Biorenewable Multiphase Polymers
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Megan L. Robertson, Marc A. Hillmyer, Anne-Cécile Mortamet, and Anthony J. Ryan Abstract Hybrid macromolecules composed of two or more covalently connected segments have the ability to self-assemble into nanostructured materials. These fascinating materials are used in applications ranging from footwear to bitumen modification to microelectronics. The number of technologies that utilize or could benefit from multiphase polymers is expanding at a rapid rate. This growth is due to the development of simple scalable synthetic technologies, a deeper understanding of their structure-property relationships, and their effectiveness as low-level additives. As industrial uses of selfassembled polymers become more prevalent, there will be a heightened focus on alternative preparative approaches that do not rely on petroleum feedstocks. Therefore the development of biorenewable multiphase polymers is an important research endeavor. In this article, we will explore the synthesis, self-assembly, and properties of renewable block and graft copolymers that contain aliphatic polyesters, as well as biosourced segmented polyurethanes. These two classes of multiphase polymers are the most promising and practical candidates for implementation in the next generation of sustainable materials.
Introduction The finite supply of petroleum and the environmental impact of petroleum processing have led to an increased emphasis on the use of annually renewable feedstocks for polymeric raw materials.1–3 Annually renewable feedstocks encompass crop sources that can be grown each year as well as bio-based products from, for example, fermentation processes. Over the last decade, there has been explosive growth in the renewable polymer arena, culminating with the production of commercial polymers such as glucose-derived polylactide4 and soybean oil-based polyurethanes (PUs). Now, with the everpresent focus on sustainability, there is a drive to build the polymeric materials we use every day from agricultural resources. The exploitation of renewable resources is now firmly embedded in polymer scientists’ awareness to develop polymers offering attractive and competitive performance portfolios. The basic research underpinnings for this paradigm shift are happening in polymer research and devel-
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opment, and current research emphases have been on efficient processing of annually renewable resources in the biorefinery, the development of new polymers from these purified feedstocks, and identifying renewable routes to the traditional petrochemical-based polymeric materials (e.g., ethanol to ethylene to polyethylene). Examples of relevant polymers derived from agricultural sources are given in Figure 1. Combining two or more chemically distinct monomers into a single macromolecule allows for optimization of the material properties. For example, block copolymers of the rigid but brittle thermoplastic polystyrene and the soft but tough hydrocarbon polyisoprene can produce materials that range from processable elastomers5 to impact-resistant plastics.6
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