Design of new responsive materials based on functional polymer brushes for smart tuning and sensoring of proteins and particles adsorption

• Applicants: Dr. Klaus-Jochen Eichhorn; Privatdozent Dr. Karsten Hinrichs; Professor Dr. Marcus Müller; Professor Dr. Manfred Stamm
• Subject Area: Experimental and Theoretical Physics of Polymers ; Experimental Condensed Matter Physics
• Term: from 2006 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 24551434

• Final Report Year: 2010

Final Report Abstract

The results demonstrate the high potential of polymer brushes for the control and switching of surface properties such as wettability and the strength and range of the hydrophobic interactions for the controlled adsorption of proteins and nanoparticles. Different brush systems like mono-, binary- and ternary brushes were successfully designed and prepared using different preparation schemes. For the analysis, complementary experimental methods and theoretical simulations were used which allowed structural and chemical insight into this promising new materials. Primarily used methods in this project were in situ ellipsometry in the visible and infrared region (VIS-Elli and IRSE), atomic force microscopy (AFM) and contact angle measurements (CA). Additional methods were used as e.g. quartz crystal microbalance (QCM) and x-ray standing waves (XSW). The complementarity allowed to determine in detail new structural information such as the pH dependent chemical composition, thicknesses, amount of adsorbed proteins and ion distributions. Each group involved in this project, including the US cooperation partners, is renowned for its expertise in their own field. Their different scientific experiences and the used methods of the groups were brought together and complemented the investigations of the studied surface systems. The US-German cooperation was a fundamental factor for the success of this project. An outstanding result was the cooperative study of all groups with respect to the controllable adsorption of proteins on switchable polymer brush films. Experiments were pushed by the mutual research-stays. The high potential of polymer brushes is discussed in a review article. In-situ IR and VIS ellipsometry allowed a robust study of the pH- and temperature dependent behavior of switchable polymer platforms and adsorption of proteins thereon. A noteworthy aspect is the high sensitivity of the ellipsometric measurements for the adsorption of thin films of proteins on the brush layers. Here temperature sensitive polymer brushes of PNIPAAm could be shown to be highly protein resistant. Thus PNIPAAm is a promising substitute for protein resistant PEG in mixed polymer brushes, with the advantage of temperature as additional external stimulus. Also environmental sensitive swelling can be successfully addressed by ellipsometry. For example, IR ellipsometric measurements allowed for the first time a direct spectral identification of the PAA-PVP complex in a certain pH range for a 12 nm polymer brush film. An outstanding highlight from a methodically point of view was the combination of IRSE, VIS-elli and XSW measurements. These measurements have led to a new insight into the chemical changes inside thin polymer brushes during switching by the pH of aqueous solutions and the role of the ions for the switching behavior. The potential of combinatorial measurements was further utilized in simultaneous VIS-elli and QCM studies of protein adsorption on PAA brushes. In combining these methods, changes in the amount of buffer molecules (water and ions) at the surface during adsorption processes can be evaluated quantitatively, increasing the insight into adsorption mechanisms.

Publications

• “In-situ infrared ellipsometric study of stimuli-responsive mixed polyelectrolyte brushes”. Analytical Chemistry, 79(20): 7676-7682, 2007
  Mikhaylova, Y.; Ionov, L.; Rappich, J.; Gensch, M.; Esser, N.; Minko, S.; Eichhorn, K.-J.; Stamm, M.; Hinrichs, K.
  
• “Chemical and Structural Changes in a pH-Responsive Mixed Polyelectrolyte Brush Studied by Infrared Ellipsometry”. Langmuir, 25(18): 10987-10991, 2009
  Hinrichs, K.; Aulich, D.; Ionov, L.; Esser, N.; Eichhorn, K.-J.; Motornov, M.; Stamm, M.; Minko, S.
  
• “Microphase separation of mixed polymer brushes: Dependence of the morphology on grafting density,composition, chain-length asymmetry, solvent quality and selectivity”. J. Phys. Chem.. B 113, 11384-11402, 2009
  Wang, J. F.; Müller, M.
  
• “Complex pH- and Temperature Sensitive Swelling Behavior of Mixed Polymer Brushes”. Journal of Polymer Science Part B: Polymer Physics, 48(14), 1606-1615, 2010
  Bittrich, E.; Kuntzsch, M.; Eichhorn, K.-J.; Uhlmann, P.
  
• “Emerging applications of stimuli-responsive polymer materials”. Nature Materials, 9, 101-113, 2010
  Cohen Stuart, M. A.; Huck, W. T. S.; Genzer, J.; Müller, M.; Ober, C.; Stamm, M.; Sukhorukov, G. B.; Szleifer, I.; Tsukruk, V. V.; Urban, M.; Winnik, F.; Zauscher, St.; Luzinov, I.; Minko, S.
  
• “In-situ studies on the switching behavior of ultrathin poly(acrylic acid) polyelectrolyte brushes in different aqueous environments”. Langmuir, 26(15): 12926-12932, 2010
  Aulich, D.; Hoy, O.; Luzinov, I.; Bruecher, M.; Hergenroeder, R.; Bittrich, E.; Eichhorn, K.-J.; Uhlmann, P.; Stamm, M.; Esser, N.; Hinrichs, K.
  
• “Memory effects of diblock copolymer brushes and mixed brushes”. Langmuir, 26, 1291-1303, 2010
  Wang, J. F.; Müller, M.
  
• “Protein Resistance of PNIPAAm Brushes: Application to Switchable Protein Adsorption”. Langmuir, 26(3): 1786-1795, 2010
  Burkert, S.; Bittrich, E.; Kuntzsch, M.; Müller, M.; Eichhorn, K.-J.; Bellmann, C.; Uhlmann, P.; Stamm, M.
  
• “Synthetic hydrophilic materials with tunable strength and the range of hydrophobic interactions”. Advanced Functional Materials, 20(14): 2240-2247, 2010
  Hoy, O.; Zydrko, B.; Lupitskyy, R.; Sheparovych, R.; Aulich, D.; Wang, J.; Bittrich, E.; Eichhorn, K.-J.; Uhlmann, P.; Hinrichs, K.; Müller, M.; Stamm, M.; Minko, S.; Luzinov, I.