The Melamine-Driven Solvation Effect Promotes Oxygen Reduction on a Platinum Catalyst: Machine Learning-Aided Free Energy Calculations.

The modification of Pt surfaces with organic compounds like melamine enhances oxygen reduction reaction activity and catalyst durability. Through first-principles free energy calculations utilizing thermodynamic integration and finite-temperature molecular dynamics, enhanced by machine learning force fields for efficient sampling of nanosecond-scale interfacial water fluctuations and incorporating corrections to accurately reproduce first-principles free energies, we demonstrate that melamine destabilizes OH adsorbates, facilitating their removal and enhancing catalytic activity. Unlike alloys, where OH destabilization is driven by changes in electronic structure and surface strain, melamine disrupts hydrogen bonding between OH and interfacial water.

Proton Transport in Perfluorinated Ionomer Simulated by Machine-Learned Interatomic Potential.

Polymers are a class of materials that are highly challenging to deal with using first-principles methods. Here, we present an application of machine-learned interatomic potentials to predict structural and dynamical properties of dry and hydrated perfluorinated ionomers. An improved active-learning algorithm using a small number of descriptors allows to efficiently construct an accurate and transferable model for this multielemental amorphous polymer.

Interfacial Distribution of Nafion Ionomer Thin Films on Nitrogen-Modified Carbon Surfaces.

Chemically modified carbon supports for the cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) show considerable promise for boosting the oxygen reduction reaction. This study evaluated the ionomer distribution of Nafion ionomer thin films on nitrogen (N)-modified carbon surfaces along their depth direction. Neutron reflectivity (NR) measurements performed using the double-contrast technique with HO and DO revealed that the introduction of N functional groups to carbon thin films promoted ionomer adsorption onto the surface under wet conditions (22 °C, 85% relative humidity).

The role of oxygen-permeable ionomer for polymer electrolyte fuel cells.

In recent years, considerable research and development efforts are devoted to improving the performance of polymer electrolyte fuel cells. However, the power density and catalytic activities of these energy conversion devices are still far from being satisfactory for large-scale operation. Here we report performance enhancement via incorporation, in the cathode catalyst layers, of a ring-structured backbone matrix into ionomers.

Porous Colloidal Hydrogels Formed by Coordination-Driven Self-Assembly of Charged Metal-Organic Polyhedra.

Introduction of porosity into supramolecular gels endows soft materials with functionalities for molecular encapsulation, release, separation and conversion. Metal-organic polyhedra (MOPs), discrete coordination cages containing an internal cavity, have recently been employed as building blocks to construct polymeric gel networks with potential porosity. However, most of the materials can only be synthesized in organic solvents, and the examples of porous, MOP-based hydrogels are scarce.

Protein-responsive protein release of supramolecular/polymer hydrogel composite integrating enzyme activation systems.

Non-enzymatic proteins including antibodies function as biomarkers and are used as biopharmaceuticals in several diseases. Protein-responsive soft materials capable of the controlled release of drugs and proteins have potential for use in next-generation diagnosis and therapies. Here, we describe a supramolecular/agarose hydrogel composite that can release a protein in response to a non-enzymatic protein.

Two-step yielding behavior of densely packed microgel mixtures with chemically dissimilar surfaces and largely different sizes.

Steady-state flow and elastic behavior is investigated for the moderately concentrated binary suspensions of soft microgels (pastes) with chemically dissimilar surfaces, and various degrees of size- and stiffness disparities. The pastes of poly(N-isopropyl acrylamide) (N) and poly(N-isopropyl methacrylamide) (NM) microgels with different values of yield strain γc (γNc > γNMc) are employed as the components. For the single microgel pastes (φ ≈ 1 where φ is apparent volume fraction), the values of γc are governed by the chemical species of constituent polymer in microgel surface whereas γc is insensitive to cross-link density and particle size.

Understanding the multiscale self-assembly of metal-organic polyhedra towards functionally graded porous gels.

