We report a partial elucidation of the relationship between polymer polarity and ionic conductivity in polymer electrolyte mixtures comprising a homologous series of nine poly(vinyl ether)s (PVEs) and lithium bis(trifluoromethylsulfonyl)imide. Recent simulation studies have suggested that low dielectric polymer hosts with glass transition temperatures far below ambient conditions are expected to have ionic conductivity limited by salt solubility and dissociation. In contrast, high dielectric hosts are expected to have the potential for high ion solubility but slow segmental dynamics due to strong polymer−polymer and polymer−ion interactions. We report results for PVEs in the low polarity regime with dielectric constants of about 1.3 to 9.0. Ionic conductivity measured for the PVE and salt mixtures ranged from about 10 −10 to 10 −3 S/cm. In agreement with the predictions from computer simulations, the ionic conductivity increased with dielectric constant and plateaued as the dielectric approached 9.0, comparable to the dielectric constant of the widely used poly(ethylene oxide).
This is the first report using an alternate soaking process (ASP) to mineralize the surfaces of thin film composite (TFC) polyamide membranes with silver chloride (AgCl) for forward osmosis (FO). Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis confirmed even distribution of AgCl particles on the top of the membrane surfaces. Surface roughness, contact angle, and zeta potential measurements show that the AgCl mineralized membranes have smoother, more hydrophilic, and more negatively charged surfaces than unmodified membranes. Under FO operation (with deionized water feed and 1 M NaCl draw), we found that the mineralized membranes exhibit higher salt rejection and water flux than the original membranes. Fouling experiments with bovine serum albumin (BSA) show that the mineralized membranes have lower water flux decline ratios in BSA aqueous solution and higher water flux recovery ratios after simple hydraulic washing than unmodified TFC membranes.
Establishing general structure−property relationships for polymer electrolytes is crucial to enable design of improved materials to advance solid-state energy storage. We report the relationship between dielectric constant, glass transition temperature, and ionic conductivity for polyether-based electrolytes with dielectric constants of the polyether host within the range 7−35 at 60 °C. The ionic conductivities of the polyether and lithium bis(trifluoromethylsulfonyl)imide mixtures ranged from 10 −7 to 10 −3 S/cm. In this higher-dielectric-constant regime, here defined as a polymer with a dielectric constant greater than that of poly(ethylene oxide) (ca. 9.0), the glass transition temperature increased with dielectric constant while ionic conductivity decreased. These results complement a recent report on the low-dielectric-constant regime, where the ionic conductivity was limited by the dielectric constant and ion dissociation. In the high-dielectric-constant regime explored here, segmental dynamics are slowed due to stronger polymer−polymer and polymer−ion interactions, resulting in decreased ionic conductivity and associated increase in neat polymer glass transition temperature. The disparate chemical structures of the polymers of this study, along with the results of past coarse-grained molecular dynamics simulations, support the generality of these conclusions and speak to the difficulty of identifying a single molecular characteristic leading to the design of high-conductivity polymer electrolytes. Widely used poly(ethylene oxide) represents a near-optimal balance between the low-and high-dielectric-constant regimes. To improve upon the ionic conductivity limitations of polymer electrolytes, single-component polymer hosts are unlikely to resolve the trade-off between the need for ion dissociation while retaining rapid segmental dynamics.
Recent changes in the legal status of cannabis augmented by a rapidly evolving social acceptance towards its consumption, highlight the immediate need for a reliable, non-invasive, point-of-use detection method for cannabis intoxication. Marijuana intoxication reduces motor coordination, slows reaction time, and impairs peripheral vision, concentration, and decision making. The rise in access and consumption of marijuana is anticipated to lead to an increase in drivers and workers impaired from its effects. Current tests for marijuana consumption are invasive (rely on blood/urine), logistically challenging (require weeks to analyze), and can only conclusively confirm use within the past month (not real-time detection). In the absence of a portable, non-invasive analytical tool to quantify marijuana intoxication, real-time THC sobriety tests rely heavily on subjective techniques that are prone to human error and/or bias. Consequently, these methods are inadequate for law enforcement, who need who need to quickly and accurately determine an individual’s state of impairment, and employers, who forbid “working under the influence”, but would allow responsible “off-duty” cannabis consumption to go unpenalized, so long as it does not affect job performance.Although there is no federal legislative consensus on the definition of marijuana intoxication, it is known that Δ9-Tetrahydrocannabinol (THC), the principle psychotropic in marijuana, has an approximate 3-hour detection window in the body that roughly correlates with symptoms of peak cannabis impairment. A small, but detectable, concentration of THC remains in equilibrium in the lungs during this 3-hour window, allowing the use of breath to be leveraged as a non-invasive method to determine recent cannabis consumption. After 3 hours, cannabinoid metabolites are rapidly diminished from the blood and lungs and absorbed into fatty tissue and the brain, reducing the efficacy of breath for use in non-invasive detection methods. While the low concentration of cannabinoids in breath ( µg/L – pg/L ) complicates detection, and there is ongoing debate as to how chronic marijuana use, gender, and body type affect baseline THC levels, there is a growing consensus that a breathalyzer will ultimately provide the best solution for a non-invasive, point-of-use detector for cannabis intoxication.Seacoast Science, Inc. is co-developing a hand-held marijuana breathalyzer in collaboration with Professors Nathaniel Lynd and Feng Zhang of UT Austin. This device will allow for the real-time, point-of-use detection and quantification of cannabinoids measured in the gas-phase. The underlying detection technology is based on the use of smart, biomimetic polymers with enhanced cannabinoid affinity measured by Micro-Electro-Mechanical Systems (MEMS) transducers (ie. chemicapacitors and chemiresistors). We will present results confirming reliable detection of a panel of gas-phase cannabinoids measured using this system in a controlled environmental chamber. The use of chemometric analysis to ...
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