Research progress on polybenzoxazine aerogels: Preparation, properties, composites and hybrids fabrication, applications

The unremitting pursuit of high-performance and multifunctional materials has consistently propelled modern industries forward, stimulating research and motivating progress in related fields. In such materials, polybenzoxazine (PBz) aerogel, which combines the virtues of PBz and aerogel, has attracted salient attention recently, emerging as a novel research focus in the realm of advanced materials. In this review, the preparation scheme, microscopic morphology, and fundamental characteristics of PBz aerogels are comprehensively summarized and discussed in anticipation of providing a clear understanding of the correlation between preparation process, structure, and properties. The effective strategies for enhancing the performance of PBz aerogels including composite fabrication and hybridization are highlighted. Moreover, the applications of PBz-based aerogels in various domains such as adsorption (including wastewater treatment, CO2 capture, and microwave adsorption), thermal insulation, energy storage as well as sensors are covered in detail. Furthermore, several obstacles and potential directions for subsequent research are delineated with a view to surmounting the prevailing constraints and achieving a realization of the shift from experimental exploration to practical applications.

Preparation and properties of benzoxazine precursors containing siloxane units and their epoxy copolymers

Four siloxane benzoxazines containing different rigid segments were successfully synthesized and characterized herein, including a benzene ring, a biphenyl, a naphthalene ring, and a diphenyl sulfone group. Different rigid segments had different effects on polymer properties. The introduction of the naphthalene ring and sulfone group considerably reduced the curing temperature of benzoxazine. Although the benzoxazine with the naphthalene ring exhibited low heat resistance, all the four samples showed a high char yield at 800°C under nitrogen atmosphere. In addition, during copolymerization with AG-80 epoxy, the introduction of epoxy promoted the curing of the benzoxazines containing the naphthalene ring and sulfone group. The heat resistance of all copolymers was considerably improved, especially for the copolymer containing the naphthalene ring, whose 5% thermal weight loss temperature ( Td5) increased from 248°C to 321°C under nitrogen atmosphere. The copolymer containing the biphenyl structure had the highest glass transition temperature, reaching 259.1°C. Copolymerization with epoxy also considerably improved the tensile strength and elongation at break of the copolymers, which were much higher than those of traditional bisphenol A-aniline based benzoxazine (BA-a). Compared with the neat benzoxazine prepared using siloxane and bisphenol A, the developed copolymers also had better tensile properties, and the copolymer containing the sulfone group showed the greatest improvement (from 49 to 69 MPa, from 3.1% to 9.12%).