Poly‐(α‐methyl benzyl methacrylate). Preparation and preliminary observations

Abstract

AbstractPoly‐(α‐methyl benzyl methacrylate) (PMBMA) polymers were prepared in isotactic, syndiotactic, and atactic forms using both optically active and racemic monomers. The isotactic material was prepared by anionic polymerization in a hydrocarbon solvent at a low temperature (∼−60°C), the syndiotactic and atactic polymers were synthesized by ultraviolet initiated free radical polymerization at –65 and 32°C, respectively. From the proton magnetic resonance spectrum, it could be determined that the isotactic polymer was of high stereochemical purity. The syndiotactic material was less pure, and the atactic polymer was largely syndiotactic. Racemic and optically active α‐methyl benzyl pivalates were prepared to serve as monomeric analogues of the polymer. The optical activity of the isotactic polymer in dioxane is one‐third greater than that of the monomeric analogue at 5890 Å; the syndiotactic polymer is slightly less optically active than the monomeric analogue, and the atactic polymer is between the syndio‐ and iso‐polymers but much nearer the syndio material. The enhancement or decrease of the optical activity is associated with the orientation correlation of successive chain segments, the specific chemical structure of the optically active group, and on solvent‐polymer interactions. The orientation correlations persist over a short range only.