ASSIGNMENT OF NMR SIGNALS FOR CHLOROPRENE RUBBER BY TWO-DIMENSIONAL NMR SPECTROSCOPY

Various pulse techniques of NMR spectroscopy were applied to CR to assign some small signals in C-13 and H-1 NMR spectra for the rubber. First, the rubber was subjected to distortionless enhancement by polarization transfer and attached proton test. The small signals in the C-13 NMR spectrum were assigned to secondary, tertiary, and quatemary carbons. Second, correlations between C-13 and H-1 were investigated by heteronuclear multiple quantum correlation, heteronuclear two bond correlation, and heteronuclear multiple bond correlation measurements to assign the small signals in the C-13 NMR spectrum in detail. By using the resulting correlations between C-13 and H-1, the small unassigned signals in H-1 NMR spectrum were assigned to methylene and methine protons of the rubber.