HYDROPHOBIC INTERACTION OF IONENES IN AQUEOUS-SOLUTION

The effect of hydrophobic interaction on the conformation of three ionene species, 2,10-Br, 6,10-Br, and 6,6-Br, in aqueous solution was studied. In the absence of added electrolytes the polymer molecules behaved as stiff rods, while in the presence of 0.4 M KBr they had a random-coil conformation typical of an ordinary uncharged polymer. The 2,10-Br coiled up more than the other ionenes, and its steric factor sigma (= <r0(2)> 1/2/ <r(f)2> 1/2) had the smallest value. This is probably due to the different distribution of CH3 groups and the hydrophobic interaction between the "hydrophobic domain" along the backbone of the chain. A conformational change on electrolyte addition was interpreted in terms of a simultaneous decrease in electrostatic repulsion and an increase in hydrophobic attraction among the methyl groups.