No abstract

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.

Iodine transfer dispersion polymerization (dispersion ITP) with CHI 3 and reversible chain transfer-catalyzed dispersion polymerization (dispersion RTCP) with N-iodosuccinimide of methyl methacrylate were performed successfully in supercritical carbon dioxide medium. Both polymerizations proceeded smoothly to B80% conversion in 6 h and yielded the polymeric product as a powder after venting the reactor. In both syntheses, the number-average molecular weights (M n ) increased with greater conversion. The ratio (M w /M n ) was maintained at comparatively low values throughout the polymerizations; the values of M w /M n were lower in the dispersion RTCP (1.3-1.4) than the dispersion ITP (1.5-1.7). A chain extension test using styrene indicated that the poly(methyl methacrylate) prepared by dispersion ITP and dispersion RTCP had high degrees of livingness (71 and 74%, respectively).

Reversible chain transfer catalyzed polymerization (RTCP) in dispersion polymerization system (dispersion RTCP) of methyl methacrylate (MMA) was performed with N‐iodosuccimide (NIS) as a nitrogen catalyst in supercritical carbon dioxide (scCO2). The solubility of NIS in scCO2 can be controlled by tuning the pressure, and this led to promote NIS partitioning into polymerizing particles. As a result, the molecular weight distribution control was successfully improved by decreasing the NIS solubility in the medium by tuning the scCO2 at a low pressure of 20 MPa. On the other hand, at the same NIS concentration, a solution RTCP of MMA in toluene as a homogeneous polymerization system did not proceed with a controlled/living manner. The importance of NIS partitioning into the polymerizing particles was also confirmed in hexane as well as scCO2 medium. From these results, it was clarified that the NIS catalyst partitioning into the polymerizing particles as main polymerization loci is a key factor to control the molecular weight distribution in the dispersion RTCP of MMA in scCO2. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 613–620

Direct synthesis of micrometer-sized, poly(methyl methacrylate)block-polystyrene (PMMA-b-PS) particles by one-pot, two-step dispersion reversible chain transfer catalyzed polymerization (dispersion RTCP) with nitrogen catalyst was successfully demonstrated in supercritical carbon dioxide (scCO 2 ). The molecular weight distribution was clearly shifted to higher molecular weight side compared to that of PMMA-I prepared in the first step, indicating the successful synthesis of the block copolymer. This was supported by thin-layer chromatographic result. The blocking efficiency, which was obtained from the two numberdistribution curves of molecular weight measured from gel permeation chromatography with dual detectors (refractive index and ultraviolet), was 87%.