Effect of aliphatic chain length on the chemical structures of low molecular weight hyperbranched polyesters

Low molecular weight hyperbranched (HB) polyesters were synthesized via melt polymerization from trimethylolpropane and three aliphatic dicarboxylic acids, namely, succinic acid (SA), adipic acid (AA) and dodecanedioic acid (DA). The degrees of branching (DBs) ranged between 30% and 75% depending on the monomer ratio. Their DB, cyclic index and terminal index were all determined, indicating that the shorter chain HB polyesters PE-SA and PE-AA showed a greater degree of intramolecular cyclization, compared to the longer aliphatic chains within PE-DA. The HB polyesters form stable colloidal suspensions in buffered aqueous media and were found to be pH responsive. The stability of the colloidal suspensions is enhanced by two factors: (1) increasing the aliphatic chain length and (2) increasing the pH of the solution for the same HB polyester