Copolymerization Mayo-Lewis scheme

The values of these coefficients for the system described within the framework of Mayo-Lewis scheme are to be equal to unity according to relations (6.13) at any monomer feed composition. This condition holds strictly under the copolymerization of styrene with methyl methacrylate (see Table 6.5) while it holds considerably worse under the copolymerization of styrene with acrylonitrile (see Table 6.7). The... 

The classical Mayo-Lewis scheme relating comonomer feeds to relative reactivity ratios (5i) is often applied to copolymerization of cyclosiloxanes. This scheme presumes that no depropagation of the copolymer occurs, that the copolymerization rate constants depend only on the ultimate comonomer units, and that instantaneous comonomer feed ratios and copolymer compositions are used in the analysis of data. When these assumptions hold, the Mayo-Lewis method is very useful for the analysis of copolymerization data. 

The effect of polarity on vinyl monomer copolymerization has long been recognized and is a major factor in the Q, e scheme and copolymerization theory. Mayo, Lewis, and Walling tabulated a number of vinyl monomers into an average activity series and an electron donor-acceptor series (62). The activity series showed the effect of substituents on the ease with which an ethylene derivative reacted with an average radical and on stabilizing the radical which was formed thereby. The electron donor-acceptor series indicated the ability of the substituents to serve as donors or acceptors in radical-monomer interactions. It is significant that in both series the dominant factor is the radical-monomer interaction. 

Anionic copolymerizations have been investigated by applying the classical Mayo-Lewis treatment which was originally developed for free-radical chain reaction polymerization [198]. The copolymerization of two monomers (Mj and M2) can be uniquely defined by the following the four elementary kinetic steps in Scheme 7.21, assuming that the reactivity of the chain end (Mj" or ) depends only on the last unit added to the chain end, that is, there are no penultimate effects. 

Attempts to obtain simple reactivity ratios from composition data by various techniquesled to the conclusion that the kinetics of the styrene-MA copolymerization do not follow the classical scheme of Mayo-Lewis and/or Alfrey-Goldfinger. All systems gave rise to Fineman-Ross and... 

Simultaneous polymerization of a mixture of cyclosiloxanes gives polymers whose microstructure is not easily predictable. Typically, the kinetics of ring-opening copolymerization is analyzed in terms of the Mayo-Lewis copolymerization equations (Scheme 5). The aim of such analysis is to determine the Mayo-Lewis reactivity ratios rD = feDD/feox and rx = fexx/fexD, which define the composition of a copolymer." The task is relatively easy when the propagation reactions are irreversible. 

On the other hand copolymer with a trioxane unit at the cationic chain end (Pi+) may be converted intp P2+ by cleavage of several formaldehyde units. These side reactions change the nature of the active chain ends without participation of the actual monomers trioxane and dioxo-lane. Such reactions are not provided for in the kinetic scheme of Mayo and Lewis. In their conventional scheme, conversion of Pi+ to P2+ is assumed to take place exclusively by addition of monomer M2. Polymerization of trioxane with dioxolane actually is a ternary copolymerization after the induction period one of the three monomers—formaldehyde— is present in its equilibrium concentration. Being the most reactive monomer it still exerts a strong influence on the course of copolymerization (9). This makes it impossible to apply the conventional copolymerization equation and complicates the process considerably. 

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