Cellulose and Cellulose Triacetate Mesophases

Abstract

Cellulose and cellulose triacetate (CTA) form mesophases in trifluoroacetate acid (TFA) - CH2Cl2 mixtures. Anisotropy is observed as low as 4% (w/w) concentrations for cellulose solutions; well below predicted values. For cellulose triacetate, the critical concentration is 20% (w/w). Both cellulose and CTA are slowly degraded in the TFA-CH2Cl2 solvent. Ternary mixtures of cellulose or CTA and polyethylene terephthalate (PET) separate into anisotropic and isotropic phase, conforming Flory's prediction, but there was not complete exclusion of the PET from the anisotropic phase. Surprisingly, fibers spun from anisotropic solutions rich in CTA contained the CTA I polymorph. Block copolymers of CTA and poly(ethylene-co-propylene adipate) (PEPA) formed mesophases. When admixed with PEPA, phase separation did not occur, suggesting molecular composites may be prepared from mixtures of block copolymers, consisting of rigid (or semi-rigid) and flexible block and flexible polymers.