PHASE-DIAGRAM AND EVOLUTION OF MESOPHASE STRUCTURE IN MIXTURES OF A LOW MOLAR-MASS SMECTIC LIQUID-CRYSTAL AND A NEMATIC SIDE-ON SIDE-CHAIN LIQUID-CRYSTALLINE POLYMER

Miscibility phase diagrams in mixtures of side-on side-chain liquid cr ystalline polymers (s-SCLCP) and low molar mass smectic liquid crystal s (K36) have been investigated by means of polarized optical microscop y. K36 is a smectic liquid crystal that exhibits a smectic-isotropic t ransition at 58 degrees C and a smectic-to-crystal transition (crystal lization) at 27 degrees C. The nematic/smectic phase diagram of the s- SCLCP/K36 has been analyzed by combining the Flory-Huggins (FH) free e nergy for isotropic demixing and the Maier-Saupe-McMillan (MSM) free e nergy for smectic ordering of the mesogens. This combined FH/MSM theor y compares reasonably well with the observed nematic/smectic phase dia grams composed of isotropic + nematic, smectic + nematic, smectic + is otropic, pure nematic, and pure smectic regions. Several temperature q uench experiments have been conducted to confirm various predicted coe xistence regions. However, at present, the combined theory does not in clude any crystallization processes occurring at a lower temperature.