Multicomponent Copolymerization Terpolymerization

Considering the speci e ease of terpolymerization of monomers Mi, M2, and M3, there are three different types of growing ehain ends, viz., wwwMi, vvwwM2, and wwwMs and nine 

We do not know the absolute values of the radical concentrations [M]i, [M]z, M]3, but we can derive the steady-state relationships for these unknown concentrations. Since in steady state, radicals of the type wwwMi are formed just as fast as they are converted to types wwwMz and WWW M3 , we may write  

The above terpolymer composition can be obtained in an equivalent form (Alfrey and Gold n-ger, 1946 Hocking and Klimchuk, 1996) as  

Steady-state relationships have also been expressed (Valvassori and Sartori, 1967) by considering only pairs of radicals. This gives  

Combining these equations with Eqs. (7.59)-(7.61) yields a simpler and shorter version of the terpolymer composition equation (Hocking and Klimchuk, 19%)  

Steady-state relationships have also been expressed (Valvassori and Sartori, 1967) by considering only pairs of radicals. This gives A i2[Mi ° ][M2] = i 2i [M2 ][Mi] 2s[M2 °][M3] = 32[Ms ][M2] and 31 [M3 ][Mi] = i3[Mi ] [M3]. Combining these equations with Eqs. (7.59)-(7.61) yields a simpler and shorter version of the terpolymer composition equation (Hocking and Klimchuk, 1996)  

Both the conventional Eq. (7.67) and the simplified Eq. (7.68) can be used for predicting terpolymer compositions as they yield similar results (see Problem 7.15). 

Problem 7.15 The ternary copolymerization of a monomer mixture containing 35.92, 36.03, and 28.05 mol% of styrene, methyl methacrylate (MMA), and acrylonitrile (AN) at 60°C for 3.5 h yielded at 13.6 wt% conversion a polymer product which analyzed C 78.6% and N 4.68% (by wt.) (Walling and Briggs, 1945). Calculate the initial ternary copolymer composition to compare with the composition obtained by the analysis. 

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The two monomers enter into the copolymer in overall amounts determined by their relative concentrations and reactivities. The simultaneous chain polymerization of different monomers can also be carried out with mixtures of three or more monomers. Such polymerizations are generally referred to as multicomponent copolymerizations the term terpolymerization is specifically used for systems of three monomers. 

The conventional [Eq. (7.77)] and simplified [eq. (7.81)] terpolymeriza-tion equations can be used to predict the composition of a terpolymer from the reactivity ratios in the two-component systems M1/M2, M1/M3, and Ms/Ms- The compositions calculated by either of the terpolymerization equations show good agreement with the experimentally observed compositions. Neither equation is found superior to the other in predicting terpolymer compositions. Both equations have been successfully extended to multicomponent copolymerizations of four or more monomers [30,31]. 

The terminal model for copolymerization can be naturally extended to multicomponent systems involving three or more monomers. Multicomponent copolymerizations And practical application in many commercial processes that involve three to five monomers to impart different properties to the final polymer (e.g., chemical resistance or a certain degree of crosslinking) [134]. There is a classical mathematical development for the terpolymerization or three-monomer case, the Alfrey-Goldfinger equation (Eq. 6.43)... 

There is considerable interest in multicomponent copolymer systems. An example of terpolymerization, that is, copolymerization of three monomers. 

The ceiling temperature constraint in the homopolymerization of alphamethyl styrene (AMS) can be circumvented by copolymerization with acrylonitrile (AN) to prepare multicomponent random microstructures that offer higher heat resistance than SAN. The feasibility of a thermal initiation of free radical chain polymerization is evaluated by an experimental study of the terpolymerization kinetics of AMS-AN-Sty. Process considerations such as polyrates, molecular weight of polymer formed, sensitivity of molecular weight, molecular weight distribution, and kinetics to temperature were measured. 

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