Microcalorimetric and SAXS Determination of PEO−SDS Interactions: The Effect of Cosolutes Formed by Ions

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• 作者：Aparecida Mageste Barbosa ; Igor Jos Boggione Santos ; Guilherme Max Dias Ferreira ; Maria do Carmo Hespanhol da Silva ; lvaro Vianna Novaes de Carvalho Teixeira ; Luis Henrique Mendes da Silva
• 刊名：Journal of Physical Chemistry B
• 出版年：2010
• 出版时间：September 23, 2010
• 年：2010
• 卷：114
• 期：37
• 页码：11967-11974
• 全文大小：288K
• 年卷期：v.114,no.37(September 23, 2010)
• ISSN：1520-5207

文摘

The effect of different ionic cosolutes (NaCl, Na₂SO₄, Li₂SO₄, NaSCN, Na₂[Fe(CN)₅NO], and Na₃[Co(NO)₆]) on the interaction between sodium dodecyl sulfate (SDS) and poly(ethylene oxide) (PEO) was examined by small-angle X-ray scattering (SAXS) and isothermal titration calorimetric techniques. The critical aggregation concentration values (cac), the saturation concentration (C₂), the integral enthalpy change for aggregate formation (ΔH_agg(int)) and the standard free energy change of micelle adsorption on the macromolecule chain (ΔΔG_agg) were derived from the calorimetric titration curves. In the presence of 1.00 mmol L⁻¹ cosolute, no changes in the parameters were observed when compared with those obtained for SDS−PEO interactions in pure water. For NaCl, Na₂SO₄, Li₂SO₄, and NaSCN at 10.0 and 100 mmol L⁻¹, the cosolute presence lowered cac, increased C₂, and the PEO−SDS aggregate became more stable. In the presence of Na₂[Fe(CN)₅NO], the calorimetric titration curves changed drastically, showing a possible reduction in the PEO−SDS degree of interaction, possibility disrupting the formed nanostructure; however, the SAXS data confirmed, independent of the small energy observed, the presence of aggregates adsorbed on the polymer chain.