Surface Grafting Polymerization On The Inoganic Nano-Particles & Study Of The Dispersibility

In recent years, nanoparticles/ polymer composites attract strong interest in the whole world due to the incorporation of nanoparticles combines the properties of the inorganic nanoparticles with those of the polymer. Controlling a homogeneous dispersion of the particles in the polymer matrix is important. The methods of controlling agglomeration are surface reactive group joined, site-polymerization and surface grafting etc. And surface grafting was interested because the dispersibility of nanoparticles in polymer matrix and good organic solvents was remarkably improved by grafting of polymers onto the surface.In the context of this work, the introduction of azo groups onto the nanoparticles including SiO2, TiO2, Si/Al-TiO2 and Al-TiO2 was achieved by the esterification of glycidyl groups, which were introduced by the reaction of hydroxyl groups on the surface with 3-glycidoxypropyltrimethoxysilane(GPS), with 4,4'-Azobis(4-cyanovaleric acid)(ACVA).The polymerization of vinyl monomers, such as methyl methacrylate(MMA), was found to be initiated by radicals formed by thedecomposition of the azo groups.In the first, the structure of produces in the process of modification was characterized. Infrared Absorption spectroscopy and Mastersizer2000 particle size analyzer proved the feasible grafting method and existent polymerization grafted onto the surface of nanoparticles. In the further, effects of BET surface area, hydroxyl group content and particle size of inorganic nanoparticles on the grafting polymerization are presented. Except percentage of grafting, they decide that GPS was grafted onto the surface of nanoparicle or the agglomeration of nanoparticles. At the same time, it was indicated that the thermal movement of the molecular chain was restricted by network of TiO2. It causes disappearance of glass transition. In addition, the initial decomposition temperature of PMMA-g-TiO2 is higher than PMMA. And thermal stability of PMMA-g-TiO2 was improved.Effect grafting polymerization on dispersion was discussed. It was found that reaction time, stirring rate and initiator concentration are the important factors affecting grafting polymerization by SEM. The PMMA-g-SiO2, PMMA-g-TiO2> PMMA-g-Si/Al-TiO2 andPMMA-g-Al-TiO2 dispersed well in grafted samples when the reaction time is 50min or 60 min, the stirring rate is up to 1.0 × 104r/min and the initiator concentration is 3.0% in the grafting polymer. The dispersion and stability of grafting polymer were investigated when the PMMA-g-nanoparticles were joined into the good solvent. It was indicated that the dispersion of PMMA-g-nanoparticles was improved by the TEM. And the stability of PMMA-g-TiO2 was better than TiO2 in acetone solution showed UV light absorption.The dispersion status of PMMA-g-SiO2, PMMA-g-TiO2 , PMMA-g-Si/Al-TiO2 and PMMA-g-Al-TiO2 in blending samples was studied. The blending samples were made of the nanoparticles modified by different methods and PMMA matrix. Only dispersed PMMA-g-nanoparticles well in PMMA matrix when blending scale (modified nanoparticles : PMMA=1:100) is 1.0%. Effect PMMA-g-SiO2 and PMMA-g-TiO2 on the dispersion is better than others in PMMA matrix. In addition, it was shown that the effect ' soft agglomeration' in grafted polymerization on preparation of composites was not serious after blend. As far as application was concerned, GPS-g-TiO2 was more fit for industry production than PMMA-g-TiO2 because of its economical technics and good dispersion in polymer matrix.