RADICAL RING-OPENING POLYADDITION OF A BIFUNCTIONAL VINYLCYCLOPROPANEBEARING A SPIROACETAL MOIETY WITH DITHIOLS

Radical polyadditions of vinylcyclopropane having spiroacetal moiety, 4,8,12,15-tetraoxatrispiro[2.2.2.2.2.2]pentadecane (1), and various di thiols were examined. 1 was prepared by the reaction of 1,1-dichloro-2 -vinylcyclopropane and pentaerythritol, and radical polyadditions of 1 and dithiols were carried out at 60 and 120 degrees C for 20 h in the presence of an appropriate initiator (3 mol % vs. 1) in degassed seal ed ampoules or at 20 degrees C under photo irradiation by using a 400 W high-pressure mercury lamp. Poly(1), pale yellow transparent viscous polymers was isolated by reprecipitation with ether containing a smal l amount of triethylamine to avoid hydrolysis of the polymer. The obta ined polymers were soluble in chlorobenzene, DMF, and chloroform but i nsoluble in ether and n-hexane. The molecular weights of the polymers obtained from aliphatic dithiols were smaller than those from aromatic ones. The structure of the polymer was determined by comparing the NM R spectra with those of the model compounds, which were obtained by ra dical addition of 1 and benzyl mercaptan. The reaction proceeded throu gh radical polyaddition of dithiol to 1 via radical ring-opening polym erization of the cyclopropane ring. (C) 1997 John Wiley & Sons, Inc.