Effect of hydration on the structures and properties of poly(p-phenylene benzobisoxazole)/poly(pyridobisimidazole) block copolymer fibers

Abstract

A rigid-rod copolymer, poly(p-phenylene benzobisoxazole)-block-poly(pyridobisimidazole) (PBO-b-PIPD), was synthesized, and the effect of hydration on the structures and performance of the block copolymer fibers was evaluated. PBO and PBO-b-PIPD as-spun fibers (AS-fibers) were prepared by dry-jet wet spinning, and subsequent thermal treatment in a nitrogen atmosphere was performed. Fourier transform infrared and wide-angle X-ray diffraction were used to characterize the structures of the thermally treated fibers. Mechanical properties of both the AS-fibers and thermally treated fibers were tested, and scanning electronic microscopy was used to observe the fracture surfaces of the fibers from tensile testing. It has been revealed that heat treatment is an effective method to remove the absorbed water to improve the orderly arrangement of chains along the fiber direction, which resulted in enhancement of the tensile modulus of the block copolymer fibers.

Investigation of the mechanical properties of the modified poly(p-phenylene benzobisoxazole) fibers based on 2-(4-aminophenyl)-1H-benzimidazol-5-amine

“…As a member of this class, the developed rigid-rod polymer poly( p -phenylene benzobisoxazole) (PBO) shows excellent thermal stability and remarkable tensile strength and modulus. 1 –4 However, even for commoditized PBO fibers, a large gap between the actual tensile modulus and the theoretical tensile modulus remains (the chain modulus of PBO calculated with Gaussian 09 is as high as 460–478 GPa). 5,6 An improvement in fiber orientation and molecular arrangement has been used as the main strategy to overcome this drawback.…”