NEW POLYMER SYNTHESES XCIII - HYPERBRANCHED HOMOPOLYESTERS AND COPOLYESTERS DERIVED FROM GALLIC ACID AND BETA-(4-HYDROXYPHENYL)-PROPIONIC ACID

The hyperbranched homopolyester of gallic acid (GA) was prepared by po lycondensation of acetylated gallic acid in bulk. Copolyesters of gall ic acid and 3-hydroxybenzoic acid (3-HBA) or beta-(4-hydroxyphenyl)pro pionic acid (HPPA) were prepared via the silylated monomers. The degre e of branching was varied in both series via the molar fraction of gal lic acid. A model reaction with silylated 4-methoxybenzoic acid sugges ts that all three acetoxy groups of gallic acid can react by ester int erchange reactions under the chosen reaction conditions. Furthermore, highly branched copolyesters derived from equimolar ratios of HPPA and 2-, 3-, or 4-hydroxybenzoic acid, vanillic acid, or 4-hydroxycinnamic acid were synthesized. All these copolyesters were found to be amorph ous with glass transition temperatures (T-g's) far below that of the h yperbranched poly(gallic acid). (C) 1998 John Wiley & Sons, Inc.