Macromolecules, Vol.28, No.7, 2396-2405, 1995
Dynamical Behavior of Poly(2-Vinylpyridine) in Solution Studied by C-13 Nuclear Magnetic-Relaxation
The dynamics of poly(2-vinylpyridine) in chloroform solution has been examined by C-13 spin-lattice relaxation time and NOE measurements as a function of temperature. The experiments were performed at 50.3 and 100.6 MHz. The backbone carbon relaxation data have been analyzed in terms of six motional models. Among these models, the models which consider conformational transitions and bond librations for the backbone were found to be more successful. Pyridyl ring motion has been modeled as a restricted rotation with the rotational amplitude varying with temperature. The activation energy parameters obtained from the relaxation data of the pyridyl ring carbon have been compared with the energy barrier for ring rotation estimated from conformational energy calculations using the AM1 semiempirical quantum chemical method. The results of the conformational energy calculations support the description of pyridyl ring motion as a restricted rotation.
Keywords:GLASS-TRANSITION TEMPERATURE;INTERNAL LIBRATIONAL MOTIONS;SPIN-LATTICE RELAXATION;LOCAL DYNAMICS;BULK POLYMERS;DILUTE-SOLUTION;ORIENTATION RELAXATION;MACROMOLECULAR CHAINS;WELL;POLYISOPRENE