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Dynamics Of The Junction Point In Model Network Polymers By (31)P Nuclear Magnetic Relaxation, William Macknight, Jie-Feng Shi, L. Charles Dickinson, James C. W. Chien
Dynamics Of The Junction Point In Model Network Polymers By (31)P Nuclear Magnetic Relaxation, William Macknight, Jie-Feng Shi, L. Charles Dickinson, James C. W. Chien
William MacKnight
Solid-state 3lP NMR spin-lattice relaxation times (2'1~) have been measured over a wide range
of temperatures for a series of network polymers with molecular weights between cross-links (M,r)an ging
from 250 to 2900. The networks were formed from poly(tetrahydr0furan) and tris(4-isocyanatophenyl)
thiophosphate. The chain length dependence of the glass transition temperature obeys the Fox-Loshaek
relation. The dominant mechanism for 3lP spin-lattice relaxation was found to be chemical shift anisotropy.
The data fitted equally well to the ColeCole or the Williams-Watts relaxation functions. The apparent and
microscopic activation energies for the motion of junction points are 44-73 and 23-30 kJjmo1, respectively, …