FTIR INVESTIGATION OF ION-DIPOLE INTERACTION IN STYRENE IONOMER POLY(ETHYLENE OXIDE) BLENDS

Fourier-transform infrared (FTIR) spectroscopy was used to examine spe cific interactions contributing to the partial miscibility in blends o f styrene-sodium methacrylate copolymer (S-NaMA) and poly (ethylene ox ide) (PEO). From the shifts of carboxylate ion and ether group stretch ing bands, an important specific interaction was found involving ion-d ipole bonding between the ionic group in styrene ionomer and the ether group in PEO. The asymmetric stretching vibration frequency of the ca rboxylate ion group increases as the fractional amount of PEO in the b lend is increased, while the symmetric stretching frequency is decreas ed. The transition value of the fraction of PEO, above which both vibr ation frequencies of the carboxylate ion mentioned above remained almo st unchanged, increases as the concentration of ionic groups in ionome r is increased. The ether group stretching band shifts to higher frequ encies as the PEO content in the ionomer/PEO blend is increased. From the differential scanning calorimetry (DSC) and FTIR studies, we find that the ion-dipole interaction is the important mechanism that determ ines the miscibility of S-NaMA/PEO blends. (C) 1994 John Wiley & Sons, Inc.