Effect of nonelectrostatic interactions on the macromolecular behavior of polyelectrolyes. II. Influence of urea and dyes on the viscometric and optical behavior of PLL

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Abstract
The effect of urea and of dyes on the viscometric behavior of aqueous solutions of PLL has been investigated. The compact structure, which is characteristic of PLL in pure water, is found to disappear progressively as the amount of urea is increased. This is interpreted as due to the destruction in such media of nonelectrostatic interactions responsible for the stabilization of the compact structure of PLL in pure water. In 8M urea, the macromolecular behavior of PLL during the ionization is dependent only on the repulsive interactions between the charged groups. The extension of PLL is then practically independent of the nature of counterions, contrary to what was observed in pure water. In the presence of dye (acridine orange), the compact form of PLL is stabilized, and the dye is found to bind for the two structures of PLL. The analogy between the behavior of Bu4N+ and that of dye is in agreement with the fact the Bu4N+ leads to a stabilization of the compact structure by way of specific interactions between N‐tetraalkylammonium counterions and the PLL chain through the structure of water. The hydrodynamic behavior of PLL is in good agreement with data obtained from potentiometric and optical activity measurements.

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