Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: POSTERS Colloids and Liquids

CPP 39.22: Poster

Thursday, March 26, 2009, 17:00–19:30, P3

Aggregation of cationic surfactants with different counterions in the presence of poly(methacrylic acid) — Dan F. Anghel, Shuji Saito, •Alina Iovescu, Adriana Baran, and Gabriela Stinga — 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 points, determined from surface tension measurements, indicated the concentrations at which primary and secondary aggregates were formed. 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). The formation of hierarchical polymer-surfactant super-structures was highly influenced by the cationic surfactant concentration and counterion nature and by the polymer hydrophobic character.