Heterophase-kinetic modeling

The mentioned results correlate with the above heterophase-kinetic model of the proeess. For example, phosphorescing triplets are observed in the films 1 only (it is assumed that they are located in incapacious nanopores and do not participate in sensitization of the photoprocess). In such aerated films, the rate of phototransformation is relatively low, but the process proceeds owing to N molecule exchange between zones. 

In this paper, the method of heterophase-kinetic modeling is used in description of a complex photochemical process of transformations sensitized by naphthalene in glassy cellulose triacetate films. The considered supramolecular model of the mentioned process quite fully reflects the presence of heterogeneous nanophases in non-ciystalline polymers, which cause the dominant influence on physical and chemical properties of additive moleculaes. 

Individual rate constants for homogeneous and heterophase DADMAC homopolymerizations have been calculated from the kinetic models above. These constants are summarized in Table 4. The overall activation energies, also given in Table 4, are relatively high. These values likely result from the electrostatic repulsion between the positively charged radicals and the monomer cations. 

Equation (8) has been used to describe the progress of the homogeneous polymerization up to conversions of approximately 60%. Experimental and calculated conversion-time curves were in good agreement, even for the case of changing experimental conditions during the polymerization [51]. For the heterophase polymerization experimental and modeled conversion-time curves coincide well if a kinetic model based on first order initiator decomposition was applied and consideration of gel effect for conversions greater than 35% was included [13]. 

The study was aimed at speeifieation and systematizing of kinetie regularities for a photoehemical naphthalene transformation in glass CTA eombined with the kinetics of induced degradation and modification of macromolecules and, based on this, at development of a kinetic model of the process using the ideas of supramolecular heterogeneous-heterophase reactions, developed in [4, 5],... 

Characteristic kinetic and morphological features of vinyl chloride radical polymerization processes were reviewed in89. While developing a mathematical model for the polymerization of this monomer, Canadian90 and Soviet91 investigators concentrated their attention on the heterophase nature of the process. In both cases the dependence of kinetic constants on the viscosity of the medium was disregarded. 

The second approach or microheterogeneous model [1, 19-22] is based upon the principle, that the kinetics of the reaction in its initial stage are not that of a homophase polymerisation in a liquid monomer-polymeric solution, but a heterophase one. The reaction proceeding at the boundary liquid monomer - solid polymer microgranules surface under gel conditions. 

The first conception (or microheterogeneous model) is based on the assumption that the main contribution to the kinetics of the process in the initial state does not lead to homophaseous polymerization in the liquid monomer/polymeric solution, but the heterophaseous one, proceeding on the solid polymer-liquid monomer boundary under the gel-effect conditions. 

In conclusion, reviewing the literature and experimental material obtained from stationary photoinitiated radical polymerization of bifunctional (meth)acrylates in bulk allowed us to obtain the kinetic equation describing the process at all depths of conversion. A mechanism of 3-D polymerization combining the kinetic schemes of homophaseous and heterophaseous processes has been proposed on the basis of the microheterogeneous model and also effective rate constants of these processes have been estimated. 

Previously, it was shown that supramolecular heterophase models of chemical transformations possess high advantages in the description of kinetic features of chain reactions of autooxidation before the traditional homogeneous model of liquid-phase oxidation of hydrocarbons [4, 5]. 

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