Jun Yin,Xueping Yao,Jiun-You Liou,Wei Sun,Ya-Sen Sun,Yong Wang
Membranes with uniform, straight nanopores have important applications in diverse fields, but their application is limited by the lack of efficient producing methods with high controllability. In this work, we reported on an extremely simple and efficient strategy to produce such well-defined membranes. We demonstrated that neutral solvents were capable of annealing amphiphilic block copolymer (BCP) films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) with thicknesses up to 600 nm to the perpendicular orientation within 1 min. Annealing in neutral solvents was also effective to the perpendicular alignment of block copolymers with very high molecular weights, e.g., 362 000 Da. Remarkably, simply by immersing the annealed BCP films in hot ethanol followed by drying in air, the originally dense BCP films were nondestructively converted into porous membranes containing highly ordered, straight nanopores traversing the entire thickness of the membrane (up to 1.1 μm). Grazing incident small-angle X-ray spectroscopy confirmed the hexagonal ordering of the nanopores over large areas. We found that the overflow of P2VP chains from their reservoir P2VP cylinders and the deformation of the PS matrix in the swelling process contributed to the transformation of the solid P2VP cylinders to empty straight pores. The pore diameters can be tuned by either changing the swelling temperatures or depositing thin layers of metal oxides on the preformed membranes via atomic layer deposition with a subnanometer accuracy. To demonstrate the application of the obtained porous membranes, we used them as templates and produced centimeter-scale arrays of aligned nanotubes of metal oxides with finely tunable wall thicknesses.
Polymerization of bicontinuous cubic (Q) liquid crystals (LCs) can be utilized to produce technologically useful polymeric materials with 3-D interconnected nanopores of ∼1 nm. However, their practical applications have been hindered by the exceptionally complicated syntheses of the needed polymerizable amphiphiles and the susceptible morphological destruction upon polymerization. Here, we present a scalable strategy to fabricate polymeric membranes with 3-D interconnected nanopores by photo-crosslinking of easily accessible Q LCs. We leverage a readily synthesized, cost-effective zwitterionic monomer as the building block to construct “normal” lyotropic double gyroid (G1) mesophases that afford radical polymerization. Although self-assembly of the amphiphile in neat water forms no Q LCs, additional phosphoric acid can drive the emergence of G1 mesophases by inducing the non-constant interfacial curvature. An intriguing advantage exhibited by this polymerizable G1 system is the ability to persist upon swelling by large volumes of commercially available cross-linkers, thereby effectively facilitating structural lock-in through photo-initiated cross-linking. High-brilliance synchrotron small-angle X-ray scattering has unambiguously confirmed the excellent retention of periodic G1 morphologies in the mechanically robust polymers. Transmission electron microscopy further provides unprecedented, detailed visualization of the spacing and symmetry in the cross-linked G1 assemblies over large areas. The exceptionally easy access to the building blocks and the high-fidelity structural preservation enable the scalable fabrication of nanoporous membranes for applications such as ionic transportation, as preliminarily demonstrated.
Haiyang Liao,Haiyan Zhang,Gai Qin,Zhenghui Li,Liuqing Li,Haoqun Hong
To develop a separator with remarkable thermal-resistance for high-safety lithium-ion (Li-ion) batteries, a graphene oxide (GO)-grafted hyper-branched polyether (GO-g-HBPE) macro-porous membrane without any polymer binder was designed and prepared using polystyrene (PS) nanoparticles as hard templates. GO (inorganic part) provides the membrane-formation ability for GO-g-HBPE separator and HBPE (polymer part) imparts excellent affinity with the liquid electrolyte (158% for liquid electrolyte uptake). The GO-g-HBPE membrane, serving as a separator for the batteries, exhibited robust thermal dimensional stability with no dimensional changes at 200 °C for 0.5 h. Moreover, it shows a better electrochemical performance (cycle performance and rate capability) than a commercialized PP separator, implying a promising potential for application in high-safety and high-power Li-ion batteries.
Ether-free polyaromatic proton exchange membranes (PEMs) are regarded as an optimal and cost-effective substitute for perfluorosulfonic acid membranes due to their excellent oxidation resistance stability, low cost and inherent low permeability. The potential applications of the branched structure are significant in enhancing membrane processability and physical stability, but the ether-free branched sulfonated polyaryl proton exchange membrane remains to be further explored. Herein, we present the synthesis of branched sulfonated poly(isatin terphenyl fluorene) (b-SPITF-x), featuring a branched comb-like structure design incorporating sturdy backbones devoid of ether, branched monomers and flexible side chains containing sulfopropyl groups at specific locations. This branched comb-like structure endows the membrane with sufficient microphase-separated morphology and dense ion clusters, thus ensuring the optimized b-SPITF-10 PEM exhibits simultaneously high H + conductivity (>185 mS cm −1 at 80 °C) and desirable physical properties. Furthermore, the b-SPITF-10 PEMFCs obtained the maximum peak power density of 819 mW cm −2 operated at 80 °C. Moreover, during a 100-h durability test carried out at a temperature of 80 °C, this particular PEM exhibited an impressively low rate of voltage degradation, measuring only 0.743 mV h −1 . The ether-free structure and branched comb-like design offer valuable insights into the advancement of polyaromatic PEMs.
危险品化学品经营许可证（带存储）