High-performance Polyphenylene Oxazin Synthesis And Characterization

As a new type of phenolic resin,polybenzoxazines have attracted much attention owing to its outstanding characteristics such as near-zero shrinkage or volumetric expansion upon curing,good thermal properties,electronic properties,and flame retardant.Recently,the demand for high performance polybenzoxazines has increased tremendously due to the rapid development of microelectronics and aerospace industries.Among the studies on polybenzoxazines,the issue of enhancing the glass transition temperatures(T_g)and flame-retardant performance of polybenzoxazines are highly expected.By taking advantage of the molecular design flexibility of benzoxazine chemistry, polybenzoxazines with high T_g or high flame-retardant have been synthesized through altering the functional groups on the amines and/or phenols.In this thesis, we described the synthesis and characterization of a series of polybenzoxazines with high Tg and high flame retardant obtained from the incorporation of rigid unit, polymerizable group,and inorganic element phosphorus into benzoxazine structure, respectively.The brief contents are shown as follows:1.The phenolphthalein-based benzoxazine monomers have been synthesized using the phenolphthalein,formaldehyde,and aniline.Subsequently,the benzoxazine monomers were thermo-cured into the polybenzoxazines.The chemical structures were identified by Fourier-transform infrared(FTIR)spectroscopy and ¹H nuclear magnetic resonance(¹H NMR)spectroscopy.The curing reaction of benzoxazine monomer was monitored by Differential scanning calorimetry(DSC)and FTIR.The thermal properties of obtained polybenzoxazines were evaluated by DSC,dynamic mechanical analyses(DMA),and thermogravimetric analyses(TGA).The obtained polybenzoxazines showed high T_g(247℃)and thermostable properties.The 5%and 10%weight-loss temperatures were 371℃and 435℃,respectively.The ultimate char yield was up to 65%at 800℃under N₂.2.A series of diamine-based benzoxazine precursors have been prepared using 4. 4-diaminodiphenyl methane,formaldehyde,and different phenol derivatives including the phenol,p-cresol,and 2-naphthol.Their chemical structures were identified by FTIR,¹H NMR,elemental analysis,and gel permeation chromatography(GPC).The curing reactions of those precursors were monitored by DSC and FTIR.The thermal properties of polybenzoxazines were evaluated by DSC, DMA,and TGA.The obtained polybenzoxazines exhibited the higher glass transition temperature and char yields than corresponding bisphenol-A based polybenzoxazines.The polybenzoxazine prepared from 2-naphthol exhibited the highest T_g at 244℃.The polybenzoxazine prepared from phenol showed the highest char yields of 65%and thermal stability with 5 and 10%weight-loss temperatures at 346 and 432℃,respectively.3.A novel benzoxaizne precursor containing phenol hydroxyl groups has been synthesized from 4,4'-diaminodiphenyl methane,bisphenol-A,and formaldehyde using the molar ratio of 1:2:4.The benzoxazine precursor was characterized by FTIR,¹H NMR,and GPC.The curing reaction was monitored by gel time,DSC,and FTIR.The starting polymerization temperature of the precursor is much lower than those of bisphenol A-based precursor and diamine-based precursor because of the presence of catalytic phenolic hydroxyl groups.The thermal properties of obtained polybenzoxazines were evaluated by DSC,DMA,and TGA.The obtained polybenzoxazine showed high T_g(192℃)and thermostable properties,with the 5% weight-loss temperatures at 346℃.4.Novel monofunctional and bifunctional benzoxazine monomers containing propargyl ether have been prepared from aniline derivative that contains a propargyl group,formaldehyde,and phenol(or phenolphthalein).Excellent thermostable polybenzoxazines were obtained by the thermal cure of the monomers.The chemical structures of these novel monomers were confirmed by FTIR and ¹H NMR.The curing reactions were monitored by DSC and FTIR.The thermal properties of obtained polybenzoxazines were evaluated by DSC,DMA,and TGA.The polybenzoxazine prepared from phenolphthalein exhibited the highest T_g at 311℃. The polybenzoxazine prepared from phenol showed the highest char yields of 64% and thermal stability with 5 and 10%weight-loss temperatures at 394 and 447℃. respectively.5.A series of benzoxazine monomers containing maleimide have been prepared from hydroxyphenylmaleimide,formaldehyde,and different amine derivatives including aniline,4,4'-diaminodiphenyl methane,and aminophenyl propargyl ether. Highly thermostable polybenzoxazines were obtained by the thermal cure of the monomers.The chemical structures of these novel monomers were confirmed by FTIR and ¹H NMR.The curing reactions were monitored by DSC and FTIR.The thermal properties of obtained polybenzoxazines were evaluated by DSC,DMA.and TGA.The polybenzoxazine prepared from aminophenyl propargyl ether showed the highest T_g at 331℃and thermal stability with 5 and 10%weight-loss temperatures at 390 and 436℃,respectively.6.The novel high flame-retardant benzoxazine precursor containing phosphorus has been synthesized from bis(4-aminophenyl)phenylphosphate,p-cresol,and formaldehyde.Subsequently,the benzoxazine precursors were thermo-cured to afford polybenzoxazine.The chemical structures were identified by FTIR,¹H NMR, and ³¹p NMR.The curing reaction was monitored by DSC and FTIR.The thermal and flame retardant properties of obtained polybenzoxazines were evaluated by DSC, TGA,and the limiting oxygen index(LOI).The obtained polybenzoxazines showed T_g at 229℃and high LOI(38.1).