Preparation And Properties Of Benzoxazines Based On Methoxyphenols And Polyetheramines

Six benzoxazines were synthesized from a set of isomeric methoxyphenols?o-,m-,and p-methoxyphenols?,polyetheramines?D230 and D400?,and formaldehyde via solution method.The chemical structures of the benzoxazines were confirmed by nuclear magnetic resonance spectroscopy(¹H NMR,¹³C NMR and DEPT-135°).The results show that each of m-methoxyphenol-based benzoxazines is a mixture of two isomers.The thermal polymerizations of the six benzoxazines were studied by Fourier transform infrared spectroscopy?FTIR?and differential scanning calorimetry?DSC?.The results show that the ring-opening polymerization occurred for the six benzoxazines.According to the position of the methoxy group on the benzen ring,the ring-opening polymerization temperature decreases in the order of ortho,para and meta.The dynamic mechanical properties of the resultant polybenzoxazines were evaluated by dynamic mechanical analysis?DMA?.The results show that the glass transition temperature and the crosslinking density increase with the rising polymerization temperature.Two series of poly?benzoxazine-co-urethane?with different components were prepared from para-methoxyphenol/polyetheramines type benzoxazines and urethane prepolymer.The copolymerization of blends of benzoxazine and urethane prepolymer were studied by FTIR and DSC.The results show the exothermic peak temperature of the DSC curves of blends of benzoxazine and urethane prepolymer are respectively higher than those of the pure benzoxazines.The dynamic mechanical properties of the resultant polybenzoxazines were measured by DMA.With the increase of urethane prepolymer content,the crosslinking density of the network of the D230 copolymers decreases,but increases for that of D400counterparts.In addition,the methoxyphenol-based polybenzoxazines and copolymers of benzoxazine and urethane prepolymer exhibit one-way dual-shape-memory behavior based on glass transition temperature.The shape memory effects were measured by tensile and bending tests.The shape recovery ratios in tensile deformation mode are low due to motion constraints.The D400-based polybenzoxazines show lower shape fixity ratios but higher shape recovery ratios compared to those of the D230-based counterparts.Comparing to the pure polybenzoxazines,D230 copolymers show higher shape fixity ratios and shape recovery ratios,and D400copolymers show higher shape fixity ratios but lower shape recovery ratios.