Study On Synthesis And Properties Of Hydrophilic Photosensitive Nanogels By Controlled/living Radical Polymerization

The water-borne polymerization technology has attracted extensively attention in the field of biomaterials due to its high efficiency,economy,environmental protection and energy saving.Photocurable biomaterials prepared by water-borne polymerization technology are broadly used in tissue engineering scaffolds and bone tissue repair.However,the limited water solubility of water-borne photoinitiators and the poor mechanical properties of water-borne photocurable biomaterials greatly limit the practical application of photocurable biomaterials.Therefore,it is of great importance to improve the water solubility of water-borne photoinitiators and the mechanical properties of water-borne photocurable biomaterials.Nanogels that have multi-functional structure,controllable size and chemical composition can be used as organic filler to enhance the mechanical strength of materials without impacting the other properties.The polymer prepared by controlled/living radical polymerization has the features of uniform particle size and narrow molecular weight distribution,which will help to form a uniform polymer network and adjust the mechanical properties of the polymer.The uniform network structure is also conducive to the loading and release of the drug.Based on the above background,we have prepared hydrophilic nanogels by atom transfer radical polymerization(ATRP),and grafted photoinitiators onto hydrophilic nanogels.Hydrophilic photoinitiator-functionalized nanogels not only have excellent water solubility,but also can effectively initiate monomer polymerization and improve the mechanical properties of photocurable biomaterials.In addition,different molecular weight and photoresponsive hydrophilic nanogels were synthesized by reversible addition fragmentation chain transfer radical polymerization(RAFT).The effect of molecular weight and particle size distribution on the loading and release of the coumarin 102-loaded nanogels was investigated in detail.The main research work and conclusions are as follows:1.Three hydrophilic photoinitiator-functionalized nanogels were designed and synthesized through activators generated electron transfer atom transfer radical polymerization(AGET ATRP)in inverse miniemulsion based on oligo(ethylene glycol)monomethyl ether methacrylate(OEOMA),polyethylene glycol dimethacrylate(PEGDMA),2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone(Irgacure2959)and hydroxyethyl methacrylate(HEMA).The structure of three hydrophilic photoinitiator-functionalized nanogels was characterized by proton nuclear magnetic resonance(1H-NMR)and the fourier transform infrared spectra(FTIR).The molecular weight of three hydrophilic photoinitiator-functionalized nanogels was characterized by gel permeation chromatography(GPC).The particle size of three hydrophilic photoinitiator-functionalized nanogels was characterized by transmission electron microscopy(TEM)and dynamic light scattering(DLS).The photopolymerization properties of the nanogels were investigated by UV/vis spectroscopy,electron spin resonance(ESR)and real-time infrared spectroscopy.The influences of nanogels on the viscosity of PEGDMA were also investigated.The results show that the three hydrophilic photoinitiator-functionalized nanogels have controllable molecular weight and uniform particle size.The nanogels present an absorption peak centered at 273 nm in acetonitrile and 277 nm in deionized water.The type of radicals generated under UV is identical as that of Irgacure2959.The nanogels can effectively initiate the polymerization of the monomers.The viscosity increased with the increase of nanogels loading.2.The water solubility and cell viability of nanogels,the mechanical properties,the glass transition temperature,thermostability,surface roughness and photolysis fragment migration of UV-cured films with the nanogels were systematically investigated.The results indicate that three nanogels have excellent solubility in aqueous solution,and the solubility of the nanogels is up to 50 wt%and much larger than that of Irgacure2959(1.5 wt%).Nanogels with uniform particle size and narrow molecular weight distribution can simultaneously improve the tensile strength and elongation at break of UV-cured films.With the addition of the nanogels,the glass transition temperature and thermal stability of UV-cured films were increased.The surface roughness is fairly small and the surface of UV-cured films containing nanogels are dense and smooth.The nanogels can also reduce the migration of photolysis fragments of UV-cured films and have good biocompatibility,leading to a potential application in biomaterial fields.3.Three photoresponsive nanogels with different molecular weight and uniform particle size distribution were successfully synthesized by reversible addition-fragmentation chain transfer radical polymerization(RAFT).The loading capacity,encapsulation efficiency and stimuli-responsive release of nanogels loaded the hydrophobic guest molecule coumarin 102,the UV/vis degradation property,thermostability and cell viability of nanogels were studied in detail.The results show that the increase of the ether chain and the molecular weight of nanogels decreases the loading capacity and encapsulation efficiency.The nanogels have an absorption peak centered at 273 nm in tetrahydrofuran.The cumulative release of the hydrophobic guest molecule coumarin 102-loaded nanogel prepared by RAFT polymerization is greater than that of the nanogel prepared by the conventional radical polymerization,indicating nanogel with uniform particle size and narrow molecular weight distribution facilitate the release of hydrophobic guest molecule.Three nanogels have good thermal stability and biocompatibility.