Molecular Systems Design & Engineering最新文献

We study a coarse-grained model of a nanocomposite consisting of a symmetric AB diblock copolymer and a planar nanoparticle (NP) using dissipative particle dynamics. The NP size exceeds the period of the lamellar domains formed by microphase separation of the copolymer blocks. The model predicts that the NP has two stable orientations due to its anisotropic nature and the difference between the NP size and the period of the matrix domains. In the case of good or poor compatibility of the NP with both copolymer blocks, the NP plane is oriented perpendicular to the plane of the matrix domains. In the case of selective interaction with the copolymer, the NP will be incorporated into the domain formed by the blocks with which it has the greatest compatibility. The appearance of the orientational ordering effect is explained by the imbalance in the distribution of copolymer blocks along the NP surface in the early stages of the microphase separation. This result allows us to consider this system as a two-state nanocomposite. It is also observed that the introduction of the NP reduces the incompatibility threshold of the copolymer blocks above which microphase separation occurs. We hope that the reported effect will be useful for the design of smart nanomaterials with switchable properties.

Singlet fission has the potential to significantly improve the efficiency of photovoltaic devices by harnessing high-energy sunlight to double the photocurrent that can be generated in standard semiconductors. The challenge is identifying materials capable of undergoing this process efficiently. Herein, we present the results of a systematic search for novel intermolecular singlet fission materials based on the recently synthesized 6,6′-biphenanthridine (biphe) framework utilizing a straightforward computational approach. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were employed to study the photophysics of various structural analogues of biphe. These analogues were generated in silico by utilizing an extensive range of transformations, including planarization, protonation, symmetric and asymmetric alkylation, electron-donating and electron-withdrawing group substitution, N-oxide substitution, and symmetric and asymmetric π-extension and contraction. Analysis of the effects of these structural modifications on the energies of the lowest singlet and triplet excited states revealed that (2,2′,10,10′-tetra-N-oxide) planar biphe has an E(S₁)/E(T₁) ratio of 2.12 and an E(T₂)/E(T₁) of 2.05, suggesting its potential for intermolecular singlet fission. Additionally, N-methylated biphe emerged as a promising contender for thermally activated delayed fluorescence. The effects of solvation are also discussed.

Structure formation and rheological properties of amphiphilic patchy nanocubes in equilibrium and under shear were investigated using hybrid molecular dynamics simulations combined with multiparticle collision dynamics that consider hydrodynamic interactions. The relationship between complex self-assembled structures and the resulting macroscopic properties has not yet been examined because of the computational complexity these multiscale problems present. The number and location of solvophobic patches on the amphiphilic nanocubes were varied at several colloid volume fractions in the liquid regime. For a pure suspension of one-patch cubes, the nanocubes self-assemble into dimers in the equilibrium state because bonded one-patch cubes have no exposed solvophobic surfaces. At low shear rates, small dimers undergo shear-induced alignment along the flow direction. This results in shear-thinning accompanied by slightly higher shear viscosity (≈15%) than homoparticle dispersions of the same concentration. As the shear rate increases further, the suspensions exhibit Newtonian-like behavior until the cluster disintegrates, followed by shear thinning with breakdown into individual cubes. For binary mixtures of one- and two-patch nanocubes, the resulting cluster shapes, which include elongated rods and fractal objects, can be controlled by the patch arrangements on the two-patch cubes. Interestingly, despite the differences in the shape and resistance of the clusters, two different mixtures undergo a similar increase in the shear viscosity (≈35%) compared to the homoparticle dispersions, to essentially exhibit rheological behavior similar that of a pure suspension of one-patch cubes. Our findings provide new insights into the correlation between microscopic (design of patchy cubes), mesoscopic (self-assembled structures), and macroscopic (viscosity) properties, and are also valuable for identifying the synthesis conditions required to realize novel materials with the desired properties and functionalities.

Optoelectronic properties of organic photovoltaics, including light absorption, intramolecular and intermolecular charge transfer, depend on the energetics of the frontier molecular orbitals of constituent organic materials. We develop a tight-binding model for an indacenodithiophene-based small molecule non-fullerene acceptor – IDTBR, which gives a high-efficiency organic photovoltaic cell in combination with poly(3-hexylthiophene) as donor. By choosing stiff conjugated ring moieties as sites, we obtain tight-binding parameters that are local to each moiety, and transferable to other chain architectures. In particular, parameters from homo-oligomers and alternating co-oligomers of constituent moieties can be used, without adjustment, to define the tight-binding model for IDTBR, which reasonably predicts the energies and wavefunctions of its frontier molecular orbitals. Transferability of model parameters will enable efficient screening and selection of molecular architectures with desirable optoelectronic properties.

The sustainable synthesis of porous polymer monoliths has significant advantages over powdered porous polymers and is capable of adsorbing multiple types of pollutants efficiently from water. They are important as an easily affordable material for water purification. Herein, we report the synthesis of mesoporous chitosan, PEG monoliths, via the crosslinking of chitosan with PEG-diacrylate macro-crosslinkers using aza-Michael reactions in water. The surface area and pore volume are tuned by varying the crosslinking density and length of the macro-crosslinker. The materials show very good thermal and chemical stability against organic and aqueous (within pH 2–9) solvents. The monolith is capable of removing a wide range of both organic and inorganic pollutants, such as anionic dyes, metal ions, iodine, and pharmaceuticals, from contaminated water. The reusability of the monolith after it is regeneration by releasing the adsorbed pollutant is important for its affordable practical application. In addition, the monolith can be completely degraded in a strong alkaline solution to quantitatively recycle the chitosan derivative.

