Energy: Sustainable Materials and Design
Functional polymers are currently attracting tremendous attention because of their use in diverse polymer applications, such as fuel cell membranes, gas separation, biomaterials, and polymer semiconductors. Versatile methods for post-polymerization functionalization are needed for the synthesis of these functional polymers with tailored structural and chemical properties. However, most current polymer functionalization methods work only with a limited range of functionalities, require high temperatures, or use expensive transition-metal catalysts. Herein, a wide-scope, facile, and robust method for post-polymerization functionalization of poly(p-phenylene oxide), or PPO, using azide-alkyne “click” chemistry is presented. PPO, a commercially available polymer with high glass transition temperature and excellent chemical stability, was modified with a diverse array of functional groups through a mild, three-step synthesis. PPO was first brominated using NBS. Azide groups were then substituted for bromine onto the PPO backbone by an sn2 reaction. The resulting polymer finally underwent copper-catalyzed azide-alkyne "click" reactions at room temperature, as well as heat-activated cycloadditions, with a variety of alkyne functionalities. This pathway was used to functionalize poly(p-phenylene oxide) with a diverse set of substrates, including alkane, aromatic, and organometallic moieties. Synthesis of these functional polymers was confirmed by IR and H-NMR analysis. Post-polymerization functionalization by azide-alkyne cycloaddition was thus shown to have high functional group tolerance, be high-yielding, and occur rapidly in mild conditions. This functionalization process is therefore a potentially powerful approach for synthesis of new functional polymer materials.
Second Award of $2,000