UV-crosslinked poly(PEGMA-co-MMA-co-BPMA) membranes: Synthesis, characterization, and CO2/N2 and CO2/CO separation

Intrinsically Microporous Polyimides Based on a Rigid-Soft Structure for Hydrogen Separation

Polyimide (PI)-based gas separation membranes are of great interest in the field of H2 purification owing to their good thermal stability, chemical stability, and mechanical properties. Among polyimide-based membranes, intrinsically microporous polyimides are easily soluble in common organic solvents, showing great potential for fabricating hollow fiber gas separation membranes. However, based on the solution-diffusion model, improving the free volume or the movability of polymer chains can improve gas permeability, but would result in poor thermal stability. Herein, we develop a carbazole-alkyl-based diamine monomer that endows PI chains with a "rigid-soft" structure to balance the trade-off between them. Soft units enhance the movability of polymer chains during the film-forming process, ensuring that rigid units achieve tight chain packing and strong intermolecular interactions. Meanwhile, bulky carbazole groups could further restrict the motion of soft units in the solid state. On the one hand, it restricts the movability of the polymer chains below Tg, enhancing the small gas selectivity for H2 and He. On the other hand, it ensures good thermal stability. Moreover, extending the length of the alkyl chains helps improve the free volume and intermolecular interactions simultaneously, thereby further optimizing the gas permeability/selectivity trade-off. As a result, the as-prepared PI shows H2 permeability of 89.61 Barrer, H2/CH4 selectivity of 87.85, and H2/N2 selectivity of 45.03 in contrast to the reference FPI TFMB-6FDA exhibiting H2 permeability of 92.95 Barrer, H2/CH4 selectivity of 72.62, and H2/N2 selectivity of 38.57. Meanwhile, a high Tg value of 334 °C is also achieved.

Conjugation of folic acid with poly (NVCL-co-PEGMA)-grafted chitosan as a new doxorubicin delivery system

This paper aimed to investigate the synthesis of a novel drug delivery system (DDS) to target tumors and implement the controlled release of doxorubicin (DOX). Chitosan was modified with 3-mercaptopropyltrimethoxysilane and subjected to graft polymerization to implement grafting with the biocompatible thermosensitive copolymer of poly (NVCL-co-PEGMA). A folate receptor-targeting agent was obtained by attaching folic acid. The DDS loading capacity for DOX via physisorption was obtained to be 846.45 mg/g. The synthesized DDS showed temperature- and pH-sensitive drug release behavior in vitro. A temperature of 37 °C and a pH of 7.4 hindered the DOX release, whereas a temperature of 40 °C and a pH of 5.5 led to DOX release acceleration. In addition, the release of DOX was found to occur in a Fickian diffusion mechanism. The MTT assay tests indicated that the synthesized DDS was not detectably toxic to cell lines of breast cancer, while the toxicity of the DOX-loaded DDS was found to be substantial. The cell absorption enhancement of folic acid led to higher cytotoxicity of the DOX-loaded DDS than bare DOX. As a result, the proposed DDS could be a promising alternative for the targeted therapy of breast cancer through controlled drug release.

Recent Advances of Polymeric Membranes in Tackling Plasticization and Aging for Practical Industrial CO2/CH4 Applications—A Review

Membranes are a promising technology for bulk CO₂ separation from natural gas mixtures due to their numerous advantages. Despite the numerous fundamental studies on creating better quality membrane efficiency, scaling up the research work for field testing requires huge efforts. The challenge is to ensure the stability of the membrane throughout the operation while maintaining its high performance. This review addresses the key challenges in the application of polymeric technology for CO₂ separation, focusing on plasticization and aging. A brief introduction to the properties and limitations of the current commercial polymeric membrane is first deliberated. The effect of each plasticizer component in natural gas towards membrane performance and the relationship between operating conditions and the membrane efficiency are discussed in this review. The recent technological advancements and techniques to overcome the plasticization and aging issues covering polymer modification, high free-volume polymers, polymer blending and facilitated transport membranes (FTMs) have been highlighted. We also give our perspectives on a few main features of research related to polymeric membranes and the way forwards. Upcoming research must emphasize mixed gas with CO₂ including minor condensable contaminants as per real natural gas, to determine the competitive sorption effect on CO₂ permeability and membrane selectivity. The effects of pore blocking, plasticization and aging should be given particular attention to cater for large-scale applications.

Insights into the Role of Polymer Conformation on the Cutoff Size of Carbon Molecular Sieving Membranes for Hydrogen Separation and Its Novel Pore Size Detection Technology

In this study, three polymer precursor conformations, dilute, semi-dilute, and concentrated, were used to fabricate carbon molecular sieving (CMS) membranes via a fixed carbonization protocol. The effects of the precursor conformation on the microstructure of the resultant CMS membranes were characterized by Raman analysis. Their ability to separate light gases, such as H₂/CH₄ and H₂/N₂, was assessed with a single-gas system. Additionally, a novel method was proposed to detect the cutoff size of the CMS membranes created in this study. The method combined high-resolution transmission electron microscopy (HR-TEM) and a focused ion beam (FIB) system. Finally, due to the semi-dilute solution's denser polymer chains and lack of severe polymer entanglement, highly graphited CMS membranes with excellent gas separation performance were successfully synthesized using a semi-dilute polyetherimide dope solution. Interlayer distances in the carbon matrix were visualized and measured using our novel probing tool (HR-TEM and FIB) and software. The CMS membrane fabricated with a semi-dilute dope exhibited the best gas separation performance of the tested membranes. It had the most ordered carbon sheet orientation and exhibited a superior selectivity of H₂/CH₄ = 293 with a hydrogen permeability of 1138.7 Barrer, far surpassing the reported permselectivity of other membranes. We believe that the high H₂/CH₄ selectivity presented here is unprecedented for CMS membranes reported in the literature.

Synthesis and gas transport properties of sulfonated poly(ether ether sulfone) membranes containing pendant sulfonic acid groups

A series of gas separation membranes based on sulfonated poly(ether ether sulfone)s (SPEESs) can be synthesized by the polycondensation and sulfonation reactions. The structural characteristics of copolymers were confirmed by 1H-NMR spectroscopy, Fourier-transform infrared spectroscopy, gel permeation chromatography, and ultraviolet–visible absorption spectroscopy. The permeability and selectivity behavior of these membranes were investigated using three single-gases (CO2, O2, and N2) at different temperatures of 25–55°C and pressures of 1.0–3.0 atm. The effect of sulfonation degree (SD), operating temperature, and pressure on gas permeability was explored and discussed. The results showed that SPEESs containing pendant sulfonic acid groups exhibited different separation performance. In particular, the SPEES-4 membrane with an SD of 67% exhibited the highest permeability (CO2 = 513.8 Barrer and O2 = 78.19 Barrer) at 55°C and 1 atm, whereas CO2/N2 and O2/N2 selectivity was 31.09 and 4.73, respectively.