LIQUID-CRYSTAL POLY(ALPHA-OXIRANES) WITH MESOGENIC SIDE-GROUPS

The paper reports the synthesis of new LC monomers, namely, of alpha-o xiranes containing p-methoxyphenylbenzoate and 4-cyanobiphenyl mesogen ic groups linked to alpha-oxirane ring via aliphatic spacers of differ ent length (n = 1 - 4, 9). The corresponding oligomers and polymers wi th a widely varying degree of polymerization were synthesized by ionic polymerization [BF3 . O(C2H5) and Al(C2H5)3/H2O/AcAc were used as cat alysts]. The effects of the degree of polymerization, spacer length, a nd the type of mesogenic group on the phase transitions and the struct ure of the synthesized oligo- and poly(alpha-oxiranes) were studied. A ll oligomers with the spacer not less than two-methylene-groups-long w ere found to form LC phases; for higher homologs, the degree of order in these phases was higher. Most of the corresponding polymers formed a crystalline phase. Copolymerization of the monomers with spacers of different length reduced the melting temperature of the crystalline ph ase, so that the resultant copolymers could form thermodynamically sta ble LC phases. The thermal properties and the structure of the formed phases as controlled by the chemical structure of the main chain in co mb-shaped LC polymers were examined.