Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 14: SYMPOSIUM: Understanding and Controlling Complex Structures: From Synthetic Polymers to Biomaterials II

CPP 14.4: Talk

Tuesday, March 9, 2004, 15:15–15:30, H 37

Structure and elastic properties of a block-copolymer bilayer doped with cationic surfactant — •Thomas Hellweg, Holger Egger, and Gerhard Findenegg — TU Berlin, Stranski Laboratorium f. Physikalische und Theoretische Chemie, Strasse des 17.Juni 112, 10623 Berlin

In recent years much attention was paid to the commercially available triblock copolymers poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO). The phase behavior of these polymers, often called pluronics, is investigated intensively in binary systems with water, as well as in ternary systems containing water and oil or in polymer mixtures by a lot of different research groups.

In the present work we study the influence of the cationic surfactant n-octyltrimethyl-ammonium-bromide (C₈TAB) on the triblock copolymer based system (EO₃₇-PO₅₈-EO₃₇)/water/o-xylene.
At sufficient high surfactant concentration the system shows an extended lamellar phase (L_α). This phase is characterized in terms of interlamellar spacing, thickness, and internal structure of the bilayers as a function of composition. The Caillé-model is used to correlate the profile of the first order Bragg peak with the elastic constants of the amphiphilic film. It is possible to obtain general trends for the dependence of the elastic constants κ and B of the block-copolymer-film on the surfactant concentration.