oxybenzoates) and flexible (methylene-CH2-, ethylene oxide-CH2CH2-O-, and dimethylsiloxane-Si(CH3)2-O-Si(CH3)2-) fragments in dilute solutions. Polyesters that do not display mesomorphic properties in the bulk show several regions of dielectric absorption with relaxation character. These regions are associated with the motions via the local mobility mechanisms of different polar fragments of the macromolecule. In solutions of polyesters that possess LC properties in the bulk, large-scale dipole polarization relaxation with long relaxation times and high activation energies was revealed along with local dielectric relaxation transitions. This process is associated with the cooperative motion of mesogenic fragments in their associates. In an external orienting electric field, the intensity of dielectric absorption usually increases for all types of dielectric transition; relaxation times and activation energies experience changes only for large-scale processes.

Dipole relaxation, intramolecular mobility, and molecular self-organization in solutions of alternating polymers with phenylazomethine and siloxane fragments

Dielectric relaxation in solutions of polyesters containing flexible siloxane and rigid phenylazomethine fragments of various structures is studied. For these polymers in solution, five relaxation processes that reflect the mobility of certain portions of the macrochain are observed. The kinetic rigidity of the macrochain increases with increasing length of the siloxane spacer. This trend is associated with rearrangement of the electronic structure of silicon atoms and phenyl rings and with ordering of rigid phenylazomethine fragments.

Synthesis of thermotropic liquid crystalline polycarbosiloxanes and manifestation of nonclassical conjugation in polymer backbone

Polysiloxanearylenes gain mesogenic ability by introduction of methylene joint group between Si-atom and phenylene core of rigid section as it was shown previously. The investigation of model compounds showed the existence of electronic interaction between Si-atom and β-carbon atom of the backbone known in siliconorganic chemistry as β-effect. The effect is considered as an example of nonclassical conjugation. An attempt to synthesize the polymer built from such segments led to obtaining of a nonclassicaly polyconjugated backbone. Preliminary characterization of polydimethylsilylxylilidene obtained as first example of nonclassicaly polyconjugated polymer is presented and mechanism of polyconjugation is proposed.