Electrical, elastic properties and defect structures of isotactic polypropylene composites doped with nanographite and graphene nanoparticles

Conducting polymers have wide technological applications in sensors, actuators, electric and optical devices, solar cells etc. To improve their operational performance, mechanical, thermal, electrical and optical properties, such polymers are doped with carbon allotrope nanofillers. Functionality of the novel nanocomposite polymers may be stipulated by size characteristics of nanoparticles and the polymer, different physical effects like charge transfer in such objects etc. We characterize and analyze structure, elastic, electric properties and of novel polymer nanocomposites, isotactic polypropylene (iPP) with high crystallinity, doped with graphene nanoplates (GNP) and nanographite particles at different concentrations and sizes about 100 nm, basing on the results of dynamic mechanical analysis (DMA), dielectric spectroscopy, small-angle neutron scattering (SANS) and theoretical modeling. Carbon NPs aggregated in fractal objects in the bulk of iPP change its mechanical plastic, elastic and electric properties comparing with pristine polymer. We study modification of nanofiller morphology with the concept of Cosserat elasticity which involves description of the behavior of linear topological defects caused aggregation of nanographite and GNPs. We supply our experimental data with numerical simulations on the lattice in frames of the model of Cosserat elasticity to estimate some mechanical characteristics of the whole composite iPP.Comment: 9 pages, 3 figures, the conference paper. arXiv admin note: text overlap with arXiv:2006.0759

Small-Angle Neutron Scattering at the Pulsed Reactor IBR-2 : Current Status and Prospects

Neutron diffraction studies on the small-angle neutron spectrometer YuMO (Joint Institute for Nuclear Research, Dubna), based on the IBR-2 pulsed reactor, have been reviewed. The main parameters of small-angle spectrometers, based on the time-of-flight technique, are considered. It is shown that the flux on sample is the key parameter of the spectrometers based on pulsed sources, which makes it possible (along with application of a multidetector system) to expand the dynamic range of scattering vector magnitudes. The history of the setting up of the first small-angle instrument based on pulsed sources is overviewed. The directions of development of small-angle spectrometers are shown. The results of YuMO studies in the fields of polymers, biology, materials science, and physical chemistry are briefly reviewed. The main strategies of development of small-angle neutron scattering on pulsed sources are considered. The possibilities of the small-angle instruments based on a synchrotron source and on a neutron pulsed source are compared

Ambiguities in and completeness of SAS data analysis of membrane proteins: the case of the sensory rhodopsin II–transducer complex

Membrane proteins (MPs) play vital roles in the function of cells and are also major drug targets. Structural information on proteins is vital for understanding their mechanism of function and is critical for the development of drugs. However, obtaining high-resolution structures of membrane proteins, in particular, under native conditions is still a great challenge. In such cases, the low-resolution methods small-angle X-ray and neutron scattering (SAXS and SANS) might provide valuable structural information. However, in some cases small-angle scattering (SAS) provides ambiguous ab initio structural information if complementary measurements are not performed and/or a priori information on the protein is not taken into account. Understanding the nature of the limitations may help to overcome these problems. One of the main problems of SAS data analysis of solubilized membrane proteins is the contribution of the detergent belt surrounding the MP. Here, a comprehensive analysis of how the detergent belt contributes to the SAS data of a membrane-protein complex of sensory rhodopsin II with its cognate transducer from Natronomonas pharaonis (NpSRII-NpHtrII) was performed. The influence of the polydispersity of NpSRII-NpHtrII oligomerization is the second problem that is addressed here. It is shown that inhomogeneity in the scattering length density of the detergent belt surrounding a membrane part of the complex and oligomerization polydispersity significantly impacts on SAXS and SANS profiles, and therefore on 3D ab initio structures. It is described how both problems can be taken into account to improve the quality of SAS data treatment. Since SAS data for MPs are usually obtained from solubilized proteins, and their detergent belt and, to a certain extent, oligomerization polydispersity are sufficiently common phenomena, the approaches proposed in this work might be used in SAS studies of different MPs