Radical Propagation Kinetics of <i>N</i>‐Vinylpyrrolidone in Organic Solvents Studied by Pulsed‐Laser Polymerization–Size‐Exclusion Chromatography (PLP–SEC)

<jats:p>Pulsed‐laser polymerization with subsequent analysis of the polymer molar mass distribution by size‐exclusion chromatography, PLP–SEC, is used to measure the propagation rate coefficient, <jats:italic>k</jats:italic><jats:sub>p</jats:sub>, of <jats:italic>N</jats:italic>‐vinylpyrrolidone (NVP) in a series of organic solvents, varying the NVP concentration from 5 to 100 wt% and varying the temperature between –5 and +80 °C. In contrast to the 20‐fold increase observed in aqueous solution upon decreasing the NVP concentration from bulk to dilute conditions, the <jats:italic>k</jats:italic><jats:sub>p</jats:sub> values of NVP in butyl acetate, <jats:italic>iso</jats:italic>‐propyl acetate, <jats:italic>N</jats:italic>‐ethylpyrrolidone, and <jats:italic>N</jats:italic>‐ethylformamide stay within 20% of the bulk value and exhibit no significant dependence on monomer concentration. The <jats:italic>k</jats:italic><jats:sub>p</jats:sub> behavior of NVP in methanol and <jats:italic>n</jats:italic>‐butanol is intermediate between the one in water and in the other organic solvents, with <jats:italic>k</jats:italic><jats:sub>p</jats:sub> increasing by about a factor of 2 upon lowering the monomer concentration from bulk to 5 wt% NVP. The activation energies for propagation in organic solvents agree within experimental uncertainty with the value reported for bulk NVP. The data demonstrate that hydrogen bonding is responsible for the increase in <jats:italic>k</jats:italic><jats:sub>p</jats:sub> upon dilution, with this effect being much stronger in an aqueous environment than in a solution of alcohol. <jats:boxed-text content-type="graphic" position="anchor"><jats:graphic xmlns:xlink="http://www.w3.org/1999/xlink" mimetype="image/jpg" position="anchor" specific-use="enlarged-web-image" xlink:href="graphic/macp201400329-abs-0001-m.jpg"><jats:alt-text>image</jats:alt-text></jats:graphic></jats:boxed-text></jats:p>