SOLVENT-INDUCED STRUCTURAL-CHANGES IN SULFONATED POLY(ETHYLENE-TEREPHTHALATE) (SPET) FIBERS

The microstructure and macrostructure of sulfonated poly(ethylene terephthalate) (SPET) fibers were studied by subjecting them to solvents with solubility parameters similar to those of the PET, Dimethyl sulfoxide (DMSO), methylene chloride (MeCl(2)), and pyridine, whose solubility parameters (delta) are close to those of the flexible aliphatic ester segment (-CO-O-CH2-CH2), the semirigid aromatic segment (-CO-C6H4), and the average delta of the PET repeating unit, respectively, were used. The solvent uptake levels of these three solvents, which were not affected by crimping or relaxing processes of the fibers, were related to their sizes, shapes, and solubility compatibility with SPET. The solvent-induced effects were strongly dependent upon the fiber structure caused by the fiber-forming processes, but were generally not as strong as the processes. The most distinct changes brought about by the solvents include overall orientation determined by birefringence and the trans-gauche ratio and extent of chain fold by FTIR measurements. (C) 1994 John Wiley & Sons, Inc.