Synthesis of dihydroxy terminated poly(chloroethyl vinyl ether)s by ' living ' cationic polymerization: evidences for side reactions and their control
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This paper reports on the synthesis of dihydroxy terminated poly(chloroethyl vinyl ether)s (PCEVE) via bifunctional living cationic polymerization. The bifunctional chain initiator is obtained by reacting malonaldehyde bis(diethyl acetal) with trimethylsilyl iodide (TMSI) to form the corresponding di-α-iodo ether derivative. The polymerization of chloroethyl vinyl ether is then triggered by ZnCl_2. The direct transformation of active ends into aldehyde terminals, as well as their derivatization into hydroxy groups, is described. The synthesis of high molar mass ditelechelics by bifunctional polymerization provides evidence for the occurrence of a monofunctional side initiation. The latter has been attributed to the hydrolysis of TMSI by adventitious water, which leads to the in situ formation of hydrogen iodide. In order to trap hydrogen iodide, the influence of different additives, bulky amines, metals and alkylaluminiums, was investigated. Therefore, in the presence of alkylalumini-um, it is possible to obtain a clean bifunctional polymerization up to relatively high molar mass ditelechelic PCEVE (M_n = 33000 g/mol, M_w/M_n = 1.11).
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