Feedback through enzyme reactions creates new possibilities for the temporal programming of material properties in bioinspired applications, such as transient adhesives; however, there have been limited attempts to model such behavior. Here, we used two antagonistic enzymes, urease in watermelon seed powder and esterase, to temporally control the gelation of a poly(vinyl alcohol)–borate hydrogel in a one-pot formulation. Urease produces base (ammonia), and esterase produces acid (acetic acid), generating a pH pulse, which was coupled with reversible complexation of PVA. For improved understanding of the pulse properties and gel lifetime, the pH profile was investigated by comparison of the experiments with kinetic simulations of the enzyme reactions and relevant equilibria. The model reproduced the general trends with the initial concentrations and was used to help identify conditions for pulse-like behaviour as the substrate concentrations were varied.

The bioinspired co-precipitation of magnetite nanoparticles (MNP) using additives to tailor particle shape is an attractive alternative to the currently favoured environmentally unsustainable methods of producing shape-controlled particles. In particular, ethylenediamine based additives are able to produce MNP with high-yield under environmentally friendly conditions, yet with the desired control over particle attributes. The effect of tetraethylenepentamine (TEPA) as an additive in the room-temperature co-precipitation (RTCP) of magnetite has been investigated in an iterative Design of Experiments (DoE) strategy, utilising Full Factorial Designs (FFD) and a Path of Steepest Ascent (PSA) optimisation through three consecutive designs. Considering the ferric ratio (Fe³⁺/Fe²⁺), Fe/additive ratio, and timepoint of additive addition as factors, the percentage of isotropic faceted particles and saturation magnetisation were measured as responses. After an initial scouting FFD, timepoint of additive addition was found to be insignificant as a factor. A second FFD followed by a PSA optimisation found higher Fe³⁺/Fe²⁺ ratios of 0.6, closer to the ideal 2 : 1 stoichiometric ferric ratio produced a higher shape response (an increase in isotropic faceted particles). The interaction between ferric and Fe/additive ratio was found to be significant, as the same level of additive concentration was not as effective at lower ferric ratios. An optimum Fe/additive ratio of 50 : 1 was established, alongside the higher ferric ratio of 0.6 to produce ∼90% isotropic faceted particles with a high magnetism of 77 emu g⁻¹, showing it is possible to synthesise MNP which are both highly magnetic and highly faceted. Since it is a requirement of many industries to use homogeneous particles, the predictive synthesis of these magnetite nanoparticles is a significant step towards the industrial production of green magnetite nanoparticles. These conditions can be utilised for further synthesis or as a basis for further optimisation of shape-tuned magnetite nanoparticle syntheses. This DoE strategy enabled the optimisation of two responses simultaneously to produce high quality MNP.

In recent years, metal–organic frameworks (MOFs) have attracted much attention due to their unique structures. With their low density, high porosity and mechanical flexibility, MOFs have great potential in the field of lubrication. This paper reviews the research progress of MOFs in the field of lubrication, systematically introduces the application of MOFs as lubricant additives and the lubrication mechanism, and also summarizes and discusses the application of MOFs in a non-liquid environment and the research findings of its super-lubrication. This review summarizes the major research of MOFs in the field of lubrication in recent years, with a view to providing assistance to relevant researchers and promoting the development of this field.

Retrosynthesis is the process of designing chemical pathways from a set of reactants to a set of desired products. However, when both the pools of potential reactants and products grow to a substantial size, this becomes infeasible without the aid of computational tools. This work uses Pickaxe, an automated network generation tool, to perform computational retrosynthesis on a pool of 297 bioprivileged candidate molecules as reactants and 44 003 potential corrosion inhibitors that were generated by a variational autoencoder. Unlike typical approaches in computational synthesis planning, the use of automated network generation allows flexibility in pathways and starting material beyond those that are documented. This work starts by replicating known pathways to corrosion inhibitors from a single bioprivileged candidate molecule and applying the constituent reaction families to the entirety of the reactant pool and concludes by generating networks with a more extensive reaction family list and two sets of co-reactants, or “helper molecules”. Network size, both from the perspective of total reactions enacted and total products formed, was analyzed.

Light-activated synthetic organic molecular motors are emerging as an excellent prospect to actuate supramolecular assemblies such as polymersomes with spatiotemporal precision. The influence on these materials depends on the motor's frequency of rotation and concentration. Therefore, we determined the rotation frequency of a motor in a poly(dimethyl siloxane)-b-poly(ethylene glycol) (PDMS₁₃-b-PEG₁₃) polymersome and compared it to the frequency observed in different organic solvents. Using UV-vis spectrophotometry and nuclear magnetic resonance spectroscopy, we measured the rate of the thermal helix inversion step, which is the rate-determining step of the rotary cycle, and obtained the activation parameters. We found that the investigated motor's frequency of rotation did not significantly change in the polymersomes and remains at around 1 mHz. Moreover, dynamic light scattering results indicate that the rotation of the motors does not cause a significant change in the structure of this type of polymersome when used at a diblock copolymer : motor molar ratio of up to 100 : 2. Our findings provide a first insight into the effect of the polymersome on the motor's frequency of rotation and vice versa. Enhancing the polymersome composition with motors can lead to novel concepts, including light-activated nanopharmaceuticals, nanoreactors, and biomimetic artificial organelles and cells.