Physics of soft matter, surfaces, and nanostructures

The research will cover several complex soft matter systems with interesting functional properties: liquid crystal (LC) elastomers, molecular motors, photonic crystals, and artificially synthesized or spontaneously self-organized micro- and nano-structures. The goal of the proposed research is to coherently use experimental, theoretical, and simulation approaches to uncover how molecular interactions lead to the formation of complex structures, their behaviours, and processes of self-organization. Particular attention will be paid to the possible applications of these systems. The proposed program consists of the tasks:2D AND 3D PERIODIC STRUCTURES (PHOTONIC CRYSTALS). Freezing and melting of colloidal particles embedded in a 2D liquid and influenced by external periodic potentials will be investigated. Further, 3D fotonic crystals, formed by colloidal micro- or nano-particles regularly dispersed in a LC matrix, and LC-polymer composites formed by the holographically modulated phase separation, will be studied. SELF-ORGANIZATION OF COLLOIDAL PARTICLES ON MICROSTRUCTURED SURFACES in the presence of a liquid medium. We are interested how structural interactions in thermotropic LCs and interactions between interfaces in aqueous solutions change on going from the micro- to nano-region. Surfaces will be patterned by AFM nano-writting, laser writting, or by classic photo lithographic methods. Presumably, a preferential adsorption of particles favouring one type of boundary condition will be achieved. STRUCTURAL AND FLUCTUATION FORCES IN LCS and model binary systems with modified surfaces. The nature of these forces in the vicinity of phase transitions will be investigated utilizing new experimental techniques of piezoresistive sensors and the total reflection microscope.LC ELASTOMERS are important multifunctional materials with the potential use even as artificial muscles. They are composed of mesogen units forming polymer chains, which are weakly cross linked. To understand molecular mechanisms of the thermo-elastic and opto-elastic effects we decided to study elastomers with admixed deuterated LC probes by deuterium NMR. A possible application of LC elastomers for new technological solutions in adaptive optics will be examined. DEFECT STRUCTURES & NEW LYOTROPIC AND GLASSY PHASES. The influence of hydrodynamic flow on the dynamics of colloids in LC medium, creation, annihilation, and decay of defects, and fluctuations of topological disclination lines will be investigated. Further we will study the influence of a weak disorder on the phases and dynamics. A particular emphasis will be given to the glass-like behaviour. NEW HIGH-CONTRAST WIDE-ANGLE LIGHT MODULATORS. Strongly twisted LC structures and effects of ionic contamination in liquid crystal displays will be modelled. The ion adsorption in boundary layers and the resulting unwanted memory effects in AM LCDs will be examined in detail. MOLECULAR MOTORS: The mechanisms of oscillatory action of motors based on a description of their chemical kinetics will be examined and models for some unconventional motors will be developed. Particular attention will be paid to the synchronization of oscillators and further to spontaneous pattern formation and wave generation in systems where motors and biopolymers interact in a solution. INORGANIC NANOTUBE SYNTHESIS and their surface functionalization. The research will be aimed towards the synthesis of new materials belonging to the family of sulfides and selenides of transition metals. Further functionalization of the nanotube surface is expected to lead to the adsorption of proteins, DNA, and nanoparticles (e.g. with ferroelectric and ferromagnetic properties). SYNTHESIS OF ORDERED SURFACE NANOSTRUCTURES BY single molecule chemistry performed in a nanoreactor based on the STM will be developed. Thermal and structural stability of nanostructures synthesized by assembling individual atoms and molecules will be studied. Further

The research of our program group is based on the synergy of experimental and theoretical methods –including optics, photonics, electromagnetism, statistical physics, microfluidics and mechanics- and highly successfully combines the phenomena from soft matter physics, surfaces, nanostructures and cellular organisms. The achievements of the group form past six years show that the group works at the cutting edge of modern science of soft matter, surfaces and nanostructures, as supported by publications in highest impact journals (Science, Nature, etc.), invited lectures at prestigious conferences (Gordon Research Conference, Liquids, ILCC, SPIE….), international awards, granted international patents and high-cited publications. In parallel with the basic understanding of complex soft matter and its composites, our also technology-oriented research is opening a direct way towards new functionalized composite materials with interesting technological applications which are made possible by specific nano and microscopic properties of the composite. Miniaturization and characteristics of such complexes are major drivers in the development of knowledge-based applications, as they not only raise the economic efficiency of the production, but also reduce the energy consumption and importantly improve the material properties and capabilities.

The results show that our program group is aimed at top-level research and innovations, based on scientific excellence. Such building upon excellence in Slovenian academic institutions and industrial attractiveness of Slovenia contributes to socioeconomic development in general. Major advantages of our program such as the complementary fundamental science and technological applicability are essential elements that can contribute to the long-term sustainable development and competitiveness of Slovenia. The research in the field of experimental and theoretical soft matter physics has a long and very successful tradition in Slovenia – and our program group is in the core of this community. In nearly 30 years of research, strong links have been tied between the two central research institutions in the field in Slovenia– the Josef Stefan Institute and the Faculty of Mathematics and Physics UL- which importantly contributed to the growth of the research quality to the top-world level. The research within our program contributes to the sustainable development of Slovenia at multiple levels. Indirect contributions: Our results are at the top-world level and as such contribute to further establishment of Slovenian national identity and international recognition of Slovenia at the world level. From another perspective, the group act also as a nucleus which attracts novel knowledge from abroad to Slovenia. Within our program group we also stress the outreach activities and presentation of science to wider public in Slovenia. Moreover our successful research is crucial for successful organization of multiple undergraduate and graduate student courses. The group has contributed to the training of excellent PhD students, and through them to the employment of high-level high-tech professionals (for more, please see the attached table). The direct contribution of our program to the economy is limited, but actually very important in specific examples in the field of optical applications, where new small and medium-size high-tech industry from Slovenia is unproportionally strong in comparison to the world level (Fotona, Balder, Optotech…) and notably it is so because of good domestic (national) knowledge in the field of physics and especially optics. Exactly along these lines, the “spin-off” company of the IJS, Balder, which is producing automated liquid crystalline optical protective filters (welding technology, medicine, …), has achieved successful affirmation within American and European market in the past decade. We should stress that the research within our program group has led to the development of new principles for the performance of specific optical shutters for eye-protection with large light yield and smaller consumption of electricity. To company Balder, this is opening direct new opportunities for development in the more-demanding fields of use of the automated eye-protection (medicine, air-traffic), which are among most rapidly developing fields. Also, this has led to collaborations in international projects (NATO, EU) and active collaboration in the work group for preparing a new ISO standard for eye-protection. Without this the new high-tech industry, which is emerging in Slovenia, can not retain its momentum and its competitiveness at the world level. Recently, Balder was acquired by the large international company Kimberly Clark, which however, due to our research support is keeping all the shutter development in Slovenia. The second relevant application direction of our program that could potentially contribut to the development of Slovenia is the synthesis and use of MoS2 nanotubes as novel lubricant and anti-wear materials. The current obstacle to full commercialization of the MoS2-nanotube technology is the development of synthesis process with kilogram-scale yields of MoS2 nanotubes, which the IJS spin-off company Nanotul can not achieve without a rather notable financial investment.