Synthesis and characterization of polyhedral oligomeric silsesquioxane (POSS) based nanocomposites by photochemical methods

The research and development of nanocomposite materials has gained significant attention in recent years due to their superior optical, thermal, electronic, photonic, magnetic, rheological, structural and mechanical properties. Automotive, coatings, biomedical and packaging industries which have a large share in the plastics industry are the important application areas.Generally, to combine the best features or to introduce a new feature of two or more materials, a material with the mixture of heterogeneous materials in the micro or macro level is called as "composite material". A nanocomposite is as a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers, or structures having nano-scale repeat distances between the different phases that make up the material. Nanotechnology research gives the chance to change structure of materials in molecular scale. The researchers playing with many functions of molecules can combined in a single product. By increasing surface area to volume ratio of substance, whereas at the nano-scale level, alters the mechanical, thermal and catalytic properties of materials. With these differences enable us to product many nanomaterials which directly affect our daily life such as, more transparent glass, more lighter and durable cars, cleaner clothes and paint with long life-time. Especially, the use of polymer nanocomposites has begun to increase in recent years with the decrease of materials costs and solution of technical difficulties which used in nanocomposite production. There are three main nanostructured additives in nanocomposite production such as, clays which are one dimension in the nano-scale, nanowires and nanotubes which are two dimensions in the nano-scale and silica, metal particles and quantum dots which are three dimensions in the nano-scale. Photopolymerization is an environmentally friendly process that transforms a monomer into a polymer initiated by the reactive species upon irradiation of photoactive species. The advantages of photopolymerization over thermal polymerization are their high reaction rates even at room temperature, consumption of small amount of energy and preparation of solvent-free systems. Moreover, photopolymerization provides the materials with desired properties; by regulating the monomer and other chemicals in the formulation, one can adjust the after-reaction properties like hardness, color, solubility, transparency, adhesion and electrical conductivity. Thus, nanocomposites with desired properties can efficiently be prepared by photopolymerization. To summarize, polymer nanocomposites based on three-dimensional nanosized POSS are prepared by photopolymerization techniques in this thesis. The obtained nanocomposites structures are characterized by various techniques such as, spectroscopy (FT-IR), thermal (DSC and TGA) and microscopy (TEM) analyses.