Self-diffusion in block copolymer solutions

Abstract

Self-diffusion of poly(sulphone-ethylene oxide) copolymer macromolecules in different solvents has been investigated by pulsed field gradient nuclear magnetic resonance. The experimental response indicates a wide distribution of self-diffusion coefficients P(D) for all samples studied. The distribution function P(D) is shown to be represented by a logarithmic normal function and parameters characterizing its width have been obtained. The width of P(D) is large at room temperature, indicating that the systems tend to gelation. The concentration dependence of the average self-diffusion coefficient D is described by the relation D ̄=φ{symbol}-α 2 (α=3.4 - 3.8) in the range of polymer concentrations φ{symbol}2=0.2 - 0.6. The effect of solvent thermodynamic quality on D ̄ is considered. Anomalous concentration dependences of D observed in a number of solutions are discussed. © 1987.