Fd. Kuchta et al., Propagation kinetics of acrylic and methacrylic acid in water and organic solvents studied by pulsed-laser polymerization, MACROMOLEC, 33(10), 2000, pp. 3641-3649
Pulsed laser-induced polymerization (PLP) in combination with analysis of f
ormed polymer by size exclusion chromatography (SEC) has been successfully
applied in determining propagation rate coefficient, k(p) of acrylic and me
thacrylic acid in organic solvents and water. For methacrylic acid solution
polymerization in methanol and in dimethyl sulfoxide (DMSO), minor but not
negligible variations of k(p) with solvent have been observed. In contrast
, k(p) values for polymerizations in water are significantly influenced by
the solvent and furthermore by monomer concentration. The k(p) values obtai
ned from polymerization experiments in water are significantly larger than
the corresponding values obtained in methanol or DMSO. Weighted nonlinear l
east-squares fitting (NLLS) has been applied to calculate frequency factors
, A, and activation energies, E-a, from the temperature dependence of k(p)
for methacrylic acid in methanol, DMSO, and water in order to underline the
reliability of the data. For acrylic acid it turns out that optimized expe
rimental conditions have to be chosen in order to determine reliable k(p) v
alues at ambient temperature. Laser pulse repetition rates of at least 90 H
z are necessary to ensure that "termination by the laser pulse" is the main
chain stopping event. Smaller values of the laser pulse repetition rate wi
ll not yield reliable k(p) data. Furthermore, evidence of at least one firs
t overtone inflection point at L-2 approximate to 2L(1) is not only recomme
nded, it is necessary to ensure a reliable measure of k(p). This is the mos
t important consistency criterion showing that experimental conditions are
suitable.