Add time:07/30/2019         Source:sciencedirect.com

Three monomers were prepared from 4,4-bis(4′-hydroxyphenyl)valeric acid (BHVA) namely its methylester (BHVAM), its bis-acetylated methylester (BAVAM) and its 4,4-bis(4′-acetoxyphenyl)valeric acid (BAVA). All three monomers were polycondensed in bulk at various temperature profiles using Ti(OBu)4, Co(OAc)2, Mn(OAc)2, Sn(OAc)2 or Bu2Sn(OAc)2 as transesterification catalysts. The structure of the resulting ‘hyperbranched’ polyesters were characterized by 1H NMR spectroscopy, MALDI-TOF mass spectroscopy and in selected cases by SEC. Regardless of the reaction conditions only low oligomers almost free of cycles were obtained from the methylesters BHVAM and BAVAM. Higher molecular weights and high contents of cycles were obtained from polycondensations of BAVA. The content of cycles increased with the conversion. Hyperbranched polyesters with cyclic core were detected up to masses around 10,000 Da. The reactivities of the three hyperbranched monomers were compared with those of bisphenol-A plus dimethyl sebacate or acetylated bisphenol-A plus sebacic acid in ‘linear polycondensations’ and close analogies were found.

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