Size selective concentrating of poly(ethylene oxide) in aqueous solution by thermosensitive hydrogels

摘要

Thermally reversible hydrogels of poly(N-isopropylacrylamide-co-acrylic acid) crosslinked with three different contents of N,N ' -methylenebis(acryl-amide) have been swollen to equilibrium at 25 degreesC. The aqueous swelling medium comprised a 1 g (.) dm(-3) solution of two species of polyethylene oxide (PEO) the fixed species being of molecular weight (M) 0.2 kg (.) mol(-1) and the other species being of M = 1, 4, 6, 10, 35, 110 or 1700 kg (.) mol(-1). The swelling ratios (= mass hydrogel/mass xerogel) of the resultant hydrogels were smaller than the corresponding values for swelling in pure water. The remaining solution (raffinate) was of enhanced total concentration. Concentrations of each of the two polymer species in initial solution and raffinate were measured by GPC. The ability of the hydrogel to concentrate a particular species is quantified by alpha, where alpha is the ratio of concentrations ofthe PEO species in raffinate to that before swelling. Th ability of hydrogel to concentrate one species in preference to a different species is quantified by lambda, where lambda is the ratio of alpha for M = 0.2 kg (.) mol(-1) to alpha for PEO of a different M. The findings are discussed in part on the basis of correlation length of gel cf. equivalent hydrodynamic radius of the PEO sample. [GRAPHICS] Values-of the size selective separation factor (lambda) for hydrogels of different crosslinker content. Contents of BIS are (lozenge) 0.25 mol-%, (square) 0.50 mol-%, (triangle) 1 mol-%. Swelling media are aqueous solutions at a total concentration of 1 g (.) dm(-3) of PEO-0.2 in admixture with PEO-M. [References: 20]