Chemical and Biomolecular Engineering - Research Publications
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ItemFenton-RAFT Polymerization: An "On-Demand" Chain-Growth Method(WILEY-V C H VERLAG GMBH, 2017-05-29)Fine control over the architecture and/or microstructure of synthetic polymers is fast becoming a reality owing to the development of efficient and versatile polymerization techniques and conjugation reactions. However, the transition of these syntheses to automated, programmable, and high-throughput operating systems is a challenging step needed to translate the vast potential of precision polymers into machine-programmable polymers for biological and functional applications. Chain-growth polymerizations are particularly appealing for their ability to form structurally and chemically well-defined macromolecules through living/controlled polymerization techniques. Even using the latest polymerization technologies, the macromolecular engineering of complex functional materials often requires multi-step syntheses and purification of intermediates, and results in sub-optimal yields. To develop a proof-of-concept of a framework polymerization technique that is readily amenable to automation requires several key characteristics. In this study, a new approach is described that is believed to meet these requirements, thus opening avenues toward automated polymer synthesis.
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ItemSono-RAFT Polymerization in Aqueous Medium(WILEY-V C H VERLAG GMBH, 2017-09-25)The ultrasonic irradiation of aqueous solution is demonstrated to be a suitable source of initiating radicals for a controlled radical polymerization when conducted in the presence of a thiocarbonylthio-containing reversible addition-fragmentation chain transfer (RAFT) agent. This allows for a highly "green" method of externally regulated/controlled polymerization with a potentially broad scope for polymerizable monomers and/or polymer structures.
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ItemFenton-Chemistry-Mediated Radical Polymerization(Wiley, 2019-09-01)In this review, the power of a classical chemical reaction, the Fenton reaction for initiating radical polymerizations, is demonstrated. The reaction between the Fenton reagents (i.e., Fe2+ and H2O2) generates highly reactive hydroxyl radicals, which can act as radical initiators for the polymerization of vinyl monomers. Since the Fenton reaction is fast, easy to set up, cheap, and biocompatible, this unique chemistry is widely employed in various polymer synthesis studies via free radical polymerization or reversible addition–fragmentation chain transfer polymerization, and is utilized in a wide range of applications, such as the fabrication of biomaterials, hydrogels, and core‐shell particles. Biologically activated Fenton‐mediated radical polymerization, which can be performed in aerobic environments, are particularly useful for applications in biomedical systems.
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ItemBlood-Catalyzed RAFT Polymerization(WILEY-V C H VERLAG GMBH, 2018-08-06)The use of hemoglobin (Hb) contained within red blood cells to drive a controlled radical polymerization via a reversible addition-fragmentation chain transfer (RAFT) process is reported for the first time. No pre-treatment of the Hb or cells was required prior to their use as polymerization catalysts, indicating the potential for synthetic engineering in complex biological microenvironments without the need for ex vivo techniques. Owing to the naturally occurring prevalence of the reagents employed in the catalytic system (Hb and hydrogen peroxide), this approach may facilitate the development of new strategies for in vivo cell engineering with synthetic macromolecules.
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ItemA novel solid state photocatalyst for living radical polymerization under UV irradiation(Nature Publishing Group: Open Access Journals - Option C, 2016-02-11)This study presents the development of a novel solid state photocatalyst for the photoinduced controlled radical polymerization of methacrylates under mild UV irradiation (λmax ≈ 365 nm) in the absence of conventional photoinitiators, metal-catalysts or dye sensitizers. The photocatalyst design was based on our previous finding that organic amines can act in a synergistic photochemical reaction with thiocarbonylthio compounds to afford well controlled polymethacrylates under UV irradiation. Therefore, in the current contribution an amine-rich polymer was covalently grafted onto a solid substrate, thus creating a heterogeneous catalyst that would allow for facile removal, recovery and recyclability when employed for such photopolymerization reactions. Importantly, the polymethacrylates synthesized using the solid state photocatalyst (ssPC) show similarly excellent chemical and structural integrity as those catalysed by free amines. Moreover, the ssPC could be readily recovered and re-used, with multiple cycles of polymerization showing minimal effect on the integrity of the catalyst. Finally, the ssPC was employed in various photo-"click" reactions, permitting high yielding conjugations under photochemical control.
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ItemBeyond Traditional RAFT: Alternative Activation of Thiocarbonylthio Compounds for Controlled Polymerization(WILEY, 2016-09)Recent developments in polymerization reactions utilizing thiocarbonylthio compounds have highlighted the surprising versatility of these unique molecules. The increasing popularity of reversible addition-fragmentation chain transfer (RAFT) radical polymerization as a means of producing well-defined, 'controlled' synthetic polymers is largely due to its simplicity of implementation and the availability of a wide range of compatible reagents. However, novel modes of thiocarbonylthio activation can expand the technique beyond the traditional system (i.e., employing a free radical initiator) pushing the applicability and use of thiocarbonylthio compounds even further than previously assumed. The primary advances seen in recent years are a revival in the direct photoactivation of thiocarbonylthio compounds, their activation via photoredox catalysis, and their use in cationic polymerizations. These synthetic approaches and their implications for the synthesis of controlled polymers represent a significant advance in polymer science, with potentially unforeseen benefits and possibilities for further developments still ahead. This Research News aims to highlight key works in this area while also clarifying the differences and similarities of each system.