Synthesis And Properties Of PEG-based Dual-stimulation Responsive Block Polymers

More and more attention is paid to stimuli responsive polymers,due to the widespread application and potential prospect in biomedical,tissue engineering,artificial muscle and drug carriers.With the development of science and technology,a single stimulus response polymer has been unable to meet the needs of society,double stimulus response polymer research gradually increased.2-(2-methoxyethoxy)ethyl methacrylate(MEO2MA)and oligo(ethylene glycol)methacrylate)(OEGMA)are novel temperature-sensitive monomers.The LCST values of the random copolymer P(MEO2MA-co-OEGMA)of these two monomers can be adjusted by changing the feed ratio of MEO2MA and OEGMA.Both MEO2MA and OEGMA are PEG-like polymers and therefore have good biocompatibility and water solubility.Polyethylene glycol(PEG)is one of the few polymers that can be injected into the human body approved by the US Food and Drug Administration(FDA).N-methylolacrylamide(HMAM)is a hydrophilic monomer with a hydroxyl group,which is introduced into a temperature-sensitive polymer to enhance its hydrophilicity,thereby adjusting the LCST of temperature-sensitive polymer.N.N-diethylaminoethyl methacrylate(PDEAEMA)is a pH sensitive monomer which is incorporated into the polymer to impart polymer pH sensitivity.Based on the good biocompatibility and hydrophilicity of PEG.MEO2MA,OEGMA and NIPAM are temperature sensitive monomers.DEAEMA is a pH sensitive monomer.HMAM is a hydrophilic monomer.First,the ABC-type triblock polymer PEG-b-P(MEO2MA-co-HMAM)-b-PDEAEM with pH/temperature double stimulus response was synthesized by reversible addition-fracture chain transfer radical polymerization(RAFT)The properties of the aqueous solution of the triblock polymer,micellization,gelation and the sustained release of bovine serum albumin were studied.Secondly,the double thermoresponsive polymer(MEO2MA-co-OEGMA)-b-PN IPAM-b-PEG-b-PNIPAM-b-P(ME02MA-co-OEGMA)was synthesised by RAFT.The properties and micellization of the pentablock polymer were studied.Specific work is as follows:1.PEG-b-(MEO2MA-co-HMAM)-b-PDEAEMA was synthesized by reversible addition-fragmentation chain transfer radical polymerization(RAFT)method with pH/temperature dual-sensitivity.The structure of the polymer was characterized by 1H NMR and FTIR.The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography(GPC).The pH and temperature sensitivity of the polymer were confirmed by the UV-Vis spectrophotometer and dynamic light scattering measurement.The critical micelle concentration of the polymer was measured by fluorescence probe technique and surface tension meter.The micelles and particle size of the polymer in aqueous solution were studied by transmission electron microscopy(TEM).The sol-gel transition behavior of the polymer was studied by the vial reversal experiment.2.P(ME02MA-co-OEGMA)-b-PNIPAM-b-PEG-b-PNIPAM-b-P(ME02MA-co-O EGMA)was synthesized by reversible addition-fragmentation chain transfer radical polymerization(RAFT)technique using PEG-CTA-PEG as a macromolecule chain transfer agent.1H NMR and FTIR were used to characterize the structure of the polymer.The molecular weight and molecular weight distribution of the polymer were determined by gel permeation chromatography(GPC).The double temperature sensitivity of the polymer was confirmed by the UV-Vis spectrophotometer.The double temperature sensitivity is related to the feed ratio of ME02MA and OEGMA of the P(MEO2MA-co-OEGMA)block.The micellization process of the polymer in water was studied by transmission electron microscopy and fluorescence probe.The CMC values of the polymer in aqueous solution were measured by fluorescence probe technique and surface tension meter.Finally,the reversible change of the particle size of the polymer with temperature was studied,which indicated that the Pentablock polymer had good sensitivity to temperature.