Cationic Polymerization of Vinyl Ethers with a Nitrogen or Sulfur Atom-containing Functional Group

To study the possibility of living cationic polymerization of vinyl ethers with a urethane, urea, and tiourethane group (2-vinyloxyethyl phenylcarbamate (1), N-vinyloxyethyl-N'-phenylurea (2), and 2-vinyloxyethyl phenylthiocarbamate (3), respectively) were polymerized with a variety of initiating systems in CH_2Cl_2 at 0～-30℃. The HCl/ZnCl_2-initiated polymerization of vinyl ether 1 proceeded in a living manner to give the polymers with narrow molecular weight distributions (MWDs) (M_w/M_n=～1.2). The poly (1) exhibited relatively high glass transition temperature (55℃) as a vinyl ether polymers. In contrast, polymerization of vinyl ether 2 involved side reactions to produce low-molecular-weight products under the same reaction condition. To examine the effect of the thiourethane group on vinyl ether polymerization, the polymerization of n-butyl vinyl ether was investigated in the presence of a thiourethane model compound ethyl thiocarbamate (4) with the CH_3CH(OiBu)OCOCH_3/SnCl_4 initiating system in CH_2Cl_2 at -30℃. The M_n of the product polymers were in direct proportion to conversion, although their MWDs were somewhat broad (M_w/M_n=～1.5). On the other hand, the polymerization of the vinyl ether 3 produced only low-molecular-weight products