Maleic anhydride copolymerization reactivity ratios

Exceptionally, when both reactivity ratios are very small, a copolymer is obtained in which both monomers alternate regularly along the chain it is the case, for example, in the copolymerization of maleic anhydride with allyl acetate or with stilbene (29, 142) ... 

An excellent example of using reactivity ratios and the synthetic versatility of nitroxide systems to prepare unusual block copolymers is the copolymerization of styrene/maleic anhydride mixtures.181 When an excess of styrene is used, the copolymerization leads to preferential and finally total consumption of maleic anhydride at conversions of styrene signifi-... 

Some typical values of reactivity ratios for monomers that will copolymerize via a free-radical route are shown in Table 1.15 (Tirrell, 1989, Allcock and Lampe, 1981). These have been selected in order to span the range of values shown in the preceding tables. It may be noted that the copolymerization of vinyl monomers with maleic anhydride will invariably lead to alternating copolymers since rj 2 0. The mechanism of alternating... 

Poly(N-vinylpyrrolidone), P(NVP), is a nonionic, water-soluble polymer with high thermal and hydrolytic stability (7-9). Copolymers of N-vinylpyr-rolidone (NVP) with various carboxylate and carboxylate-precursor monomers (e.g., acrylic acid, sodium acrylate, crotonic acid, itaconic acid, and maleic anhydride) are also well-known (10). In addition, the homo- and copolymerization kinetics of these monomers are well-established. On the other hand, reports of copolymerizations of NVP with sulfonate monomers are sparse 11, 12). This chapter describes the synthesis, kinetics, and reactivity ratios for the copolymerization of NVP and some of the newer sulfonate monomers. A comparison of some of the solution properties for such copolymers is also included. 

Limited information exists in the literature, however, on the homo- or copolymerization of vinyl ethylene carbonate, 1 (VEC or 4-ethenyl-l,3-dioxolane-2-one) for the preparation of cyclic carbonate functional polymers. A few comments regarding polymerization of VEC are given in an early patent [9], In the only reported study of the copolymerization behavior of VEC, Asahara, Seno, and Imai described the copolymerization of VEC with vinyl acetate, styrene, and maleic anhydride and determined reactivity ratios [10. Their results indicated that VEC would copolymerize well with vinyl acetate, but in copolymerizations with styrene, little VEC could be incorporated into the copolymer. VEC appeared to copolymerize with maleic anhydride, however the compositions of the copolymers was not reported. Our goal was to further explore the use of VEC in the synthesis of cyclic carbonate functional polymers. 

In fact, recent theoreticaP and experimental studies of small radical addition reactions indicate that charge separation does occur in the transition state when highly electrophilic and nucleophilic species are involved. It is also known that copolymerization of electron donor-acceptor monomer pairs are solvent sensitive, although this solvent effect has in the past been attributed to other causes, such as a Bootstrap effect (see Section 13.2.3.4). Examples of this type include the copolymerization of styrene with maleic anhydride and with acrylonitrile. Hence, in these systems, the variation in reactivity ratios with the solvent may (at least in part) be caused by the variation of the polarity of the solvent. In any case, this type of solvent effect cannot be discounted, and should thus be considered when analyzing the copolymerization data of systems involving strongly electrophilic and nucleophilic monomer pairs. 

With Q-e values (20), the reactivity ratios of comonomers, rj and r, can be estimated using Equations 2 and 3. Monomer reactivity ratios can also be determined empirically by carrying out a series of copolymerizations and determining the polymer composition at low conversions. (20b) The reactivity ratios can be used to predict the nature of the copolymer type from a polymerization. For example, when the product of q and r has a value of zero, an alternating copolymer is likely to result from the copolymerization. On the other hand, when the product is near the value of one, the copolymer is likely to be a random copolymer. In a copolymerization process, if one of the comonomers does not homopolymerize, such as in the copolymerization of styrene (rj=0.019) and maleic anhydride (rj=0.0) at 50 °C (20,21), the polymer produced would be an alternating copolymer (Reaction 4). 

It was reported by Barb in 1953 that solvents can affect the rates of copolymerization and the composition of the copolymer in copolymerizations of styrene with maleic anhydride [145]. Later, Klumperman also observed similar solvent effects [145]. This was reviewed by Coote and coworkers [145]. A number of complexation models were proposed to describe copolymerizations of styrene and maleic anhydride and styrene with acrylonitrile. There were explanations offered for deviation from the terminal model that assumes that radical reactivity only depends on the terminal unit of the growing chain. Thus, Harwood proposed the bootstrap model based upon the study of styrene copolymerized with MAA, acrylic acid, and acrylamide [146]. It was hypothesized that solvent does not modify the inherent reactivity of the growing radical, but affects the monomer partitioning such that the concentrations of the two monomers at the reactive site (and thus their ratio) differ from that in bulk. 

Table 2.13 (Section 2.16.5) gives the reactivity ratios for free-radical copolymerization of styrene with (a) butadiene, (b) methyl methacrylate, (c) methyl acrylate, (d) acrylonitrile, (e) maleic anhydride, (f) vinyl chloride and (g) vinyl acetate. For each of these copolymerizations calculate ... 

A recent huge advance in this chemistry is reported by Sikes [142], and shown in Scheme 11. This significant technology advance allows the synthesis of water-soluble reactive intermediates by copolymerizing monosodium aspartate with aspartic acid in a pre-selected ratio. The intractable polysuccinimide intermediate obtained in other polymerizations of aspartic acid and ammonia / maleic anhydride mentioned earlier in alternative approaches is avoided and the copolymer is soluble in water for further functionalization. Easier handling is very important for future characterization and development of applications. 

Versions of the Bootstrap model have also been fitted to systems in which monomer-monomer complexes are known to be present, demonstrating that the Bootstrap model may provide an alternative to the MCP and MCD models in these systems. For instance, Klumperman and co-woikers have snccessfiilly fitted versions of the penultimate Bootstrap model to the systems styiene with maleic anhydride in butanone and toluene, " and styrene with acrylonitrile in varions solvents. This latter woik confirmed the earUer observations of Hill et alP for the behavior of styrene with aciylonitiile in bulk, acetonitrile and toluene. They had concluded that, based on sequence distribution data, penultimate unit effects were operating but, in addition, a Bootstrap effect was evident in the coexistent curves obtained when triad distribution was plotted against copolymer composition for each system. In the copolymerization of styrene with aciylonitiile Klumperman et alP a variable Bootstrap effect was required to model the data. Given the strong polarity effects expected in this system (see Section 12.2.2), part of this variation may in fact be caused by the variation of the solvent polarity and its affect on the reactivity ratios. In aity case, as this work indicates, it may be necessary to simultaneously consider a number of different influences (such as, for instance, penultimate unit effects. Bootstrap effects, and polarity effects) in order to model some copolymerization systems. 

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