Preparation And Properties Of Benzoxazines With Active Hydroxyl And Their Derivatives

Four mono-functional benzoxazines containing active hydroxyl were synthesized from diglycolamine,paraformaldehyde and four phenols(phenol,p-cresol,o-cresol and o-allylphenol)via solution method.Then,eight bi-functional benzoxazines were synthesized from two bi-functional isocyanates(hexamethylene diisocyanate(HDI)and 2,4-toluene diisocyanate(TDI))and four mono-functional benzoxazines containing active hydroxyl.In addition,six phenol-alcohol-based benzoxazines were synthesized from two phenol-alcohols(o-hydroxybenzyl alcohol and p-hydroxybenzyl alcohol),three diamines(polyetheramines and 3-[2-(3-aminopropoxy)ethoxy]propan-l-amine(DGB))and paraformaldehyde.The chemical structures of the benzoxazines were confirmed by nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy.The structural changes and thermal polymerization reaction of the benzoxazines were studied by Fourier transform infrared spectroscopy and different scanning calorimetry.The dynamic mechanical properties and thermal stability of the resultant polybenzoxazines were determined by dynamic mechanical analysis and thermalgravimetric analysis,respectively.The results show that the chemical structures of the benzoxazines change with rising reaction time.The activity of the benzoxazines were affected by the nature and position of substituents and the chain structures between oxazine rings.The dynamic mechanical properties and thermal stability of the resultant polybenzoxazines are different,respectively.For the bifunctional benzoxazines based on diisocyanates,the initial curing temperatures are in the order ortho->para->un-substituted.In addition,the initial curing temperatures of the benzoxazines based on HDI are higher than those of the benzoxazines based on TDI.The glass transition temperatures,cross-linking densities and thermal stability of polybenzoxazines based on ortho-,para-substituted phenols are lower than those of their counterpart based on un-substitued phenol.In addition,the storage modulus of polybenzoxazines based on TDI are lower than those of their counterpaers based on HDI,but the glass transition temperatures,crosslinking densities and thermal stability of the former are higher than those of the latter.Furthermore,the polybenzoxazines based on HDI exhibit one-way dual shape memory behavior based on glass transition temperature.For phenol-alcohol-based benzoxazines,the initial curing temperatures of D230-based benzoxazines are lower than D400-based counteparts and close to DGB-based analogues.The glass transition temperatures,crosslinking densities and thermal stability of D400-based polybenzoxazines are lower than those of D230-based polybenzoxazines,but the storage moduli of the former are higher than those of the latter.The glass transition temperatures and thermal stability of DGB-based polybenzoxazines are lower than those of D230-based counterparters,but the crosslinking densities of the former are higher than those of the latter.In addition,the introduction of active hydroxyl can improve the reactivity of monomers and the storage modulus,glass transition temperatures,crosslinking densities and thermal stability of the resultant polybenzoxazines compared with the traditional polybenzoxazines.The resultant polybenzoxazines exhibit one-way dual shape memory behavior based on glass transition temperature.