ASYMMETRIC POLYMERIZATION

Asymmetric polymerizations of various monomers were surveyed, classifying them into four categories, and several examples of application were described. Many studies have been reported on asymmetric synthesis polymerization. The problem in this topic is the difficulty in determination of the optical purity of the asymmetric centers; direct determination has been done only for 1,3-diene polymers. The template polymerization method, which is aimed at polymers with a chiral main-chain configuration, seems to be able to realize higher order stereoregulation than those in conventional catalytic polymerizations, although this type of polymerization has the same problem. The template method is also effective in preparation of chiral cross-linked polymers. This method is noteworthy not only as an effective synthetic way but also as a method of recording information on the molecular shape of the template into the structure of the polymer. Optically active polymers with a helical structure have been produced from several types of monomers. Such polymers might be obtainable from other monomers by considering the spatial requirement for a specific conformation. The helical polymers are effectively applied for the HPLC stationary phase, and this is the only successful application of the polymers prepared by asymmetric polymerization. The helical polymers may possibly be utilized for other purposes such as asymmetric polymer catalysts and polymer liquid crystals, in which the specific chiral structure of the polymers may play a significant role. In enantiomer-selective polymerization, a high selectivity was achieved in the polymerization of MBMA with Grignard reagent‒(‒)-Sp initiator systems. Such a drastic improvement is considered to be possible for other enantiomer-selective polymerization systems by devising appropriate catalysts. © 1994, American Chemical Society. All rights reserved.