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H₂S/CH₄and CO₂/CH₄separations show opposing trends, making simultaneous improvement challenging. This is addressed by increasing free volume to enhance competitive sorption effects and boosting diffusion selectivity throughin situcrosslinking. 

We report a scalable synthesis of high-molecularweight poly(arylene ether)s (PAEs) using decafluorobiphenyl under SNAr reaction conditions and the preparation of enantiopure (R,R)-6,11-di(tert-butyl)triptycene-1,4-hydroquinone. The nonfluorinated biphenyl-based PAE was also synthesized using Pdcatalyzed C−O coupling methods, and structure−property comparisons were made from the different biphenyl-based polymers. The integration of free-volume-promoting triptycene moieties on the main chain gives rise to intrinsic porosity, which can be further modulated by incorporating biphenyl or perfluorobiphenyl comonomers. The nonfluorinated PAE exhibited a BET surface area of 270 m2 g−1, whereas the racemic and enantiopure fluorinated PAEs showed higher BET surface areas of 454 and 368 m2 g−1, respectively. WAXS analysis revealed that all of the polymers tested have a greater disruption of chain packing compared to related polyimides, with the fluorinated PAEs having the highest average interchain spacing. The fluorinated PAEs also demonstrated high gas permeability as a result of their free volume. The triptycene-based PAEs also were resistant to plasticization even at CO2 pressures of ∼31 bar. 

Elevated levels of ammonia in breath can be linked to medical complications such as chronic kidney disease (CKD) that disturb the urea balance in the body. However, early-stage CKD is usually asymptomatic and mass screening is hindered by high instrumentation and operation requirements, accessible and reliable detection methods for CKD biomarkers, such as trace ammonia in breath. Enabling methods would have significance in population screening for early-stage CKD patients. We herein report a method to effectively immobilize transition metal selectors in close proximity to single-walled carbon nanotube (SWCNT) surface using pentiptycene polymers containing metal-chelating backbone structures. The robust and modular nature of the pentiptycene metallopolymer/SWCNT complexes create a platform that accelerates sensor discovery and optimization. Using these methods, we have identified sensitive, selective, and robust copper-based chemiresistive ammonia sensors displaying low parts per billion detection limits. We have added these hybrid materials into the resonant radio frequency circuits of commercial near-field communication (NFC) tags to achieve robust wireless detection of ammonia at physiologically relevant levels. The integrated devices offer a non-invasive and cost-effective approach for early detection and monitoring of CKD. 

Chemical sensing has a vital role in promoting security and welfare. Functionalized carbon nanotubes (CNTs) possess unique electronic, mechanical and chemical properties, rendering them as exceptional transducers for developing highly sensitive, selective and robust chemical sensors. In this Primer, we discuss the progress and challenges associated with chemiresistive sensing using functionalized CNTs, providing an introductory overview, spanning from theoretical to experimental aspects. Various covalent and non-covalent CNT functionalization strategies that contribute to enhancing the sensitivity and selectivity of chemiresistive sensors are discussed, along with their respective merits and drawbacks. Additionally, this Primer focuses on the critical facets of experimental design, including material selection, device architecture and fabrication and best practices for sensor testing. This Primer also discusses the significance of rigorous data interpretation, analysis and reporting, ensuring reproducibility and reliability. Finally, this Primer highlights the existing limitations of CNT-based chemiresistive sensors and investigates potential strategies for enhancing sensor selectivity and sensitivity that may broaden their applicability in diverse fields, from environmental monitoring to biomedical diagnostics. By emphasizing the need to understand the molecular interactions between the sensor and target analyte to improve selectivity, this Primer aims to offer a comprehensive understanding of the current state of CNT-based chemiresistive sensing. 

This study details the enhancement of CO2 selectivity in ring opening metathesis polymerization (ROMP) polymers that contain nitrile moieties and micro-pore generating ladder side chains. A material, CN-ROMP homopolymer, with nitriles in the ladder side chains was originally targeted and synthesized, however its low molecular weight and backbone rigidity precluded film formation. As a result, an alternative method was pursued wherein copolymers were synthesized using norbornene (N) and nitrile norbornene (NN). Herein, we report an investigation of the structure–property relationships of backbone functionalization and grafting density on the CO2 transport properties in these ROMP polymers. Nitrile-containing copolymers showed an increase in CO2/CH4 sorption selectivity and a concomitant increase in CO2/CH4 permselectivity when compared to the unfunctionalized (nitrile free) analogs. The stability in CO2 rich environments is enhanced as grafting density of the rigid, pore-generating side chains increases and an apparent tunability of CO2 plasticization pressure was observed as a function of norbornene content. Lower loadings of norbornene resulted in higher plasticization pressure points. Gas permeability in the ROMP copolymers was found to correlate most strongly with the concentration of ladder macromonomers in the polymer chain.