SUMMARY: Diethyl L-aspartate was polymerized by proteinase at a temperature between 4 and 50 8C to yield poly(ethyl a,b-L-aspartate). Bulk polymerization of diethyl L-aspartate, especially at temperatures between 40 and 50 8C, and preferably using alkalophilic proteinase with the addition of a small amount of water gave poly(ethyl L-aspartate) as a white powder with a molecular weight of up to 3 600 and having about 88% a-linkages.
It is well-known that a mixture of isotactic and syndiotactic polymethyl methacrylate (PMMA) forms a stereocomplex consisting of a multihelical structure in which an isotactic chain is surrounded by a syndiotactic chain. Here, we report the basic structure of the stereocomplex formed when the syndiotactic PMMA chains are tethered to a silicon substrate and form a high-density polymer brush. The influence of geometric confinement was investigated by preparing the high-density polymer brushes on a flat and spherical substrate. In both cases, mixing the untethered isotactic PMMA with the grafted syndiotactic PMMA led to the formation of a stereocomplex with a multihelical structure. Static contact angle measurements showed a hindered surface mobility at the outermost surface of the polymer brush, indicating that the stereocomplex forms a crystalline structure. A syndiotactic polymer brush with substituted fluoroalkyl groups was prepared to increase the contrast for grazing incidence wide-angle X-ray diffraction (GIWAXD) measurements. The GIWAXD results verified that the stereocomplex forms a crystalline structure oriented perpendicular to the substrate with a relatively low degree of orientation.
This study investigates the effect of ionic liquids (ILs) on the anionic polymerization of methyl methacrylate (MMA). Polymethyl methacrylate (PMMA), an isotactic polymer, is prepared by anionic polymerization at a high reaction temperature with an IL that acts as both solvent and additive. The most plausible reaction mechanism is determined using 1H NMR and Fourier‐transform infrared spectroscopy. The electrostatic interaction between MMA and the IL increases the apparent steric hindrance in MMA, resulting in the isotactic PMMA.
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