Aramid nanochannels, rapid penetration, a new method for environmentally friendly water treatment!

Background

Aquaporins can quickly transport water molecules while removing salt, and play an important role in maintaining water-salt balance in organisms. Inspired by this, the study of artificial water channels has become a hot topic in the field of water purification and desalination. However, problems such as stability, scalability, and cost limit the widespread application of protein-based membranes. Therefore, the development of new artificial water channel materials has become a top priority.

Experimental methods

The materials synthesis research team synthesized polymers and macrocyclic compounds with specific structures. Monomer 2 was synthesized through a six-step reaction, and the living polymerization method was used to slowly add monomer 2 to a solution containing an initiator and a condensing agent to react at 55°C. By controlling the ratio of monomer to initiator, polymers of different lengths (Poly-10mer, Poly-20mer, Poly-30mer) and macrocyclic compounds (3 and 4) were synthesized.

Material Characterization The synthesized materials were characterized using a variety of techniques: Nuclear Magnetic Resonance (NMR): used to analyze the end groups and molecular structure of the polymers. Mass Spectrometry (MALDI-ToF): used to determine the molecular weight distribution of polymers and macrocyclic compounds. Size Exclusion Chromatography (SEC): used to analyze the molecular weight and polydispersity of polymers. Circular Dichroism (CD): used to study the conformation and thermal stability of polymers in solution. Small Angle X-ray Scattering (SAXS): used to further verify the folding structure of the polymer. Single Crystal X-ray Diffraction: used to determine the precise structure of macrocyclic compounds and the formation of nanochannels. Water Permeability and Ion Selectivity Tests The water permeability of the materials in lipid bilayer membranes was evaluated by measuring the light scattering intensity of the vesicle suspension using a stopped-flow light scattering instrument. At the same time, the transport of cations, anions and protons was detected using fluorescent dyes HPTS and lucigenin, respectively, to evaluate the ion selectivity of the materials.

Experimental Results and Discussion

Synthesis and characterization of polymers

Polymers and macrocyclic compounds with narrow polydispersity were successfully synthesized. MALDI-ToF mass spectrometry and NMR analysis confirmed the structure and molecular weight of the polymer. CD spectra showed that the polymer had a helical conformation in solution and remained stable at different temperatures. SAXS analysis further supported the folded structure of the polymer, and Kratky plots showed that the polymer had a compact folded morphology.

Water permeability In lipid bilayer membranes, synthetic polymers and macrocyclic compounds showed significant water permeability. In particular, Poly-20mer showed the highest water permeation rate, close to the performance of natural aquaporins. Molecular dynamics simulations showed that the length of Poly-20mer best matched the thickness of the lipid bilayer, which helped it form an effective water channel in the membrane.

Ion selectivity

Through fluorescence detection, Poly-20mer exhibited good repulsion to Na⁺, K⁺, H⁺ and Cl⁻ ions, indicating that it has excellent ion selectivity. This is mainly due to the hydrophobicity and specific chemical modification of the polymer cavity, which effectively prevent the passage of ions.

Summary and Outlook

The study successfully designed and synthesized a series of high-performance artificial water channels with efficient water transport capacity and good ion rejection. In particular, Poly-20mer has performance close to that of natural aquaporins and better stability. This work provides a solid foundation for the next generation of water purification and desalination technologies. Future research will further optimize the structure and performance of these water channels to achieve water transport rates that exceed those of natural aquaporins and explore their potential in practical applications.