Synthesis, Characterization, and Structure–Property Investigations of Benzoxazine Resins with Low Surface Free Energy

Low surface free energy materials have garnered significant attention due to their exceptional properties and extensive applications, which play a pivotal role in diverse fields such as biotechnology, metallurgical processes, and electronic device manufacturing. To investigate the influence of electron effect derived from substituents on the surface properties of benzoxazine resins, three distinct benzoxazine monomers, characterized by different substituent groups, are synthesized. The monomer structures are verified using Fourier transform infrared and nuclear magnetic resonance spectroscopy. Differential scanning calorimetry tracks the polymerization behavior of benzoxazine resins, while thermogravimetric analysis valuates the thermal stability of the resulting polybenzoxazines. Then the surface properties are systematically investigated through contact angle measurement and surface free energy calculation, facilitating a comprehensive discussion on the impact of different substituents on the surface energy. These findings demonstrate that introducing trifluoromethyl leads to a substantial reduction in the surface energy of uncured resin. On the other hand, there is minimal impact on the surface free energy after undergoing elevated temperature treatments. The current study provides a foundation understanding for further developing polymers with low surface free energy.