Cryochemical conversion

VI. Theoretical Treatment of Autowave Processes in Solid-State Cryochemical Conversions (The Simplest Model)... 

VI. THEORETICAL TREATMENT OF AUTOWAVE PROCESSES IN SOLID-STATE CRYOCHEMICAL CONVERSIONS (THE SIMPLEST MODEL)... 

The next important step in the study of the regularities of the autowave modes of cryochemical conversion was to perform a series of experiments with thin-film samples of reactants. The changeover to such objects, characterized by the most intense heat absorption, allowed the realization of quasi-isothermal conditions of the process development and thus favored the manifestation of the abovementioned isothermal mechanism of wave excitation, which involves autodispersing the sample layer by layer due to the density difference between the initial and final reaction products. The new conditions not only not suppressed the phenomenon, but made it possible to reveal some details of the traveling-wave-front structure, which will be discussed here and also in Section X. 

Cryochemical synthesis of Ag-PPX systems and their structures were studied in references 24, 34, 36, 37, and 44. The simultaneous vapor deposition of PX-, CN-PX-, and Cl-substituted PX (Cl-PX) with Ag at 77 K does not lead to complexation or the formation of any organometallic compounds [24, 36, 44]. In the case of PX and Cl-PX, such deposition proceeds without polymerization. The co-deposition of CN-PX with Ag is accompanied by the partial polymerization of monomer. The initial condensates at 77 K contain a small amount of Ag nanocrystals that can be revealed and characterized using UV-Vis spectroscopy because such crystals have the specific absorption band of surface electron plasmons of about 430nm [3] (Figure 2.5 and 2.6). UV irradiation of these condensates at 77 K leads to the total conversion of monomers to the corresponding polymers (PPX, CIPPX, and CNPPX). However, intensity (D ), maximum position (Vax), and half-width (Ai ) of the nanocrystals plasmon band do not practically change in the course of cryopolymerization (Figures 2.5 and 2.6, Table 2.1). 

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