Polymer brushes are functional coatings that allow to manipulate multiple surface properties including wetting, adhesion, and color based on the response of the polymer to external stimuli such as the temperature, fluid composition, optical and electric fields. At the PCF group, we aim to develop ‘intelligent’ surfaces that are able to process fluids, ‘remember’ contact with fluids and perform complex operations depending on memorized experiences from the past. In this context, understanding the dynamics of solvent transport in these layers is crucial.
Our workhorse are amorphous polymer brushes that we can swell with solvent to a variable degree. By locally desorbing some of the solvent through laser-induced heating, we can generate non-equilibrium patterns of solvent distribution that will eventually relax back to a homogeneous configuration.
The purpose of this project is to follow these relaxation processes by optical microscopy and to analyze the pattern decay quantitatively by comparing either to a simple one-dimensional analytical or to a numerical model.
Thickness profile of a partially swollen polymer brush next to an oil drop (top left in inset). A numerical data analysis procedure allows to convert the interference colors into thickness. (see publications below)
The key challenges are as follows:
· How accurately does the pattern decay allow to determine diffusion coefficients?
· Is the pattern decay a linear or a non-linear process?
· How does the diffusion coefficient depend on the local swelling?
We have recently developed a detailed model based on the decay of profiles as shown above. By generating laser-written line patterns of variable periodicity, we should be able to test these theories with higher accuracy and get access to the poorly understood difference between tracer and collective diffusivity that is crucial in many soft matter systems.
Contact & supervisory team:
· Vincent Siekmann (V.D.Siekman@twente.nl)
· Dr. Chandeshwar Misra (t.b.d. – starting 01-09-26)
· Frieder Mugele (f.mugele@utwente.nl)
Literature:
Ö. Kap, et al. J. Chem. Phys. 158, 174903 (2023).
V.D. Siekman et al., Europ. Phys. J. E 49, 67 (2026).