| Popis: |
Publisher Summary The unique features of polybenzoxazines make them attractive for a wide range of applications. The characteristics of polybenzoxazines such as excellent dimensional stability, lower surface energy, higher Tg, and lower moisture absorption are attributed to the stable intramolecular hydrogen bonding in their network structure. The features make polybenzoxazines excellent candidates for the applications that require near zero shrinkage and high dimensional stability. Polybenzoxazines are formed by the autocatalytic polymerization of benzoxazine monomers. Polybenzoxazines are well known as a new class of thermoset polymers used for high performance applications. They provide the characteristic properties found in phenolic resins, such as high thermal stability, excellent electrical properties, good mechanical properties, and better flame retardancy. Furthermore, they have the advantages of requiring no harsh initiators or catalysts for polymerization and of forming no byproduct upon polymerization. This chapter highlights the different approaches to the synthesis of benzoxazine monomers polymerized at a lower temperature by the autocatalytic effect on the ring-opening benzoxazine polymerization. The various approaches are mostly based on the introduction of electron-withdrawing or electron-donating groups, or acidic groups that can activate the ring opening or stabilize the intermediates. In particular, we have focused on the DSC thermograms to find out the exothermic peaks of the monomers under study. From the systematic studies of the substituted benzoxazine monomers, carboxylic acid and hydroxyl containing benzoxazine monomers, it was clearly demonstrated that all the aforementioned systems represent successful approaches to improving the autocatalytic ring opening of the benzoxazine monomers. |
