Preparation Of Nanosilica Particles And The Application In Photopolymerization

Silica particles,as an important functional material,are widely used in photopolymerization.They can play an important role in enhancing mechanical properties,thermal properties and aging resistance.At present,a great deal of effort has been made to solve the uniformity dispersion problem of inorganic phase and polymer organic phase.However,few reports have been made on the special properties of heterogeneous dispersion of in polymers.This paper based on heterogeneous dispersion,the surface of silica particles was modified,and realized the photopolymerization gradient distribution system,resulting in the enrichment of silica particles on the surface and improving the material surface mechanical properties at the same time.Specifically,the surface migration of fluorocarbon chains and acetophenone groups were induced into the particle surface,resulting the surface enrichment of initiator,the low initiator content in the system was on duty for polymerization.The oxygen inhibition in polymerization was overcome.By induce crosslinking double bond into particle surface,the particles was covalent bonded to the polymer network,realized the stability of inorganic organic composite materials,and further enhanced the surface properties.Acetophenone groups,fluorocarbon chain and double bond give the particles properities like migration,photoinitiation and crosslinking.In addition,the micron-scale photoinitiatable particles were prepared,and the gradient,photoinitiator-free polymer was prepared.The main research contents and conclusions are as follows.1.Nanosilica particles was surface modified by fluorinated and silanated coupling agent,and the photochemical properities of the particles were studied.Results showed that this particle could be used as crosslinker in free radical photopolymerization and could migrate to the air-liquid surface.The final double bond conversion could be 60%.Large amount of SiO2 would gather at the coating surface which would lead to improvement of surface properities.The results indicated that the wettability and hardness of the cured coating were enhanced due to the introduction of nanosilica particles.With 1 wt%,the hardness of poly(methacrylic acid,two methylamine(DMAEMA))coating can be increased from 3B to 2H.2.Two fluorine-and silane-containing photoinitiators were synthetized and they would provide a method to check the activity differences between benzoyl radicals and hydroxyalkyl radicals.XPS and RTIR were used to study the radical activities,and the results showed that hydroxyalkyl radicals were more active than benzoyl radicals towards acrylates.This simple method could be used in other radical research and find its application in surface modifications.3.Then,rmigratory photoinitiatable nanosilica particles were prepared and its photochemical properties were studid.These nanosilica could be used as migratory photoinitiators and oxygen inhibition was reduced.The final double bond conversion could be 80%.This was because the particles would migrate to the surface and consume oxygen after radiation so that the oxygen diffusion would stop.And the surface properties of the cured coating could be enhanced which indicated its potential application in photocuring.With 1 wt%,the hardness of poly(methacrylic acid,two methylamine(DMAEMA))coating can be increased from 3B to 2H.4.Nanosilica was surface modified by fluorine groups,photocuring groups and photoinitiatable groups at the same time.When the amount of the additive is no more than 5 wt%,the transparency of the coating is not affected.These new particles can act as photoinitiators,surface additives and crosslinking agents.It was proved that the particles had good resistance to oxygen.The double bond conversion was up to 70%and the migration was confrmed.The results also indicated that this kind of particles could be used to produce functional gradient materials.5.A silane photoinitiator was prepared through the reaction between hydroxyl and isocyanate,and its structure was characterized.Then silica particles were prepared by changing the catalyst dosage,and BP-Si was used to modify the surface of the silica particles.Large amount of characterization was used and the results showed that the silica particles would deposite at the bottom of fomula.It can be used to prepare initiator-free polymers,high molecular weight polymers(up to 1.12×106)with narrow molecular(PDI was 1.5)weight distribution,and other gradient polymers(from 5.5×103 to 1125×1O3).These characteristics indicate that it might find its application in coatings for food and medicine.