Papers by Author: M.B. Plavšić

Abstract: Properties of four materials based on styrene-butadiene rubber (SBR), one without filler and the other three with the same amount but different types of silica fillers, are investigated. The fillers used are Vulkasil S and two new fillers, differing in nano-structures: specific surface area and particle aggregate morphology. All other components in the material formulations are the same as well as the procedures of material preparation. Thermal and thermo-mechanical properties of all four materials are investigated by modulated differential scanning calorimetry (MDSC) and dynamic mechanical analysis (DMA). Morphology of the materials is studied using scanning electron microscopy (SEM). The results for glass transition temperature (Tg ) of gum rubber and three filled rubbers, obtained by MDSC are for all four materials Tg = -50±1 0C, and by DMA loss tangent measurements also for all of them Tg = -29±1 0C. It indicates no significant influence of active silica fillers on the rubber network segment dynamics, in the temperature range close to Tg of SBR. But, at higher temperatures MDSC gives insights into dynamic transitions that are under the influence of filler interactions and sensitive to filler structure. The difference in Tg results obtained for the same material by MDSC and DMA can be understood in terms of different sensitivity of network segment dynamics to conditions provided by those two measuring methods.

Abstract: Scaling of the real and the imaginary part of dynamic moduli with frequency, for fully cured elastomer materials as gum and active carbon black filled butyl rubbers, is considered experimentally and theoretically. For gum rubber in different ranges of frequency complete agreement with G''-scaling predicted by the Rouse theory is obtained. Obtained slopes for all G' and G'' of filled rubber are much lower.

Abstract: Our recently proposed quantum approach to biomolecular recognition processes is hereby additionally supported by biomolecular Resonant Recognition Model and by quantum-chemical theory of biomolecular non-radiative resonant transitions. Previously developed general quantumdecoherence framework for biopolymer conformational changes in very selective ligandproteins/ target-receptors key/lock biomolecular recognition processes (with electron-conformational coupling, giving rise to dynamical modification of many-electron energy-state hypersurface of the cellular quantum-ensemble ligand-proteins/target-receptors biomolecular macroscopic quantum system, with revealed possibility to consider cellular biomolecular recognition as a Hopfield-like quantum-holographic associative neural network) is further extended from nonlocal macroscopicquantum level of biological cell to nonlocal macroscopic-quantum level of biological organism, based on long-range coherent microwave excitations (as supported by macroscopic quantum-like microwave resonance therapy of the acupuncture system) - which might be of fundamental importance in understanding of underlying macroscopic quantum (quantum-holographic Hopfieldlike) control mechanisms of embryogenesis/ontogenesis and morphogenesis, and their backward influence on the expression of genes.

Abstract: Silica fillers are used in rubber composites to modify their dynamic-mechanical properties. Three fillers are used: a commercial filler of precipitated silica type Vulkasil- S and two fillers obtained by its treatment in different ways: thermally and hydrothermally. The purpose is not only to obtain higher hysteresis of the composite at low temperatures and lower hysteresis at elevated temperature (which is optimal for good tire performance), but to understand the reasons of such changes in elastomer materials behavior and also possibilities to increase the corresponding trends. Both modified fillers exhibited required trends in comparison with the original commercial one. More detailed analyses of their dynamical behavior indicate interdependence between of filler particle size, morphology of particle aggregates and ratio of elastic to loss moduli, influencing all together the dynamic properties of products.

Abstract: In this paper we describe the biopolymer chain folding problem in the framework of the so-called quantum decoherence theory. As we propose a rather qualitative scenario yet bearing generality, it seems this provides promising basis for the solution-in-principle of the (semi) classically hard kinetic problem of biopolymer chain folding from coiled to native conformation in highly selective ligand proteins/target-receptors biomolecular recognition processes, implying underlying macroscopic quantum nonlocality on the level of biological cell.

Abstract: The change in elastomer tensile moduli, as formulated in the Gaussian statistical theory of rubber elasticity, with deformation, is considered both experimentally and theoretically. Gum elastomers of different structures and corresponding materials filled with carbon black, as reinforcing filler, are investigated experimentally. For all materials considered, the same scaling pattern with negative and low slope for small deformations, and positive and higher slope for large deformations is obtained, indicating two distinct mechanisms of elastic response. Most pronounced is the similarity of small deformation responses for filled materials. Considering the modulus as an elastic energy density gradient dependent on structure changes with deformation, and interpreting the changes for small deformations in terms of conformational energy change, the fractal dimension of a new type is formulated. It describes the decrease in elastomer network connectivity with deformations, which is discussed in terms of conformon dynamics. Possibilities of application of Faynman's path integral method and statistical method of random walk to the lattice are considered for the conformon, as well.