Radical polymerization of N-vinylpyrrolidone in the presence of syndiotactic poly(methacrylic acid) templates

Radical polymerization of N-vinylpyrrolidone along poly(methacrylic acid) templates of high syndiotactic content was followed dilatometrically in dimethylformamide, which was used as solvent. The effects of template concentration, template molar mass, and temperature on polymerization rate and average molar mass of the formed polyvinylpyrrolidone (PVP) were examined. Template concentrations were varied around the critical concentration for homogeneous segmental distribution, C. Below this concentration, template coils can act as separate microreactors wherein growing PVP radicals exhibit maximum rate enhancement, i.e., relative rate upsilon/sub R/ = upsilon/sub R max/. In the free solution, blank polymerization occurs, i.e., upsilon/sub R/ = 1. Consequently, upsilon/sub R/ can be approximated by the equation ν/sub R/ = phiν/sub R/max/ + (1 - phi), where phi represents the volume fraction occupied by template coils. The slight increase in ν/sub R/ and PVP molar mass with the template chain length is supposed to be caused by the influence of translational diffusion on the termination step. Over the investigated temperature range of 50 to 700C, the activation energy and entropy were almost identical for blank and template polymerization. An expected decrease of ΔE not equal to and ΔS not equal to in template systems is supposed to be compensated by the effects of desolvation of the template macromolecules during the propagation step