Dresden 2009 – wissenschaftliches Programm

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SYSO: Symposium Self-organizing Surfaces and Interfaces

SYSO 5: Self-Organizing Surfaces and Interfaces IV

SYSO 5.5: Vortrag

Donnerstag, 26. März 2009, 12:00–12:15, GÖR 226

Lamella and Cylinder Morphologies in Confined Copolymer-Homopolymer Mixtures — •Kostas Daoulas and Marcus Müller — Institut für Theoretische Physik, Georg-August-Universität, Göttingen

The Self Consistent Field Theory (SCFT) is a powerful method for predicting the morphologies in dense, self-organizing, polymeric systems. Usually within SCFT the chain architecture is captured via a Gaussian chain model, while non-bonded interactions are considered within a Flory-Huggins approach under the assumption of total or finite incompressibility of the liquid. In the later case, the spatial density variations are commonly described within the Helfand's quadratic potential. Here we present an alternative approach, using a more elaborated representation of the non-bonded interactions in spirit of a third order virial expansion with respect to the densities of the system components. The approach allows the description of the coexistence of the polymer liquid with its vapor; an important issue when modeling thin polymer films and topographical properties (e.g. terrace formation) of the free polymer surface. The approach is illustrated considering thin films formed by blends of PEO-b-PS (polyethylene oxide, polystyrene) copolymers with PAA (polystyrene-co-acrylic acid) homopolymers. We discuss how the parameters of the model should be selected such that a specific polymeric system (here, the PEO-b-PS/PAA blends) is represented. The morphologies are studied as a function of the PAA molecular weight and concentration in the mixture, showing that they change from cylinders to lamellae upon increasing the PAA content.