Polymer chemistry: Still in control.

T he design of polymeric materials with useful and tunable properties continues to be critical in existing and emerging technologies. Advances in polymer chemistry spanning new polymerization and functionalization methods have enabled the preparation of complex, multifunctional materials. As a result, polymer science has impacted numerous areas such as supramolecular chemistry, nanotechnology, biomaterials, energy and sustainable materials. This influence was evident in the diverse range of topics, from fundamental to applied technological problems, discussed at the Warwick 2012 Polymers conference in July. Joseph DeSimone (University of North Carolina) described developments in top-down nanofabrication to create polymeric microparticles and nanoparticles of various shapes, sizes and compositions. This process, termed particle replication in non-wetting templates (PRINT), uses crosslinkable perfluoropolyethers to create low surface energy, chemically resistant moulds and replicas for nanoimprint lithography 1. These PRINT particles can be prepared in appreciable quantities using roll-to-roll processing methods. A major thrust of the DeSimone group is the use of PRINT particles for biomedical applications — as vehicles for drug delivery, short interfering RNA (siRNA) delivery, prodrug incorporation, and combined chemotherapy and imaging capabilities 2,3. In the realm of materials chemistry, the PRINT process has been used to generate mesoscopic analogues to synthetic macromolecules, termed mesopolymers, which are composed of one-dimensional polymeric materials. Recent efforts have generated segmented mesopolymers with an ABA-triblock composition that incorporates discrete hydrophilic and hydrophobic segments in each block (Fig. 1a) 4. Using the same technique, DeSimone and colleagues could also make rod-like particles that contain one polymeric component, diblock and multiblock systems. The mesoscopic ABA-triblock particles self-assemble at a water/oil interface to form ordered ribbon structures (Fig. 1b). This side-to-side aggregation is a consequence of enthalpic associations between the different polymeric segments — presenting a mesoscopic analogue to self-organization observed on the molecular length scale within block copolymer and micellar systems. On a different note, controlled radical polymerization (CRP) proved to be a widely used tool for the research presented at the conference. The field of CRP, since its inception in the 1990s 5 , has seen the rise of systems including atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization for the preparation of well-defined free radically derived polymers. Kris Matyjaszewski (Carnegie Mellon University), a leading expert on ATRP, discussed developments in CRP. At the heart of his efforts has been the quest for the ideal catalytic system, which has spawned improvements on ATRP, such as …