Study On Synthesis And Properties Of Self-initiating Nanogels

Photopolymerization technology is an environment-friendly technology that has low energy consumption and fast polymerization rate.However,photopolymerizable materials have shortcomings of volumetric shrinkage and the migration of low molecular weight photo initiators.These shortcomings restrict the application of photopolymerization technology.Therefore,reducing the volume shrinkage of photopolymers and the migration of low molecular weight photoinitiators to prepare more environment-friendly materials has great significance.We have introduced benzophenone into nanogels and synthesized five kinds of self-initiating nanogel.Meanwhile,we have synthesized nanogels with the uniform particle size distribution and controlled molecular weight and low polydispersities through emulsion polymerization based on Atom Transfer Radical Polymerization(ATRP)mechanism.The effect of particle size and PDI of the nanogels on the performance of UV-curable systems was systematically investigated.The main research work and the conclusions are as follows:1.Five kinds of self-initiaitng nanogels were synthesized based on dual-end terminated methacrylate-modified polysiloxane,isobornyl methacrylate(IBMA),urethanedimethacrylate(UDMA),2-isocyanatoethyl methacrylate(IEM)and 4-hydroxybenzophenone(HBP).Their structures were characterized by proton nuclear magnetic resonance(’H NMR),Fourier transform-infrared spectroscopy(FTIR),transmission electron microscopy(TEM),gel permeation chromatography(GPC)and dynamic light scattering(DLS).Their properties of initiating photopolymerization were studied by ultraviolet absorption spectroscopy,laser flash photolysis,electron spin resonance(ESR)and real-time infrared spectroscopy.The results show that the five kinds of self-initiaitng nanogels all appear microspheres.Polydispersity index,particle size and the molecular weight of the nanogels increased with the increase of benzophenone content.The all of nanogels have an absorption peak centered at 275 nm.They have longer triplet lifetime compared with the benzophenone.The self-initiaitng nanogels can produce amino radicals,aminoalkyl radicals and thioalkyl radicals to effectively initiate polymerization under UV irritation.2.The influences of the self-initiating nanogels on the viscosity,shrinkage,physical and mechanical properties,glass transition temperature(Tg),thermostability,surface properties and migration photolysis fragments of triethylene glycol dimethacrylate(TEGDMA)UV-curable systems were investigated in detail.The results indicate that when the nanogels were added at 10-20 wt%,the viscosity of TEGDMA systems with the nanogels was minimal;when addition amount of the nanogels reached 30wt%,the viscosity increased obviously.With the increase of particle size and molecular weight of the nanogels,the viscosity increased sharply.The nanogels can effectively reduce the volume shrinkage and increase the thermal stability and hydrophobicity of cured films.With the increase of the nanogels,Tg and elongations at break of UV-cured films were increased,while the tensile strength of UV-cured films was decreased.The nanogels prevented the migration of fragments from the photopolymers.3.Three kinds of nanogels with the uniform particle size distribution and controlled maolecular weight were synthesized through emulsion polymerization based on ATRP.The viscosity of the nanogels and the physical and mechanical properties,glass transition temperature(Tg),thermostability,surface contact angle and surface energy,surface topography and migration of photolysis fragments of TEGDMA UV-cured films with the nanogels were studied.The results show that with the increase of the content and particle size of nanogel,the viscosity of the TEGDMA systems increased.However,the more uniform particle size distribution of the nanogels is,the lower viscosity of the system with the nanogels is.With the addition of the nanogels with the uniform particle size distribution into TEGDMA,the contact angle of the TEGDM cured films increased,and the surface energy and the water absorption decreased.The smaller particle size and the more uniform particle size distribution,the better toughening,compacting and hydrophobic properties of the UV-cured films are.The TEM and EDS tests show that TEGDMA UV-cured films with the nanogels have obvious irregular bulges that were caused by the aggregation of organic silicone.