Dresden 2009 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 11: POSTERS Amphiphilic Systems

CPP 11.8: Poster

Dienstag, 24. März 2009, 14:00–16:30, P3

Aggregation of cationic surfactants with different counterions in the presence of poly(methacrylic acid) — •Alina Iovescu, Dan-Florin Anghel, Shuji Saito, Adriana Baran, and Gabriela Stînga — Department of Colloids, *Ilie Murgulescu* Institute of Physical Chemistry, Spl. Independentei 202, Bucharest, Romania

Counterions effect of a cationic surfactant upon its interaction with poly(methacrylic acid) (PMA) was investigated and compared with the analogous in poly(acrylic acid) (PAA) systems. Decylammonium (DeA+) with different counterions (Cl-, SCN-, acetate (Ac-) and butyrate (Bu-) were employed. The interaction critical concentrations, determined from surface tension measurements, were the critical aggregation concentration (cac or T1) at which the surfactants are abruptly bound to the polymer chain in a micellar form (the primary aggregates), T2' at which the isolated primary aggregates on the polymer chain begin to contact with each other forming secondary aggregates, and T2 at which free micelles appear in equilibrium. For each counterion, T1 with PMA was higher than the respective T1 with PAA. In aqueous solution, PMA was compactly coiled up forming hydrophobic microdomains (HMD) in the chain. The surfactants were first bound to the HMD, and at T1 the free ones cooperatively formed primary aggregates on the other parts of PMA. Different from PAA systems, T1 with PMA was the sum of the surfactant amount bound to HMD and the ordinary cac. For both polymers, T1 raised in the order DeA-Ac < DeA-Bu < DeA-Cl < DeA-SCN, which was opposite to the order of the respective critical micellar concentration (cmc).

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