کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
600609 1454305 2012 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Salt effect on microscopic structure and stability of colloidal complex obtained from neutral/polyelectrolyte block copolymer and oppositely charged surfactant
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی شیمی کلوئیدی و سطحی
پیش نمایش صفحه اول مقاله
Salt effect on microscopic structure and stability of colloidal complex obtained from neutral/polyelectrolyte block copolymer and oppositely charged surfactant
چکیده انگلیسی

The salt effect on complex formation of poly(acrylamide)-block-poly(acrylic acid) (PAM-b-PAA) and dodecyltrimethylammonium bromide (DTAB) at different NaBr concentrations, CNaBr, was investigated by laser light scattering (LLS) and small angle neutron scattering (SANS). LLS and SANS clearly indicates that the aqueous solution of PAM-b-PAA and DTAB associate into colloidal complexes. For low surfactant-to-polymer charge ratio Z lower than the critical value ZC, the colloidal complexes are single DTAB micelles dressed by a few PAM-b-PAA. Above ZC, the colloidal complexes form a core–shell microstructure. The complex formation in the PAM-b-PAA/DTAB is enhanced by addition of salt: ZC decreases with increasing CNaBr. This is considered to similar to the cmc behavior for the pure surfactant system. The core of the complex consists of densely packed surfactant micelles (DTA+), and PAA block chains bind to these micelles, displace their counteranions (Br−) and bridge them. The corona of the complex is constituted from the PAM. Since the interaction between polyelectrolyte and oppositely charged surfactant is primarily electrostatic in nature, the core radius and the intermicellar distance of the DTA+ micelles inside the core depend on CNaBr. The addition of salt screens the electrostatic attraction between oppositely charged PAA block and DTAB, which weakens the interaction. With increasing CNaBr, therefore, the core of the colloidal complex is considered to swell, which leads to the increases in the core radius RC and the intermicellar distance of the DTA+ micelles inside the core. The aggregation number expressed in terms of DTA+ micelles per complex is also evaluated using the analogy with the homopolyelectrolyte/surfactant system.

Figure optionsDownload as PowerPoint slideHighlights
► Salt effect on microscopic structure and stability of colloidal complex.
► Complex consists of neutral/polyelectrolyte block copolymer and oppositely charged surfactant.
► The core consists of densely packed surfactant micelles and polyelectrolyte chains.
► The corona of the complex is constituted from the neutral chains to maintain steric stability.
► With increasing salt concentration, the core of the complex swells.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Colloids and Surfaces B: Biointerfaces - Volume 99, 1 November 2012, Pages 127–135
نویسندگان
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