Monomer reactivity ratios in copolymerization

Fineman, M. Ross, S.D. Linear method for determining monomer reactivity ratios in copolymerization. J. Polym. Sci. 1950, 5, 259-262. Tiidos, F. Kelen, T. Foldes-Berezsnich, T. Turcsanyi, A. Evaluation of high conversion... 

TABLE XIII Monomer Reactivity Ratios in Copolymerization of Chloroprene"... 

The initial methods to fabricate GI preforms took advantage of the difference in monomer reactivity ratios in copolymerization reactions. These methods are of two types photo-copolymerization [4-6] and interfacial-gel copolymerization [7, 8]. 

One final point should be made. The observation of significant solvent effects on kp in homopolymerization and on reactivity ratios in copolymerization (Section 8.3.1) calls into question the methods for reactivity ratio measurement which rely on evaluation of the polymer composition for various monomer feed ratios (Section 7.3.2). If solvent effects arc significant, it would seem to follow that reactivity ratios in bulk copolymerization should be a function of the feed composition.138 Moreover, since the reaction medium alters with conversion, the reactivity ratios may also vary with conversion. Thus the two most common sources of data used in reactivity ratio determination (i.e. low conversion composition measurements and composition conversion measurements) are potentially flawed. A corollary of this statement also provides one explanation for any failure of reactivity ratios to predict copolymer composition at high conversion. The effect of solvents on radical copolymerization remains an area in need of further research. 

For copolymerizations between non protie monomers solvent effects are less marked. Indeed, early work concluded that the reactivity ratios in copolymerizations involving only non-protic monomers (eg. S, MMA, AN, VAe, etc.) should show no solvent dependence.100101 More recent studies on these and other systems (e.g. AN-S,102-105 E-VAc,106 MAN-S,107 MMA-S,10s "° MMA-VAc1" ) indicate small yet significant solvent effects (some recent data for AN-S copolymerization are shown in Table 8.5). However, the origin of the solvent effect in these cases is not clear. There have been various attempts to rationalize solvent effects on copolymerization by establishing correlations between radical reactivity and various solvent and monomer properties.71,72 97 99 None has been entirely successful. 

TABLE 6-2 Monomer Reactivity Ratios in Radical Copolymerization ... 

Another characteristic feature of ionic copolymerizations is the sensitivity of the monomer reactivity ratios to changes in the initiator, reaction medium, or temperature. This is quite different from the general behavior observed in radical copolymerization. Monomer reactivity ratios in radical copolymerization are far less dependent on reaction conditions. 

Discuss the general effects of temperature, solvent, and catalyst on the monomer reactivity ratios in ionic copolymerizations. How do these compare with the corresponding effects in radical copolymerizations ... 

The polymerization of a mixture of more than one monomer leads to copolymers if two monomers are involved and to terpolymers in the case of three monomers. At low conversions, the composition of the polymer that forms from just two monomers depends on the reactivity of the free radical formed from one monomer toward the other monomer or the free radical chain of the second monomer as well as toward its own monomer and its free radical chain. As the process continues, the monomer composition changes continually and the nature of the monomer distribution in the polymer chains changes. It is beyond the scope of this laboratory manual to discuss the complexity of reactivity ratios in copolymerization. It should be pointed out that the formation of terpolymers is even more complex from the theoretical standpoint. This does not mean that such terpolymers cannot be prepared and applied to practical situations. In fact, Experiment 5 is an example of the preparation of a terpolymer latex that has been suggested for use as an exterior protective coating. 

The interpretation presented above appears reasonable so far, but it lacks clear-cut support because of the intricate mechanism of the cationic homopolymerization. Therefore, it is interesting to investigate the effect of an electric field on the monomer reactivity ratios in the copolymerizations, which depend on the rates of propagation only. 

In the alkyllithium initiated polymerizations of vinyl monomers, Lewis bases such as ethers and amines alter the kinetics, stereochemistry, and monomer reactivity ratios for copolymerization. In general, the magnitude of these effects has been directly or indirectly attributed to the extent or nature of the interaction of the Lewis base with the organolithium initiator or with the organolithium chain end of the growing polymer. Unfortunately, all of these observed effects are kinetic in nature, and therefore the observed effects of solvent represent a composite effect on the transition-state versus the ground state as shown below in Eq. (6), where 5 represents the differential... 

The relative reactivity of the macromonomer in copolymerization with a common comonomer, A, can be assessed by l/rA=kAB/kAA> i-e-> the rate constant of propagation of macromonomer B relative to that of the monomer A toward a common poly-A radical. In summarizing a number of monomer reactivity ratios in solution copolymerization systems reported so far [3,31,40], it appears reasonable to say that the reactivities of macromonomers are similar to those of the corresponding small monomers, i.e., they are largely determined by the nature of their polymerizing end-group, i.e., essentially by their chemical reactivity. 

These equilibria also strongly affect copolymerization. Monomer reactivity ratios in controlled/living systems should be identical to those in conventional cationic copolymerizations, if the comonomers react exclusively with carbocationic species. The equilibrium between active and... 

In copolymerizations of cyclic ethers, too, basicity of the monomers seems to correlate well with the reactivity ratios determined from copolymer composition. Recently, Saegusa et al. [54] have pointed out that the apparent values of the monomer reactivity ratios in cyclic ether copolymerizations may be more influenced by the exchange... 

Monomer reactivity ratios for copolymerization of the itaconates with other monomers are listed in Table 4. Solvent and pH changes which... 

Random copolymerization of MMA with other polar monomers proceeds in a living fashion with relative monomer reactivity ratios in the order BuA > MMA = EtMA > /-PrMA when mediated by 4(Sm Me)/THF [60, 89]. Block polymerization of MMA with other polar monomers as lactone yields ideal living copolymers (PDI = 1.11-1.34) under these conditions. Similarly, ABA triblock copolymers were obtained by sequential addition of MMA, BuA, and MMA [89]. AB block copolymers could be obtained by sequential addition of (L,L)-lactide and (D,D)-lactide (PDI = 1.38) as well as -caprolactone and (l,l)- lactide monomers (PDI = 1.36) in the presence of Y(OCH2CH2NMe2) [82]. 

Table 8.3 Representative Monomer Reactivity Ratios in Anionic Copolymerization...

The Alfrey-Price Q and e values (17) were calculated from the monomer reactivity ratios in the copolymerization with 4VP = 0.68 and ex = 0.58. 

The monomer reactivity ratios in the anionic copolymerization of methacrylates are listed in Tables 17 and 18. ) in the copdyn rizations of... 

Table 17. Monomer reactivity ratios in the copolymerization of methyl methacrylate(Mj) with various methacrylates(M2) by BuLi in toluene and in tetrahydrofuran at -78 C, Ref. ...

Table 18. Monomer reactivity ratios in the anionic copolymerization of methacrylates... 

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