Abstract
The ladder polymer poly[(7-oxo-7H, 10H-benz(d, e)imidazo(4', 5':5, 6)-benzimidazo(2, l-a)isoquinoline-3, 4:10, ll-tetrayl)-10-carbonyl] (BBL) was synthesized in polyphosphoric acid (PPA) at a concentration of 15% by weight. The polymer had an intrinsic viscosity of 8.75 dl/g in methanesulfonic acid (MSA) at 30°C. Highly oriented BBL fiber was spun by a dry-jet wet-spin process with a spin-draw-ratio of 8 to 1. After neutralization, the fiber exhibited a phosphoms content below the detectable limit (0.04%) by elemental analysis. This fiber, after a heat treatment at 300°C for 30 seconds under tension, showed a Young's modulus of 120 GPa, a tensile strength of 830 MPa and a compressive strength of 410 MPa. The fiber was also heat-treated at temperatures from 100°C to 600°C at 50°C increments for electrical conductivity measurements. It was found that room temperature DC conductivity of the BBL fiber increased dramatically from 2×10-8 S/cm with 100°C heat treatment to 3×10-4 S/cm with 350°C heat treatment and then decreased to 6×10-7 S/cm with 600°C heat treatment. The enhanced conductivity of heat-treated BBL fiber is believed due to the improved structural order in the BBL fiber and the thermally excited charge carriers.
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Acknowledgement
This work was supported by Air Force Contract No. F33615-87-C-5241. The authors are grateful to T. T. Tsai for synthesizing the BBL polymer, J. R. Miller for spinning the fiber and W. E. Click for testing the mechanical propereties.
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Wang, C.S., Lee, C.YC. & Arnold, F.E. Mechanical and Electrical Properties of Heat-Treated Ladder Polymer Fiber. MRS Online Proceedings Library 247, 747–752 (1992). https://doi.org/10.1557/PROC-247-747
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DOI: https://doi.org/10.1557/PROC-247-747