Dispersion Reversible Chain Transfer Catalyzed Polymerization (Dispersion RTCP) of Methyl Methacrylate in Supercritical Carbon Dioxide: Pushing the Limit of Selectivity of Chain Transfer Agent

We demonstrated a dispersion reversible chain transfer catalyzed polymerization (dispersion RTCP) of methyl methacrylate (MMA) with 1-phenylethyl iodide (PE-I) as chain transfer agent and GeI₄ as catalyst in supercritical carbon dioxide (scCO₂), where the PE-I was known as noneffective chain transfer agent for polymerization of MMA in RTCP. The dispersion RTCP in scCO₂ proceeded with control/livingness. On the other hand, in bulk system (bulk RTCP) and in dispersion iodine transfer polymerization (dispersion ITP) in scCO₂ under the same conditions except for GeI₄, no livingness was maintained. From these results, it was assumed that the reason for the living character in the dispersion RTCP in scCO₂ is based on an accelerated reversible chain transfer reaction in scCO₂. Based on the insight, when the dispersion RTCP of MMA was carried out at higher scCO₂ pressure, poly­(MMA) (PMMA) having a narrower molecular weight distribution was obtained because of the higher degree of PMMA plasticization by scCO₂. Moreover, we advanced the idea to synthesize polystyrene (PS)-b-PMMA, of which synthesis was difficult in homogeneous systems, by seeded dispersion RTCP of MMA with PS-I as macro-chain-transfer agent and GeI₄ as catalyst in scCO₂.