Diffusion of low-molecular weight poly(ethylene oxide) in water

Abstract

The diffusion coefficients in water of ethylene glycol and several poly(ethy1ene oxides) of low molecular weight have been measured at 15, 25 and 35°C. The activation energies of diffusion are in the range 19-21 kJ mol-' in agreement with published results on more rigid molecules. The Stokes-Einstein diffusion radii increase with temperature probably as a result of conformational changes in the polyoxyethylene chain. After allowing for hydrogen bonding of water molecules at the terminal hydroxyl groups, the diffusion coefficients are found to be inversely proportional to the root mean square distance (F)+ of a chain element from the molecular centre of mass. This relationship holds over the whole molecular weight range studied, and no evidence for free-draining is found.Comparison with the theory of Kirkwood and Riseman shows that the actual value of (?)* is 1.95

Viscosity B coefficients of polyethyleneglycols in water

“…G was practically independent of the solute concentration. This is consistent with the finding that the partial specific volume of polyethylene glycol is independent of its concentration [7]. In addition, the partial molal volumes, 17, of the polyethylene glycols were not significantly different from the corresponding values of ~.…”

“…[3) can be evaluated, provided that the values of K and V for each polyethylene glycol are known. Previous studies [7][8][9] showed that similar polyethylene glycols behave as impermeable spheres in aqueous solution. Hence, the value of K can be taken as 2.5.…”

“…It is reasonable to assume that K is independent of the concentration of polyethylene glycol in the concentration range used, because they behave as impermeable spheres in aqueous solutions [7][8][9]. Therefore, Kc is 2.5 and d~ is the density of water.…”

The Effect of Molecular Size on Diffusion Characteristics in Soil

“…Price (1959) have found that the intrinsic viscosity of PEGS up to a molecular weight of 10 000 is given by the equation The accuracy of this expression may be tested by calculating the diffusion coefficient of PEG 1540. Couper and Stepto (1969) have measured this as 2.173 x cm2 s-' at 25 "C in aqueous solution. The diffusion coefficient was constant between concentrations of 0 and 1.1 g/lOO ml of water.…”

“…The root mean square distance between the ends of PEG 4OOO is calculated as 3.40 nm (Couper and Stepto, 1969). If PEG 4OOO can be regarded as a non-freedraining sphere, its diffusion radius may be calculated as 19Onm (Tanford, 1961).…”