The investigation on the radical polymerization reactivity of 4-pentenoyloxypentafluoropropene [CH2=CH-CH2CH2-COOC(CF3)=CF2] (PPF) was carried out since cyclopolymerization of perfluoroisopropenyl vinylacetate [CH2=CH-CH2-COOC(CF3)=CF2] takes place under radical polymerization condition to produce the polymer possessing 5-membered-ring structure in main chain. The soluble polymer of PPF yielded by allyl polymerization bearing 1.8 x 10(4) ((DP) over bar = 78) as the highest molecular weight initiated with di-tert-butyl peroxide was produced instead of cyclized polymer bearing 6-membered-ring structure. The polymer possesses perfluoroisopropenyl groups in side chains. (c) 2007 Elsevier Ltd. All rights reserved.