Per Claesson, Professor
In general terms my research interest can be described as being directed towards fundamental surface chemical issues in the areas of Interfacial Forces, Adsorption and Self-Assembly. At the same time, I often find that the topics that I decide to work on are inspired by the needs of industry. Perhaps it can be described as industry-inspired fundamental research.
Interfacial Forces: I have worked in this area since the beginning of my research career. Initially studying the effects of electrolytes and surfactants on surface interactions. Later, surface forces induced by polymers and polyelectrolytes became the main topic, until mixtures of polyelectrolytes and surfactants became my favourite theme. Perhaps it still is. The reason is the complexity of such systems, where changes in polyelectrolyte structure results in dramatic changes of interfacial properties. A fascinating, and industrially very important, aspect of many of these systems is that non-equilibrium effects are important since polyelectrolyte-surfactant mixtures are prone to be trapped in non-equilibrium states. There is clearly a need to find methods and procedures to study non-equilibrium states in a reproducible manner. In the last few years, I have also developed an interest for understanding the molecular mechanisms of friction between polymer bearing surfaces.
In my studies I have used a range of techniques, SFA, MASIF, AFM, and TFPB. I must admit that my favourite technique is the SFA, since it provides a superb control of the experiment due to the possibility of watching what happens than two surfaces are brought close together, surface deformations can be followed, particulate contaminants be detected, and the sudden changes that occurs than molecular layers are removed from between surface can be followed. Nevertheless, I recognize the power of AFM and use it with increasing frequency in my research.
Adsorption: In most projects where I investigate interfacial forces I also investigate adsorption. At first, I saw this as a complement to the surface force studies, but nowadays this has developed into a research area of its own. The reason for this is the wealth of information that can be obtained with the battery of modern techniques that we now have available in our laboratory. AFM, DPI, QCM-D, ellipsometry, reflectometry, ESCA and VSFS. Particularly fascinating is the QCM-D that allows us to study adsorption from turbid solutions and also allow us to characterize the viscoelastic properties of adsorbed layers. However, QCM measures the mass that oscillates with the crystal, i.e. the mass of the adsorbing species and that of the solvent that is associated with the layer. Thus, it is an advantage to combine QCM measurements with measurements using e.g. an optical technique. I also note an increasing use of Dual Polarization Interferometry in my research. This technique allows accurate measurement of both layer thickness and refractive index of thin adsorbed layers, but, of course, the definition of “layer thickness” is not straightforward when dealing with non-homogeneous layers. In the future I foresee an increased used of NMR to study adsorption from complex mixtures, and these studies will be carried out in collaboration with the Physical Chemistry Division at KTH.
In the area of adsorption the current main interest lies in following adsorption from polyelectrolyte-surfactant mixtures, in building responsive polyelectrolyte multilayers to control adhesion and friction, in using layers formed by conducting polymers to combat corrosion, and in understanding and using the surface properties of some surface active proteins.
Self-Assembly: My interest in this research area was inspired by some odd surface force results obtained when surfactants were added to preadsorbed polyelectrolyte layers. It turned out that ordered, self-assembled polyelectrolyte-surfactant complexes were formed at the solid-liquid interface. To gain further understanding we varied the polyelectrolyte architecture and surfactant concentration, and of course realized that there is a link between self-assembly at interfaces and in bulk solution. As a result, I got an interest also in self-assembly in bulk and started with small-angle and light scattering studies. This was certainly not my area of expertise, but I was lucky to find excellent co-workers. I have made progress in this area, not the least due to a recent sabbatical with Prof. Jan Skov Pedersen at Aarhus University. I do not think that I ever will be an expert in scattering, but at least I have learned enough to appreciate the power of scattering techniques, and their pitfalls. I am looking forward to do more work in this area, studying polyelectrolyte-surfactant complexes, polyelectrolyte complexes and protein self-assembly both in bulk and at interfaces. In the future, I foresee that my research in this area will utilize the combination of surface sensitive techniques, NMR and scattering techniques, indeed a powerful combination.
