SynopsisBulk radical polymerization of N-vinylcaprolactam was studied at temperatures between 60 and 120'C. with different initiators. Satisfactory results were obtained with azobisisobutyronitrile, terl-butyl perbenzoate, and tert-butyl peroxide as initiators. The polymerization reaction of N-vinylcaprolectam with these initiators is first order witch respect to the monomer and 0.5 order with respect to the initiator. A linearity of the kinetic curves up to high conversions was observed. The cause of this behavior is a feeble gel effect, which also induces an increase of the molecular weight during polymerization.N-vinylcaprolactam polymerization was studied with HzOz and benzoyl peroxide as initiators at temperatures over 100°C. ; low molecular weight polymers were Satisfactory results were obtained with azobisisobutyronitrile as initiator13 but there are no published data on the kinetics of this reaction. ExperimentalThe monomer was obtained by vinylation of caprolactam with acetylene in the presence of caprolactyl N-Vinylcaprolactam was isolated from the reaction mass by distillation at reduced pressure (8-10 mm.) under argon; it then was purified by being distilled twice under argon at 8-10 mm. through a rectification column (4 = 30 mm., h = 700 mm.) filled with glass rings (4 = 4 mm., h = 5 mm.), the reflux ratio being SOTo; the fraction was collected directly in ampules at temperatures between 11O.S and 111.2"C. The ampules containing pure monomer were closed under argon. I n such conditions pure N-vinylcaprolactam (ng = 1.5057, freezing point 345°C.) may be conserved a long time at room temperature in the dark.The pure moiiomer was handled only uiider dry, inert atmosphere. The precautionary measures of purifying, conserving, and handling of the N-vinylcaprolactam were necessary because of the sensitivity of this monomer to the action of oxygen, which oxidizes rapidly to a brown-yellow compound. The presence of such compounds diminishes considerably the activity of N-vinylcaprolactam in the polymerization reaction, and the results of kinetic measurements became unreproducible. 1843

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