Analysis of the linear methods for determining copolymerization reactivity ratios. II. A critical reexamination of cationic monomer reactivity ratios

Abstract

A thorough examination of some cationic copolymerization systems by a new method has shown that many published r values have to be corrected significantly and that some are erroneous and meaningless, because for these systems the conventional copolymer compositions equation does not hold. Available information in regard of cationic copolymerizations has been treated in terms of three classes: (a) Systems in which the conventional copolymer composition equation adequately describes the copolymerization mechanism and previous authors justifiably used the two parameter model to calculate reactivity ratios. Our results show that the discrepancy between published r values and the more precise values obtained in this work is about ±23%. (b) Systems in which the approximations implicit in the conventional copolymer composition equation do not hold and the calculated r values are erroneous and misleading. Monomer pairs comprising monomers of significantly different reactivities belong to this class indicating that in copolymerizations in general and in cationic copolymerizations in particular a strong cast system exists, i.e., copolymerization can readily occur within the cast (between monomers of similar reactivities); however, only with difficulty if at all between casts (between monomers of differing reactivities). (c) Systems in which the use of the copolymer composition equation is completely unjustified, the calculated r values are meaningless and in some cases the existence of true copolymers is questioned.

The Influence of Pendant Carboxylic Acid Loading on Surfaces of Statistical Poly[(4‐hydroxystyrene)‐co‐styrene]s

“…The copolymer reactivity ratios were calculated using the method of Kelen and Tüdös [18,19] in order to investigate the copolymer sequence composition. Accordingly copolymerizations with 10, 20, 40, 60, 80, and 90% of tBS and S were performed.…”

Size Shrinkage of Methacrylate-based Terpolymer Latexes Synthesized by Free Radical Polymerization: Kinetics and Influence of Main Reaction Parameters

“…22 Copolymerization can readily occur between monomers of similar reactivities and only with difficulty between monomers of differing reactivities. 23 As a consequence, a batch polymerization can yield a wide spectrum of polymer compositions and thus physical properties. To obtain a polymer with a constant composition, it is necessary to continuously readjust the composition of the system during the reaction to avoid obtaining a heterogeneous material that forms a biphasic structure in the solid state.…”

Synthesis of Ultrahigh-Molecular-Weight Ethylene-1-Hexene Copolymers with High Hexene Content via Living Polymerization with Fluorinated Bis(phenoxy-imine) Titanium(IV)

“…[ 27 ] The good linear relationships are evident in Figure 2 another FI-Ti catalyst bearing a methyl group ortho to the oxygen atom in the ligand. [ 5 ] The fi rst-order Markov model and random monomer distribution appeared to be applicable for both EH and EO copolymerization with fl uorinated FI-Ti catalysts.…”