Termination Kinetics of N-Vinyl Formamide Radical Polymerization in Aqueous Solution

Abstract

Termination kinetics of radical polymerization of N-vinyl formamide (NVF) in aqueous solution has been measured via SP–PLP–NIR, i.e., single pulse (SP) initiation of pulsed laser polymerization (PLP) in conjunction with microsecond time-resolved near-infrared (NIR) detection of monomer concentration. Experiments are performed at initial NVF weight fractions from 0.20 up to bulk NVF, at monomer conversions up to 40%, and at temperatures from 40 to 70 °C as well as pressures from 500 to 2500 bar. Applying high pressure improves signal-to-noise quality. Data obtained upon pressure variation allow for extrapolation toward ambient pressure. The primary quantity from SP–PLP–NIR is k_p/<k_t>, i.e., the ratio of propagation rate coefficient, k_p, to apparent chain-length-averaged termination rate coefficient, <k_t>. With k_p being available from literature, k_p/<k_t> yields <k_t>. This quantity is relevant for modeling polymerization rate and polymer properties. Termination in the initial polymerization period turns out to be controlled by segmental diffusion and, at higher degrees of monomer conversion up to 40%, by translational diffusion.