Rational Design of Two-Dimensional Hydrocarbon Polymer as Ultrathin-Film Nanoporous Membranes for Water Desalination

Membrane-based water desalination has drawn considerable attention for its potential in addressing the increasingly limited water resources, but progress remains limited due to the inherent constraints of conventional membrane materials. In this work, by employing state-of-the-art molecular simulation techniques, we demonstrated that two-dimensional hydrocarbon polymer membranes, materials that possess intrinsic and tunable nanopores, can provide opportunities as molecular sieves for producing drinkable water from saline sources. Moreover, we identified a unique relationship between the permeation and selectivity for membranes with elliptical pores, which breaks the commonly known trade-off between the pore size and desalination performance. Specifically, increase in the area of elliptical pores with a controlled minor diameter can offer an improved water flux without compromising the ability to reject salts. Water distributions and water dynamics at atomic levels with the potential of mean force profiles for water and ions were also analyzed to understand the dependence of permeation and selectivity on the pore geometry. The outcomes of this work are instrumental to the future development of ultrathin-film reverse osmosis membranes and provide guidelines for the design of membranes with more effective and efficient pore structures

Controllable Multigeometry Nanoparticles <i>via</i> Cooperative Assembly of Amphiphilic Diblock Copolymer Blends with Asymmetric Architectures

Multigeometry nanoparticles with high complexity in composition and structure have attracted significant attention for enhanced functionality. We assess a simple but versatile strategy to construct hybrid nanoparticles with subdivided geometries through the cooperative assembly of diblock copolymer blends with asymmetric architectures. We report the formation of multicompartmental, vesicular, cylindrical, and spherical structures from pure AB systems. Then, we explore the assemblies of binary AB/AC blends, where the two incompatible, hydrophobic diblock copolymers subdivide into self-assembled local geometries, and the complexity of the obtained morphologies increases. We expand the strategy to ternary AB/AC/AD systems by tuning the effect of phase separation of different hydrophobic domains on the surface or internal region of the nanoparticle. The kinetic control of the coassembly in the initial stage is crucial for controlling the final morphology. The interactions of copolymers with different block lengths and chemistries enable the stabilization of interfaces, rims and ends of subdomains in the hybrid multigeometry nanoparticles. With further exploration of size and shape, the dependence of local geometry on the volume fraction is discussed. We show an efficient approach for controllable multigeometry nanoparticle construction that will be useful for multifunctional and hierarchical nanomaterials

Tunable Permeability of Cross-Linked Microcapsules from pH-Responsive Amphiphilic Diblock Copolymers: A Dissipative Particle Dynamics Study

Using dissipative particle dynamics simulation, we probe the tunable permeability of cross-linked microcapsules made from pH-sensitive diblock copolymers poly­(ethylene oxide)-<i>b</i>-poly­(<i>N</i>,<i>N</i>-diethylamino-2-ethyl methacrylate) (PEO-<i>b</i>-PDEAEMA). We first examine the self-assembly of non-cross-linked microcapsules and their pH-responsive collapse and then explore the effects of cross-linking and block interaction on the swelling or deswelling of cross-linked microcapsules. Our results reveal a preferential loading of hydrophobic dicyclopentadiene (DCPD) molecules in PEO-<i>b</i>-PDEAEMA copolymers. Upon reduction of pH, non-cross-linked microcapsules fully decompose into small wormlike clusters as a result of large self-repulsions of protonated copolymers. With increasing degree of cross-linking, the morphology of the microcapsule becomes more stable to pH change. The highly cross-linked microcapsule shell undergoes significant local polymer rearrangement in acidic solution, which eliminates the amphiphilicility and therefore enlarges the permeability of the shell. The responsive cross-linked shell experiences a disperse-to-buckle configurational transition upon reduction of pH, which is effective for the steady or pulsatile regulation of shell permeability. The swelling rate of the cross-linked shell is dependent on both electrostatic and nonelectrostatic interactions between the pH-sensitive groups as well as the other groups. Our study highlights the combination of cross-linking structure and block interactions in stabilizing microcapsules and tuning their selective permeability

Tuning and Designing the Self-Assembly of Surfactants: The Magic of Carbon Nanotube Arrays

Controlling the self-assembly and polymorphic transition of surfactants is a challenging but meaningful topic for chemists and materials scientists, which is significant for the preparation of advanced nanomaterials. We presented coarse-grained (CG) molecular dynamics (MD) simulations on the self-assembly of surfactants confined within the carbon nanotube (CNT) arrays. Under the effect of confinement, an intriguing “rod-double helix-hexagon-worm” polymorphic transition was observed with varying the size of the confining space. The simulations also showed that the confinement of CNT arrays does not break the characteristic of surfactant assemblies at certain concentration. Based on these results, a plausible strategy for designing complex assemblies was presented. And then, “nano-drill” and “dartboard” assemblies were created with the strategy. This work demonstrated that the confinement of CNT arrays may be an efficient method to tune and design the self-assembly of surfactants, shedding light on the development of nanotechnology and advanced materials