Thèse de doctorat en Physique - Chimie
Sous la direction de Günter Reiter.
Soutenue en 2007
à Mulhouse .
Transforming thin solid films of PS-PBLG into solutions, via exposure to solvent vapor, allowed us to nucleate and grow in such solutions ordered ellipsoidal 3D structures containing millions of molecules. These structures were randomly oriented but homogeneously distributed on the film surface and possessed an anisotropic shape which we attributed to asymmetric growth in lateral directions. The experiments presented in this work proved that the size of ellipsoidal structures (limited due to decrease of supersaturation) was found to be increasing with the decrease of polymer concentration in film solution. Consequently, the ordering of polypeptides in a film solution at two consecutive polymer concentrations led to a bimodal distribution of ellipsoidal structures on the film surface. Performing experiments under different environmental conditions allowed us to conclude that polymer solubility could be influenced via surrounding gas-phase humidity variation. Increasing the humidity of the surrounding gas-phase led to a decrease of the value of polymer solubility and to an increase of interfacial tension between the ordered structures and the solution. We proposed that complexation of PBLG by water, via hydrogen bonding interactions, led to a "new" polymer which causes the formation of solid ordered structures also at low polymer concentrations. We tested this hypothesis by using besides water also other protic nonsolvents like methanol or trifluoroacetic acid. At the end, we have shown that the process of ordered structure formation was reversible upon varying humidity or vapor pressure of a protic non-solvent in the surrounding gas-phase.
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