DIFFUSION IN AQUEOUS-SOLUTIONS OF POLY(ETHYLENE GLYCOL) AT LOW CONCENTRATIONS

We have observed the scaling behavior of the diffusion coefficient of poly(ethylene glycol) (PEG) ranging from dimer to n-mer of 14 000 ethy lene glycol units in D2O and in a (1:1) mixture of D2O and diethylene glycol, solvents of both low and moderate viscosities. The accepted sc aling relationship for diffusion of polymers at infinite dilution is D -0 = KM(-alpha), where a ranges from 0.5 for a Theta solvent to 0.6 fo r a good solvent, as originally proposed by Flory. Measuring D-0 as th e extrapolated value of D versus concentration in a PGSE-NMR experimen t, we find a surprisingly good fit to this scaling relationship over t he entire molecular weight range for both solvent systems. The values of alpha obtained in D2O at 25 degrees C, D2O at 5 degrees C, and a D2 O/diethylene glycol mixture at 25 degrees C were 0.597 +/- 0.020, 0.53 4 +/- 0.021, and 0.542 +/- 0.058, respectively. The extension of the s caling behavior down to the dimer species is believed to be due to the high local segmental friction coefficient of the ethylene oxide unit.