Understanding transient phenomena in so-called “stimulus-responsive nano-reactors” that consists in a catalyst coated with a polymer-shell responsive to external triggers (e.g. pH, temperature, light) is a complex physico-chemical problem. Here, we will examine a Polymer-Membrane-Catalyst Assembly (PCMA) system consisting of PET membranes with a well-defined pore structure decorated with poly(n-isopropylacrylamide) or p-NIPAM, which is a thermo-responsive polymer coupled to an in-situ ATR-IR cell containing a sensing layer of palladium catalyst supported on g-Al2O3. This PCMA model is designed to mimic the structure of a core-shell catalyst structure of stimulus-responsive nano-reactors. Surprisingly, we observed that at low temperatures (&lt; 32 °C), where p-NIPAM is swollen and no mass transport limitation should be present, the addition of polymer brushes caused a delay in CO chemisorption on Pd. The opposite trend was observed when the polymer collapsed (T&gt;32 °C). That is that the CO-Pd saturation was faster. Our multi-physics model of the CO transport and chemisorption on the PCMA suggests that the delay is caused by the strong affinity of the CO molecules with the polymer brushes. Notably, this behavior could be reversed by increasing the amount of polymer on the surface with respect to the pores. The complex interplay between diffusion and absorption determines the dynamic behavior of the system. This will knowledge provides new opportunities for developing self-regulating catalysts with faster transitions between ON- and OFF- states.

Dynamics of polymer-membrane-catalyst assemblies revealed via In-situ ATR-IR spectroscopy

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.