Studies of relationship between polymer structure and hydration environment in amphiphilic polytartaramides

Monodentate Acetate Anion Enhanced Hydrogel Electrolyte for Long-Term Lifespan Zn-Air Batteries

Flexible Zn-air batteries (FZABs) hold significant promise in diverse application scenarios with high safety and compatibility yet are still impeded by byproduct formation and poor water retention. Here, the neutral hydrogel electrolyte GAHE is engineered by in situ polymerizing acrylamide (AM) in a solution composed of cationic guar gum (CGG) and acetate salts to conquer the above challenges. The acetate anions (OAc-) exert a pH near 7 to effectively inhibit the side reactions triggered by H+. Meanwhile, the monodentate OAc- ions in LiOAc have fast ion diffusion kinetics and form hydrogen bonds between the released carbonyl groups and H2O to further suppress water activity for great side reaction prevention and water retention. Additionally, the in situ polymerization strategy realizes a polymer with high mechanical properties and great electrochemical interfacial stability and further improves the water retention property with hydrophilic groups. Consequently, GAHE gives the FZABs a lifespan of 2050 h at room temperature and 2940 h at -35 °C. This work provides concepts for electrolyte design for water retention and side reaction inhibition properties of aqueous devices.

Fine Tuning Water States in Hydrogels for High Voltage Aqueous Batteries

Hydrogels are widely used as quasi-solid-state electrolytes in aqueous batteries. However, they are not applicable in high-voltage batteries because the hydrogen evolution reaction cannot be effectively suppressed even when water is incorporated into the polymer network. Herein, by profoundly investigating the states of water molecules in hydrogels, we designed supramolecular hydrogel electrolytes featuring much more nonfreezable bound water and much less free water than that found in conventional hydrogels. Specifically, two strategies are developed to achieve this goal. One strategy is adopting monomers with a variety of hydrophilic groups to enhance the hydrophilicity of polymer chains. The other strategy is incorporating zwitterionic polymers or polymers with counterions as superhydrophilic units. In particular, the nonfreezable bound water content increased from 0.129 in the conventional hydrogel to >0.4 mg mg-1 in the fabricated hydrogels, while the free water content decreased from 1.232 to ∼0.15 mg mg-1. As a result, a wide electrochemical stability window of up to 3.25 V was obtained with the fabricated hydrogels with low concentrations of incorporated salts and enhanced hydrophilic groups or superhydrophilic groups. The ionic conductivities achieved with our developed hydrogel electrolytes were much higher than those in the conventional highly concentrated salt electrolytes, and their cost is also much lower. The designed supramolecular hydrogel electrolytes endowed an aqueous K-ion battery (AKIB) system with a high voltage plateau of 1.9 V and contributed to steady cycling of the AKIB for over 3000 cycles. The developed supramolecular hydrogel electrolytes are also applicable to other batteries, such as aqueous lithium-ion batteries, hybrid sodium-ion batteries, and multivalent-ion aqueous batteries, and can achieve high voltage output.

MXene-Induced Flexible, Water-Retention, Semi-Interpenetrating Network Hydrogel for Ultra-Stable Strain Sensors with Real-Time Gesture Recognition

As water-saturated polymer networks, hydrogels are a growing family of soft materials that have recently become promising candidates for flexible electronics application. However, it remains still difficult for hydrogel-based strain sensors to achieve the organic unity of mechanical properties, electrical conductivity, and water retention. To address this challenge, based on the template, the excellent properties of MXene nanoflakes (rich surface functional groups, high specific surface area, hydrophilicity, and conductivity) are fully utilized in this study to prepare the P(AA-co-AM)/MXene@PDADMAC semi-interpenetrating network (semi-IPN) hydrogel. The proposed hydrogel continues to exhibit excellent strain response and flexibility after 30 days of storage at room temperature, and its performance do not decrease after 1100 cycles. Considering these characteristics, a hydrogel-based device for converting sign language into Chinese characters is successfully developed and optimized using machine learning. Therefore, this study provides novel insight and application directions for hydrogel families.

Structural Behavior of Amphiphilic Triblock Copolymer P104/Water System

A detailed study of the different structural transitions of the triblock copolymer PEO₂₇-PPO₆₁-PEO₂₇ (P104) in water, in the dilute and semi-dilute regions, is addressed here as a function of temperature and P104 concentration (C_P104) by mean of complimentary methods: viscosimetry, densimetry, dynamic light scattering, turbidimetry, polarized microscopy, and rheometry. The hydration profile was calculated through density and sound velocity measurements. It was possible to identify the regions where monomers exist, spherical micelle formation, elongated cylindrical micelles formation, clouding points, and liquid crystalline behavior. We report a partial phase diagram including information for P104 concentrations from 1 × 10^-4 to 90 wt.% and temperatures from 20 to 75 °C that will be helpful for further interaction studies with hydrophobic molecules or active principles for drug delivery.

