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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 35: Poster Session II

CPP 35.12: Poster

Wednesday, March 29, 2023, 11:00–13:00, P1

Measurement of diffusion and thermodiffusion of polydisperse polymers by means of a compact optical beam deflection setup — •Mareike Hager, Roman Reh, and Werner Köhler — Universität Bayreuth, Physikalisches Institut, Germany

We have performed diffusion and thermodiffusion experiments on solutions of polydisperse polymers by means of a newly developed double-pass optical beam deflection (OBD) instrument. The aim is to develop a model for the description of the multimodal OBD signals and to develop the technique into a method for polydispersity analysis. The double-pass OBD instrument utilizes a laser beam that is reflected behind the Soret cell and passes the sample volume a second time. In the cell a vertical temperature gradient is applied that leads to thermodiffusion in the sample and, thus, to a concentration gradient and a gradient of the refractive index. The laser beam that traverses the cell twice is deflected and detected on a camera where the time dependent laser position is recorded. From the measured OBD signal the diffusion, thermodiffusion and Soret coefficients can be extracted. The multimodal time traces are evaluated with an adapted version of the CONTIN program for the solution of inverse problems. It is shown that diffusion coefficients extracted in this way agree with literature data. The results of the measurements of samples with two polymers of different sizes are in accordance with the results for the single components. Based on these results, polymers with a broad molar mass distribution can now be investigated.