ON THE STRUCTURE OF CHLORINATED NATURAL-RUBBER - H-1-NMR AND C-13-NMR DATA

1H- and 13C-NMR spectra of compositionally homogeneous samples of chlorinated natural rubber containing 0.4-3.0 Cl/C5 have been investigated. In the samples of composition Cl/C5 ≤ 1 there are no units containing > 1 chlorine atom, meaning that chlorine docs not add to CC double bond. Simultaneously, unsaturation of the polymer decreases by approx. 10%. These data support a hypothesis about cyclization of the chain during the fast stage of chlorination (up to Cl/C5 = 1). However, quaternary C atoms typical of 6-membered cyclic structures, as postulated in the literature, have not been observed in spectra. Weak signals in the region 75-76 ppm indicate the existence of {A figure is presented} fragments. The data obtained suggest that 5- not 6-membered cycles are formed during chlorination of natural rubber. With an increase of the chlorination degree, signals in the olefinic region of spectra appear, indicating formation of exo- and internal CC double bonds differing from analogous fragments forming in the fast stage of the reaction. © 1990.