S. Aoshima et al., LIVING CATIONIC POLYMERIZATION OF TERT-BUTYL VINYL ETHER BY ORGANOALUMINUM HALIDES IN THE PRESENCE OF ADDED BASES, Polymer Journal, 26(3), 1994, pp. 335-341
Living cationic polymerization of tert-butyl vinyl ether (TBVE) was ac
hieved by the 1-(isobutoxy)ethyl acetate (1)/Et1.5AlCl1.5 initiating s
ystem in the presence of THF in hexane at - 20-degrees-C. The polymers
had a very narrow molecular weight distribution (M(w)BAR/M(n)BAR less
-than-or-equal-to 1.1), and M(n)BAR increased directly proportional to
the monomer conversion. On the other hand, under conditions suitable
for the living polymerization of isobutyl vinyl ether (e.g., 1/EtAlCl2
initiating system, methyl acetate as added base, temperatures higher
than 0-degrees-C), non-living polymers of TBVE with a broader molecula
r weight distribution were obtained. For the living polymerization of
such a highly reactive monomer as TBVE, combinations of added bases ha
ving stronger basicity, weaker Lewis acid activators, and low temperat
ure turned out to be indispensable. Using this system, the high molecu
lar weight poly(TBVE) with a narrow molecular weight distribution was
also obtained (M(n)BAR = 1.1 x 10(5), M(w)BAR/M(n)BAR = 1.11). The ter
t-butyl groups of the poly(TBVE) were quantitatively deprotected (99.9
%) by bubbling HBr gas, to yield poly(vinyl alcohol). To elucidate the
polymerization characteristics of TBVE, neo-pentyl vinyl ether and th
ree isomers of butyl vinyl ethers (n-butyl vinyl ether, isobutyl vinyl
ether, and sec-butyl vinyl ether) were polymerized, and polymerizatio
n behavior is discussed on the basis of the sterical structures of sid
e alkyl groups.