Below follow a short description of some selected research projects that currently are under investigation.
Interfacial properties of bottle-brush polyelectrolytes: This project has been going on for a number of years, and we have by now published a large number of articles on this topic. There are, as always, more to do. Interactions between preadsorbed bottle-brush layers, and proteins and polyelectrolytes of the same and opposite charge as the bottle brush is now in focus. Some additional studies on the lubrication properties of bottle-brush polyelectrolytes are also planned.
Solution properties of bottle-brush polyelectrolytes: In this project we use small-angle scattering techniques, static and dynamic light scattering as well as NMR to gain information on solution conformation of the polyelectrolytes alone, and on the structures formed when the bottle-brush polyelectrolytes are mixed together with surfactants.
Mixed micelles: In this project we follow the evaluation of the micelle structure when two surfactants that form micelles with vastly different shapes are mixed. Small-angle scattering is the main technique that is used.
Short-range interactions between lipids: In this project we aim at elucidating the effect of charges and hydration water on short-range interactions. To this end we will employ surface force techniques and vibrational sum frequency spectroscopy, VSFS. The interactions between lipid layers and peptides will also be elucidated.
“Hydrophobic” interactions: The long-range attraction observed between non-polar surfaces across water has interested me for a long period of time. Initially, we investigated this phenomena using model flat surfaces. In recent years we have, together with industry researchers, detected the same type of interaction between more realistic surfaces, including talc and pitch. In future research we aim at controlling the surface topology and elucidate the relation between surface roughness, strength and range of the attraction, and the related phenomenon of capillary evaporation.
Surface-active proteins: In some cases Nature uses surface active proteins for controlling adhesion. Mussel adhesive proteins constitute one class of such proteins, and another class is the hydrophobins used by mushrooms. We have entered into a research project where we aim at characterizing the adsorption properties of these proteins. At the same time we investigate, together with industrial partners, their use in some novel applications.
Polyelectrolyte multilayers: The layer-by-layer method for directed assemblies of polyelectrolyte multilayers is well established. In this area we have made some efforts in understanding the forces involved in the multilayer formation process, and in understanding the transition between linear and exponential growth. In the future we will use some novel concepts to build responsive multilayers for control of adhesion and friction. We will also, together with industrial partners, make some studies of penetration of small molecules through multilayer coatings.
Polyelectrolyte complexes: Polyelectrolyte complexes formed in solution can be used for surface modification, but also for creating hierarchical nanoparticles formed by self-assembly. In this project we build such water-soluble hierarchical nanoparticles by using functional polyelectrolytes of opposite charge.
Temperature-responsive polymer layers: The classical example of a temperature-responsive polymer is polyNIPAM. We make use of modified polyNIPAM particles to create surface layers that respond to changes in temperature and pH. We also investigate modified cellulose polymers with intriguing temperature-responsive properties, the latter in collaboration with industrial partners.
Conducting polymers: Together with the corrosion science division, we build new corrosion-inhibiting layers based on conducting polymers. The initial results are very promising, and this research will continue with focus on finding the optimal doping density, primer and surface topology. Some of the research activities are carried out in collaboration with industrial partners.
Urval av nyare publikationer
Zhou, Y., Gorochovceva, N., Makuska, R., Dedinaite, A., and Claesson, P.M.
“Non-specific protein adsorption on surfaces coated with chitosan derivatized by poly(ethylene oxide) prepared by adsorption from solution and by µ-contact printing”
J. Colloid Interface Sci., 305, 62-71,(2007)
Wallqvist, V., Claesson, P.M., Swerin, A., Schoelkopf, J., and Gane, P.A.C.
“Interaction Forces between Talc and Pitch Probed by Atomic Force Microscopy”
Langmuir 23, 4248-4256 (2007)
Bastardo, L.A., Iruthayaraj, J., Lundin, M., Dedinaite, A., Vareikis, A., Makuska, R., van der Wal. A., Furo, I., Garamus, V.M., and Claesson, P.M.
