Stereospecific anionic polymerization of chiral benzyl ?-[(1-phenylethoxy)methyl]acrylate

Abstract

A novel chiral monomer, benzyl α‐[(1‐phenylethoxy)methyl]acrylate was synthesized, and the stereoregularity and chiroptical property of the polymers obtained by radical and anionic polymerizations were investigated. Anionic polymerization in toluene provided a polymer with high isotacticity regardless of optical purity of the monomer and difference of counter cations, Li+ and Mg2+, while radical polymerization appears to yield an atactic polymer. The isotactic copolymers anionically obtained from a mixture of (R)‐ and (S)‐monomers showed peak splitting probably due to the triad arrangement of (R) and (S) groups of side chains in the resonance of 13C‐NMR spectra. The isotactic polymer prepared from enantiomerically pure (R)‐monomer ([α] 25 365 = +157°) with n‐BuLi in toluene exhibited higher specific rotation ([α] 25 365 = +262°) than that of the radical polymer ([α] 25 365 = +162°). This may be explained by regular arrangement of optically active groups along the polymer chain of the isotactic polymer. Chirality 10:711–716, 1998. © 1998 Wiley‐Liss, Inc.

Strategy for rational control of stereosequence in free radical polymerization of acrylates

“…Another catalyst, for instance, should be necessary to obtain a polymer with designed tacticity even in an anionic polymerization. Among chain polymerizations, in particular, tacticity control is much more difficult in a radical polymerization . Up to now there have been a lot of attempts to attain such a stereocontrol, and some progresses have been made in radical polymerizations in physically restricted systems including matrix, intercalation, and inclusion media, and the polymerization using Lewis acids or alcohols as a complexing or solvating agent, and also using bulky monomers .…”

“…Among chain polymerizations, in particular, tacticity control is much more difficult in a radical polymerization. 5 Up to now there have been a lot of attempts to attain such a stereocontrol, and some progresses have been made in radical polymerizations in physically restricted systems including matrix, intercalation, and inclusion media, and the polymerization using Lewis acids or alcohols as a complexing or solvating agent, and also using bulky monomers. 6 However, the isotacticity (mm) of poly(MMA), for instance, increased only from 8% to 18% by complexation with SnCl 4 (MMA/SnCl 4 5 2/1) in the polymerization at 278 8C under c-ray irradiation.…”