Coatings with "Inverse Switching" Behaviour: New Applications of Core-Shell Hydrogel Particles

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Coatings can provide complex functionalities to surfaces, changing the properties of the underlying material significantly. In particular the design of a new generation of smart materials requires new concepts, e.g. for tissue engineering and cell growth, for creation of intelligent breath-active and water-repelling textiles, for self-regulating valves and micro-fluidic devices. We have already developed a general approach to smart surfaces that become hydrophilic in polar and hydrophobic in apolar solvents. However, for many practical applications the inverse, much less natural response on external stimuli would be desired. The project focuses on the design of the inversely switching system, which is hydrophilic in the dry state, but becomes hydrophobic in water. To realize this, the hydrophilic substrate will be modified with core-shell hydrogel micro-particles (HMPs) containing a water-swellable core and a hydrophobic shell permeable for water. In dry state, the minor part of the surface will be occupied by the hydrogel particles, and properties of the composite surface will be highly defined by the properties of the hydrophilic substrate. In water (or in water vapor) the HMPs swell and cover the whole surface. In this state the surface properties will be defined by the properties of the hydrophobic character of the shell. This new concept will be realized by the combination of polymer chemical and physical concepts based on hydrogels with particular structure and functionality, and thus requires expertise both in synthetic and dedicated characterization techniques present at IPF in an ideal way.