The effect of two types of carbon nanoparticles, i.e., shungite carbon (SC) and multiwalled carbon nanotubes (MWCNTs), on the mesomorphic and rheological properties of cholesteric mesogen in the con centration range of 0.005-0.04 wt % has been reported. The main physical parameters for tribological appli cations, such as phase transition temperature, viscosity, elastic modulus G', loss modulus G'', and complex viscosity η*, have been studied. The preference of using SC as a lubricating coolant additive component has been shown in the comparison with MWCNTs.
The possibility of supramolecular organization modeling of a cholesteric liquid crystalline (ChLC) matrix was shown by molecular dynamics simulation using the all-atom model. The supramolecular organization of ChLC mesogen and ChLC -a single walled carbon nanotube composite was estimated and 3D-model of a cholesteric phase of the studied compound was obtained. The effect of a carbon nanotube on the order parameter of ChLC molecules in the cholesteric phase was determined. MO.QEIU1POBAH�E B3AVlMO.QE�CTBVI� XViPAIlbHOrO ME30rEHA C yrIlEPO.QHOVI HAHOTPY6KO� CMV1pHoBa (TiKeMCeBa) M. B. 1 , COL-IKV1� B. B. 2 , CMV1pHOBa A. lt1.
Background: Polysaccharide hydrogels draw attention due to the ability to form mechanically tough gels at low concentrations (typically 1 wt% or lower), combined with biocompatibility and biodegradability. Biopolymer hydrogels can be used as a matrix for cell growth, in order to obtain materials for the replacement of damaged tissues. “Physical” gels with macromolecules cross-linked by dynamic reversible cross-links are of great interest due to their self-healing ability. However, investigation of the native un-perturbed structure of such hydrogels presents a challenge, since they collapse upon drying, and present a difficulty for preparing a thin specimen for cryo-TEM experiments due to very high viscosity. The aim of this work is to study the native structure of hydrogels of an anionic polysaccharide – carboxymethyl hydroxypropyl guar (CMHPG) – cross-linked by borax. Methods: Freeze-fracture transmission electron microscopy (FF-TEM) was conducted on a Phillips EM-301 microscope. A small volume of the sample (100 μl) was put into the copper cell and cooled down by liquid nitrogen, put under vacuum (10−5 torr) at continuous cooling with liquid nitrogen, and fractured. The surface was etched for 10–20 min at 10−5 torr and then replicated by spraying platinum and carbon. Results: The gels have a microphase-separated microstructure – a rather thick (several nm) polymer backbone is seen, which is presumably formed by multiple aggregated macromolecules, and meshes between the backbone do not contain polymer and are filled with solvent. Mesh size determined from the micrographs qualitatively coincides with the value determined from the elastic modulus of the gels. Upon increasing the concentrations of cross-linker, the network becomes denser: the mesh size becomes lower, and the thickness of the backbone increases. Thus, the addition of cross-linker favors the aggregation of polymer chains forming the backbone. Conclusion: It was shown by FF-TEM that cross-linked CMHPG gels have a microphase-separated structure with a dense backbone formed by polymer chains and rather large meshes between them.
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