Effect of solvents and initiators on the cationic copolymerization of 1,3-dioxolane with 5-methyl-2,3-dihydro-2-furanone

The cationic copolymerization of 1,3-dioxolane ( 1 ) with 5-methyl-2,3-dihydro-2-furanone ( 2 ) which has two functional groups, a carbon-carbon double bond and a lactone ring, was carried out with three triethyloxonium salts (Et₃O⁺Y^?, Y^?: BF, FeCl and SbCl), with the boron trifluoride ethyl ether complex, and with tin tetrachloride in nitrobenzene, dichloromethane, and toluene at 0°C. On the basis of the NMR analysis of the microstructure of the copolymer, it was revealed that the growing species of 1 attacked exclusively the carbon-carbon double bond of 2 in the cross-propagation from 1 to 2 , regardless of the solvents and initiators used, except when triethyloxonium hexachloroantimonate was used as initiator. With the latter initiator, the ring opening reaction of 2 by the attack of the growing species of 1 occurred competitively with the usual vinyl addition, although the latter mode of reaction was predominant. The ring opening reaction of 2 with this initiator is probably caused by some specific interaction of monomer 2 with the counter anion.