Preparing Multifunctional High-Performance Cross-Linked Polybenzoxazole Aerogels from Polybenzoxazine

Polybenzoxazole (PBO) aerogels have such valuable properties as excellent thermal and chemical stability, good fire resistance, and electronic transmission. However, the current processes to produce these aerogels tend to be complex and inefficient, and they are difficult to process into complex shapes. In this paper, we report a strategy to prepare cross-linked PBO (cPBO) aerogels by the polybenzoxazine. The polybenzoxazine aerogels were obtained first and then converted into cPBO aerogels through heat treatment. The prepared cPBO aerogels not only had low thermal conductivity (0.030 to 0.039 W m–1 K–1) but also possessed excellent mechanical properties (compressive modulus of 84.68 MPa) and low dielectric properties (1.51 at 1 kHz). These are attributable to the intrinsic structure of cPBO and the high porosity of aerogels in general. Because small-molecule ortho-functionalized benzoxazine has good solubility and can be used to prepare homogeneous solutions with various solid contents, this preparation strategy avoids the defect of directly using PBO resin, which has poor solubility and poor processability. Moreover, the pores of the cross-linked polybenzoxazine aerogels can be retained to the greatest extent during heat treatment. The preparation process is simple, efficient, and has a good application prospect.