Berlin 2012 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 16: Poster: Colloids and Complex Liquids
CPP 16.15: Poster
Tuesday, March 27, 2012, 18:15–20:45, Poster A
Transient cage forming in polymer solutions by hot gold colloids — •Florian Schwaiger and Werner Köhler — Physikalisches Institut, Universität Bayreuth, Germany
Utilizing laser heated gold colloids with a radius of 125 nm as nanoscopic heat sources, we investigated the concentration bleaching in binary polymer solutions of polystyrene and toluene due to the Soret effect. Laser irradiation causes a significant temperature rise T∝ 1/r due to the high absorbance at their surface plasmon resonance around 532 nm. As a consequence of the strong nonlinear coupling of the local order parameter to the temperature gradient, it induces a complex concentration field c(t, r, Mw, T(r)). We analyze in detail the stationary temperature, concentration and viscosity profiles. Furthermore, we present experimental results both on the observation of the concentration field and on the diffusion of heated colloids within their self-created cage. We find increasing anomalous diffusion with increasing laser power represented by a negative minimum in the step correlation function of the random walk.