Complexation between complementary macromolecules

Complexes stabilized by entropic driving forces become stronger with increases in temperature. Examples include polyelectrolytes in aqueous solutions [1], some polypeptides [79], and hydrogen bonded complexes of PMAA which undergo secondary stabilization via hydrophobic [33,37,39,40] interactions. Furthermore, binding between complementary macromolecules may be in competition with binding of microions in the solution [1,2,7-13,16,22,27,29]. This competition may lead to dissociation of the macromolecular complex when the complex is exposed to a high concentration of electrolyte. 

Interactions between chemically and structurally complementary macromolecules have usually a cooperative character. Probably, the formation of cooperative systems involving two (or more) types of bonds at the same time (e.g. of ionic and hydrogen bonds)63 is possible. It should be mentioned here that hydrophobic interactions play an important role in the stabilization of synthetic and natural polyelectrolyte complexes and also of complexes with hydrogen bonds. The contribution of either interactions may be different, depending on the chemical structure of the components of the polycomplex and the nature of the medium. 

One can differentiate two main methods for obtaining polymer-polymer complexes 1) formation of complexes from pre-existing chemically and structurally complementary macromolecules 2) polymerization of monomers in the presence of matrix macromolecules introduced in the reaction media. Such matrix polymerization is accompanied by the formation of polymer complexes. In the first case, the chemical reaction proceeds via complex formation by random contacts between reacting chains. Then, these sequences of pairs of connected chains grow. In matrix polymerization, the complex is formed by the mechanism of consecutive addition of monomer along the chain leading to the formation of the so-called zip-up (double-stranded) structure, due to matrix control of polymerization. One can expect that the various mechanisms lead to the formation of complexes with a different structure and properties. Indeed, a difference in the composition and properties of complexes obtained by various methods has been found So, the comparison of complexes poly(methacry-lic acid)-poly(2-N,N-dimethylaminoethyl methacrylate), obtained by mixing of equimolar quantities of components in solution and also by the matrix polymerization of dimethylaminoethyl methacrylate in water in the presence of PMAA, shows a difference in composition. In the first case, the content of acid in the complex is always... 

The study of interaction between two complementary macromolecules and the aggregation of the resulting complexes to a supramolecular structure in solution is of special interest, because biological phenomena, such as enzymatic processes and muscle contraction are based on the specific interactions of protein-protein type. 

Intermacromolecular hydrogen bonds, interactions of non-polar groups in water, and electrostatic interactions between macromolecules lead to the formation of polymer complexes consisting of cooperatively bonded continuous sequences of monomer units of complementary polymer chains or to the formation of poly-... 

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