Benzoxazine Miniemulsions Stabilized with Multifunctional Main-chain Benzoxazine Protective Colloids

The morphology control of thermoset systems is one of the key challenges to obtain high performance materials like structural adhesives or advanced protective coatings. Usually applied from solvents, it is highly desirable to transfer this concept to environmentally benign aqueous dispersions, although typical disadvantages like increased water uptake or reduced adhesion have to be minimized. In this respect, we introduce two different types of main-chain benzoxazine protective colloids, one of them additionally showing a lower critical solution temperature (LCST) characteristics, that provide colloidal stability in dispersion and become covalently incorporated into the network upon curing to suppress typical negative side effects. Furthermore, these multifunctional agents can be designed to undergo simultaneously a tailored chemically induced phase separation (CIPS) in order to obtain a desired morphology and to improve the overall mechanical and thermal properties of the resulting thermoset materials. The two examples were characterized by H-1 NMR, FT-IR, DSC, and TGA. The colloidal stability was characterized by DLS and turbidity measurements. The thermoset morphologies were investigated by TEM.