Carbon-13 NMR investigation of spin-lattice relaxation mechanism of poly(4-methyl-1-pentene)

Carbon-13 spin-lattice relaxation rates (1/T1) and nuclear Overhauser enhancement (NOE) measurements were performed on poly(4-methyl-1-pentene) above the glass transition temperature in order to explain the segmental motion of the molecule by means of high resolution nuclear magnetic resonance spectroscopy. Experiments were carried out for poly(4-methyl-1-pentene) with low, medium, and high molecular weights. The similarity of the T1 values showed that for polymers with a degree of polymerization (DP) > 100 the relaxation behavior of the carbon atoms no longer depends on molecular weight. The temperature effects were studied at 358, 363, 373, 383, 393, and 403 K, both on 25.18 and 100.61 MHz magnetic fields. Finally, several mathematical T1 models were applied to study the change of T1 encountered by the individual carbon atoms. The results reveal that the more factors being considered in the calculation the more consistent will be the results obtained with the T1 model. A comparison showed that parameters used in the DLM T1 model gives the best fit. © 1994 John Wiley & Sons, Inc.