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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 24: Responsive and Adaptive Systems I

CPP 24.4: Talk

Wednesday, March 20, 2024, 10:30–10:45, H 0110

Vibrational Spectroscopy of Perdeuterated Poly(N-isopropylacrylamide) Solutions and Hydration Changes Across the Demixing-Transition — •Alfons Schulte¹, Nicolas Harms¹, Eric Rende¹, Dharani Mullapudi¹, Alec Nieth¹, Christopher Bennett¹, Dirk Schanzenbach², André Laschewsky^2,3, and Christine M. Papadakis⁴ — ¹Physics Department, University of Central Florida, Orlando, USA — ²Universität Potsdam, Institut für Chemie, Potsdam-Golm — ³Fraunhofer-Institut für Angewandte Polymerforschung, Potsdam-Golm — ⁴TUM School of Natural Sciences, TU Munich, Garching

We investigate concentrated aqueous solutions of perdeuterated poly(N-isopropylacrylamide) (PNIPAM-d10) employing Raman scattering and infrared absorption spectroscopy. In comparison to PNIPAM the cloud point temperature increases by several degrees in PNIPAM-d10. In the Raman and infrared spectra four C-D bands are discernible due to stretching vibrations of the alkyl groups. These are analogous to the C-H bands in hydrogenated PNIPAM, however they are shifted to lower frequencies by a factor of 1.4 as expected for the isotope effect. With increasing temperature we observe abrupt red-shifts of the peak frequencies of the C-D bands near 36 C at the demixing transition which are attributed to dehydration of the polymer chains at their coil-to-globule transition.

Keywords: responsive polymers; hydration; vibrational spectroscopy; deuteration