Synthesis And Application Of Thermo-responsive Core Cross-linked Star(CCS) Polymers

Core cross-linked star(CCS)polymers represent a broad class of branched macromolecular architectures with linear “arms” radiating from a central branching point,typically referred to as the “core”.Potential applications of these materials have been demonstrated in drug delivery,catalysis,emulsions and other fields.Polymers that respond with a property alteration towards environmental changes are often referred to as “stimuli-responsive”,“smart”,or “intelligent” materials.In cases where the external trigger is temperature,the polymer is said to exhibit thermo-responsive properties.An interesting feature of thermo-responsive polymer is its temperature dependant solubility in aqueous systems.In this work,a series of thermo-responsive core cross-linked star polymers were successfully prepared,and used for smart catalysis and specific separation of glycoprotein.The experiments showed that the resulting core cross-linked star polymers showed good thermal response behavior.The main contents of this paper are as follows:A series of water-soluble thermo-responsive core cross-linked star polymers(P(PEGA-DEGA)CCS),in which poly(methoxypolyethylene glycol-co-di(ethylene glycol)ethyl ether acrylate)(P(PEGA-DEGA))served as the thermo-responsive arm,and poly(2-(dimethylamino)ethyl methacrylate-co-divinylbenzene)(P(DMAEMA-DVB)as the functionalized core have been successively prepared via reversible addition-fragmentation chain transfer(RAFT)polymerization using the “arm-first” approach.The factors for the core cross-linked star polymers preparation,such as the molar ratio of crosslinking agent and arm,reaction time and space monomer DMAEMA were optimized.The effects of different conditions such as the pH value and the molar ratio of PEGA and DEGA on the LCST of the core cross-linked star polymer were investigated.Owing to the presence of DMAEMA in the core,P(PEGA-DEGA)CCS could reduce HAuCl4 without adding external reducing agent and function as supporting materials to immobilize the in situ formed Au nanoparticles simultaneously,leading to the formation of P(PEGA-DEGA)CCS@Au nanocomposite.The thermosensitive P(PEGA-DEGA)shell with swollen or collapsed properties can tune the aggregation or dispersion of Au nanoparticles,which leads to an increase or decrease of catalytic activity.The obtained P(PEGA-DEGA)CCS@Au was investigated to have a thermally adjustable catalytic activity for the reduction of 4-nitrophenol.A series of water-soluble thermo-responsive core cross-linked star polymers(P(AAPBA-AM)CCS),in which poly(3-acrylamidophenylboronic acid-co-acrylamide)(P(AAPBA-AM))served as the functionalized arm,and poly(N-isopropyl acrylamide-co-styrene-co-N,N'-methylenebisacrylamide)(P(NIPAM-St-Bis))as the thermo-responsive core have been successively prepared via reversible addition-fragmentation chain transfer(RAFT)polymerization using the “arm-first” approach.The effects of different conditions such as the pH value and the amount of styrene on the LCST of the core cross-linked star polymer were investigated.The thermosensitive P(NIPAM-St-Bis)core can tune the aggregation or dispersion of P(AAPBA-AM)CCS and boronic-acid-functionalized arm P(AAPBA-AM),making P(AAPBA-AM)CCS can applied as an enrichment material to selective enrichment of trace glycoproteins.The factors for the sensor preparation,such as the amount of AAPBA and length of arm were optimized.The prepared P(AAPBA-AM)CCS exhibited faster rebinding kinetics(reached saturated adsorption within 20 min),higher adsorption capacity(208 mg/g)and specific recognition behavior toward HRP in adsorption experiment.