Properties of polymers depend not only on their molecular weight or composition, but also on the stereochemical arrangement of substituents. Stereoregular polymers are usually prepared by heterogeneous polymerization and are limited to a few systems. We plan to synthesize and to study various properties of polymers which will contain stereocenters in the main and in side chains, We expect that in some systems polymers which will contain stereocenters in the main and in side chains. We expect that in some systems chirality of substituents may affect the microstructure and also may lead to control of the direction of polymer helical structure. The latter case will be very important for polysilanes which have promising nonlinear optical properties. The first part of the larger proposal is focused, however, on cationic polymerization. Recently a few systems leading to well-defined polymers by cationic polymerization of alkenes have been reported. They are based either on the combination of the strongly nucleophilic anion with an activator such as Lewis acid, or on the addition of relatively strong nucleophiles, such as aromatic amines or ethers. In both these systems, the lifetime of the carbenium ion is very short, and it remains in dynamic equilibrium with prevailing covalent active centers or onium ions. Polymerization is much slower than in the typical cationic system but the transfer and termination reactions are suppressed. Cationic polymerization of alkenes leads usually to atactic polymers. The presence of chiral center in the closest surrounding of active site may induce asymmetric control in the propagation step. Therefore, the proportion between meso and racemic diads should by dependent on the chirality of the counterion or nucleophilic additive. We plan to prepare optically active 1-phenylethyl acetates, such as phenylpropionate or chloropropionate, and use them as initiators in the polymerization of styrenes and vinyl ethers. The NMR studies of microstructure of resulting polystyrenes and poly(vinyl ethers) should give not only better understanding of mechanism of living cationic polymerization, but also yield polymers with controlled tacticity and potential industrial importance.
