Hyperbranched polymers: from synthesis to applications

Over the past 15 years, hyperbranched polymers have received much attention due to their unique chemical and physical properties as well as their potential applications in coatings, additives, drug and gene delivery, macromolecular building blocks, nanotechnology, and supramolecular science. Hyperbranched polymers can be prepared by means of single-monomer methodology (SMM) and double-monomer methodology (DMM). In SMM, the polymerization of an AB, or latent AB(n) monomer leads to hyperbranched macromolecules. SMM consists of at least four components: (1) polycondensation of AB(n) monomers; (2) self-condensing vinyl polymerization; (3) self-condensing ring-opening polymerization; (4) proton-transfer polymerization. In DMM, direct polymerization of two suitable monomers or a monomer pair gives rise to hyperbranched polymers. A classical example of DMM, the polymerization of A(2) and B-n (n > 2) monomers, is well known. Recently, a novel DMM based on the in situ formation of AB(n) intermediates from specific monomer pairs has been developed. This form of DMM is designated as 'couple-monomer methodology' (CMM) to clearly represent the method of polymerization. Many commercially available chemicals can be used as the monomers in these systems, which should extend the availability and accessibility of hyperbranched polymers with various new end groups, architectures and properties. Because a number of comprehensive reviews have been published on SMM, research involving DMM is emphasized here. In addition, recent developments in the modification, functionalization and application of hyperbranched polymers are described. (C) 2004 Elsevier Ltd. All rights reserved.