Polymer composites, in photonic applications

Ordered macroporous materials (OMMs) are a new family of porous materials that can be synthesized by using colloidal microspheies as the template. - The most unique characteristics of OMMs are their uniformly sized macropores arranged at micrometer length scale in three dimensions. Colloidal microspheres (latex polymer or silica) can self assemble into ordered arrays (synthetic opals) with a three-dimensional crystalline structure. The interstices in the colloidal crystals are infiltrated with a precursor material such as metal alkoxide. Upon removal of the template, a skeleton of the infiltrated material with a three-dimensionally ordered macroporous structure (inverse opals) is obtained. Because of the 30 periodicity of the materials, these structures have been extensively studied for photonic applications. In this paper, the synthesis and characterization of highly ordered macroporous materials with various compositions and functionalities (silica, organosilica, titana, titanosilicate, alumina) are presented. The application potential of OMMS in adsorption/separation is analyzed and discussed. 

Titania (Ti) is another promising partner for the polymer in hybrid composites that are useful for photonic applications because of its high refractive index. When Ti02 is obtained by the sol-gel method, however, it is not easy to prepare hybrid composite thin films of Ti with polymers because of the fast hydrolysis reaction and thus the extremely fast gelation of titanium aUcoxide. Therefore, only a few studies have been reported that describe polymer-Ti composites. Instead, attempts to form composites... 

Liquid crystalline polymer composites have become an increasingly important material for technological field involving photonic applications. Several attractive features such as dielectric anisotropy present in the mesophase, reasonably wide temperature range, low thermal expansion coefficient, high chemical resistance, specific thermo-mechanical response etc. make them more attractive. Of comse several limitations have to overcome in order to avail the total benefit of using such materials for opto-electronic applications. 

Recent developments in polymer chemistry have allowed for the synthesis of a remarkable range of well-defined block copolymers with a high degree of molecular, compositional, and structural homogeneity. These developments are mainly due to the improvement of known polymerization techniques and their combination. Parallel advancements in characterization methods have been critical for the identification of optimum conditions for the synthesis of such materials. The availability of these well-defined block copolymers will facilitate studies in many fields of polymer physics and will provide the opportunity to better explore structure-property relationships which are of fundamental importance for hi-tech applications, such as high temperature separation membranes, drug delivery systems, photonics, multifunctional sensors, nanoreactors, nanopatterning, memory devices etc. 

Hybrid polymer silica nanocomposites formed from various combinations of silicon alkoxides and polymers to create a nanoscale admixture of silica and organic polymers constitute a class of composite materials with combined properties of polymers and ceramics. They are finding increasing applications in protective coatings (Figure 7.1), optical devices, photonics, sensors and catalysis.1... 

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