NEW POLYMER SYNTHESES .78. STAR-SHAPED AND HYPERBRANCHED POLYESTERS BY POLYCONDENSATION OF TRIMETHYLSILYL 3,5-DIACETOXYBENZOATE

3,5-Diacetoxybenzoic acid and its trimethylsilyl ester were polycondensed in bulk at various temperatures to optimize the reaction conditions. Whereas polycondensations of the free acid above 250 degrees C resulted in partial cross-linking, the silylated monomer yielded perfectly soluble hyperbranched polyesters even at 280 degrees C. Addition of Ti(OPr)(4) as a transesterification catalyst gave lower molecular weights. H-1 NMR spectroscopy indicates a degree of branching around 0.5 regardless of the reaction conditions. GPC measurements revealed M(w)/M(n) ratios > 5 and weight-average molecular weights (M(w)) up to 700 x 10(3). Copolycondensations with acetylated Bisphenol-P yielded star-shaped hyperbranched polyesters. Their molecular weight can be varied by the feed ratios of monomer and comonomer. H-1 NMR spectroscopy allowed the determination of their average degrees of polymerization. Further starshaped polyesters with dendritic star arms were prepared by polycondensations of silylated 3,5-diacetoxybenzoic acid with acetylated tetraphenols.