Hydrogen-Bonding-Driven Complexation of Polystyrene-block-poly(ethylene oxide) Micelles with Poly(acrylic acid)

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• 作者：Shuguang Yang ; Xinfei Yu ; Lian Wang ; Yingfeng Tu ; Joseph X. Zheng ; Junting Xu ; Ryan M. Van Horn ; Stephen Z. D. Cheng
• 刊名：Macromolecules
• 出版年：2010
• 出版时间：March 23, 2010
• 年：2010
• 卷：43
• 期：6
• 页码：3018-3026
• 全文大小：954K
• 年卷期：v.43,no.6(March 23, 2010)
• ISSN：1520-5835

文摘

Hydrogen-bonding complexation between spherical diblock copolymer polystyrene-block-poly(ethylene oxide) (PS-b-PEO) micelles and poly(acrylic acid) (PAA) was systematically investigated. We prepared the micelles by gently adding a selective solvent, water, to a PS₂₄₀-b-PEO₁₈₂/N,N-dimethylformamide (DMF) solution. After DMF was removed by dialysis, the diluted micelles were associated with PAA at different pH values. The complexation behavior was studied via ultraviolet−visible spectroscopy, laser light scattering, ζ-potential, and transmission electron microscopy techniques. As the pH value varied, the complexation between the PS₂₄₀-b-PEO₁₈₂ micelles and PAA behaved differently. At pH < 3.0, the system was in the flocculation region where large aggregates of the micelles formed spontaneously. A single-micelle, stepwise adsorption region could be observed when the pH value was in the range of 3.0−4.8. Above a pH value of 4.8, no adsorption could be found. The value of pH 3.0 was recognized as the onset pH value for the micellar flocculation. At this value, the micelle flocculating rate was very slow, and thus the flocculating process was able to be monitored. A “pearl-necklace-like” morphology at pH 3.0 was observed, and its formation mechanism was also discussed.