Synthesis cryochemical solid-state

The nanocrystals of such type form in various liquid media, such as organic solution [77, 81] or the softened quasi-liquid glass [82, 83], where there are no steric hindrances for the growth of equilibrium crystals without surface defects. At the same time, barriers for aggregation of clusters or atoms to metal nanocrystals in solid system that arises during the cryochemical solid-state synthesis favor the formation of crystals with structural defects,... 

Films of pure PPX and PPX composites with nanoparticles of various metals resulted from cryochemical solid-state synthesis were studied by the dielectric spectroscopy method [104], Dielectric spectroscopy has proven very useful for studying the structure and dynamics of polymer materials as well as the transport mechanism of charge carriers. To study features of the polymer structure dielectric test methods were used due to their high sensitivity to morphological changes. 

Inorganic nanoparticles such as metal/semiconductors (M/SC) immobilized in polymer matrices have attracted considerable interest in recent years due to their distinct individualistic and cooperative properties [84]. Although the control of size and shape of M/SC nanoparticles has been widely investigated, the fundamental mechanism of nanostructural formation and evolution is still poorly understood. A novel cryochemical solid-state synthesis technique has been developed to produce M/SC nanocomposites [85]. This method is based on the low-temperature cocondensation of M/SC and monomer vapors, followed by the low-temperature solid-state polymerization of the cocondensates. As a result of the method of stabilizing the metal particle without requiring any specific coordination bonds between the particle surface and the polymer matrix, generated nanoparticles (Ag-nanocrystal mean size 50 A) were embedded in the polymer matrix with well-controlled shapes and a narrow size distribution [86]. 

Based on spectral data, it has been concluded that the change of Ag content in the cryochemically synthesized hlms Ag-PPX and Ag CIPPX from 0.3 to 2 vol. % (that is, 4-20 at. %) does not influence d of Ag nanocrystals formed as a result of the cluster aggregation [36, 44]. The same result has been obtained for Pb-PPX Aims with Pb content varied from 0.01 to 1 vol. % [52]. Unlike other similar systems, PbS-PPX nanocomposites were studied at high PbS loading in the range from 4.7 to 10.2 vol. % of PbS. In this case according to X-ray data, d of PbS nanocrystals also does not depend on PbS content [53]. Thus, it may be concluded that the independence of the nanocrystal mean size from the metal or semiconductor content is a general feature of nanocomposites resulted from solid-state synthesis. 

Simultaneous evaporation of metal with organic and inorganic substances followed by vapor deposition on a substrate allows the production of composite films containing M nanoparticles stabilized in various dielectric matrices [2, 28]. The use of monomer molecules in this process polymerizing during deposition or as a result of the subsequent reactions yields polymeric nanocomposite films with metal inclusions [2, 3, 28, 37]. The new low-temperature synthesis of polymeric nanocomposite films has been elaborated recently. This synthesis is based on the deposition of M/SC and monomers vapors at temperature 80 K followed by low-temperature solid-state polymerization of obtained films in conditions of frozen thermal movement of molecules (cryochemical synthesis) [2], This synthesis has important features, which will be considered further. 

As mentioned above, the new method of cryochemical synthesis of polymer nanocomposite films has been developed based on co-deposition of M/ SC and monomer vapors at temperature 80K and subsequent low-temperature solid-state polymerization of monomer matrix ([2] and works cited herein). It has been established that a number of monomers (acrylonitrile, formaldehyde, /i-xylylene and its derivatives) polymerize in solid state in absence of thermal movement of molecules owing to own specific supra-molecular structure. When reaction is initiated by y- or UV-radiation the formation of a polymer matrix occurs even at the temperatures close to temperature of liquid helium [66-69]. 

The cryochemical vapor deposition synthesis of metal-polymer films (from the gaseous state to the solid polymer one, bypassing the liquid phase) allows the production of both new organometallic structures and new valuable composites with high concentrations of nano-sized metal or semiconductor particles. 

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