Sulphonation of maleated block-copoly(styrene/ethylene-butylene/styrene) and preparation of ionomer based on its sodium salt

Sulphonation of maleated block-copoly(slyrene/ethylene-butylene/styrene) (m -SEBS) by acetyl sulphate, followed by neutralisation of the sulphonated pr oduct, leads to the formation of a new block copolymer ionomer with Na+ and both carboxylate and sulphonate anions. Small angle X-ray scattering studi es show the presence of the ionic peak in the scattering profile of the ion omer and Fourier transform infrared spectroscopy confirms the presence of b oth carboxylate and sulphonate anions (i.e. mixed anions). For comparison, an ionomer with carboxylate anions was prepared by neutralisation of m-SEBS . The ionomer with carboxylate anions shows the ionic peak at a lower scatt ering vector than the mixed anions. Dielectric thermal analyses of the iono mer show high temperature relaxation has occurred, which is not observable in m-SEBS. Tt is also observed that incorporation of ionic groups in m-SEBS decreases the dielectric constant of the polymer. Two values of activation energy for the high temperature dielectric relaxation refer to the presenc e of two types of ionic aggregates, multiplets and clusters. The ionomer sh ows higher stress-strain properties at 25 degrees C and greater retention o f the properties at elevated temperature (i.e. 50 and 75 degrees C) than th e corresponding base polymer. PRCPA/1482 (C) 1998 The Institute of Material s.