Molecular Motion in Solid Polymers

1 Characteristics of ESR for Studying Molecular Motion in Solid Polymers 

2 Evaluation of Correlation Time for Molecular Motion from ESR Spectra 

Freed et al. [3] evaluated the relaxation rate of polymer chains by the analysis of the anisotropic spectra of nitroxide spin labels. The main triplet spectrum was due to hyperfine coupling caused by the nitrogen nucleus. It narrowed with an increase in mobility of the radicals because of motional averaging of the anisotropic hyperfine interaction. The rotational correlation time of nitroxide spin labels can be estimated using the procedure of Freed et al. by taking into account the anisotropic rotational motion. The ESR line width, AHmsi of the spectrum can be expressed as follows  

Freed et al. [4, 5] proposed also an equation for the calculation of the correlation time based on the simulation of the spectra. This equation is widely applied even in the case of slow rate of molecular motion (10 tc(s) 10 )  

3 Glass-Rubber Transition Detected by the Spin Label Method for Polystyrene (PS) Molecular Weight Dependence 

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Since about 1960 nuclear magnetic resonance (NMR) spectroscopy has become an important tool for the study of chain configuration, sequence distribution and microstructure of polymers. Its use started from early broad-line studies of the one-set of molecular motion in solid polymers and passed through the solution studies of proton NMR, to the application of the more difficult but more powerful carbon-13 NMR methods to both liquids and solids. 

Saito, N., Okano, K., Iwayanag, S., Hideshima, T., in Solid state fdiysics Sdtz, F., Turnbull, D., eds. New York Academic Press, 1963, VoL XIV, p. 343 Saito, S. Study of molecular motions in solid polymers by the dielectric measurements. Res. of flie Electrotechn, Lab., Tolofo, Japan, PubL No. 648,1964 Saito, S., Sasabe, H., Nakajima, T., Yada, K. J. Pohmu ScL, Part A-2,6,1297 (1968)... 

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