Antifouling graphene oxide membranes for oil-water separation via hydrophobic chain engineering

Engineering surface chemistry to precisely control interfacial interactions is crucial for fabricating superior antifouling coatings and separation membranes. Here, we present a hydrophobic chain engineering strategy to regulate membrane surface at a molecular scale. Hydrophilic phytic acid and hydrophobic perfluorocarboxylic acids are sequentially assembled on a graphene oxide membrane to form an amphiphilic surface. The surface energy is reduced by the introduction of the perfluoroalkyl chains while the surface hydration can be tuned by changing the hydrophobic chain length, thus synergistically optimizing both fouling-resistance and fouling-release properties. It is found that the surface hydration capacity changes nonlinearly as the perfluoroalkyl chain length increases from C₄ to C₁₀, reaching the highest at C₆ as a result of the more uniform water orientation as demonstrated by molecular dynamics simulations. The as-prepared membrane exhibits superior antifouling efficacy (flux decline ratio <10%, flux recovery ratio ~100%) even at high permeance (~620 L m^-2 h^-1 bar^-1) for oil-water separation.

Synchronous Engineering for Biomimetic Murray Porous Membranes Using Isocyanate

Highly permselective and durable membranes are desirable for massive separation applications. However, currently most membranes prepared using nonsolvent-induced phase separation (NIPS) suffer from low permeability and a high fouling tendency due to the great challenges in a rational design and also practical approach for membrane optimization. Inspired by the natural Murray network from vascular plants, we developed a hierarchical membrane via a straightforward yet robust strategy, using isocyanate as a multifunctional additive. Thanks to the integrated functions of a phase separation regulator, blowing agent, cross-linker, and functionalization anchor of isocyanate, our strategy is featured as a perfect combination of a phase separation and chemical reaction, and it enables synchronous engineering of the membrane hierarchy on porosity and components. The representative membrane exhibits superior water permeance (334 L/m²·h·bar), protein retention (>98%), and antifouling ability (flux recover ratio ∼ 98%). This work highlights a versatile path for pursuing a highly enhanced performance of NIPS-made membranes, from the fancy perspective of Murray bionics.

Kinetic Inhibition of Clathrate Hydrate by Copolymers Based on N-Vinylcaprolactam and N-Acryloylpyrrolidine: Optimization Effect of Interfacial Nonfreezable Water of Polymers

Amphiphilic polymers have now been designed to achieve an icephobic performance and have been used for ice adhesion prevention. They may function by forming a strongly bonded but nonfreezable water shell which serves as a self-lubricating interfacial layer that weakens the adhesion strength between ice and the surface. Here, an analogous concept is built to prevent the formation of clathrate hydrate compounds during oil and natural gas production, in which amphiphilic water-soluble polymers act as efficient kinetic hydrate inhibitors (KHIs). A novel group of copolymers with N-vinylcaprolactam and N-acryloylpyrrolidine structural units are investigated in this study. The relationships among the amphiphilicity, lower critical solution temperature, nonfreezable bound water, and kinetic hydrate inhibition time are analyzed in terms of the copolymer compositions. Low-field NMR relaxometry revealed the crucial interfacial water in tightly bound dynamic states which led to crystal growth rates changing with the copolymer compositions, in accord with the rotational rheometric analysis results. The nonfreezable bound water layer confirmed by a calorimetry analysis also changes with the polymer amphiphilicity. Therefore, in the interface between the KHI polymers and hydrate, water surrounding the polymers plays a critical role by helping to delay the nucleation and growth of embryonic ice/hydrates. Appropriate amphiphilicity of the copolymers can achieve the optimal interfacial properties for slowing down hydrate crystal growth.

Hydrophobic hydration affects growth of clathrate hydrate: insight from an NMR relaxometric and calorimetric study

Water tightly bound to the kinetic inhibitors of tetrahydrofuran hydrate is related to the hydrophobic hydration effect of the inhibitors.

Amphiphilic Copolymers Containing POSS and SBMA with N-Vinylcaprolactam and N-Vinylpyrrolidone for THF Hydrate Inhibition

Icelike gas hydrates deposited in the pipelines under low temperatures and high pressures could remarkably reduce the transport efficiency, and a low dosage of water-soluble polymers could act as kinetic hydrate inhibitors (KHIs) to prevent gas hydrate formation. It was believed that the hydrophobic moiety in the water-soluble polymers played a vital role in enhancing the KHI performance. In this work, amphiphilic copolymers containing hydrophobic polyhedral oligomeric silsesquioxane (POSS) and superhydrophilic sulfobetaine methacrylate (SBMA) as well as N-vinylcaprolactam (VCap) and N-vinylpyrrolidone (VP) were prepared, and an efficient effect of the obtained amphiphilic copolymers on tetrahydrofuran (THF) hydrate inhibition was found. When a certain amount of the amphiphilic copolymers was introduced, the THF hydrate as an analogue of structure II gas hydrates presented a prolonged induction time and gave rise to a looser state rather than a crystalline solid. Analyses of low-field nuclear magnetic resonance and differential scanning calorimetry verified that there were strong interactions between the copolymer and water molecules by incorporation of SBMA units, which could enhance the KHI properties of the prepared amphiphilic copolymers. Additionally, the hydrophobic POSS in the amphiphilic copolymers could possibly modulate the hydrophilic/hydrophobic balance, contributing to the synergistical ability of the copolymers for THF hydrate inhibition. It was suggested that the amphiphilic copolymers containing POSS and zwitterionic units with VCap or VP could have potential for the inhibition and antiaggregation of gas hydrates in the transportation pipelines.