Ternary Copolymerizations

Monomer reactivity ratios (see Chapter 9), obtained from binary copolymerization, have long been used for comparison of the reactivities of monomers toward reference polymer radicals.However, the same procedure is unreliable for polymer radicals showing very low reactivities toward their own monomer. pointed out that in such cases, which includes 

useful information may be obtained from terpolymerization studies. 

Alfrey et developed triangular diagram concepts and equations to 

Yamashita also concluded it was not possible to use the known theory of ternary polymerizations to explain the observations that the donor-acceptor pair was always incorporated in a 1 1 fashion in the polymer. 

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Terpolymerizations or ternary copolymerizations, as the names suggest, are polymerizations involving three monomers. Most industrial copolymerizations involve three or more monomers. The statistics of terpolymerization were worked out by Alfrey and Goldfinger in 1944.111 If we assume terminal model kinetics, ternary copolymerization involves nine distinct propagation reactions (Scheme 7.9). 

Brandley and Schnaar [140] immobilized a synthetic nonapeptide, Tyr- Ala-Val Thr-Gly Arg-Gly-Asp-Ser, on a polyacrylamide gel, which had been prepared by a ternary copolymerization of acrylamide, bisacrylamide and the acrylic ester of. V-hydroxysuccinimide. They reported that Balb/c 3T3 mouse fibroblast cells (in Hepes-buffered Dulbecco s modified Eagle medium) adhered readily to the peptide-derivatized surfaces, even in the absence of serum, although long-term cell growth required the presence of serum. It was noticed that reference nonapeptide. Tyr-Arg-Leu-Glu-Asp-Pro-Ala-Met-Trp, which has no RGD sequence, failed to promote cell-attachment. 

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. 

TERNARY COPOLYMERIZATION AND COPOLYMERIZATION OF MORE THAN THREE MONOMERS... 

When evaluating the results of ternary copolymerizations by means of the Alfrey-Gold-finger scheme, the stationary character of copropagation should be critically established. With non-stationary processes, the uncertainty of interpretation becomes more serious, even when the experimental results agree with theory. 

We have considered so far free-radical polymerizations where only one monomer is used and the product is a homopdlymer. The same type of polymerization can also be carried out with a mixture of two or more monomers to produce a polymer product that contains two or more different mer units in the same polymer chain. The polymerization is then termed a copolymerization and the product is termed a copolymer. Monomers taking part in copolymerization are referred to as comonomers. The simultaneous polymerization of two monomers is known as binary copolymerization and that of three monomers as ternary copolymerization, and so on. The term multicomponent copolymerization embraces all such cases. The relative proportions of the different mer units in the copolymer chain depend on the relative concentrations of the comonomers in the feed mixture and on their relative reactivities. This will be the main subject of our discussion in this chapter. 

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. 

Among other vinylazole-based MCMs it would be interesting to investigate M(VIA)4(0C0CH3)2, where M = Co(II), Ni(II) or Zn(II). Ternary copolymerizations of these complexes with V-vinylpyrollidone and divinyl-benzene have been conducted in an aqueous buffer solution under radiation initiation [121],... 

Braun, D., and Czerwinski, W. K. 1987. Recent investigations on the rate of binary and ternary copolymerizations. Makromol. Chem. 10 415-439. 

Figure 22-6. Ternary copolymerization of the acrylonitrile/2.5-dichlorostyrene/styrene system at 60 C. Arrows on the axes give azeotropic compositions for the bipolymerizations. Left variation of copolymer composition with comonomer composition. Right partial azeotrope diagram for this system. (After P. Wittmer, F. Hafner, and H. Gerrens.)...

For reasons explained on p. 20 a modified N,N-dimethyl-polyacrylamide support was introduced [83] into the system of the Merrifield synthesis. This polar polymer is prepared by a ternary copolymerization of N,N-dimethyl-acrylamide, N,N-bisacryloylethylenedi-amine and N-tert.butoxycarbonyl-j3-alanyl-N -acryloylhexamethylenediamine (Fig. 27). 

Ternary Copolymerization. As technical polymerization processes with more than two monomers are frequently met, it is an interesting question whether a correlation corresponding to equation 34 will hold for terpolymerizations. The resulting expression for terpolymerization would read... 

For unequal reactivity of the vinyl gronps, the scheme corresponds to that of ternary copolymerization. Therefore, there is exclnsively intramolecular crosslinking at the beginning of process. Cycles of various sizes are formed, with the smallest cycles having the highest probability of formation. A very important cyclization can be observed when the reaction systan contains a large amount of divinyl monomer (Vlad and Vasiliu 2010). However, a sharp decline in the pendant double bonds reactivity appears. This feature of crosslinking (co)polymerization is explainable because many of these links are trapped inside cycles. For a complete conversion of monomers, the presence of donble bonds in the reaction system supports the inaccessibility of these links. 

As the acceptor MA concentration is increased, the rate of copolymerization increases and reaches a maximum at 65-70 mol %, but the rate decreases as the content of VTES in the initial mixture is increased. The observed changes in the kinetic parameters suggest that CTC formation between the monomers exerts a substantial effect on the kinetics of ternary copolymerization. In addition, the results suggest that copolymerization by both the Sty-MA-VTES and (Sty-MA)-(VTES-MA) charge-transfer complexes occur and theoretical equations of binary copolymerization are applicable to the system. 

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