SYNDIOTACTIC POLY[(R,S)-BETA-HYDROXYBUTYRATE]ISOLATED FROM METHYLALUMINOXANE-CATALYZED POLYMERIZATION

Poly[(R,S)-A-hydroxybutyrate] was prepared via the methylaluminoxane-catalyzed polymerization of (R,S)-beta-butyrolactone, fractionated, and characterized by H-1 and C-13 nmr, gel permeation chromatography, differential scanning calorimetry, and x-ray diffraction. All the material isolated from these reactions was identified by nmr as poly(beta-hydroxybutyrate), but in each case, C-13 nmr showed that a portion of the material contained more syndiotactic than isotactic diads. Although this new syndiotactic material was low in molecular weight, it showed crystallinity by differential scanning calorimetry and x-ray diffraction, with d-spacings different in value and relative intensity from those of the isotactic polymer.