Enzymatic Catalysis For RAFT Polymerization And Bio-Click Reaction To Prepare Precision Polymers

Enzymatic catalysis is a green,efficient and selective catalytic technology,which has a wide range of applications in biotechnology,organic synthesis and polymer chemistry.Taking advantage of the unique properties of enzyme catalysis for synthesis and functionalization of polymer materials is a sustainable strategy and may open up an exciting new direction in polymer chemistry.In this dissertation,horseradish peroxidase?HRP?was used as a green catalyst to efficiently catalyze reversible addition-fragmentation chain transfer?RAFT?polymerization,thiol-ene and Diels-Alder reactions to precisely prepare well-defined polymers.A novel strategy that employing pyranose-2-oxidase?P2Ox?for deoxygenation and HRP for radical generation has been developed for the RAFT syntheses of ultra-high molecular weight?UHMW?PDMAs and polymer nanoparticles.The polymer materials were characterized and analyzed by ¹H NMR,GPC,UV,IR and DLS.Specifically,we have demonstrated a new concept in polymer chemistry that employing the promiscuity of HRP for efficient and versatile synthesis and modification of well-defined polymers.The new concept of one-enzyme triple catalysis includes:1.HRP-initiated RAFT polymerization:HRP catalyzes oxidation of ACAC by H₂O₂ to generate ACAC radicals,which subsequently initiate well-controlled RAFT polymerization in the presence of chain transfer agents?CTAs?.Finally,we obtained threekindsofpolymermaterialsincludingPDMA₉₇-co-PALAM₁₁,PDMA₁₄₄-co-PHEA₃₆and PPEGMA₅₈polymer materials.2.HRP-catalyzed thiol-ene click reaction:HRP catalyzes H₂O₂ to generate hydroxyl radicals,which subsequently initiate thiol-ene click reactions of mercaptoethanol and the vinyl group.Correspondingly,three polymer materials of PDMA₉₇-co-PALAM-S,PDMA₁₄₄-co-PHEAA₁₈-S and PPEGMA₃₇-S were obtained.3.HRP-mediated Diels-Alder click reaction:HRP catalyzes oxidation of dihydrotetrazine to produce tetrazine compound in the presence of oxygen,and the tetrazine compound further reacts with norbornene on the side chains of the polymers to obtain PDMA₁₄₄-co-PHEAA₁₆-Tz and PPEGMA₃₆-Tz.The P2Ox-HRP enzymatic cascade catalysis strategy was engaged in RAFT for the synthesis of well-defined polymeric materials with excellent oxygen tolerance.Generally,P2 Ox consumes oxygen with glucose to generate H₂O₂,which is subsequently utilized by HRP to produce ACAC radicals to initiate RAFT polymerization.Herein,RAFT polymerization carried out in air includes:1.Synthesis of UHMW PDMAs.UHMW PDMAs with different DPs of 9300,18800 and 27000 were finally obtained by the P2Ox-HRP enzymatic cascade catalysis.All MWs determined by GPC were close to theoretical values and dispersities were relatively low?D?1.37?.2.One-pot synthesis of block copolymer nanoobjects via RAFT dispersion polymerization.2-methoxyethyl acrylate?MEA?and diacetone acrylamide?DAAM?were chosen as the monomers for RAFT dispersion polymerization employing water-soluble PAML macro-CTAs to obtain three types of PAML-b-PMEA,PAML-b-PDAAM and PAML-b-P?DAAM-co-DMA?nanoobjects.