Long-chain branched random poly (butylene adipate-co-ethylene terephthalate) tetrapolymers: synthesis and rheological properties

A set of long-chain branched (LCB) random aliphatic-aromatic tetrapolymers with tailored properties were synthesized. Three branching agents including trimellitic anhydride (TMA), trimethylolpropane (TMP), and pentaerythritol (PER) were used to investigate the effects of the chemical structure and functionality of the branching agent on the properties of the LCB copolyesters. Among the branching agents, the influence on the rheological properties can be sorted as PER TMP TMA. In other words, PER with 4 analogous active alcohol sites had the most branching efficiency and influence on the properties. Although both TMP and TMA have potentially three active sites, the reactivity of the TMA may be less than TMP due to the adjacency of the active sites and hindrance effects.