Large-Scale Nanofiber Manufacturing| Poly(p-Phenylene Benzobisoxazole)Nanofber: A Promising Nanoscale BuildingBlock Toward Extremely Harsh Conditions

Zhang Meiyun & Yang Bin Team ACS Nano | Research Progress on Preparation, Properties and Applications of PBO Nanofibers

Since the invention and commercialization of poly(p-phenylene benzobisoxazole) (PBO) fibers, numerous breakthroughs have been achieved in military and aerospace applications due to their exceptional properties. Particularly, PBO nanofibers not only retain the high performance of PBO fibers but also exhibit impressive nanoscale characteristics and good processability, enabling widespread applications under extreme conditions. However, no comprehensive review has summarized the preparation, applications and potential challenges of PBO nanofibers.

Prof. Zhang Meiyun and Assoc. Prof. Yang Bin from Shaanxi University of Science & Technology published a review summarizing preparation methods for PBO nanofibers, including 1D fibers, 2D films/nanopapers and 3D gels. The construction strategies and diverse applications of PBO nanofiber-based advanced materials are discussed. The excellent mechanical, insulating and thermal stability properties of PBO nanofibers facilitate their applications in thermal protection, electrical insulation, batteries and flexible wearable devices. Finally, prospects and challenges in PBO nanofiber preparation and applications are highlighted. This review was published in ACS Nano as "Poly(p-Phenylene Benzobisoxazole) Nanofiber: A Promising Nanoscale Building Block Toward Extremely Harsh Conditions."

Figure 1. Performance characteristics and research status of PBO fibers and PBO nanofibers.

PBO nanofibers find applications across 1D fibers, 2D films and 3D aerogels, particularly in functional films for thermal insulation/flame retardancy, composite reinforcement, electrical insulation, battery separators, electromagnetic shielding, wave absorption and flexible sensing (Figures 2-3).

Figure 2. Multidimensional material construction based on PBO nanofibers.

Construction Strategies for PBO Nanofiber-Based Advanced Materials:
1D fibers: Reconstituting nanofibers into 1D fibers via wet-spinning improves performance. PBO nanofiber-based 1D fibers offer flexibility, with future potential for precise shape/size control via microfluidic spinning.

2D films/nanopapers: Prepared by blade-casting, spraying or filtration. Aligning PBO nanofibers is crucial for enhancing mechanical strength, achievable through designed nanosheet assembly strategies.

3D gels: Primarily aerogels with ultralow density and high porosity. Preparation methods include solvent exchange, supercritical drying and freeze-drying. Current challenges include limited development and high material costs hindering large-scale production.

Figure 3. Applications of PBO nanofibers.

Applications Under Extreme Conditions:
Flame retardancy/thermal insulation: PBO nanofibers enable excellent thermal insulating materials for thermal management.

Electrical insulation/heat dissipation: Meet mechanical strength and insulation requirements for flexible electronics.

Electromagnetic protection: Effectively address electromagnetic pollution with superior shielding/absorption performance.

Structural reinforcement: Improve mechanical interlocking of PBO fibers, providing new approaches for material enhancement.

Figure 4. Future research directions for PBO nanofibers.

Summary: PBO nanofibers can be obtained via bottom-up (electrospinning, self-assembly, crystallization) or top-down (mechanical fibrillation, protonation) methods. The protonation method is particularly notable for its simplicity and retention of the original PBO fiber's thermal resistance, insulation and mechanical strength. Processed PBO nanofibers yield 1D fibers, 2D films and 3D aerogels that leverage their inherent mechanical strength, flame retardancy and electrical insulation. Composites enable applications in flame retardancy/insulation, electrical insulation, electromagnetic shielding, wave absorption, structural reinforcement, battery separators and flexible wearables. With advancing technology, PBO nanofibers - as promising nanoscale building blocks - will realize broader applications through focused research on efficient, controllable and low-cost preparation, scalable production and diversified applications (Figure 4).