Branched polyesters: recent advances in synthesis and performance

The synthesis, characterization, physical properties, and applications of branched polyesters are discussed. This review describes recent efforts in the synthesis of statistically and tailored branched systems, and performance advantages compared to linear counterparts. In particular, an emphasis is placed on long-chain branching, where the branches are sufficiently long enough to form entanglements. Step-growth polymerization methodologies that employ various combinations of multi and mono-functional groups to achieve different levels of branching are reviewed in detail. The performance of branched polyesters, including behavior in dilute and semi-dilute solutions, and melt and solid-state properties are discussed. The implications of topological parameters including branch length, number of branches, and branching architecture on rheological performance are also reviewed. Although the majority of this review focuses on the synthesis and rheological behavior of branched polyesters, some discussion is devoted to the influence of branching on solid-state properties, sub-micron fiber formation, and controlled biodegradation for drug-delivery applications. Finally, a perspective of future directions in high performance applications for branched polyesters is provided. (c) 2005 Elsevier Ltd. All rights reserved.