Mechanical and Electrical Properties of Heat-Treated Ladder Polymer Fiber

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.

Facile Synthesis of Solubilizing a Group-Free, Solution-Processable p-Type Ladder Conjugated Polymer and Its Thermoelectric Properties

“…Ladder-type conjugated polymers are a fascinating class of semiconducting polymers with high thermal, chemical, and mechanical stabilities owing to their double-stranded fused-ring backbone. − This class of polymers was prepared and investigated for various applications since the 1960s but has met many inherent synthetic challenges arising from cross-linking side reactions (insolubility) and low-molecular-weight polymers (poor film-forming properties). ,− ,− The former is a result of uncontrollable interchain reactions caused by reactive functional groups at elevated temperatures while the latter is a consequence of low solubility of the starting materials and reaction intermediates. The insolubility and poor film-forming properties severely limit their use in thin film polymer electronic applications.…”

Phenazine-Substituted Poly(benzimidazobenzophenanthrolinedione): Electronic Structure, Thin Film Morphology, Electron Transport, and Mechanical Properties of an n-Type Semiconducting Ladder Polymer

“…The average elastic modulus of BBL film (E BBL ) was found to be 7.9 ± 0.4 GPa, which is within a reasonable range of reported values. 89,90 An elastic modulus of about 4 GPa was reported for a BBL filter cake (25 mm) via dynamic mechanical analysis 89 while that of heat-treated highly oriented BBL fibers was found to be 120 GPa. 90…”

“…89,90 An elastic modulus of about 4 GPa was reported for a BBL filter cake (25 mm) via dynamic mechanical analysis 89 while that of heat-treated highly oriented BBL fibers was found to be 120 GPa. 90…”