Porous carbon fibers from gel-spun polyacrylonitrile and poly(methyl methacrylate)-block-poly(acrylonitrile)

Abstract

Block copolymer (BCP)-based porous carbon fibers represent an emerging structural and functional material for mechanical reinforcement and electrochemical energy storage. Herein, by gel-spinning polymer precursors of poly(acrylonitrile) (PAN) and poly(methyl methacrylate)-block-poly(acrylonitrile) (PMMA-b-PAN), we have produced a series of carbon fibers and systematically studied the morphological, mechanical, and electrochemical properties. Porous carbon fibers with BCP in the sheath exhibit a tensile strength of 1.1 GPa, tensile modulus of ∼190 GPa, and electrochemical capacitance of 11 F g−1 at 10 mV s−1 when pyrolyzed at 1315 °C under tension. Without tension and at a pyrolysis temperature of 800 °C, the fibers with BCP as both the sheath and core components achieve the highest electrochemical capacitance of 70 F g−1 at 10 mV s−1. The characteristic correlation length of PMMA-b-PAN calculated through thermodynamically governed computational method, provides an estimate of pore size in the carbon fibers. Pore generation and their size in the carbon fibers were driven by kinetic processing parameters, in addition to the thermodynamic phase separation. This study shows that gel-spinning of bicomponent PAN/PMMA-b-PAN fibers provide a versatile means for tuning the mechanical and electrochemical properties of porous carbon fibers, thus allowing for their potential use as structural energy storage materials.