Co-catalytic system design for deriving reactive diluent to construct robust benzoxazine resin with microphase-separated structure

Exploitation a facile and effective strategy for preparing benzoxazine resins with outstanding processability and robust mechanical properties still exists a challenge. In this work, a co-catalytic concept was proposed to fabricate high-performance benzoxazine resin by employing curing agent to derive reactive diluent to construct microphase-separated system. Given on the design, the reactive diluent dissolved solid benzoxazine into a low-viscosity solution, after which the curing agent presented a catalytic effect on diluent and benzoxazine to optimize the curing crosslinking reactions. As a result, it not only increased crosslinking density for a stable mechanical network, but also induced a microphase-separated structure to effectively dissipate energy for a strong yet tough resin system, as proved by Fourier transform infrared, differential scanning calorimetry, and dynamic mechanical analyses measurements. Moreover, the as-prepared modified benzoxazine resin showed great potential to fabricated composites with glass fiber, in which the values of tensile strength, elongation at break, and toughness presented an improvement of 212.1%, 106.8%, and 75.0% compared to composite with pristine PH-ddm and glass fiber, respectively. These results suggested an effective path to improve the processability and overall mechanical properties of benzoxazine resins, opening a new strategy to develop high-performance benzoxazine materials.