Abstract: Influence of added salts on the conformation of 6,10 Br ionene polymer has been examined by viscometry. Molecular dimensions of 6,10 Br in aqueous KBr solutions for the range between 0 to 0.4 mol L~(-1) were calculated. Results showed that corresponding changes had taken placed in four parameters which indicated the long-range interactions: the Huggins constant K' increased the Mark-Houwink exponent a decreased until approximated to 0.5, the solvent-polymer interaction parameter B reduced nearly to zero, and the expansion factor a decreased until approximated to unity when the concentration of KBr increased. These results showed that the 0.4 mol L~(-1) KBr aqueous solution was close to θ-condition. However, the parameters which related to the short-range effects (K_0 and the steric factor σ) did not appear to be affected by the concentration of added salt.
A conformational change was observed for 6,10Br from a swollen random coil in medium of low ionic strength to a compact random coil in medium of high ionic strength. The transition was interpreted in terms of simultaneous decrease in electrostatic repulsion and an increase in hydrophobic attraction among the methyl groups. Since the former interaction was more sensitive to salts than the latter did, a break appeared in the curve of log [η] plotted against the salt concentration C_s....