Living cationic polymerization of vinyl ether with a cyclic acetal group

The living cationic polymerization of 5-ethyl-2-methyl-5-(vinyloxymethyl)1,3-dioxane (1), a vinyl ether with a cyclic acetal unit, was investigated with various initiating systems in toluene or methylene chloride at 0 to -30 degrees C. With initiating systems such as hydrogen chloride (HCl)/zinc chloride (ZnCl2), isobutyl vinyl ether-acetic acid adduct [CH3CH(OiBu)OCOCH3]/tin tetrabromide (SnBr4)/di-tert-butylpyridine (DTBP), and CH3CH(OiBu)OCOCH3/ethylaluminum sesquichloride (Et1.5AlCl1.5)/ethyl acetate (CH3COOEt), the number-average molecular weights (M.'s) of the obtained poly(1)s increased in direct proportion to the monomer conversion and produced polymers with relatively narrow molecular weight distributions [MWDs; weight-average molecular weight/number-average molecular weight (M,/M-n) = 1.2-1.3]. To investigate the living nature of the polymerization with CH3CH(OiBu)OCOCH3/SnBr4/DTBP, a second monomer feed was added to the almost polymerized reaction mixture. The added monomer was completely consumed, and the M-n values of the polymers showed a direct increase against the conversion of the added monomer, indicating the formation of a long-lived propagating species. The glass transition temperature and thermal decomposition temperature of poly(1) (e.g., Mn = 13,600, M-w/M-n = 1.30) were 29 and 308 degrees C, respectively. The cyclic acetal group in the pendants of the polymer of 1 could be converted to the corresponding two hydroxy groups in a 65% yield by an acid-catalyzed hydrolysis reaction. (c) 2007 Wiley Periodicals, Inc.