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Poly(p-phenylene terephthalamide)(PPTA)is a famous aramid polymer.Its totally aromatic,rod-like structure facilitates the fabrication of fibers(e.g.,Kevlar)with a very high orientation from a liquid crystalline solution.1 These fibers have ultrahigh tensile strength and modulus,exceptional heat and flame resistance as well as chemical,solvent and environmental stabilities,and have been used as reinforcing materials of composites in wide applications such as military,aeronautics,astronautics,automobiles,and sports.