ION-CONTAINING POLYMERS .1. SYNTHESIS AND PROPERTIES OF POLY(1,4-BUTYLENE ISOPHTHALATE) CONTAINING SODIUM-SULFONATE GROUPS

Poly(1,4-butylene isophthalate)s containing sodium sulfonate groups we re prepared from dimethyl isophthalate, 3,5-bis(carbomethoxycarbonyl) benzenesulfonate (5SIPNa) and 1,4-butanediol. Polymers of fairly high molecular weight were obtained with a content of ionic comonomeric uni ts up to 16.7 mol%; however, increasing amounts of 5SIPNa led to a dec rease in the molecular weight and to an increase in the COOH/OH termin al-group ratio. The ionomer samples were characterized for chemical st ructure, terminal groups, the concentration of sulfonate groups, solub ility and their thermal properties. Results from different methods of terminal-group and sulfonate-group analysis were compared. Solubility was found to be strongly affected by the introduction of sulfonate gro ups, and samples containing 16.7 mol% of SO3Na groups were water dispe rsible. D.s.c. studies on samples containing sulfonate groups, either in the free acid or sodium salt form, suggested that the effects on gl ass transition temperature and crystallization were due to the introdu ction of bulky sulfonate groups into the polymer backbone rather than to ionic interactions. Thermogravimetry showed that SO3H groups decrea sed the thermal stability significantly, while SO3Na groups had only a limited effect with respect to pure poly(1,4-butylene isophthalate).