The Stability Study of Thermodynamic Parameters of Sorption of Light Hydrocarbons on Poly [Trimethylsilyl (Propyn-1)] at Different Temperatures

Chromatographic determination of the thermodynamic parameters of sorption for light hydrocarbons retention on a stationary phase based on poly [trimethylsilyl (propyn-1)] (PTMSP) was performed and the effect of column preheating at temperatures up to 260°C on the retention of analytes was investigated. It was shown that heating the column to 130°C does not affect the retention of the analytes. At temperatures above 130°C, the gradual decrease of the retention of analytes on PTMSP stationary phase is observed. The process is non-selective and proceeds at the same extent for all the studied hydrocarbons, regardless of the size and geometry of the molecule. Values of enthalpy and entropy of sorption of light hydrocarbons are determined for the original column and after its aging at 200°C. The enthalpy of sorption of the analytes at the PTMSP phase is practically independent on the heating temperature of the PTMSP phase, whereas the loss of entropy increases after heating. The increase of the entropy factor after the heating of the PTMSP stationary phase is associated with its aging and is confirmed by the construction of compensation functions for treated and untreated columns.

Multifunctional wafer-scale graphene membranes for fast ultrafiltration and high permeation gas separation

Reliable and large-scale manufacturing routes for perforated graphene membranes in separation and filtration remain challenging. We introduce two manufacturing pathways for the fabrication of highly porous, perforated graphene membranes with sub-100-nm pores, suitable for ultrafiltration and as a two-dimensional (2D) scaffold for synthesizing ultrathin, gas-selective polymers. The two complementary processes-bottom up and top down-enable perforated graphene membranes with desired layer number and allow ultrafiltration applications with liquid permeances up to 5.55 × 10^-8 m³ s^-1 Pa^-1 m^-2. Moreover, thin-film polymers fabricated via vapor-liquid interfacial polymerization on these perforated graphene membranes constitute gas-selective polyimide graphene membranes as thin as 20 nm with superior permeances. The methods of controlled, simple, and reliable graphene perforation on wafer scale along with vapor-liquid polymerization allow the expansion of current 2D membrane technology to high-performance ultrafiltration and 2D material reinforced, gas-selective thin-film polymers.