Interplay of Electrostatic and Hydrophobic Effects with Binding of Cationic Gemini Surfactants and a Conjugated Polyanion:  Experimental and Molecular Modeling Studies

• Published in: The journal of physical chemistry. B 2007-05, Vol.111 (17), p.4401-4410
• Main Authors: Burrows, Hugh D, Tapia, María J, Silva, Claudia L, Pais, Alberto A. C. C, Fonseca, Sofia M, Pina, João, Seixas de Melo, J, Wang, Yujie, Marques, Eduardo F, Knaapila, Matti, Monkman, Andrew P, Garamus, Vasil M, Pradhan, Swapna, Scherf, Ullrich
• Format: Article
• Language: English
• Subjects: Alkanesulfonates - chemistry; Cations - chemistry; Computer Simulation; Fluorenes - chemistry; Hydrophobic and Hydrophilic Interactions; Models, Molecular; Molecular Structure; Neutrons; Photochemistry; Polymers - chemistry; Static Electricity; Surface Properties; Surface-Active Agents - chemistry
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp070100s

Understanding factors responsible for the fluorescence behavior of conjugated polyelectrolytes and modulation of their behavior are important for their application as functional materials. The interaction between the anionic poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl}copolymer (PBS−PFP) and cationic gemini surfactants α,ω-(C m H2 m +1N+(CH3)2)2(CH2) s (Br-)2 (m-s-m; m = 12, s = 2, 3, 5, 6, 10, and 12) has been studied experimentally in aqueous solution. These surfactants are chosen to see whether molecular recognition and self-assembly occurs between the oppositely charged conjugated polyelectrolyte and gemini surfactant when the spacer length on the surfactant is similar to the intercharge separation on the polymer. Without surfactants, PBS−PFP exists as aggregates. These are broken up upon addition of gemini surfactants. However, as anticipated, the behavior strongly depends upon spacer length (s). Fluorescence measurements show three surfactant concentration regimes:  At low concentrations (