Interactions of Ionic Surfactants With PEO-PBO-PEO Triblock Copolymers in Aqueous Solutions

Abstract

The interactions of triblock copolymers (TBP) with ionic surfactants were studied employing surface tensiometry, electrical conductivity, steady-state fluorescence (SSF), and dynamic light scattering (DLS) techniques. An increasing trend in the critical micelle concentration (CMC) of SDS/CTAB in the presence of triblock copolymers was observed especially at higher polymer to surfactant ratio. The delay in the CMC of surfactants was more pronounced in the presence of E₄₈B₁₀E₄₈ possibly due to its less hydrophobic nature. The negative values of free energy of micellization (ΔG_m) both in case of SDS and CTAB confirmed the spontaneity of the processes. The aggregation number (N_agg) and hydrodynamic radius (R_h) of polymer/surfactant mixed systems were determined by SSF and DLS. The suppression of the surfactant micelle size in the presence of TBP was confirmed by SSF and DLS studies.

Keywords:

• Block copolymer
• critical micelle concentration
• CTAB
• DLS
• N_agg
• pyrene
• R_h
• SDS

Acknowledgments

The authors are highly grateful to Dr. Peter M. Budd and Dr. Carin Tattershall, University of Manchester, UK, for synthesis of the copolymers. Thanks is also extended to Prof. Dr. Guangzhao Zhang USTC for his kind cooperation and helpful discussion. A. Khan is grateful to the Higher Education Commission, H.E.C, Pakistan for its financial support under indigenous Ph.D. fellowship scheme and IPFP-program. He also wishes to acknowledge the Third World Academy of Sciences for a split Ph.D. research fellowship to work in the Department of Chemical Physics, University of Science and Technology, Hefei, China.

Notes

^a,b,c Values from Refs.^[11–13]

^a,b,c,d Values from Refs.^{[ 30 – 33 ]}