Regensburg 2013 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 9: Poster: Interfaces and Thin Films (joint session with DECHEMA and VDI)
CPP 9.5: Poster
Montag, 11. März 2013, 17:30–19:30, Poster C
Static and dynamic properties of cross-linked and non cross-linked polymer brushes. — Michael Lang1, Max Hoffmann2, •Marco Werner1,3, and Jens-Uwe Sommer1,3 — 1Leibniz-Institut für Polymerforschung Dresden, Germany — 2Universität Heidelberg, Germany — 3Technische Universität Dresden, Germany
We compare dense layers of surface-grafted polymer chains (polymer brushes) with and without additional random cross-links between the chains using the bond fluctuation model. In non cross-linked brushes with intermediate and low grafting densities, chain conformations can be described by random walks in a parabolic potential. Cross-linking leads to a reduction of brush height, whereby a large fraction of this reduction stems from cross-links between monomers of the same chains. Most cross-links between different chains do not contribute to a significant collapse of the brush, because they are established between monomers of similar contour distance to the grafting points, where the balance of stretching forces and chain elasticity stays almost unmodified by a cross-link. Chain dynamics of non cross-linked brushes is dominated by arm retraction processes suggesting an exponential increase of relaxation time as function of chain length. The largely confined motion of non cross-linked grafted chains inside a cross-linked brush highlights the recently discovered critical behavior [D. Romeis, H. Merlitz and J.-U. Sommer, J. Chem. Phys. 136 (2012) 044903] of monodisperse brushes as well as the dominance of arm retraction processes for the ultimate relaxation of the chains.