Interpolymer complexes selectivity

Interpolymer complexation between water-soluble polymers by hydrogen bonding was a frontier subject in the 1970s. Polyfcarboxylic acids), mainly po-lyfacryhc acid) (PAA) and poly( methacryflc acid) (PMAA), served as the most common proton-donating components. As for the proton-accepting polymers, poly(ethylene oxide ) (PEO or PEG) and poly(M-vinyl-2-pyrrolidone) (PVPo) were often used. The important results on the formation of complex aggregates and its dependence on the structur prameters have been reviewed [2,3,8]. In this section we select a few representative topics to look at recent advances in interpolymer complexes in aqueous media, with the emphasis on fluorescence probe studies. 

In this review, the problems of complex formation in different systems of interacting macromolecules namely in polymer-polymer, polymer-alternating or statistical copolymer systems are discussed. The influence of solvent nature, the critical phenomena, equilibrium, selectivity and co-operativity in reactions are considered. The perspectives of development of this field of polymer science and the potential practical applications of interpolymer complexes are pointed out. 

In some cases of the titration of one polymer with another one (polymers are complementary, i.e. they contain groups, which are capable to interact specifically, e.g. poly(acrylic add) and the copolymer of N-vinylpyrrolktone and acrylic add) no inflection point on the titration curves were observed. Therefore, the titrations do not indicate the interaction in PAA-VP/AA system, in contrast to systems composed of poly(methacrylic acid) and the copolymer N-vi nylpyrrolidone and acrylic add221 (Fig. 2). Apparently, subtle differences in the chemical structure of components predetermine the possibility or impossibility of complex formation, which is an evidence for a high selectivity of the polymer-polymer interactions. Even when one of the components is a low molecular compound (Fig. 1, curve 1), complex formation is not observed. Interpolymer complexes can be divided into several types, due to the kind of the dominating interaction ... 

Interpolymer-complexation-induced morphology evolution in selective solvents was reported by Salim et al. 

Complexation in its various forms plays a key role in the homo- and copolymerization of 1-alky 1-4-vinylpyridinium ions. Intermonomer associations are believed responsible for the enhanced poly-merizability of monomers with long alkyl chains (C , n > 6) on nitrogen, the ability of the title monomers to copolymerize with anionic and Ti-rich monomers, and the strong dependence on concentration for homopolymerization of all these cationic monomers. Hydrophobic interactions between lipophilic monomers, electrostatic attraction between cationic and anionic monomers, and charge-transfer complexation between Ti-rich and Ti-deficient monomers have all been observed to control polymer formation. Monomer organization/orientation on polyanion templates, at organic solvent-water interfaces and in ordered multiple-phase systems such as micelles, membranes, vesicles, and microemulsions have been used with limited success in attempts to control the microstructure (e.g. tacticity, monomer sequence) in the related polymers. Interpolymer complexes of poly(l-alky 1-4-vinylpyridinium ions) with natural and synthetic poly anions represent a rich resource for the development of selective electroanalytical methods, for efficient new separation procedures, for manipulation of biomembranes in drug dehvery, and numerous other applications. 

In the case of the OEI-POE-PMAA system [OEI = oligo(ethyleneimine)], from the elemental analysis as summarized in Table 12.4, OEI was discovered in the precipitate at the low pH region. Moreover, in the higher pH region, (pH = 10), the precipitate is not obtained. From these results, the selective formation of interpolymer complexes can be represented by the following equations. 

Table 12.4. Selective interpolymer complexation in the PMAA-POE-OEP systems...

Using other polymers, e.g. poly(acrylamide) (PA Am), poly(iV-vinyl-2-pyrrolidone) (PVPo), and poly(vinyl alcohol) (PVA), the ability of selective interpolymer complex formation was studied. The order is as follows ... 

As mentioned previously, selective interpolymer complexation depends on the magnitude of the total bond energy between each pair of polymers. Therefore, if PI can interact with P2 more strongly than P3, the interchain macromolecular substitution reaction of P3 and PI should take place on the addition of PI to the P2-P3 complex solution. In this system, a cooperative interpolymer substitution reaction is... 

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