Reactivity Ratios Estimation Based on Copolymer Composition Data

2 Reactivity Ratios Estimation Based on Copolymer Composition Data 

The problem of the computation accuracy of these kinetic parameters is dependent first of all on the validity of the copolymer composition determination. As a criterion here one may use the closeness to each other of the values of this composition obtained via the different experimental methods. It is possible to judge about the degree of such a closeness using Tables 6.1 and 6.2 where the data on both chemical analysis and spectroscopy are presented. One can see that, as for the considered cases, the different experimental methods provide quite close values of the copolymer compositions within the accuracy in the range of 5%. Authentic evidence concerning the feasibility to reach such a degree of accuracy is furnished by the data on copolymer composition obtained via independent methods in the different systems, for instance, under the copolymerization of p-chlorstyrene with methyl acrylate [32], of 4-methylstyrene with methyl methacrylate or acrylonitrile [213], and also of styrene with acrylic or methacrylic acids [214], 

Another reason for errors of the reactivity ratio values are an exactitude in the course of the treatment of the experimental data using the differential or integrated form of the copolymer composition equation. In the first pase, the dependence of X(x°) on the monomer feed composition x° experimentally determined at low conversions is used. In the second case, one should use the data on the dependence of the copolymer composition on conversion p or the current values of x under the measurements of p. 

A number of well-known procedures of r, r2 estimations within the framework of the terminal copolymerization model share the following general expression  

The intersection procedure put forth in the pioneer report by Mayo-Lewis (ML) [19] assumes expression (6.1) to adopt the following form  

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