Molecular Design And Polymer Properties Of Novel Fluorene-containing Benzoxazines

Benzoxazine resin is a new type of thermosetting resin with broad application prospects.Compared with traditional phenolic resin,it is easy to polymerize,has no small molecule release during polymerization,is easy to molecular design,and has good heat resistance and stability.It has a wide range of applications in aerospace,power electronics,new glass materials and other fields.Polyfluorene and its derivatives have characterizes of high fluorescence efficiency,extraordinary thermodynamics and chemical stability,and are among the most promising substances in the fields of materials,pharmaceuticals and electronics.In this paper,the functionalization of benzoxazine was directly carried out on 2 position of fluorene by molecular design,and four kinds of benzoxazine monomers containing fluorenyl structure were obtained,and then the corresponding benzoxazine polymers were prepared by thermal curing.The synthesis of monomers firstly take fluorene as raw materials,reacts with nitric acid to generate 2-nitrofluorene,2-aminofluorene was obtained by reduction of 2-nitrofluorene with zinc powder.Four benzoxazine monomers were obtained by one-pot reaction with amino fluorene,four different phenols and polyformaldehyde,which are respectively 3-fluorenyl-3,4-dihydro-1,3-benzo xazine?FBZ-1?,3-fluorenyl-6-methyl-3,4-dihydro-1,3-benzoxazine?FBZ-2?,3-fluore nyl-6-methoxy-3,4-Dihydro1,3-benzoxazine?FBZ-3?and 3-fluorenyl-6-hydroxymeth yl-3,4-dihydro1,3-benzoxazine?FBZ-4?.The monomer structure was confirmed by FT-IR,MS,¹H NMR,¹³C NMR.The thermal properties of the monomers we re investigated by TG and DSC.DSC curves of monomers at different heating rates were measured to study the curing kinetics of monomers.Three different methods were used to calculate the activation energy of monomers curing reaction.The curing temperature curve of each system was fitted linearly,and the curing temperature when the heating rate was zero was obtained by extrapolation,so as to determine the optimal curing condition.Using the curing conditions established by DSC data,the four monomers were thermallypolymerizedto obtainpolymers,andthe polymerstructurewas confirmed by FT-IR.The thermal stability and flame retardancy of the polymer were investigated by TG,and the fluorescence of the polymer in the solution was examined.