Abstract
This paper reports the first synthesis of A2 + B3 highly branched polyesters with the minimal formation of cyclics in the absence of a polymerization solvent. Highly branched poly(ether ester)s were synthesized in the melt phase using an oligomeric A2 + B3 polymerization strategy. Condensation of poly(propylene glycol) (Mn ∼1060 g/mol) and trimethyl 1,3,5-benzenetricarboxylate in the presence of titanium tetraisopropoxide generated highly branched structures with high molar mass when the reaction was stopped immediately prior to the gel point. Size exclusion chromatography (SEC) and 1H NMR spectroscopy were used to monitor molar mass as a function of monomer conversion and to determine the gel point. Monomer conversions at both the theoretical and experimental gel points for an A2:B3 = 1:1 molar ratio agreed well. Thus, cyclization reactions, which are common in A2 + B3 polymerization in solution, were negligible in the melt phase. The degree of branching (DB) increased with an increase in monomer convers...
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