Role of chlorine atoms in the relaxation behavior of chlorine-containing polymers

Examination of the internal friction spectra of PVC and polychloroprene and of their nonlinear analogs, PE and polybutadiene, showed that relaxation transitions in various linear chlorine-containing polymers were differently affected by chlorine atoms present in the polymer chains. Relaxation transitions of group I are associated with mobility of the CH2-groups (beta(CH2)-relaxation) and breakage of the C-C bonds (delta(C)-relaxation). Both processes are virtually independent of the presence of chlorine atoms. Other carbochain polymers also experience the above relaxation transitions at similar temperatures. Relaxation transitions of group II involve the alpha-relaxation (segmental mobility) and lambda-relaxation processes (at temperatures above T-g), which are related to decomposition of microvolume knots representing associates of segments. Chlorine atoms are not responsible for the above long-range relaxation transitions, but their temperatures and activation energies are affected by chlorine atoms involved in intermolecular interactions. Relaxation transitions of group III (the beta(Cl), pi(Cl), and delta(Cl)-relaxation) are attributed only to the presence of chlorine atoms in polymer chains. The beta(Cl)-relaxation is associated with the mobility of chlorine-containing groups in polymer chains, the pi(Cl)-relaxation is explained by the breakage of the lateral dipole-dipole bonds (local physical nodes), and the delta(Cl)-relaxation is related to the breakage of C-Cl bonds. In PE and polybutadiene, no relaxation transitions of group III are observed absent.