Nanoscopic studies of light-induced changes in azobenzene-containing polymer films

• Applicant: Professor Dr. Dieter Neher
• Subject Area: Experimental and Theoretical Physics of Polymers ; Preparatory and Physical Chemistry of Polymers
• Term: from 2004 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5446345

• Final Report Year: 2009

Final Report Abstract

We performed a series of simulations aimed on reproducing the properties of the azobenzene containing LC elastomers observed experimentally. To our best knowledge, this is the first atom-based molecular dynamics simulation of such systems. Due to the complexity of the properties and limitations imposed on the system size and the length of simulation runs, we concentrated on basic physical effects and not on detailed description of the chemical details of some particular material. In this way, the temperature, density and other parameters were not intended to be mapped onto the experimental values, for this purpose much thorough work should be done on the model potentials. The model elastomer was prepared from the melt of side-chain LC molecules and crosslinked in the smectic phase. A technique for efficient crosslinking was developed and is explained in detail in this report. A number of important effects are reproduced throughout our study, namely: • Stabilization of the smectic phase due to the crosslinking (a shift of smectic-isotropic temperature of about 5° was observed), in accordance with experimental observations • Elastic properties of the elastomer in the isotropic phase (T=510K) • Stress relaxation upon compression of the elastomer parallel to the director • Reversibility of the shape and the order when the elastomer is driven through the smectic-isotropic transition • Stress-induced smectic phase by stretching the isotropic sample • Stress-induced smectic-isotropic transition • Stress-induced reorientation of the smectic layers or deformation and breakage of the lamellar structure, depending on the temperature The study can be seen as the first step to the following research that might concentrate more on further refinement of the model parameters and being aimed on some particular material. One can also improve the crosslinking strategy to achive a single-network case. The other aspects that are left aside so far (due to an immense length of the simulations required) are the peculiarities of the photo-response of such materials, this can be done as a continuation of the research undertaken during the projects.

Publications

• "How does the scaling for the polymer chain in the dissipative particle dynamics hold?" Seminar of the Statistical Physics group, Laboratory of the material Physics, University Nancy II, Nancy, France, 26 November 2007
  J.M. Ilnytskyi, Yu. Holovatch
  
• "Scaling taws for the polymer chain in mesoscale simulations", Soft matter Physics Group, Institute of Physics and Astronomy, University of Potsdam, 12 December 2007
  J.M. Ilnytskyi, Yu. Holovatch
  
• How does the scaling for the polymer chain in the dissipative particle dynamics hold? Condens. Matt. Phys. Vol. 10, No 4, pp. 539-551 (2007)
  J.M. Ilnytskyi, Yu. Holovatch
  
• "Computer simulations of photo-induced effects in azo-polymers", Seminar in Department of Chemical Physics I, Universidad Complutense Madrid, 22 September 2008
  J. Ilnytskyi, D. Neher, M. Saphiannikova
  
• "Computer simulations of photo-induced effects in azo-polymers". Seminar in Fraunhofer IAP, 28 August 2008, Potsdam
  J. Ilnytskyi, D. Neher, M. Saphiannikova
  
• "Molecular dynamics simulation of photo-induced deformations in azobenzene-containing polymers", 10th Granada Seminar on Computational and Statistical Physics: Modeling and Simulation of New Materials, University of Granada, 16 September 2008
  J. Ilnytskyi, D. Neher, M. Saphiannikova
  
• "Morphological changes in polymer liquid crystals under external fields by computer simulations", 7-th International Conference "Electronic Processes in Organic Materials" (ICEPOM-7), 28 May 2008, Lviv, Ukraine
  J. Ilnytskyi, D. Neher, M. Saphiannikova, M.R. Wilson
  
• "Photo-induced deformations in optically active polymers by molecular dynamics simulations", 33rd Conference of the Middle European Cooperation in Statistical Physics (MECO-33), 14 April 2008, Puchberg/Wels, Austria
  J. Ilnytskyi, D. Neher, M. Saphiannikova
  
• Molecular dynamics simulations of various branched polymeric liquid crystals. Molecular Crystals and Liquid Crystals, Vol. 496, pp. 186-201 (2008)
  Ilnytskyi J.M., Neher D., Saphiannikova M., Wilson M.R., Stimson L.M.
  
• Polymers films with indandione derivatives as alternatives to azobenzene polymers for optical patterning, Thin Solid Films, vol. 516, issue 24, pp. 8893-8898 (2008)
  Stiller, B.; Saphiannikova, M.; Morawetz, K.; Ilnytskyi, J.; Neher, D.; Muzikante, I.; Pastors, P.; Kampars, V.
  
• Molecular Dynamics Simulations of Photoinduced Deformations in Azobenzene-containing Polymers, in CP 1091, Modeling and Simulation of New Materials, Tenth Granada Lectures, ed. P. Garrido, P.I. Hurtado, J. Marro, AIP, 2009, pp. 253-255
  J.M. Ilnytskyi, D. Neher, M. Saphiannikova