Dynamics in Soft Materials Group of Dr. Sokolov Dynamics in Soft Materials UT ORNL

Soft Matter Polymers Liquid Crystals Glass-forming Systems Colloids Foams and Gels Biological Systems

Dynamics is the Key to many Macroscopic Properties of Soft Materials Characteristics of Soft Materials: Variety of states and large degrees of freedom, metastable states; Delicate balance between Entropic and Enthalpic contributions to the Free Energy; Large thermal fluctuations and high sensitivity to external conditions; Macroscopic softness. Soft Matter Physics: Extremely high complexity of the systems and of the physical phenomena Traditional approximations often fail Mostly phenomenological level, qualitative considerations Many assumptions, some of them are not justified Dynamics is the Key to many Macroscopic Properties of Soft Materials

Main directions of research in our group Polymer Dynamics, Glass Transition Dynamics and Function of Biopolymers DNA Protein Lysozyme RNA Nanostructured and Nanocomposite Materials Nano-Photonics, Plasmonics

Main Experimental Techniques Light scattering: Raman and Brillouin scattering spectroscopy, plus dynamic light scattering cover the frequency range from mHz up to ~100 THz (corresponding time scales from hours to femtoseconds ). Dielectric relaxation spectroscopy covers frequency range from mHz up to ~50 GHz. Neutron scattering: use of SNS facilities at ORNL, NIST facilities, and also facilities in Europe. Although frequency range in that case is more limited (from MHz to ~100 THz), neutron scattering provides detailed microscopic information. Optical microscopy combined with spectroscopy (Raman, fluorescence, etc.): - confocal with lateral resolution ~0.5 mm; apertureless near-field microscopy with ~20 nm lateral resolution.

Collaborations USA International NIST Polymer Division IA&E Russ.Ac.Sciences Russia Center for Neutron Research Bayreuth University Germany AFRL Research Center Juelich Germany NRL University Paris Sud France ORNL ILL & ESRF, Grenoble France Johns Hopkins University Chalmers Univ.of Technology Sweden University of Maryland Universita di Messina Italy Kent State University Universita ‘La Sapienza’ Italy Bridgestone/Firestone University of Oxford UK Lubrizol Horiba JY France Silesian University Poland

Main Philosophy in our Group After one year in my group I expect from a graduate student: Independence in your research, I’m just an advisor Even “wrong” ideas are better than no ideas at all You propose what should we do (not me telling you what to do) Team work Presentation of results is very important part of your work; every student gives presentations a few times per year on the group meetings; good students attend national and international meetings You are writing papers, I’m just helping and teaching you how to write and how to deal with referees

Polymer Dynamics, Glass Transition The main goal is fundamental understanding of molecular motion and its relationship to macroscopic properties of polymeric and other glass forming materials. We study, among other questions: Glass transition; Cooperativity in molecular motions; Role of dynamic heterogeneities Temperature variations of viscoelastic and mechanical properties, Decoupling phenomena in dynamics … As an example: Our recent finding – universality of chain relaxation behavior for many polymers when presented vs Tg/T [PRL 102, 248301(2009); Macromolecules 39, 3322 (2006)]. Back

Dynamics and Functions of Biopolymers The main goal is fundamental understanding of dynamics in proteins, RNA and DNA, and relationship between molecular motion and functions of biological macromolecules. Recent finding: We unravel the nature of the dynamic transition in biological macromolecules [Phys.Rev.Lett. 100, 108103 (2008); J.Chem. Phys. 128, 195106 (2008)]. Understanding the influence of solvents on protein dynamics, activity and stability is another goal of our research. It is important for preservation of protein based products (pharmaceuticals, vaccines, food additives), cells and tissues. We designed a formulation where proteins can be preserved at room temperature up to ~10 years!!! Back

VT1.45±0.1 km/s Nano-composite and Nano-structured Materials Mechanical Properties of Viruses Localized mode provides estimate: Sub-monolayer WIV 500nm VT1.45±0.1 km/s Propagating and localized modes provide consistent estimates of the elastic constants. Virus appears to be stiffer than hard plastics Back Phys.Rev.E 78, 21907 (2008)

Nano-optics, Plasmonics Enhanced field Near-field ~10 nm Plasmon particle Laser beam AFM tip Laser spot ~1 mm Far-field We are developing: Apertureless near-field optics based on local enhancement of optical signals in the vicinity of plasmon particles (e.g. Ag, Au). Chemical mapping with ~20 nm lateral resolution Topography Raman 180nm 0nm 60nm 2000nm 1200 Topography Raman Back