Multidimensional benzobisoxazole rigid‐rod polymers. I. Preparation and characterization

Abstract

Two-and three-dimensional rigid-rod polymers containing benzobisoxazole structures were prepared through the polycondensation in polyphosphoric acid of 4-[5-amino-6-hydroxybenzoxazol-2-yl]benzoic acid (ABA) with trimesic acid and 1,3,5,7-tetrakis(4-carboxylatophenyl)adamantane, respectively. Thermal properties of the polymers were determined by differential scanning calorimetry, thermogravimetric/ mass spectral analysis, and isothermal aging studies. The multidimensional polymers exhibited lower solution viscosities and lower thermooxidative stabilities than the onedimensional polymer generated by the homopolymerization of ABA under identical reaction conditions.

A Tetramethylbiphenyl Poly(benzobisthiazole): Synthesis, Chracterization, Fiber Spinning, and Properties

“…Because of the instability of the fluorene moiety at high temperature, it has actually been introduced in PBZT to achieve intermolecular cross-links. 21 While the structures in parts b and c of Figure 4 can account for the observed chemical shift at 39 ppm, the structure in Figure 4b also accounts for the evolution of methane. On the basis of this discussion, we conclude that the intermolecular cross-link in Figure 4b and the intramolecular cross-link in Figure 4d are both present in the free-annealed fiber.…”

“…On the basis of these considerations, the probability of the existence of the structure shown in Figure e was considered extremely low, if not nonexistent. Because of the instability of the fluorene moiety at high temperature, it has actually been introduced in PBZT to achieve intermolecular cross-links . While the structures in parts b and c of Figure can account for the observed chemical shift at 39 ppm, the structure in Figure b also accounts for the evolution of methane.…”

Dendrimers Derived from 1 → 3 Branching Motifs

“…Chapman et al reported in a communication the formation of “polycules” 458 , which were generated from “quasi-atoms”, specifically, substituted 1,3,5,7-tetraphenyladamantanes and the related diadamantanes. Treatment of the tetraacyl core 456 − with the 1 → 3 adamantyl building block 457 gave the desired tetraester 458 (Scheme ). This example only appeared in a meeting abstract, and the details were not reported.…”

Rigid‐Rod Polymers

“…By incorporating a thermally reactive cross-linking moiety fluorene into PBZT (267,268), iii. Cross-linking benzobisthiazole rigid-rod copolymers via labile methyl or dimethylephenoxy pendent groups (261,(269)(270)(271)(272)(273)(274)(275), or forming copolymers of tetramethylbiphenyl PBZT/PBZT (276,277), iv. Cross-linking PBO fibers with polyphenylene sulfide pendent groups (278), and v. Cross-linking PBZT by introducing benzocyclobutene (BCB) crosslinking moieties in PBZT backbone (264,270,(279)(280)(281)(282).…”

“…The ABA copolymers made with carboxy-terminated PBZT and 3,4-diaminobenzoic acids demonstrate much better tensile strength (up to 33%) than the blends (436,437). The graft copolymers of PEK and PBZT improve processability of the composites (438) and exhibit advantages in preventing the segregation of PBZT molecules (439,440). The toughness of composites increases with the increase in the rigid-rod polymer content (441).…”