Abstract
Transport in ternary polymer 1, polymer 2, solvent systems has been investigated using an n.m.r. spin-echo technique. The dependence of the self-diffusion coefficient of poly(ethylene oxide) polymers on the concentration and molecular size of dextran in aqueous solution has been measured. Monodisperse poly(ethylene oxide) fractions ( M ̄ w=7.3×10 4 , 2.8·10 5 and 1.2·10 6) and dextrans ( M ̄ w=2·10 4 , 1·10 5 and 5·10 5) have been employed over a range of concentration up to the miscibility limit in each system. It is found that when the molecular size of the diffusant is commensurate with or exceeds that of the matrix polymer, a relationship of the form: ( D D 0 ) PEO = exp−k(C[η]) is applicable, where C[ η] refers to the dextran component and is considered to describe the extent of coil overlap in concentrated solution. ( D D 0 ) is independent of the molecular size of the poly(ethylene oxide), at least in the range studied ( M w <300 000).
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