Abstract
AbstractRadical polymerization of N‐vinylpyrrolidone along poly(methacrylic acid) templates of high syndiotatic 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 νR = νR,max. In the free solution, blank polymerization occurs, i. e., νR = 1. Consequently, νR can be approximated by the equation νR = ϕνR,max + (1 − ϕ), where ϕ represents the volume fraction occupied by template coils. The slight increase in UR 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 50–70°C, the activation energy and entropy were almost identical for blank and template polymerization. An expected decrease of ΔE≠ and ΔS≠ in template systems is supposed to be compensated by the effects of desolvation of the template macromolecules during the propagation step.
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