Crystalline stereocomplex formation of isotactic poly(methyl methacrylate) (it-PMMA) and syndiotactic poly(methyl methacrylate) (st-PMMA) induced by high-pressure CO2 at pressures in the 5−35 MPa range and at temperatures in the 30−110 °C range was demonstrated by means of differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) investigations as a function of treatment pressure, temperature, and the it-PMMA/st-PMMA ratio. At a constant it-PMMA/st-PMMA ratio, the melting temperature of the stereocomplexes was shown to increase with increasing treatment pressure and temperature. The amount of the stereocomplex formed by high-pressure CO2 was found to be higher than that by thermal annealing in bulk. The heat of melting of the stereocomplex was the highest for the 1/2−1/1 it-PMMA/st-PMMA ratio. Compared with amorphous PMMA, the crystalline stereocomplex induced by high-pressure CO2 contributes to the superior morphology of the microcellular foams obtained. For the CO2-treated polymer, the average cell size decreases and the average cell density increases as the amount of the stereocomplex that was formed increases.

We have synthesized a hybrid subtilisin the solubility of which can be regulated by photoirradiation through coupling with a photoresponsive copolymer that carries spiropyran groups in its side chains. The copolymer was synthesized by polymerization of methacrylate, methacrylic acid, and spiropyran-carrying methacrylate. It was then covalently bonded to the amino groups of subtilisin Carlsberg via its carboxyl groups using a carbodiimide coupling agent. The hybrid subtilisin was perfectly soluble in toluene and efficiently catalyzed transesterification. After ultraviolet irradiation, the hybrid subtilisin precipitated and was easily and quantitatively recovered by centrifugation. Recovered hybrid subtilisin, resolubilized by visible light irradiation, retained its original transesterification activity even after several cycles of precipitation and solubilization.

Crystalline stereocomplexes of highly stereoregular isotactic poly(methyl methacrylate) (it-PMMA; mm ) 97.2%) and syndiotactic poly(methyl methacrylate) (st-PMMA; rr > 86.1%) blends formed by treatment with supercritical CO 2 at pressures from 5 to 25 MPa and at temperatures in the 30-170 °C range were investigated by means of differential scanning calorimetry (DSC) measurements as a function of treatment temperature, pressure, and it-PMMA/st-PMMA mixing ratio. The ∆H of the stereocomplex had a maximum at 33 wt % it-PMMA content, in agreement with stereocomplexes formed in some solvents and in bulk thermal annealing methods. For the case of over 50% it-PMMA content, two endothermic peaks, T m 1 and Tm 3 , were detected. Examination of the effect of heating rate from 5 to 40 °C/min on the DSC results showed that the melting temperatures, Tm 1 and Tm 3 , corresponded to the fringed micellar structure and the lamellar crystallites of the complexed sections, respectively. For 33% or less it-PMMA content, the crystalline stereocomplex formed by supercritical CO2 had only one endothermic peak that occurred over a narrow temperature range, which was comparable with that obtained by thermal annealing or solvent treatment.

Crystalline stereocomplexes of highly stereoregular isotactic poly(methyl methacrylate) (it-PMMA) and syndiotacitc poly(methyl methacrylate) (st-PMMA) blends formed by treatment with supercritical CO 2 were investigated by means of differential scanning calorimetry (DSC) measurements as a function of PMMA molecular weight. The rates of stereocomplex formation obtained with supercritical CO2 treatment were faster than those obtained by thermal treatment. The higher rates of stereocomplex formation can be attributed to the plasticizing effect of CO2 molecules in the PMMA. The heat of melting of the stereocomplex (∆H) decreased with increasing PMMA molecular weight and was found to be independent of it-PMMA and st-PMMA mixing ratio. For the case of it-PMMA/st-PMMA of 1:1, the stereocomplexes obtained by thermal and CO2 treatment had two endothermic peaks. The relative intensity of the second endothermic peak (∆H3/∆H) decreased with increasing PMMA molecular weight and showed stronger dependence on it-PMMA molecular weight than on the st-PMMA molecular weight.

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