“Soluble Complexes in Aqueous Solutions of Low Charge Density Comb Polyelectrolytes and Oppositely Charged Surfactants Probed by Scattering and NMR”
J. Colloid Interface Sci., 312, 21-33 (2007)
Kaufman, E.D., Belyea, J., Johnson, M.C., Nicholson, Z.M., Ricks, J.L., Bayless, M., Pettersson, T., Feldotö, Z., Blomberg, E., Claesson, P.M., and Franzen, S.
“Probing Protein Adsorption on Mercaptoundecanoic Acid Stabilized Gold Nanoparticles and Surfaces by Quartz Crystal Microbalance and z-Potential Measurements”
Langmuir, 23, 6053-6062 (2007)
Tyrode, E., Johnson, C.M., Rutland, M.W., and Claesson, P.M.
“Structure and Hydration of Poly(ethylene oxide) Surfactants at the Air/Liquid Interface. A Vibrational Sum Frequency Study”
J. Phys. Chem. C. 111, 11642-11652 (2007)
Lundgren, S.M., Persson, K., Mueller, G., Kronberg, B., Clarke, J., Chtaib, M., and Claesson, P.M.
“Unsaturated Fatty Acids in Alkane Solutions: Adsorption to Steel Surfaces”
Langmuir 23, 10598-10602 (2007)
Macakova, L., Blomberg, E., and Claesson, P.M.
“The Effect of Adsorbed Layer Roughness on the QCM-D Response: Focus on Trapped Water”
Langmuir, 23, 12436-12444 (2007)
Naderi, A., Iruthayaraj, J., Vareikis, A., Makuska, R., and Claesson, P.M.
“Surface Properties of Bottle-Brush Polyelectrolytes on Mica: Effects of Side Chain- and Charge Density”
Langmuir, 23, 12222-12232 (2007)
Stubenrauch, C., Langevin, D., Exerowa, D., Manev, E., Claesson, P.M., Boinovich, L.B., and v. Klitzing, R.
“Comments on “Hydrophobic Forces in the Foam Films Stabilized by Sodium Dodecyl Sulfate: Effect of Electrolyte” and Subsequent Criticism
Langmuir, 23, 12457-12460 (2007)
Mohanty, B., Verma, A.K., Claesson, P., Bohidar, H.B.
“Physical and anti-microbial characteristics of carbon nanoparticles prepared from lamp soot”
Nanotechnology, 18, 2007 (article 445102)
Lundin, M., Macakova, L., Dedinaite, A., and Claesson, P.M.
“Interactions between Chitosan and SDS at a Low Charged Silica Substrate Compared to Interactions in the Bulk. The Effect of Ionic Strength”
Langmuir, 24, 3814-3827 (2008)
Blomberg, E., Verall, R., Claesson, P.M.
“Interactions between Adsorbed Layers of Cationic Gemini Surfactants”
Langmuir, 24, 1133-1140 (2008)
Adhikari, A., Claesson, P., Pan, J., Leygraf, C., Dedinaite, A., and Blomberg, E.
“Electrochemical Behavior and Anticorrosion Properties of Modified Polyaniline Dispersed in Polyvinylacetate Coating on Carbon Steel”
Electrochimica Acta, 53, 4239-4247 (2008)
Pettersson, T., Naderi, A., Makuska, R., and Claesson, P.M.
“Lubrication Properties of Bottle-Brush Polyelectrolytes: An AFM Study on the Effect of Side-Chain – and Charge Density”
Langmuir, 24, 3336-3347 (2008)
Aulin, C., Varga, I., Claesson, P.M., Wågberg, L., Lindström, T.
“The Build-Up of Polyelectrolyte Multilayers of Poly(Ethylene Imine) and Microfibrillated Cellulose Studied by in situ Dual Polarization Interferometry and Quartz Crystal Microbalance with Dissipation”
Langmuir, 24, 2509-2518 (2008)
Iruthayaraj, J., Olanya, G., and Claesson, P.M.
“Viscoelastic Properties of Adsorbed Bottle-Brush Polymer Layers Studied by Quartz Crystal Microbalance – Dissipation Measurements”