Hans R. Kricheldorft, Olaf Stoeber, Dierk Luebbers
Mar 1, 1995
Citations
0
Influential Citations
31
Citations
Journal
Macromolecules
Abstract
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 °C resulted in partial cross-linking, the silylated monomer yielded perfectly soluble hyperbranched polyesters even at 280 °C. Addition of Ti(OPr) 4 as a transesterification catalyst gave lower molecular weights. 1 H 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. 1 H NMR spectroscopy allowed the determination of their average degrees of polymerization. Further star-shaped polyesters with dendritic star arms were prepared by polycondensations of silylated 3,5-diacetoxybenzoic acid with acetylated tetraphenols.