Polymer complex, complexation/dissociation change

Change of Association-Dissociation Interactions in Polymer Complexes... 

The time dependency in Figure 1 suggests that the self-association of the nucleic acid bases in the poly(ethyleneimine) derivatives dissociated slowly by accompanying change in conformation, and formed the intermole-cular polymer complex by the interaction between adenine and thymine bases. Similar results were reported on the polymer complex formation between poly(methacrylate) derivatives of uracil and adenine, where the self association of the uracil bases in the polymer inhibited the polymer complex formation.22 23,26 Therefore, the conformational change of the synthetic polymers seems to be important for the formation of a stable polymer complex. 

In the open system, the complex once formed is dissociated into two component polymers according to the changes in environmental factors, and then a different pair of component polymers forms another type of complex. On the contrary, in a closed system, before the complex is completely destroyed, the third component polymer interacts with the complex to form a ternary polymer complex, and the first component polymer is dissociated from the ternary complex. In the closed system, the substitution reaction, especially the releasing process of the first component polymer, seems to be accelerated when the interaction force between a parent polymer matrix chain and the third component polymer chain is stronger. 

The several theoretical and/or simulation methods developed for modelling the solvation phenomena can be applied to the treatment of solvent effects on chemical reactivity. A variety of systems - ranging from small molecules to very large ones, such as biomolecules [236-238], biological membranes [239] and polymers [240] -and problems - mechanism of organic reactions [25, 79, 223, 241-247], chemical reactions in supercritical fluids [216, 248-250], ultrafast spectroscopy [251-255], electrochemical processes [256, 257], proton transfer [74, 75, 231], electron transfer [76, 77, 104, 258-261], charge transfer reactions and complexes [262-264], molecular and ionic spectra and excited states [24, 265-268], solvent-induced polarizability [221, 269], reaction dynamics [28, 78, 270-276], isomerization [110, 277-279], tautomeric equilibrium [280-282], conformational changes [283], dissociation reactions [199, 200, 227], stability [284] - have been treated by these techniques. Some of these... 

The large contraction change shown by curve 2 is due to polymer dehydration or precipitation induced by complexation between PEO and PMAA. It is evident that the dehydration or precipitation is enhanced by complexation compared to curve 1. Furthermore, curve 2 indicates a reversible contraction/ recovery change, suggesting that complexation and dissociation occur reversibly with temperature changes within the PMAA gel. This drastic contraction change can be applied to temperature sensitive hydrogels as well. 

Fibrin polymers are responsible for the fibrin-dependent enhancement of Factor XIII activation (Greenberg et al, 2003). The mechanism for this effect involves the formation of a tight ternary complex between fibrin, Factor XIII, and thrombin, accompanied by a conformational change of Factor XIII that exposes the active site, after which Factor XHIa remains bound to fibrin. However, the B chains dissociate, which is necessary to expose the active site cysteine of plasma Factor XIII. Platelet Factor XIII without the B chains, is more rapidly activated by thrombin than plasma Factor XIII because of the time that it takes for the B chains to dissociate. 

This implies that the reactivity of the polyanion chain partially covered by the polycation may be considered to be higher than that of the free chain, probably owing to the changes of conformation, dissociation and microenvironment in the doamin of the polymer chain. Therefore, completely neutralized polyelectrolyte complexes and completely free polyelectrolytes coexist in the solution (for detail see Sect. 3.2.2). 

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