ALL-AROMATIC HYPERBRANCHED POLYESTERS WITH PHENOL AND ACETATE END-GROUPS - SYNTHESIS AND CHARACTERIZATION

This report describes the synthesis of all-aromatic hyperbranched poly esters with phenol and acetate end groups. The synthesis was based on the melt condensation of the A2B monomers 3,5-bis-(trimethylsiloxy)ben zoyl chloride (2) and 3,5-diacetoxybenzoic acid (3). The trimethylsily l groups of the polyesters from monomer 2 are hydrolyzed during workup , resulting in polymers with phenol terminal groups. Although the acet ate groups of polymers prepared from 3 are quite stable and remain in the polymer, conditions were found where they could be hydrolyzed to g ive a phenolic polymer similar to that obtained from 2. The special st ructure of the monomers results in highly branched (hyperbranched) mat erials with a high number of terminal groups. Comparison of Mark-Houwi nk plots of linear polystyrene and a hyperbranched polyester sample an d Mark-Houwink ''a'' values of less than 0.5 for numerous samples were consistent with highly branched structures. These polyesters are nonc rystaline and are thermally stable to at least 350-degrees-C. As predi cted for such step-growth polymerizations, the molecular weight distri butions broadened significantly at high conversions.