Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 23: Poster: Semicrystalline Polymers, Polymer Crystallization and Self-Assembly
CPP 23.14: Poster
Dienstag, 15. März 2011, 18:00–20:00, P2
Morphological study of Langmuir films of Polyglutamate — •Renate Reiter1, Frédéric Wintzenrith2, and Günter Reiter1 — 1Physikalisches Institut, Universität Freiburg, Germany — 2Ecole Polytechnique, France
Langmuir monolayers are ideal systems for experimental studies of two dimensional physical phenomena. Poly-γ-benzyl-L-glutamate (PBLG) forms rigid rods with flexible side chains when it is in α-helical conformation. Liquid crystalline- and gel-phases have been observed in organic solvents. When these hydrophobic molecules are confined to the air water interface, the rods lay down flat and can form network-like structures. We want to understand the mechanisms governing the formation of these structures. With a Langmuir trough we investigated phase transitions in such PBLG- layers by recording surface pressure (π) versus area (A) isotherms. Furthermore, the temporal evaluation of π gave valuable information on relaxation processes. The obtained film morphologies were visualized directly on the water surface by means of BAM and, after film transfer onto solid substrates, with AFM. Our results strongly suggest that isotherms recorded in the standard way do never represent equilibrated states. At constant area, a complex, non-uniform decay of π in time was observed indicating molecular rearrangement. At high packing densities π slowly decays to zero. Surprisingly, even after such relaxation, a layer with fibrillar morphology was transferred. Moreover, the isotherms showed intricate hysteretic and relaxation behavior. Can we achieve nematic-like structures in quasi 2D films?