PEG Containing Thiol–Ene Network Membranes for CO2 Separation: Effect of Cross-Linking on Thermal, Mechanical, and Gas Transport Properties

Diffusion-based culture and real-time impedance monitoring of tumor spheroids in hydrogel microwells of a suspended membrane under microfluidic conditions

Tumor spheroids are widely studied for in vitro modeling of tumor growth and responses to anticancer drugs. However, current methods are mostly limited to static and perfusion-based cultures, which can be improved by more accurately mimicking pathological conditions. Here, we developed a diffusion-based dynamic culture system for tumor spheroids studies using a thin membrane of hydrogel microwells and a microfluidic device. This allows for effective exchange of nutrients and metabolites between the tumors and the culture medium flowing underneath, resulting in uniform tumor spheroids. To monitor the growth and drug response of the spheroids in real-time, we performed spectroscopic analyses of the system's impedance, demonstrating a close correlation between the tumor size and the resistance and capacitance of the system. Our results also indicate an enhanced drug effect on the tumor spheroids in the presence of a low AC electric field, suggesting a weakening mechanism of the spheroids induced by external perturbation.

Covalent connections between metal-organic frameworks and polymers including covalent organic frameworks

Hybrid composite materials combining metal-organic frameworks (MOFs) and polymers have emerged as a versatile platform for a broad range of applications. The crystalline, porous nature of MOFs and the flexibility and processability of polymers are synergistically integrated in MOF-polymer composite materials. Covalent bonds, which form between two distinct materials, have been extensively studied as a means of creating strong molecular connections to facilitate the dispersion of "hard" MOF particles in "soft" polymers. Numerous organic transformations have been applied to post-synthetically connect MOFs with polymeric species, resulting in a variety of covalently connected MOF-polymer systems with unique properties that are dependent on the characteristics of the MOFs, polymers, and connection modes. In this review, we provide a comprehensive overview of the development and strategies involved in preparing covalently connected MOFs and polymers, including recently developed MOF-covalent organic framework composites. The covalent bonds, grafting strategies, types of MOFs, and polymer backbones are summarized and categorized, along with their respective applications. We highlight how this knowledge can serve as a basis for preparing macromolecular composites with advanced functionality.

Photopatterning of two stage reactive polymer networks with CO2-philic thiol–acrylate chemistry: enhanced mechanical toughness and CO2/N2 selectivity

Two stage reactive polymer (TSRP) networks can be programmed with spatially varying heterogeneity, presenting a new way of designing material structure and controlling or enhancing properties.

Tailoring Crosslinked Polyether Networks for Separation of CO2 from Light Gases

Crosslinked poly(ethylene oxide) or poly(ethylene glycol) (PEG) is an ideal membrane material for separation of CO₂ from light gases (e.g., H₂ , N₂ , O₂ , CH₄ etc). In these membranes, crosslinking is used as a tool to suppress crystallinity of the PEG segments. In spite of the extensive effort to develop crosslinked PEG membranes in the last two decades, it remains a challenge to establish the structure-property relationships. This paper points out the fundamental limitations to correlate the chain topology of a network with the gas permeation mechanism. While a quantitative comparison of the molecular weight between crosslinks of networks and gas permeation mechanism reported by different research groups is challenging, effort is made to draw a qualitative picture. In this review, a focus is also put on the progress of utilization of dangling chain fractions to tailor the gas permeation behavior of PEG networks.

