乙基醋酸纤维素溶致性液晶的研究

乙基醋酸纤维素溶于三氟乙酸、二氯乙酸、醋酸中.在浓度大于临界浓度时,形成胆甾型液晶态.溶液随浓度的增加,从各向同性态经两相共存转变成液晶态.在加热液晶溶液时,溶液转变成各向同性态.降低温度,液晶相再生成.在形成液晶过程中,存在过冷现象.在一定的条件下,液晶相以球状的形式存在.溶液的双折射△n在两相共存与完全液晶态间相互转变时会发生较大变化.乙基醋酸纤维素大分子链的刚性随有机酸溶剂体系的酸强度的增大而增大,使临界浓度C_1~*随溶剂酸强度的增大而减小.

STUDIES ON LYOTROPIC LIQUID CRYSTAL OF ETHYL-ACETYL CELLULOSE

Ethyl-acetyl cellulose ((E-A)C) could dissolve in organic acid solvent such as trifluoro-acetic acid (TFA), dichloroacetic acid (DCA) and acetic acid (AA) and form lyotropic liquid crystal above the critical concentration C1. With increasing concentration the solutions transformed form isotropic to anisotropic phase through a biphasic range. When the an-isotropic solutions were heated, they changed first to the biphase and then to the isotropic phase. The mesomorphic phase could form again when the solutions were cooled. There was a supercooling phenomenon for the solutions in the process of forming the liquid crystal. Birefringence of the solutions varied greatly at the transition between biphasic and anisotropic phases. In some conditions there were spherulitic liquid crystals in the anisotropic solutions. The rigidity of the chains of (E-A)C increased with increasing acidity of the organic acid solvent systems. It caused the critical concentration C1 to decrease with increasing the acidity of the solvents.