Regensburg 2010 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 37: Poster: Colloids and Complex Liquids
CPP 37.10: Poster
Mittwoch, 24. März 2010, 17:30–19:00, Poster B2
Optical Tweezers to Measure the Interaction Forces between Poly(2-vinylpyridine) Brushes — •Mahdy M. Elmahdy1,3, Alla Synytska2, Astrid Drechsler2, Christof Gutsche1, Petra Uhlmann2, Manfred Stamm2, and Friedrich Kremer1 — 1Institute of Experimental Physics I, Leipzig University, Linnéstrasse 5, 04103, Leipzig, Germany — 2Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden, Germany — 3Department of Physics, Mansoura University, Mansoura 35516, Egypt
Forces of interaction within single pairs of poly(2- vinylpyridine) (P2VP) grafted colloids have been measured by optical tweezers (OT) with an extraordinary resolution of *0.5 pN. Parameters to be varied are the concentration and type of salt (KCl, CaCl2, and LaCl3) of the surrounding medium as well as its pH. The observed force-distance relation is quantitatively described by the Jusufi model [Colloid Polym. Sci. 2004, 282, 910-917] for spherical polyelectrolyte brushes which takes into account the entropic effect of the counterions and enables one to estimate the ionic concentration inside the brush. The transition from an osmotic to the salted brush regime is analysed in detail. For the scaling of the brush height a power law is found having an exponent of 0.24*0.01 which ranges between the values expected for spherical and planar brushes. At pH 4 a strong transition from a brush to a pancake conformation takes place.