Aqueous phase size-exclusion-chromatography used for PLP-SEC studies into free-radical propagation rate of acrylic acid in aqueous solution

Pulsed laser polymerization (PLP) in conjunction with analysis of the resul ting polymer by size-exclusion-chromatography (SEC) was used to measure pro pagation rate coefficients, kp, of acrylic acid (AA) in aqueous solution at concentrations of 20 and 40 wt % and temperatures between 2.6 and 28.5 deg reesC. Under these conditions, more than 99% of acrylic acid exists in the nonionized form. The molecular weight distribution MWD) of poly(AA) is dire ctly measured by aqueous SEC. The kp values at 20 wt 7( are about 60% highe r than at 40 wt %. The activation energy of hp is close to 12.0 kJ . mol(-1 ) at both concentrations. At 25 degreesC and 20 wt %, k(p) of AA in aqueous solution exceeds 100 000 L . mol(-1).s(-1) which is the highest kp value d etermined by the PLP-SEC technique so far.