Wetting and interfacial tension of polymers
There is currently an increasing interest to control wetting and interfacial tension of polymeric materials for different applications and technologies such as coating, printing, gluing, biocompatibility, self-cleaning, patterning and microfluidics. The desired surface properties range from complete release toward all contacting gaseous, liquid or solid substances to irreversible covalent bonding to other substrates of interest.
Our preferred stategies to determine experimentally these parameters are contact angle measurements and the determination of the surface tension of polymer melts by drop shape analysis and modified Wilhelmy techniques.
For the determination of the surface tension of solid polymers, we use indirect methods based on wetting (contact angle) measurements in combination with specific approaches of interfacial energetics (e.g. equation of state approach for solid-liquid interfacial tensions). In the case of porous polymeric systems, such as powders, granules, fiber bundles or membranes, we developed a new strategy to characterize the surface-energetic properties of these materials by capillary penetration experiments with liquids of different surface tension and polarity.
In the focus of our work are interrelations between the surface tension and wettability of polymer surfaces and adhesion phenomena and the correlation of these macroscopic interfacial properties with the microscopic and molecular surface structure.
- Approaches to estimate the surface energetics of polymers from wetting and surface tension measurements (interpretation of contact angle data; thermodynamic status of contact angles; contact angle hysteresis on imperfect solid surfaces, e.g. rough or heterogeneous surfaces; porous solid systems)
- in situ methods (captive bubble technique) to study the adsorption of surfactants and proteins or the wettability of hydrogels
- New strategies to determine experimentally the surface tension of polymer melts at elevated temperatures (simultaneous determination of surface tension and density of polymer melts)
- Influence of roughness on the wettability (polymers with self-cleaning properties)
- Effect of additive type and structure on surface tension of mixtures
- Complex behavior of the surface tension of reactive multi-component polymer systems
- How does the surface tension of a polymer material reflect a systematic change in its bulk and surface structure (structure-property relations)
- Wetting and adhesion phenomena in technologically relevant systems (coatings, composites, blends)
- Understanding and controlling of interfacial interactions in semiconductor manufacturing processes (e.g. photolithography, packaging of chips)
Selected publications (in textbooks, review)
K. Grundke, K. Pöschel, A. Synytska, R. Frenzel, A. Drechsler, M. Nitschke, A. L. Cordeiro, P. Uhlmann, P. B. Welzel
Experimental studies of contact angle hysteresis phenomena on polymer surfaces - toward the understanding and control of wettability for different applications,
Advances in Colloid and Interfaces Science (2014) in press
Characterization of polymer surfaces by wetting and electrokinetic measurements- contact angle, interfacial tension, zeta potential,
in: Polymer Surfaces and Interfaces, Characterization, Modification and Applications (Chapter 6),
Edited by M. Stamm. Springer, 2008, pp. 103-138
Surface-energetic properties of polymers in controlled architecture,
in: Molecular interfacial phenomena of polymers and biopolymers (Chapter 10),
Edited by P. Chen, Woodhead Publ., 2005, pp. 323-374
K. Grundke, M. Nitschke, S. Minko, M. Stamm, C. Froeck, F. Simon, S. Uhlmann, K. Pöschel, M. Motornov Merging two concepts: Ultrahydrophobic polymer surfaces and switchable wettability,
in: Contact Angle, Wettability and Adhesion, Volume 3,
Edited by K. L. Mittal, VSP, 2003, pp. 267-291.
Wetting, Spreading and Penetration, in: Handbook of Applied Surface and Colloid Chemistry (Chapter 7), Edited by Krister Holmberg. John Wiley & Sons Ltd., 2002, pp. 119-140