Synthesis of thermally‐induced phase separating polymer with well‐defined polymer structure by living cationic polymerization. I. Synthesis of poly(vinyl ether)s with oxyethylene units in the pendant and its phase separation behavior in aqueous solution

Abstract

Living cationic polymerization of alkoxyethyl vinyl ether [CH 2CHOCH 2 CH 2 OR; R: CH 3 (MOVE), C 2 H 5 (EOVE)] and related vinyl ethers with oxyethylene units in the pendant was achieved by 1‐(isobutoxy)ethyl acetate (1)/Et 1.5 AlCl 1.5 initiating system in the presence of an added base (ethyl acetate or THF) in toluene at 0°C. The polymers had a very narrow molecular weight distribution (M̄w/M̄n = 1.1–1.2) and the M̄n proportionally increased with the progress of the polymerization reaction. On the other hand, the polymerization by 1/EtAlCl 2 initiating system in the presence of ethyl acetate, which produces living polymer of isobutyl vinyl ether, yielded the nonliving polymer. When an aqueous solution of the polymers thus obtained was heated, the phase separation phenomenon was clearly observed in each polymer at a definite critical temperature (Tps). For example, Tps was 70°C for poly(MOVE), and 20°C for poly(EOVE) (1 wt % aqueous solution, M̄n ∼ 2 × 10 4). The phase separation for each case was quite sensitive (Δ Tps = 0.3–0.5°C) and reversible on heating and cooling. The Tps or ΔTps was clearly dependent not only on the structure of polymer side chains (oxyethylene chain length and ω‐alkyl group), but also on the molecular weight (M̄n = 5 × 10 3‐7 × 10 4) and its distribution. © 1992 John Wiley & Sons, Inc.