PHASE-BEHAVIOR OF ROD WITH FLEXIBLE SIDE CHAINS COIL/SOLVENT SYSTEMS - POLY(ALPHA,L-GLUTAMATE) WITH TRI(ETHYLENE GLYCOL) SIDE-CHAINS, POLY(ETHYLENE GLYCOL), AND DIMETHYLFORMAMIDE/

Phase behaviour is investigated for ternary solutions composed of rodl ike alpha-helical poly(alpha,L-glutamate) having triethylene glycol mo nomethyl ether at the end of the side chains (P3EGLG), randomly-coiled poly(ethylene glycol), and N,N-dimethylformamide (DMF) as solvent. Th e solution containing lower molecular weight poly(ethylene glycol) (PE G10) separates into an isotropic phase, which is rich in PEG10, and an anisotropic (cholesteric) phase, which is rich in P3EGLG, when the to tal polymer Volume fraction is higher than ca 0.13. The homogeneous an isotropic region, in which a detectable amount of PEG10 exists, is rec ognized along the P3EGLG-DMF axis in the triangle phase diagram. When the molecular weight of poly(ethylene glycol) is larger, additional ph ase-separation regions are observed: That is, isotropic-isotropic biph asic region and anisotropic-isotropic-isotropic triphasic region. Theo retical treatments based on the lattice model for nematic solutions ar e conducted for these rod/coil/solvent ternary systems. Calculated pha se diagrams with considering flexible side chains of rodlike solute an d isotropic interaction parameters are found to qualitatively reproduc e the variation of the experimental phase behaviour with the change of the molecular weight of the coiled component. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.