Thermally Rearranged (TR) Polybenzoxazole: Effects of Diverse Imidization Routes on Physical Properties and Gas Transport Behaviors

Thermally Rearranged Poly(benzoxazole) Copolymer Membranes for Improved Gas Separation: A Review

Polymeric membranes for gas separation have application in a wide range of industries such as natural gas sweetening and air enrichment. Recently, high-performance gas separation polymeric membranes have been developed based on a novel thermal rearrangement process that produces the resistant poly(benzoxazole) (TR-PBO). This review reports on the current state of the art TR-PBO membranes for gas separation and the underlying chemistry needed to achieve such high separation performance. Particular focus is applied to copolymers based on TR-PBO for membranes as these have attracted considerable research interest recently for their gas separation performance and superior mechanical properties compared with TR-PBO. Also included in this review is a discussion of the future directions of research on TR-PBO-based membranes for gas separation.

A facile method for transparent carbon nanosheets heater based on polyimide

Transparent carbon nanosheet film heaters are fabricated by spin-coating of poly(amic acid) on quartz substrates following by carbonization process. These thin films show the transparency of 55–90% at 550 nm and sheet resistance of 14.7 to 1.6 kΩ sq⁻¹.

Sorption Behavior of Compressed CO2 and CH4 on Ultrathin Hybrid Poly(POSS-imide) Layers

Sorption of compressed gases into thin polymeric films is essential for applications including gas sensors and membrane based gas separation. For glassy polymers, the sorption behavior is dependent on the nonequilibrium status of the polymer. The uptake of molecules by a polymer is generally accompanied by dilation, or swelling, of the polymer material. In turn, this dilation can result in penetrant induced plasticization and physical aging that affect the nonequilibrium status of the polymer. Here, we investigate the dilation and sorption behavior of ultrathin membrane layers of a hybrid inorganic-organic network material that consists of alternating polyhedral oligomeric silsesquioxane and imide groups, upon exposure to compressed carbon dioxide and methane. The imide precursor contains fluoroalkene groups that provide affinity toward carbon dioxide, while the octa-functionalized silsesquioxane provides a high degree of cross-linking. This combination allows for extremely high sorption capacities, while structural rearrangements of the network are hindered. We study the simultaneous uptake of gases and dilation of the thin films at high pressures using spectroscopic ellipsometry measurements. Ellipsometry provides the changes in both the refractive index and the film thickness, and allows for accurate quantification of sorption and swelling. In contrast, gravimetric and volumetric measurements only provide a single parameter; this does not allow an accurate correction for, for instance, the changes in buoyancy because of the extensive geometrical changes of highly swelling films. The sorption behavior of the ultrathin hybrid layers depends on the fluoroalkene group content. At low pressure, the apparent molar volume of the gases is low compared to the liquid molar volume of carbon dioxide and methane, respectively. At high gas concentrations in the polymer film, the apparent molar volume of carbon dioxide and methane exceeds that of the liquid molar volume, and approaches that of the gas phase. The high sorption capacity and reversible dilation characteristics of the presented materials provide new directions for applications including gas sensors and gas separation membranes.

Towards high water permeability in triazine-framework-based microporous membranes for dehydration of ethanol

The microstructural evolution of a series of triazine framework-based microporous (TFM) membranes under different conditions has been explored in this work. The pristine TFM membrane is in situ fabricated in the course of polymer synthesis via a facile Brønsted-acid-catalyzed cyclotrimerizaiton reaction. The as-synthesized polymer exhibits a microporous network with high thermal stability. The free volume size of the TFM membranes gradually evolved from a unimodal distribution to a bimodal distribution under annealing, as analyzed by positron annihilation lifetime spectroscopy (PALS). The emergence of the bimodal distribution is probably ascribed to the synergetic effect of quenching and thermal cyclization reaction. In addition, the fractional free volume (FFV) of the membranes presents a concave trend with increasing annealing temperature. Vapor sorption tests reveal that the mass transport properties are closely associated with the free volume evolution, which provides an optimal condition for dehydration of biofuels. A promising separation performance with extremely high water permeability has been attained for dehydration of an 85 wt % ethanol aqueous solution at 45 °C. The study on the free volume evolution of the TFM membranes may provide useful insights about the microstructure and mass transport behavior of the microporous polymeric materials.

Highly lithium-ion conductive battery separators from thermally rearranged polybenzoxazole

Lithium ion battery separators were fabricated for the first time from thermally rearranged poly(benzoxazole-co-imide) (TR-PBOI) nanofibrous membranes coated with TR-PBO nanoparticles.

Gas separation membranes made through thermal rearrangement of ortho-methoxypolyimides

ortho-Methoxypolyimides were prepared from 3,3ʹ-dimethoxybenzidine (DMAB) and hexafluoroisopropylidene diphthalic anhydride (6FDA).

Tröger's base-based copolymers with intrinsic microporosity for CO2 separation and effect of Tröger's base on separation performance

“Polymers of intrinsic microporosity” (PIMs) have recently received considerable attention as powerful and promising membrane materials for gas separation, especially for CO₂ separation.

Simultaneous microfabrication and tuning of the permselective properties in microporous polymers using X-ray lithography

Microchannels are fabricated using a photosensitive polymer to which microporosity is tuned with different X-ray doses. Using hard X-ray irradiation, the micropattern is positioned with various geometries in a multi-level, three-dimensional structure, while controlling the pore size and transport properties of small molecules. This highly reliable fabrication process has potential for use in microfluidic devices with enhanced transport properties through microchannels.

Polymers of Intrinsic Microporosity

This paper focuses on polymers that demonstrate microporosity without possessing a network of covalent bonds—the so-called polymers of intrinsic microporosity (PIM). PIMs combine solution processability and microporosity with structural diversity and have proven utility for making membranes and sensors. After a historical account of the development of PIMs, their synthesis is described along with a comprehensive review of the PIMs that have been prepared to date. The important methods of characterising intrinsic microporosity, such as gas absorption, are outlined and structure-property relationships explained. Finally, the applications of PIMs as sensors and membranes for gas and vapour separations, organic nanofiltration, and pervaporation are described.