Abstract: The heteronuclear cross-relaxation rates in polymers were determined by selective and conventional ~(13)C spin-lattice relaxation experiments, the proton-carbon distances were calculated by the theoretical formula, and two-dimensional NOE spectra of the polymers were also measured. The results showed that (1) the measured proton-carbon distances coincide with the distances from molecular models, (2) there is the observable dipolar cross-relaxation effect between the quaternary carbons and their neighboring protons, and (3) the optimum mixing times depend on the relaxation properties of the proton and carbon.

Key words: ¹³C spin lattice relaxation, Proton-Carbon distance, Two-dimensional heteronuclear NOE spectroscopy, Poly(2,6-dimethyl-1,4-phenyleneoxide), Polyisobutylene