POLYSTEREOISOMERS WITH 2 STEREOGENIC CENTERS OF MALIC-ACID 2-METHYLBUTYL ESTER CONFIGURATIONAL STRUCTURE PROPERTIES RELATIONSHIP/

Poly(beta-malic acid alkyl esters) with two stereogenic centers have b een synthesized by anionic ring-opening polymerization of racemic and optically active 4-[(2-methylbutyl)oxycarbonyl]-2-oxetano and characte rized. The two asymmetric centers have been introduced in the monomer by using malic acid or aspartic acid enantiomers as chiral synthons an d 2-methyl-1-butyl alcohol enantiomers as lateral ester groups. By com bining the different enantiomers during the beta-substituted beta-lact one synthesis route, it has been possible to prepare five stereoisomer s which have conducted to five different stereocopolymers. The configu rational structure of racemic and optically active poly(2-methylbutyl beta-malates) has been determined by C-13 NMR analysis, and differenti ation between polydiastereoisomers has been possible by using this spe ctroscopy method. Several main-chain and side-chain carbon atoms were stereosensitive to the presence of the two asymmetric centers per repe at unit, and the optical purities of main-chain and side-chain stereog enic centers have been deduced from C-13 NMR spectra. Thermal properti es of the different polystereoisomers have been correlated with the co nfiguration of the two chiral sites in the macromolecular chain. It ha s been shown that crystallinity was dependent on the configurational s tructure of the main chain and very poorly sensitive to the enantiomer ic composition of the ester pendant group.