Synthesis And Properties Of Benzoxazines Based On Siloxane-Containing Diphenol/p-Substituted Aniline

Two allyl-containing monofunctional benzoxazines(oAP-pa and oAP-4fa)were synthesized from o-allylphenol,formaldehyde and two kinds of amines(p-methoxyaniline and 4-fluoroaniline).The structures of the two benzoxazines were confirmed by 1H,13 C and 19 F nuclear magnetic resonance(NMR)spectroscopy and Fourier transform infrared(FTIR)spectroscopy.Two siloxane-containing benzoxazines(TMDSBPDP-pa and TMDSBPDP-4fa)were synthesized by hydrosilylation of the two allyl-containing monofunctional benzoxazines with tetramethyldisiloxane in the presence of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum.The chemical structures of the two siloxane-containing benzoxazines were confirmed by 1H,13 C,29Si and 19 F NMR and FTIR.The thermally activated polymerization behaviors of the two siloxane-containing benzoxazines were investigated by FTIR and differential scanning calorimetry(DSC).The peak temperatures of the DSC curves are 226°C and 244°C for TMDSBPDP-pa and TMDSBPDP-4fa,respectively.Their thermal stability and dynamic mechanical properties were investigated by thermogravimetry and dynamic mechanical analysis(DMA),respectively.With increasing curing time,the storage modulus in the glassy state of poly(TMDSBPDP-4fa)gradually decreases.The glass transition temperature of poly(TMDSBPDP-pa)is 89°C.Poly(TMDSBPDP-pa)shows a dual-shape memory effect,and the shape fixation rate(Rf)and shape recovery rate(Rr)are 95.1% and 81.6% in tensile stress-strain mode,respectively.The loss factor curves of poly(TMDSBPDP-4fa)show two peaks,and poly(TMDSBPDP-4fa)exhibits a triple-shape memory effect.Rf and Rr in tensile stress-strain mode decrease with increasing of polymerization time,and Rr is low.The experimental results show that the Rrs of polybenzoxazines are not only affected by the network structure,but also related to the test mode.In addition,benzoxazine/epoxy copolymers were prepared by copolymerizing TMDSBPDP-4fa with bisphenol A epoxy resin.The heat release behavior was studied by DSC.The thermal stability was studied by thermogravimetry.The dynamic mechanical properties and shape memory effects were studied by DMA.