Influence of External Factors on the Micellization Process and Aggregate Structure of Poly(oxy)styrene-Poly(oxy)ethylene Block Copolymers

详细信息    查看全文

• 作者：Emilio Castro ; Silvia Barbosa ; Josué ; Ju&aacute ; rez ; Pablo Taboada ; Issa A. Katime ; Ví ; ctor Mosquera
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：May 1, 2008
• 年：2008
• 卷：112
• 期：17
• 页码：5296 - 5304
• 全文大小：135K
• 年卷期：v.112,no.17(May 1, 2008)
• ISSN：1520-5207

文摘

Solutions of the polyoxystyrene-polyoxyethylene block copolymer SO₁₇EO₆₅, where SO denotes polystyreneoxide block as the hydrophobic block and EO the polyethylene oxide block as the hydrophilic block, inmixtures of water (a selective solvent for the EO blocks) and 1,4-dioxane (a good solvent for both blocks)were studied by surface tension and light scattering measurements. Surface and micellar structural parametershave been analyzed as a function of solvent composition. The critical micelle concentration increases and themicellar aggregation number decreases, respectively, as the amount of 1,4-dioxane in the binary solventincreases as a consequence of the enhanced solubility of the SO blocks in the solvent mixture, causing thelowering of the interfacial tension between the hydrophobic blocks in the micellar core and the solvent;therefore, to achieve thermodynamic equilibrium, the micelle size decreases. In addition, static light scattering(SLS) has been proved to be a useful technique to detect the lower boundary of the transition between adilute micellar solution (sol) to a local-ordered micellar solution (soft gel) resulting from a percolationmechanism. Comparison of the sol-soft gel boundaries obtained from SLS for copolymers SO₁₇EO₆₅ andEO₆₇SO₁₅EO₆₇ with those previously derived by rheology is made. Finally, changes in the autocorrelationfunction of the solutions at the boundary obtained from dynamic light scattering are also analyzed.