Preparation And Study Of High-refractive-index PMMA Organic/Inorganic Nanocomposites

In recent years, due to the extensive application of optical materials, polymerhybrid organic/inorganic nanocomposites have been widely studied. Polymer canmaintain its own performance as well as having some special properties and featuresby adding inorganic fillers. Polymethyl methacrylate (PMMA) is one of the mostsuitable polymers which are used in optical materials. PMMA has the advantage oflight weight, low cost and good transparency, but with low refractive index (1.49).Inorganic materials such as TiO2or ZrO2always have high refractive index, however,they have the disadvantage of poor transparency and poor mechanical properties. Sohigh-refractive-index materials with the combination of both polymers and inorganicmaterials will certainly have an important application in optical materials. In thisarticle, we develop a novel, easier method—solvothermal method to try to have TiO2,ZrO2and silicon incorporated into PMMA matrix. The obtained hybrid materials werecharacterized and their optical properties and thermal properties have been studied.Generally, there are two conventional methods: sol-gel method and mechanicalmixing. Although these two methods have already been widely studied, these methodsare complicated and with a lot of steps. So we develop a novel method—solvothermalmethod to prepare high-refractive-index PMMA hybrid materials with differentinorganic fillers.Firstly, we used one-step solvothermal method to prepare PMMA/TiO2hybridmaterials. Methyl methacrylate (MMA), vinyltrimethoxysilane (VTMO), titaniumbutoxide [Ti(OBu)4], were added into a reaction vessel altogether and thepolymerization of PMMA matrix and the formation of nano-TiO2composite carriedout simultaneously. The results indicate that TiO2nanoparticles produced bydecomposition of Ti(OBu)4are anatase and dispersed homogeneously in the PMMA matrix. The size of TiO2crystals in PMMA/TiO2nanocomposites is about5–6nm.The hybrid films have a good transparency (over80%) in the visible region, a goodthermal stability and a UV-shielding property after the incorporation of TiO2. Therefractive index of as-formed PMMA/TiO2nanocomposites increases up to1.839at633nm as the content of Ti(OBu)4is50.00wt%.Then, we still used one-step solvothermal method to prepare PMMA/ZrO2hybridmaterials. MMA, VTMO and zirconium n-propoxide were added into a reactionvessel altogether. ZrO2were connected onto PMMA by covalent bond in in-situ way.And acetylacetonate was used as stabilizer in order to prevent the agglomeration ofZrO2by chelation with zirconium. The results showed that ZrOCl28H2O were firstprepared after the hydrolysis of zirconium n-propoxide, and then amorphous ZrO2were generated after the annealing. The obtained hybrid materials have a goodtransparency (over85%) in the visible region. The refractive index can be increasedto1.680at633nm as the content of zirconium n-propoxide is29.58wt%.Finally, we tried to make silicon incorporated into PMMA matrix. We dispersedthe silicon powder which we bought by ultrasonic and used VTMO to coat on siliconpowders first. And then the silicon with pretreatment was added into monomer MMAand polymerized by solvothermal method. Results showed that the diameter of thesilicon we bought is about100nm. The silicon powder has a low density and highspecific surface area so that the refractive index can be further improved. Theobtained hybrid films have a good transparency (over80%) in the visible region. Therefractive index can be increased to2.651at633nm as the content of Si is3×10-4wt%.