Physchem, Volume 2, Issue 1 (March 2022) – 5 articles

All-atom molecular dynamics (MD) simulations are employed to compare the lower critical solution temperature (LCST) behaviors of poly(N-isopropylacrylamide) (PNIPAM) and elastin-like polypeptides (ELPs) with the canonical Val-Pro-Gly-Val-Gly ((VPGVG)_n) sequence over a range of temperatures from 280 K to 380 K. Our simulations suggest that the structure of proximal water dictates the conformation of both the (VPGVG)_n ELPs and PNIPAM chains. Specifically, the LCST transition in ELPs can be attributed to a combination of thermal disruption of the network of the proximal water near both hydrophilic and hydrophobic groups in the backbone and side-chain of (VPGVG)_n, resulting in a reduction in solvent accessible surface area (SASA). This is accompanied with an increase in the secondary structure above its LCST. In the case of PNIPAM, the LCST transition is a result of a combination of a reduction in the hydrophobic SASA primarily due to the contributions of isopropyl side-chain and less to the backbone and the formation of intra-chain hydrogen bonds between the amide groups on the side-chain above its LCST. Full article

Almandine garnet has received considerable amounts of interest due to its application in manufacturing and engineering processes. Defect processes, Fe-ion diffusion pathways, and promising dopants on the Al, Fe, and Si sites are examined using classical pair potential simulations in almandine garnet. The cation antisite (Al–Si) defect cluster is the most favourable defect, highlighting the cation disorder in this material. A three-dimensional long-range Fe-ion diffusion pathway with an activation energy of 0.44 eV suggests that the ionic conductivity in this material is high. The most favourable isovalent dopants on the Fe, Al, and Si sites were found to be the Mn, Ga, and Ge, respectively. Subvalent doping of Ga on the Si site is a favourable process to increase the Fe content in this material. Full article

The review contains information o; n the properties of phase-change materials (PCM) and the possibilities of their use as the basis of thermal energy storage. Special attention is given to PCMs with a phase transition temperature ranging between 20 and 80 °C since such materials can be effectively used to reduce temperature variations in residential and industrial rooms. Thus, the application of PCMs in the construction industry enables one to considerably reduce the power consumption and reduce the negative environmental impact of industrial facilities. Thermophysical characteristics of the main types of PCMs are presented. The heat balance for a room with walls made of PCM-added materials is estimated. The calculations demonstrate that such structures can stabilize the temperature in practical applications as a result of the usage of such materials. The construction of a thermal accumulator on the basis of PCM is proposed and analyzed. This facility uses water as a working fluid and paraffin as a PCM. The thermal accumulator has a modular structure so that the number of similar modules is determined by the quantity of energy to be stored. The potential of wide application of PCMs as a basis for thermal energy storage is rather limited due to a very low conductivity (less than 1 W/(m K)) inherent to these materials. This drawback can be overcome by adding carbon nanoparticles whose thermal conductivity is four to five orders of magnitude greater than that of the matrix material. The problem of fabrication of polymer composites with enhanced thermal conductivity due to nanocarbon particles doping is discussed in detail. Full article

Detection of intermediates during the catalytic process by infrared techniques has been widely implemented for many important reactions. For the reduction of CO₂ into hydrocarbons on metal surfaces, CO molecule is one of the most important transient species to be followed due to its involvement in several products’ pathways, and its distinct vibrational features. Herein, basic understandings behind these utilized infrared techniques are illustrated aiming for highlighting the potential of each infrared technique and its advantages over the other ones for detecting CO molecules on metal surfaces. Full article