Spatial heterogeneity and gradients within porous materials are key for controlling their mechanical properties and mass/energy transport, both in biological and synthetic materials. However, it is still challenging to induce such complexity in well-defined microporous materials such as crystalline metal-organic frameworks (MOFs). Here we show a method to generate a continuous gradient of porosity over multiple length scales by taking advantage of the amorphous nature of supramolecular polymers based on metal-organic polyhedra (MOPs).

Criteria for colloidal gelation of thermo-sensitive poly(N-isopropylacrylamide) based microgels.

Hypothesis: Suspensions of the poly(N-isopropylacrylamide) (PNIPAM) based temperature(T)-sensitive microgels can undergo colloidal gelation forming a three-dimensional sparse network-like structure in the hydrophobic and shrunken state of T > T* (T*: volume transition temperature), despite their considerably low particle volume fractions (<0.2). The effective surface charge density is expected to be a key factor governing the colloidal gelation and gel modulus.

The structure and properties of natural sheep casing and artificial films prepared from natural collagen with various crosslinking treatments.

The structure and properties of natural sheep casing and collagen films with various crosslinking treatments have been investigated in detail to develop satisfied artificial casings prepared from collagen. The sheep casing consists of large number of thick collagen fibers oriented at ±45° from longitudinal direction with high-density interwoven network structure. The structural feature of sheep casing gave the special mouthfeel of 'cracking bite' of sausages.

Post-assembly Fabrication of a Functional Multicomponent Supramolecular Hydrogel Based on a Self-Sorting Double Network.

Living cells exhibit sophisticated functions because they contain numerous endogenous stimuli-responsive molecular systems that independently and cooperatively act in response to an external circumstance. On the other hand, artificial soft materials containing multiple stimuli-responsive molecular systems are still rare. Herein, we demonstrate a unique multicomponent hydrogel composed of a self-sorting double network prepared through a post-assembly fabrication (PAF) protocol.

Beads-on-String-Shaped Poly(azomethine) Applicable for Solution Processing of Bilayer Devices Using a Same Solvent.

Solvent-based deposition techniques for fabrication of organic field-effect transistors (OFETs) generally require orthogonal solvents for deposition of a conjugated polymer layer on a polymer gate insulator layer. Here, we found significantly reduced dissolution rate of the polymeric film in the same solvent after casting a homegeneous polymerization solution of -bis(3-aminopropyl)hexaisobutyl-substituted T cage () with terephthalaldehyde. The limited dissolution rate in the solvent provided enough chance for fabrication of a regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) layer on the present polymer films without using an orthogonal solvent.

Viscoelasticity of dense suspensions of thermosensitive microgel mixtures undergoing colloidal gelation.

Dense suspensions of temperature (T)-sensitive poly(N-isopropyl acrylamide) (N) and poly(N-isopropyl methacrylamide) (NM) microgel mixtures with different volume transition temperatures (T and T, respectively; T < T) exhibit a characteristic T-dependent viscoelasticity due to T-induced changes in the type of interparticle interaction as well as the volume fraction of each gel. In the range of T < T, where the swollen microgels with repulsive interparticle interactions are densely packed, the equilibrium modulus (G) decreases upon heating due entirely to the packing effect, i.e.

Publisher Correction: An adaptive supramolecular hydrogel comprising self-sorting double nanofibre networks.

In the version of this Article originally published online, in Fig. 4b, in the lower-right image, the value of r was incorrect; it should have read 'r = 0.72'.

An adaptive supramolecular hydrogel comprising self-sorting double nanofibre networks.

Novel soft materials should comprise multiple supramolecular nanostructures whose responses (for example, assembly and disassembly) to external stimuli can be controlled independently. Such multicomponent systems are present in living cells and control the formation and break-up of a variety of supramolecular assemblies made of proteins, lipids, DNA and RNA in response to external stimuli; however, artificial counterparts are challenging to make. Here, we present a hybrid hydrogel consisting of a self-sorting double network of nanofibres in which each network responds to an applied external stimulus independent of the other.