Ionic liquid tethered PEG-based polyurethane-siloxane membranes for efficient CO2/CH4 separation

This study introduces a new polyethylene glycol (PEG) based polyurethane-siloxane membrane containing a quaternary ammonium ionic liquid for CO₂/CH₄ separation. The designed ionic liquid was prepared in two steps: (i) (3-chloropropyl)triethoxysilane (CPS) and N,N-dimethylpropyl amine (NDPA) were reacted with each other to form the methoxysilane-functionalized quaternary ammonium component, then (ii) chloride ion (Cl^-) of the product was exchanged with tetrafluoroborate ion (BF₄^-). The resulting compound, a reactive methoxysilane-functionalized ionic liquid (Si-IL) was chemically anchored to the polymer backbone through the sol-gel hydrolysis and condensation reaction. Based on the permeation tests, the IL containing PEG-based polyurethane-siloxane membranes at different concentration of Si-IL (XSi-PPUIL) were found to be potential candidates for CO₂ removal from CH₄. For instance, the CO₂/CH₄ selectivity of XSi-PPUIL membranes with the Si-IL content of 10 wt% was 3.3-fold greater than the Si-IL free membranes; while, the CO₂ permeability for IL tethered membranes was 9.7% higher than the corresponding IL-free membrane.

Nanostructured poly(l-lactic acid)-poly(ethylene glycol)-poly(l-lactic acid) triblock copolymers and their CO2/O2 permselectivity

Biodegradable poly(l-lactic acid)-poly(ethylene glycol)-poly(l-lactic acid) (PLLA-PEG-PLLA) copolymers were synthesized by ring-opening polymerization of l-lactide using dihydroxy PEG as the initiator. The effects of different PEG segments in the copolymers on the mechanical and permeative properties were investigated. It was determined that certain additions of PEG result in composition-dependent microphase separation structures with both PLLA and PEG blocks in the amorphous state. Amorphous PEGs with high CO₂ affinity form gas passages that provide excellent CO₂/O₂ permselectivity in such a nanostructure morphology. The gas permeability and permselectivity depend on the molecular weight and content of the PEG and are influenced by the temperature. Copolymers that have a higher molecular weight and content of PEG present better CO₂ permeability at higher temperatures but provide better CO₂/O₂ permselectivity at lower temperatures. In addition, the hydrophilic PEG segments improve the water vapor permeability of PLLA. Such biodegradable copolymers have great potential for use as fresh product packaging.

High-performance Polymer Membranes with Multi-functional Amphiphilic Micelles for CO2 Capture

Herein, we report a high performance polymer membrane with simultaneously large improvements in the CO2 permeability and CO2/N2 selectivity. These improvements are obtained by incorporation of a multi-functional amphiphilic comb copolymer micelle, that is, poly(dimethylsiloxane)-g-poly(oxyethylene methacrylate) (PDMS-g-POEM), into a poly(amide-b-ethylene oxide) (Pebax) matrix. Both CO2 and N2 permeabilities continuously increased with PDMS-g-POEM content, whereas the CO2/N2 selectivity increased up to 40 wt % of PDMS-g-POEM, which enabled the maximum performance to approach the upper bound limit (2008). The membranes with PDMS-g-POEM exhibited greater CO2 permeability and CO2/N2 selectivity than those with a zeolitic imidazolate framework (ZIF-8), a well-known expensive inorganic filler, indicating the effectiveness of PDMS-g-POEM micelles for CO2 capture.

Tough and biocompatible hydrogels based on in situ interpenetrating networks of dithiol-connected graphene oxide and poly(vinyl alcohol)

An interpenetrating network (IPN) strategy has been widely facilitated to construct strong and tough hydrogels, but most of the efforts have been focused on organic/organic networks. Herein, aqueous dispersible 2,2'-(ethylenedioxy)-diethanethiol (EDDET) cross-linked graphene oxide (E-cGO) skeleton was in situ incorporated into a PVA matrix, resulting in novel inorganic/organic IPN hydrogels with super mechanical and chondrocyte cell-adhesion properties. The unique interpenetrating structure and hydrogen bonding were demonstrated to play critical roles in enhancing the compressive property of the IPN hydrogels, in comparison to the GO and thermally reduced graphene oxide (T-rGO) filled hydrogels. It is critical that the E-cGO/PVA hydrogels have been demonstrated as being biocompatible, which make the E-cGO/PVA hydrogels promising candidate biomaterials for load-bearing biotissue substitution.