Mesoporous Polyimide Thin Films as Dendrite-Suppressing Separators for Lithium-Metal Batteries

Lithium-metal batteries require the effective suppression of lithium dendrites to guarantee both high performance and safety. Today's separators have macropores allowing lithium dendrites to traverse, leading to internal short circuits and other catastrophic results. Herein, we report a mesoporous polyimide separator for dendrite suppression. The polyimide separator exhibits mesopores of 21 nm width and a high storage modulus of 1.80 GPa. This mesoporous polyimide separator assists in the electrodeposition to form flat-top protrusions instead of sharp dendrites, therefore, allowing the safe cycling of lithium-metal batteries. This work is expected to advance the development of dendrite-suppressing strategies and contribute to the revival of lithium-metal batteries.

Mesoporous polyetherimide thin films via hydrolysis of polylactide-b-polyetherimide-b-polylactide

Hydrolyzing polylactide-b-polyetherimide-b-polylactide triblock copolymers produces mesoporous polyetherimide thin films with an average pore width of 24 nm.

Sub-10 nm domains in high-performance polyetherimides

After condensation with polystyrene oligomers, ultra-low-molecular-weight polyetherimide-based triblock copolymers form disordered nanostructures with domain sizes less than 8 nm.

A facile route to bespoke macro- and mesoporous block copolymer microparticles

A facile and versatile strategy to fabricate macro- and mesoporous block copolymer microparticles with bespoke characteristics using supercritical CO₂.

Phosphorus-containing polyimide fibers and their thermal properties

Submicron fibers based on phosphorus-containing polyimide were successfully prepared and characterized for their thermal properties.

Functionalized nanoporous polyethylene derived from miscible block polymer blends

Functionalized nanoporous polyethylene (PE) was prepared through controlled introduction of thermo-responsive poly[2-(2-methoxyethoxy)ethyl methacrylate] (PMe(OE)(2)MA), or poly{2-[2-(2-methoxyethoxy)ethoxy]ethyl methacrylate} (PMe(OE)(3)MA) onto the pore walls. The compatibility of polylactide (PLA) and PMe(OE)(x)MA (x = 2, 3) was investigated by blending the corresponding homopolymers. The blends showed only one glass transition when the molar masses of both components were relatively low, whereas two glass transitions were observed in case of higher molar mass samples. PMe(OE)(x)MA-b-PE-b-PMe(OE)(x)MA (x = 2, 3) block polymers were synthesized by a combination of ring-opening metathesis polymerization, atom transfer radical polymerization, and hydrogenation. Those block polymer blends formed a disordered bicontinuous structure consisting of a mixed PLA/PMe(OE)(x)MA domain and a semicrystalline PE domain. The PLA component was selectively removed from those blends by mild base treatment. The resulting nanoporous polyethylene showed an improved water uptake as a result of the hydrophilic PMe(OE)(x)MA on the pore walls.

Electrochemical impedance spectroscopy studies of organic-solvent-induced permeability changes in nanoporous films derived from a cylinder-forming diblock copolymer

In this paper we report electrochemical investigations of the influence of organic solvents dissolved in aqueous solution on the permeability of nanoporous films derived from a cylinder-forming polystyrene-poly(methyl methacrylate) diblock copolymer (CF-PS-b-PMMA). The nanoporous films (ca. 30 nm in pore diameter) were prepared on planar gold electrodes via UV-based degradation of the cylindrical PMMA domains of annealed CF-PS-b-PMMA films (30-45 nm thick). The permeability of the electrode-supported nanoporous films was assessed using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The faradic current of Fe(CN)(6)(3-/4-) decreased upon immersion in aqueous solutions saturated with toluene or methylene chloride (5.8 mM and 0.20 M, respectively). EIS data indicated that the decrease in faradic current mainly reflected an increase in the pore resistance (R(pore)). In contrast, R(pore) did not change in a saturated n-heptane solution, 0.17 M ethanol, or 5.8 mM aqueous solutions of methylene chloride, diethyl ether, methyl ethyl ketone, or ethanol. Atomic force microscopy images of a nanoporous film in aqueous solution with and without 5.8 mM toluene showed a reversible change in the surface morphology, which was consistent with a toluene-induced change in R(pore). The solvent-induced increase in R(pore) was attributed to the swelling of the nanoporous films by the organic solvents, which decreased the effective pore diameter. The reversible permeability changes suggest that the surface of CF-PS-b-PMMA-derived nanoporous films can be functionalized in organic environments without destroying the nanoporous structure. In addition, the solvent-induced swelling may provide a simple means for controlling the permeability of such nanoporous films.

Surface modification of nanoporous 1,2-polybutadiene by atom transfer radical polymerization or click chemistry

Surface-initiated atom transfer radical polymerization (ATRP) and click chemistry were used to obtain functional nanoporous polymers based on nanoporous 1,2-polybutadiene (PB) with gyroid morphology. The ATRP monolith initiator was prepared by immobilizing bromoester initiators onto the pore walls through two different methodologies: (1) three-step chemical conversion of double bonds of PB into bromoisobutyrate, and (2) photochemical functionalization of PB with bromoisobutyrate groups. Azide functional groups were attached onto the pore walls before click reaction with alkynated MPEG. Following ATRP-grafting of hydrophilic polyacrylates and click of MPEG, the originally hydrophobic samples transformed into hydrophilic nanoporous materials. The successful modification was confirmed by infrared spectroscopy, contact angle measurements and measurements of spontaneous water uptake, while the morphology was investigated by small-angle X-ray scattering and transmission electron microscopy.