Magnetization-transfer NMR determination of rates of exchange of solvent in and out of gel polymer beads

Abstract

Rate constants for exchange of toluene in and out of swollen beads of a 10% crosslinked copolymer of styrene and chloromethylstyrene and for spin-lattice relaxation of the toluene methyl carbon atom inside and outside the beads have been determined by 13C NMR magnetization-transfer kinetics. Evaluation of complementary selective inversion, single selective inversion, and nonselective inversion data by Marquardt nonlinear least-squares analysis showed that only complementary selective inversion experiments were adequate for calculation of the exchange rate constants. A DANTE pulse sequence was used for the selective 180° pulse.