Alfrey-Price parameters

Acrylamide (AM), 1.288-301, 410 Alfrey-Price parameters, 7 617t economic aspects, 1 295-296 health and safety factors, 1 297-300 manufacture, 1 293-295 monomer, 20 460-461 monomer for amino acid resins,... 

Acrylic tow, 11 212 Acrylic weak base resins, 14 389 Acrylonitrile (AN), 1 397—414 10 665-666 11 5 17 228 24 272 acetylene-derived, 1 229 Alfrey-Price parameters, 7 617t azeotropes, l 399t... 

Alfrey-Price parameters, 7 617t reactivity ratio from Alfrey-Price scheme compared with experimental data, 7 618t... 

Hexene, 17 722 20 414 Alfrey-Price parameters, 7 617t catalytic aerogels for epoxidation, l 763t... 

Isophthaloyl chlorides, 19 715 Isophytol, 24 502, 550 Isopolytungstate compounds structures of, 25 383-384 Iso prefix, 13 594-595 Isoprene, 24 501 Alfrey-Price parameters, 7 617t block copolymer synthesis, 7 647t butyl rubber polymers, 4 433 commercial block copolymers, 7 648t glass transition and melting... 

Methyl methacrylate (MMA), 16 227 Alfrey-Price parameters, 7 617t azeotropic mixtures with, 16 236t block copolymer synthesis, 7 647t C-2 routes to, 16 252-254 C-3 routes to, 16 246—252 C-4 routes to, 16 254—257 carbon monoxide in production of, 5 6 chain-transfer constants for, 16 284t comonomer with acrylonitrile, 1 451t cumene as feedstock, 8 156 in flame-retardant resin formulation,... 

Alfrey-Price parameters, 7 617t alkoxycarbonylation of, 16 252 alkylation of, 2 176, 182, 188 20 782 ammoxidation to acrylonitrile,... 

The results of the Alfrey-Price Q-e parameters [76] (where Q and e take into account the stabilization by resonance and the polar effects of the monomer) are commonly used to predict the monomer reactivity ratios. The Alfrey-Price parameters are known for AN, MAN, MVCN, and MATRIF [68]. The calculated values of the reactivity ratios, and r2, and the product (rj x rj) are summarized in Table 20.2. 

TABLE 20.2 Reactivity Ratios of Cyano Monomers (r ) and MATRIF (rj) and the Values of the Product (r X Calculated from the Alfrey-Price Parameters (T = 80° C) [73]... 

Acrylamide copolymerizes with many vinyl comonomers readily. The copolymerization parameters ia the Alfrey-Price scheme are Q = 0.23 and e = 0.54 (74). The effect of temperature on reactivity ratios is small (75). Solvents can produce apparent reactivity ratio differences ia copolymerizations of acrylamide with polar monomers (76). Copolymers obtained from acrylamide and weak acids such as acryUc acid have compositions that are sensitive to polymerization pH. Reactivity ratios for acrylamide and many comonomers can be found ia reference 77. Reactivity ratios of acrylamide with commercially important cationic monomers are given ia Table 3. 

When the reactivity ratios ry can be expressed in terms of the parameters of the well-known Q-e scheme of Alfrey-Price [20,157], the condition (4.20) always holds [147, 150] and in the case of terpolymerization the general Eqs. (3.8) and (4.10) transform into the simplified equation [158]. It is rather curious that similar equations have been derived at the end of the 1940s [159] within the framework of the Alfrey-Price scheme, being investigated even for the general case of copolymerization of arbitrary number m of monomer types. 

The violation of the condition (4.20) for the particular system means that the latter can not be described by the Q-e scheme. However, in addition to this scheme, there are known some others, also applied for the description of the reactivity of the polymer radical in propagation reactions [160], One such scheme proposed by Bamford [161, 162] was successfully used by Jenkins [163] for an interpretation of the experimental values [150] of parameter H for a number of ternary systems. For many of these the values of H are noticeably different from unity, as it has to be according to the predictions of the Alfrey-Price scheme, but are in satisfactory agreement with the values calculated through the Bamford scheme [163, 160],... 

