9 Environmentally Friendly Synthesis of Polymer-Grafted Nanoparticles
Inorganic nanoparticles such as silica, and titanium oxide, are widely used industrially as fillers and pigments for polymer materials, because inorganic nanoparticles have excellent properties such as chemical, heat and weather resistance, lightweight, thermal conductivity and low thermal expansion. On the other hand, nanocarbons, such as carbon black, nanodiamond, and carbon nanotube, are well known as one of the industrially important carbon materials. Carbon materials also have outstanding properties such as electro-conductivity, heat-resistance, biocompatibility, and chemical-resistance. Carbon nanotubes in particular have attracted attention as nanotechnology related materials. In general, dispersing inorganic nanoparticle and nanocarbons uniformly into a polymer or an organic solvent is very difficult because of aggregation. In addition, the mechanical properties of polymer composite from nanoparticles and nanocarbons are considered to depend on not only the mechanical properties of the polymer matrix but also on the properties of interfacial regions between surface of nanoparticles and matrix polymers. The chemical and physical modifications of inorganic nanoparticle and nanocarbon surfaces, therefore, have been extensively studied. The chemical modification of surfaces is permanent, but physical modification is temporary. We have pointed out that the dispersibility of silica nanoparticles and nanocarbons is extremely improved by surface grafting of polymers, namely, chemical binding of polymers, onto nanoparticle and nanocarbon surfaces (Tsubokawa, 1999; Tsubokawa, 2002; Tsubokawa, 2007). In addition grafting of polymers onto these surfaces interests us for designing new functional composite materials which have the excellent properties both of nanoparticles as mentioned above and of grafted polymers, such as photosensitivity, biorepellent activity, antibacterial activity, and pharmacological activity (Tsubokawa, 2007). We have succeeded in the grafting of various polymers such as vinyl polymer (Tsubokawa et al., 1988a; Tsubokawa et al., 1990; Fujiki et al., 1990; Tsubokawa et al., 1992a), polyester (Tsubokawa et al., 1982; Tsubokawa et al., 1983), polyether (Tsubokawa et al., 1986; Tsubokawa et al., 1988b), poly(organophosphazene) (Tsubokawa et al., 1992b), and poly(dimethysiloxane) (Tsubokawa et al., 1992c) onto silica nanoparticle and carbon black surfaces using surface functional groups as grafting sites. Furthermore, many experimental attempts by other researchers also have been made to graft polymers onto silica nanoparticle and carbon black surfaces.
Radical graft polymerization of vinyl monomers onto nanoparticles in ionic liquid initiated by azo groups introduced onto the surface
The radical graft polymerization of vinyl monomers, such as styrene and methyl methacrylate, initiated by azo groups introduced onto silica nanoparticle and carbon black surfaces in room temperature ionic liquid (IL) were investigated. In this work, 1-butyl-3-methylimidazolium hexafluorophosphate ([C 4 mim][PF 6 ]) was used as IL. The percentage of polystyrene and poly(methyl methacrylate) grafting onto silica nanoparticle and carbon black increased with increasing reaction time. The percentage of grafting in IL was much larger than that in 1,4-dioxane. The molecular weight of polystyrene grafted onto the silica surface in IL was almost equal to that in 1,4-dioxane. The result indicates that the amount of grafted polystyrene in IL is five times that in 1,4-dioxane. This may be due to the fact that lifetime of the surface radical formed by the group of azo is prolonged because of high viscosity of IL. Therefore, the surface azo groups were effectively used as initiating sites for the graft polymerization. In addition, the reduction of waste solvent was achieved by use of IL as reaction solvent, because unreacted monomer could be removed under vacuum after the reaction and the reuse of IL was easily achieved.
CULTURE, SUSTAINABLE URBAN DEVELOPMENT AND URBAN REGENERATION
Concerns about the conflict between economy, development on one hand and urban cultural heritage on the other hand, have made the urban development to be lately one of the most important themes at European level. Also, another issue of concern is social equity, aiming to strike a balance between economic development and equal access to culture for all generations of inhabitants of urban communities. Basically, ensuring these balances between urban cultural heritage, economy and social equity we express the essence of the concept of sustainable development from the perspective of culture. Urbanization is an ongoing process in all the cities of the world, but urban cultural heritage is a crucial element in the development of the cities and has an important impact over the quality of life of that community. Castles, churches, fortresses, squares and public buildings all contribute at the creating of the community history and of their characteristics.