AbstractThe purpose of this paper is to report the application of infrared spectroscopy to the preparation and polymerization of vinylcyclopropane, vinylcyclopentane and vinylcyclohexane. Carbon‐hydrogen stretching frequencies in the 3005 and 3080‐cm.−1regions were utilized in the evaluation of products and reactions. Precursors to vinylcyclopropane and these bands afforded independent evidence for the retention of the three‐membered ring in crystalline polyvinylcyclopropane. Absorptions characteristic of the cyclopentyl and the cyclohexyl groups were found to be of less utility in the analysis of processes leading to crystalline polyvinylcyclopentane and crystalline polyvinylcyclohexane, while bands in the 3020–3081‐cm.−1region aided the establishment of type and location of unsaturation in sev