The electron richness of vinylferrocene as a monomer has been demonstrated in its copolymerization with maleic anhydride, in which 1 1 copolymers were obtained over a wide range of feed ratios and ri r2 = 0.003 [13]. Subsequent copolymerization of vinylferrocene with classic organic monomers, such as styrene [13], Ai-vinyl-2-pyrrolidone [15], methyl methacrylate [13] and acrylonitrile [13] were carried out and the Alfrey-Price Q and e parameters [16] determined. The value of e is a semiempirical measure of the electron richness of the vinyl group. The best value of e for vinylferrocene is about —2.1, which, when compared with the e values of maleic anhydride (-H 2.25), p-nitrostyrene (-1-0.39), styrene (—0.80), p-Ai,Ai -dimethyl-aminostyrene ( — 1.37) and l,T-dianisylethylene ( — 1.96), again emphasizes the electron rich nature of the vinyl group in vinylferrocene. 

These parameters also have been useful through the Alfrey-Price Q e scheme (33) for assessing the merit of new monomers in multicomponent macromolecular compositions. From the data just cited for ionogenic monomers and from the strength of associations that affect significant viscosity increases cited in Chapters 18 and 21-27 for hydrophobic monomers, it... 

Table 7.2. Correlation parameters for the reactivity of monomers towards radical polymerization in terms of the Alfrey Price (Q, e), Bamford -Jenkins (a, P), and Ito hfetsuda (AT, P) schemes...

The relation between monomer reactivity ratios and the Alfrey-Price Q-e parameters is explained in the introduction to the tables of monomer reactivity ratios and Q-e values, compiled by Robert Z. Greenley and published in the present volume (1,2). Although very widely used, the Q-e scheme is well known to have serious limitations (3), which have prompted several attempts to improve upon it. Qne such endeavour was the Patterns of Reactivity scheme, first described as long ago as 1959 (4-7), when the Q-e scheme was only about ten years old despite the indisputably more satisfaetory basis of this procedure, it did not achieve popularity but recent revisions have greatly improved both its accessibility and its accuracy (3,8,9). 

The Price-Alfrey approach begins by defining three parameters-P, Q, and e-for each of the comonomers in a reaction system. We shall see presently that the parameter P is rapidly eliminated from the theory. As a result, the Price-Alfrey system is also called the Q-e scheme for copolymerization. 

Alfrey and Price proposed a means of predicting monomer reactivity in copolymerization from two parameters, (a measure of resonance) and e (a measure of polar effects) (8). These parameters have been related to the reactivity ratios by equations 15—17. 

These are simply the equations of Alfrey and Price (1 j, which relate monomer reactivity ratios to Q and e values, and in which the reasonable values of 2 = and 2 = 1 re substituted, with the convention that the reference standard, ethylene, is monomer 2. In Equation 6 it is seen that the Qi value is simply a ratio of propagation rate constants unmodified by the presence of differences in e values, as is the case in the styrene-based scheme. This would seem to be a more desirable type of parameter to deal with, simply because its meaning is perfectly straightforward. 

All the above factors controlling monomer and radical reactivities contribute to the rate of polymerization, but in a manner which makes it difficult to distinguish the magnitude of each effect. Attempts to correlate copolymerization tendencies based on these factors are thus mainly of a semiempirical nature and can, at best, be treated as useful approximations rather than rigorous relations. However, a generally useful scheme was proposed by Alfrey and Price [23] to provide a quantitative description of the behavior of diferent monomers in radical polymerization, with the aid of two parameters, for each monomer rather than for a monomer pair. These parameters are denoted by Q and e and the method has been called the Q — e scheme. It allows calculation of monomer reactivity ratios r and T2 from properties of monomers irrespective of which pair is used. The scheme assumes that each radical or monomer can be classified according to its reactivity or resonance effect and its polarity so that the rate constant... 

Taking into account polarity, steric factors, and resonance stabilization, T. Alfrey and C. C. Price (7) developed a Q-e scheme and predicted monomer reactivity. The effect of polarity on vinyl monomer copolymerization was recognized by F. R. Mayo and coworkers (8), who distinguished between monomers of average activity and those acting as electron donors or acceptors. By combining these theories with experimental data, calculation of product probabilities of various monomer combinations and determination of monomer reactivity parameters were possible. 

Alfrey and Price [24, 25] devised a new set of parameters, analogous to Hammett s, but specific to homolytic reactions. Their substituent constant Q was based on the 16 possible radical polymerisations involving styrene, methyl methacrylate, acrylonitrile and vinylidine chloride. Styrene was taken as the... 

The reactivity ratios depend on the system used for their determination and must be determined for each monomer pair of interest. Alfrey and Price -recognized the need for general and constant parameters by which a given monomer could be characterized. This led to the development of the Q-e... 

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