Synthesis and characterization of diamine and diol based benzoxazines

Abstract

Benzoxazines undergo ring opening polymerization through newlinethermal curing to form oxazine ring. Many research groups suggest different newlinereaction mechanism. It has been proposed that polymerization of newlinepolybenzoxazines takes place via ring opening process which involves the newlineformation of carbocation and an iminium ion in an equilibrium state. newlinePolymerization also occurs via electrophilic substitution by the carbocation to newlinethe benzene ring. This process can also takes place via electron transfer in free newlineortho and para positions of the phenolic group. The most limiting factor in newlinethis reaction is the stability of the iminium ion which greatly affects the newlinepropagation rate. newlineTo overcome this setback, benzoxazines were first blend with an newlineepoxy resin to enhance its performance via copolymerization reaction. newlineThe addition of epoxy into the polybenzoxazines network greatly influence newlinethe crosslink density of the thermosetting matrix and strongly influences its newlinemechanical properties. The crosslinked polymer made with benzoxazine newlinemonomers, preferably occurs at ortho and para positions depending on the newlineattack from the monomers. In the benzoxazine preparation method mannich newlinecondensation takes place in a solvent at low temperature, first amine reacts newlinewith formaldehyde forming N,N-dihydroxy methylamine derivative, which newlinethen reacts with the labile hydrogen of the hydroxyl group and ortho position newlineof the phenol at the elevated temperature form the oxazine ring. The desirable newlineproperties of epoxy resins have been enhanced by blending newlinebenzoxazine/MWCNT. To synthesize polybenzoxazines their respective newlinediamine-based benzoxazine monomers undergo thermal heating and newlineirradiation by microwave methods (in step by step and single step method) newlinewas confirmed by FT-IR newline