Living cationic polymerization of vinyl ethers with a bifunctional initiator

Abstract

AbstractA new bifunctional initiator, CF3COOCH(CH3)OCH2CH2OC6H4C(CH3)2C6H4OCH2CH2OCH(CH3)OCOCF3 (2), was prepared from the corresponding divinyl ether and trifluoroacetic acid in carbon tetrachloride at 0°C. The 2/ethylaluminium dichloride (EtAlCl2) initiating system induced well‐defined living cationic polymerizations of isobutyl vinyl ether (IBVE; in hexane CH3(CH2)4CH3) and 2‐acetoxyethyl vinyl ether (2‐vinyloxyethyl acetate, AcOVE; in toluene) at temperatures up to +40°C in the presence of an excess amount of 1,4‐dioxane (an added base for cation stabilization). The number‐average molecular weights (M̄n) of the polymers increased in direct proportion to monomer conversion, continued to increase on addition of fresh monomer, and were close to the calculated values assuming that each molecule of 2 produces one living polymer chain. The bifunctionality of the living polymers was confirmed by comparing the polymerizations with 2 and its monofunctional analog C6H5OCH2CH2OCH (CH3)OCOCF3 (3), and further shown by quenching the living ends with the sodiomalonic ester Na⊕ ⊖CH(COOC2H5)2 to form telechelic polymers with malonate groups. The diester terminals could be transformed into the corresponding carboxylic acids by hydrolysis followed by decarboxylation. Sequential living polymerization of IBVE and AcOVE with the 2/EtAlCl2 initiating system in the presence of 1,4‐dioxane and subsequent hydrolysis of the pendant ester groups led to ABA‐type amphiphilic triblock copolymers where the hydrophilic poly(2‐hydroxyethyl vinyl ether) segment could be either center or outer blocks.