Humidity-Controlled Preparation of Flexible Porous Carbon Fibers from Block Copolymers

Abstract

Growing demands in flexible electronics have stimulated the rapid development of electrodes with multifaceted attributes. Porous carbon fibers (PCFs) provide a potential means to simultaneously achieve flexibility, durability, and energy density. High energy density often necessitates large surface areas and thus pores, but pores generally diminish the mechanical properties. Here, we electrospin poly­(methyl methacrylate)-block-poly­(acrylonitrile) (PMMA-b-PAN) and examine the changes in the polymer morphology and resulting PCF porosity and flexibility in response to relative humidity (R.H.). The determining factors of the fiber morphology evolve from block copolymer microphase separation at 40–50% R.H. to vapor-induced phase separation (VIPS) combined with microphase separation at 60–70% R.H. and to vapor-induced precipitation at 80–90% R.H. After pyrolysis, the PCFs show the corresponding porosity, flexibility, and electrochemical properties. Because VIPS enables the polymer fibers to outwardly reorganize PAN and produce continuous graphitic structures, PCFs prepared from polymer fibers electrospun at 70% R.H. develop a mesoporous core and long-range graphitic carbon sheath. Owing to the core–sheath structure, these PCFs exhibit mechanical strength to withstand repeated bending while retaining a 249 ± 20 F g–1 capacitance in flexible capacitor assemblies. This work highlights the potential for controlling block copolymer morphologies by processing conditions and PCF properties, providing a platform for designing flexible PCFs for energy and environmental sciences.

Mesoporous Carbon-Based Materials: A Review of Synthesis, Modification, and Applications

“…The usual materials used in capacitor electrodes should have a large surface area to improve the electrochemical performance of supercapacitors. Recently, mesoporous carbons garnered much attention as electrodes of supercapacitors because of their ease of operation, high chemical stability, large pore sizes, and high specific surface areas [72]. In this regard, many studies have been conducted [73][74][75][76][77][78][79][80][81][82], and descriptions of selected ones are the subject of the following section: Lufrano et al [78] prepared mesoporous CMK-3-type carbon using SBA-15 silica as a template material and sucrose as the carbon source and used them as electrodes for solid-state supercapacitors.…”

Block Copolymer Derived Porous Carbon Fiber: An Emerging Structural Functional Material

“…95 The heteroatoms affect the surface energy, hydrophobicity, ion/surface interactions, and electrochemical properties. The processing conditions, including solvents, temperature, pressure, and even humidity, 94 can affect porous carbon fibers' structure, properties, and functionality.…”

“…Fiber spinning conditions and thermal processing also play essential roles in controlling the pore size and fiber properties. 94,95 Figure 3. Representative synthesis of porous carbon fibers from (A) SiO 2 @PAN, 78 (B) the cryogenic method, 79 and (C) polymer blends.…”

“…By controlling the block copolymer molecular weight and composition, the porous carbon fibers have tunable uniform pore sizes in the 10–20 nm range. Fiber spinning conditions and thermal processing also play essential roles in controlling the pore size and fiber properties. , …”

Versatile Ion‐Gel Fibrous Membrane for Energy‐Harvesting Iontronic Skin

“…There are various approaches to preparing micro/nanofibers, such as stretching method, microphase separation, solution method, spin-coating method, and electrospinning process. [58][59][60][61] In the case of ion-gel fibrous membrane, the most commonly used methods are spin-coating and electrospinning. Although the spin-coating method is simple to operate, the formed film is poorly uniform and generally has some morphological defects.…”