Phase transition behavior of a poly(oxyethylene-b-butylene adipate) ionomer with shape memory properties

Abstract

A series of biodegradable poly(oxyethylene-b-butylene adipate) ionomers (POBAi) were prepared by two-step in situ polymerization using adipic acid, 1,4-butanediol and mixed monomers of bis(poly (oxyethylene)) sulfonated dimethyl fumarate. The chemical composition of these POBAi was ascertained by H-1 NMR spectroscopy. The objective of this study was to investigate the shape memory effect of POBAi containing ionomer compared to non ionic POBA. It was observed that POBA5.0i showed a good shape memory effect than that of POBA 2.5 mol% or none of ionic group due to much physical cross-linking point by rich ionic group. Stress-induced phase transition was investigated during the shape deformation and recovery process using a wide-angle X-ray diffractometer (WAXD). The POBA crystal phase transition from beta- to alpha-form was observed in all POBA samples by either thermal treatment or physical drawing. The alpha-form crystal did not recover to the initial beta-form during the recovery process because the monoclinic alpha-form crystal is structurally more stable than the orthorhombic beta-form crystal.