Concentration frequency dependence of short range chain fluctuations observed in concentrated polymer solutions from nuclear magnetic relaxation rates

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Abstract
Relaxational modes of short range chain fluctuations in concentrated polymer solutions are investigated by studying the proton magnetic relaxation rates. The relaxation rate in the rotating frame and the spin-lattice relaxation rate observed in polyisobutylene chains are found to be independent of the molecular weight in the range 5 x 104 to 106. They are governed by a mechanism which is ascribed to high frequency chain fluctuations controlled by the solvent concentration through the static free volume introduced into the Williams-Landel-Ferry equation. Free volume parameters are evaluated