Synthesis and applications of polyester dendrimers and hyperbranched polymers

Dendrimers are an important new class of macromolecule which have many potential applications from drug delivery to metal extraction. A number of methods have been developed for the synthesis of dendrimers and related hyperbranched polymers. We chose the divergent initiator core method to synthesise three series of dendrimers with phloroglucinol, hydroquinone and naphthalene-2,6-diol as the core moieties, using DCC in the presence of DPTS as the esterification agent. The fluorescence of the naphthalene core was used to investigate the microenvironment of the core. Early investigations indicate there is a marked change in the core’s environment between generations two and four. MALD1-MS was tested as a method for the analysis of dendrimers and hyperbranched polymers. Molecular masses of dendrimers were obtained within 2 Da in every case, although low mass ions are sometimes observed. The origin of the low mass species is not yet entirely clear although there are indications that these arise from both the MALDI-MS process and during synthesis. 'lhe synthesis of poly(3,5-dihydroxybenzoic acid), again using the DCC- DPTS esterification agent was investigated. This method was found to give hyperbranched polymers which were difficult to handle. Studies by MALDI-MS indicate the difficult handling properties are a result of DCC being bound to the hyperbranched polymer. Thus, a modification of Frechet’s method was used to prepare poly(3,5-dihydroxybenzoic acid). It was demonstrated that the hydroxyl terminated dendrimers and hyperbranched polymers could be functionalized at the branch termini with units such as acetyl, pent-4-enoyl, oleoyl and lineoyl. Epoxy terminated dendrimers and hyperbranched polymers were also prepared. The epoxy terminated dendrimers were analysed as potential crosslinking agents for polyester powder coatings. Initial results indicate that the epoxy groups prefer to react with one another rather than with the resin and thus little curing of the resin was observed.