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 resulting polymer by size-exclusion-chromatography (SEC) was used to measure propagation rate coefficients, k p, of acrylic acid (AA) in aqueous solution at concentrations of 20 and 40 wt % and temperatures between 2.6 and 28.5 °C. Under these conditions, more than 99% of acrylic acid exists in the nonionized form. The molecular weight distribution (MWD) of poly(AA) is directly measured by aqueous SEC. The k p values at 20 wt % are about 60% higher than at 40 wt %. The activation energy of k p is close to 12.0 kJ·mol -1 at both concentrations. At 25 °C and 20 wt %, k p of AA in aqueous solution exceeds 100 000 L·mol -1 ·s -1 which is the highest k p value determined by the PLP−SEC technique so far.