Enzymes are essential to many reactions in vivo and in benchtop synthesis, but the use of enzymes in synthetic chemistry sometimes faces limitations with respect to solubility, stability, and scalability. Post-synthetic modifications of polymers can be used to target a wide array of structured materials, making them tunable scaffolds that have the potential to mimic enzymes’ protein scaffolds. Our lab is interested in the construction of a system including a structured polymer scaffold directly bound to a transition metal catalyst. We hypothesize that the polymeric environment will alter the reactivity at the catalytic metal center compared to a free small molecule catalyst. This project focuses on synthesizing star polymers by an arm-first approach with reversible addition-fragmentation chain transfer (RAFT) polymerization. RAFT was chosen due to high tolerance of functional groups without chemically changing the metal “active site” that will be inserted into the core. RAFT is used to synthesize the linear polymer “arms” - forming the corona of the star polymer - and then covalently connect them through a reinitiation of the polymerization with cross-linkers as comonomers - forming the core of the star polymer. NMR spectroscopy helps determine linear polymer size by end-group analysis and GPC determines relative molecular weight, dispersity of our linear and star polymers, and the number of arms per star (using a multi-angle light scattering detector). The choice of star polymers as the scaffold is motivated by the highly crosslinked core, which allows us to embed the transition metal complex with high control of the microenvironment around that active metal center.Tuning aspects of the synthesis grants access to well-defined star polymers that we will use as scaffolds for catalysis.

Arm-first synthesis of styrenic and acrylamide-based star polymers by RAFT polymerization for enzyme mimics

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