Self-association of decyl moieties covalently linked to a polyelectrolyte in a small amount

Self-association behavior of random copolymers of sodium 2-(acrylamido)-2-m ethylpropane sulfonate (AMPS) and N-dodecylmethacrylamide (DodMAm) with low DodMAm contents (f(Dod)) of 2.5-10 mol% was investigated mainly by QELS. I n the case of the copolymer with f(Dod) = 10 mol%, the relaxation time dist ribution is unimodal independent of the polymer concentration. On the other hand, in the case of the copolymers with f(Dod) = 2.5-7.5 mol%, the relaxa tion time distributions became bimodal at polymer concentrations > 5 g/L, i ndicating interpolymer associations occurring at higher concentrations of t he polymers. From QELS results, apparent values of hydrodynamic radii (R-h) for unimers and the interpolymer associates were estimated to be ca 6-7 an d ca. 120 nm, respectively. The interpolymer associates were found to be di srupted by the addition of a nonionic surfactant n-dodecyl hexaethylene gly col monoether.