Dresden 2026 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 46: Poster II

CPP 46.36: Poster

Thursday, March 12, 2026, 09:30–11:30, P5

Tuning PNIPAM Phase Transition and Interfacial Structures — •Zugeng Cong, Michael Hardt, and Björn Braunschweig — University of Münster, Institute of Physical Chemistry, Münster, Germany

In this work, we aim to introduce the concept of a self-regulating negative-feedback system in which an exothermic photochemical process would be coupled to the thermo-responsive polymer PNIPAM. In such a scheme, reaction-generated heat would raise the solution temperature, trigger PNIPAM collapse, increase turbidity, and thereby limit light penetration---providing an intrinsic mechanism to suppress further heat generation. For that, we characterize the PNIPAM phase transition through temperature-dependent turbidity measurements while varying SDS and NaCl concentrations as well as the water-ethanol co-solvent composition. To elucidate interfacial contributions, surface-specific sum-frequency generation (SFG) spectroscopy is used to probe adsorption layers at the air-water interface, taken as a model for micellar environments. These measurements reveal how surfactant loading, solvent composition, and electrolyte concentration reorganize interfacial structures below and above the PNIPAM phase-transition temperature. This provides the physicochemical basis required for designing a feedback-controlled photochemical soft matter system.

Keywords: Stimulus-responsive materials; PNIPAM; Sum-frequency generation spectroscopy; Photochemical reactions; Self-regulation system