An investigation of the free-radical bulk photopolymerization of 1-vinyl-2-pyrrolidinone (NVP) with an NVP-based crosslinker, 1,6-(bis-3-vinyl-2-pyrrolidillonyl)hexane (BNVP), and an NVP-based comonomer, 3-hexyl-1-vinyl-2-pyrrolidinone (VHP), was carried out. The enthalpies of polymerization were determined for NVP and VHP to be 30.8 and 35.7 kJ/mol, respectively. The rates of polymerization were determined for NVP/VHP and NVP/BNVP systems at various temperatures. These photopolymerization studies revealed that the overall rates of polymerization of these 3-alkylated-2-pyrrolidinone derivatives increased with substitution onto the pyrrolidinone ring. A series of pyrrolidinone-based additives in bulk NVP were used in model photopolymerizations of NVP for the evaluation of plasticizer effects.