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CPP: Chemische Physik und Polymerphysik

CPP 11: POSTER Disperse Polymer Systems

CPP 11.20: Poster

Dienstag, 28. März 2006, 17:00–19:00, P3

Drying of polymer dispersions during film formation monitored via beam bending — •Kerstin von der Ehe and Diethelm Johannsmann — Institute of Physical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Strasse 4, 38678 Clausthal-Zellerfeld

Film formation from aqueous polymer dispersions takes place in several steps including loss of water, compactification of particles, and polymer interdiffusion. In the process, large in-plane stresses develop, which may induce cracking of the dry film. Large stresses are often encountered when the coating to be formed has a high mechanical modulus.

This work deals with polymer dispersions prepared via mini-emulsion polymerization. Mini-emulsion polymerization offers a good synthetic flexibility. In particular, nanocomposites can be created. By variation of surfactant concentration and time of sonication we obtain dispersions with different particle sizes. We work with dispersions of PBuMA, PMMA and poly(BuMA-co-MMA) with different solid contents.

For analyzing the behavior of the dispersions throughout film formation in regard to internal stresses we use a cantilever technique. [1] The films are prepared and dried on a flexible substrate fixed at one end. Bending of the substrate under stress is detected by a laser beam which is deflected from the free end of the substrate. With these experiments we find a dependence of the deflection on material parameters. The results are discussed in the frame of recent theoretical models of the film formation. [2]

References: [1] C. Peterson, C. Heldmann, D. Johannsmann, Langmuir 1999, 15, 7745 [2] A.F. Routh, W.B. Russel, Langmuir 1999, 15, 7762