Polymer conformation neutralization effects

To isolate the pH effect on the polymer conformation, the diffusion of a neutral redox-active molecule, Fc(CH20H)2, was examined assuming that it does not electrostatically interact with the polymer chains. The limiting current of Fc(CH20H)2 decreased only by 30% (Fig. 8.11b) with no abrupt change when pH was lowered from neutral to acidic, which should result exclusively from the conformational changes in the PDMAFMA chains. 

Synthetic optically active polymers and their chiroptical properties during neutralization was thoroughly studied by Selegny, Vert et al. [78—80]. For further details see the lecture of M. Vert, this Symposium. Though beyond the scope of this chapter a special case of reaction between two optically active polyelectrolytes should be described. As models for connective tissue systems the interaction between mucopolysaccharides and cationic polypeptides were studied by Blackwell et al. [44]. The results of CD measurements indicate that the mucopolysaccharides have a conformation directing effect on polypeptides such that the polypeptides adopt the a-helical conformation. The strength of the interaction and the stoichiometry depend on position, number and type of anionic groups attached to the polysaccharide backbone. 

Conformations of the polymers were studied by CD and optical rotation measurements. Poly-L-lysine is known to exist in disordered, helical and -conformation, depending on the temperature, pH of the system and the solvent used. The side chain of the polymer has a significant effect on the backbone conformation. At neutral pH, poly-L-lysine exists in a random coil structure while at pH above 10, the e-amino group becomes a neutral form and the polymer undergoes transition to a helical structure. In order to elucidate the effect of base substituents on the conformation of poly-L-lysine, CD spectra of the copolymer were measured. 

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