Novel copolyester-based ionomer for a shape-memory biodegradable material

A series of biodegradable poly(oxyethylene-b-butylene adipate) ionomers (POBAis) were synthesized by bulk polymerization of adipic acid and mixed monomers of bis(poly(oxyethylene)) sulfonated dimethyl fumarate and 1,4-butanediol. The POBAis exhibited notable recovery rate ranging from 81% to 95% at near body temperature, depending on the content of ionic group. From the dynamic mechanical analysis it was found that storage modulus above rubbery plateau region significantly increased as ionic monomer was introduced up to 2.5 mol%, indicating a good dimensional stability above glass transition region. Wide angle X-ray analysis was carried out to investigate the structural variation over shape deformation and/or recovery. WAXD pattern of POBAi-2.5 revealed that α–β transition of crystal occurred during recovery process. These results may provide crucial information of the crystallizable ionomers as a potential shape-memory polymer (SMP).