Synthesis And Preparation Of Heterocycle Compounds/POSS Composites

Polybenzoxazine(PBZ),as a new kind of thermosetting resin,can be synthesized from inexpensive raw materials and has received more and more attention because of its good performances.Polyhedral oligomeric silsesquioxanes(POSS)are a family of nanoscale chemical structures that contain a silicon/oxygen core based on(SiO_1.5)_n and have each apex(i.e., silicon atom)connected to some organic group.In the work,POSS were used as the reinforcement phases to modify the polybenzoxazinePhenolphthalein(3,3-B is(4-hydroxyphenyl)-1(3H)-isobenzo furanone, B-hpi),reacted with paraformaldehyde and allylamine by the Mannich Reaction,was investigated as the acid ingredient for the first time,and a novel benzoxazine was synthesized.In order to confirm the structure of benzoxazine,benzyl terminated phenolphthalein(3,3-Bis (4-benzyloxyphenyl)-1(3H)-isobenzofuranone,B-bpi)were prepared.The chemical structures of B-hpi,B-bpi and benzoxazine were compared by FT-IR,¹H-NMR and ¹³C-NMR,it demonstrated that lactone structure remains in benzoxazine(3,3-Bis(3-allyl-3,4-dihydro-2H-1,3-benzoxazine) -1(3H)-isobenzofuranone,B-adi)molecular structure.B-adi transited into quinoid-structure in basic medium similar to that of phenolphthalein. Software of Accelrys' materials studio(DMol³),FT-IR and UV/Vis spectrophotometer were employed to investigate the properties of quinoid-structure of B-adi and B-hpi.In-situ FT-IR spectra showed the thermal curing behavior of B-adi.The char yield of PolyB-adi was about 40%by weight at 800℃in nitrogen atmosphere determined by TGA.Tg for this polyB-adi were as high as 273℃and 295℃from the maximum of loss modulus and tanδby DMTA,respectively.A novel 2-oxazoline-benzoxazine(POB)is synthesized with 2-(hydroxylphenyl)-2-oxazoline,1,3,5-triphenylhexahydro-1,3,5-triazine and paraformaldehyde.The chemical structure of the pure monomer is confirmed by FT-IR,¹H-NMR,¹³C-NMR and MS.The curing behavior of the monomer is detected by DSC and FT-IR,and its ring-opened reaction occurs at 187.5℃.The results of DMTA and TGA demonstrate that the thermal properties of PPOB-m(polymer for POB monomer)are more excellent than PPOB-p(polymer for POB precursor),the reason being that the oligomer in benzoxazine precursor decreases the perfection of the polymer's network structure;it also can be found that the thermal properties of PPOB are much better than a common polybenzoxazine and a composite material of benzoxazine and 2-oxazoline.Oxazolines are five-membered heterocyclic compounds having one double bond,and that can react with carboxylic acid,anhydrides, aldehydes,epoxides,amines and hydroxyl groups and so on.The other people in our lab had investigated the hybrid nanocomposite of polybenzoxazine(PBZ)and POSS were prepared with the presence of compatilizer—bisoxazoline,which improve the miscibility and adhesion between benzoxazine and POSS.In the work,Octa(aminophenyl) silsesquioxane was also synthesized and incorporated in POB to prepare the nanocomposites.The ¹H-NMR spectra of the formulated POB and OAPS solution depicted the reaction of 2-oxazoline ring and amino group at room temperature,the reaction mechanism was suggested for the first time,and finally the product containing benzamidine structure was obtained.DMTA results showed that little content of OAPS(0.5wt%) remarkably enhanced the thermal properties of PolyPOB,however,much more content of OAPS may be impair the thermal properties of the nanocomposite instead.It's speculated that the introduced OAPS decreased the packing density of PolyPOB,which led to the decreasing of char yield(at 800℃)with the increasing of OAPS contents.The TEM micrographs indicated that 0.5wt%content of OAPS homogenously dispersed in PolyPOB matrix,while the aggregation will be occurred in the nanocomposites containing 5wt%of OAPS.Bismaleimide-triazine resins(BT resins),derived from the blend of dicyanate ester and bismaleimide resins,claim superiority over the component homopolymers in terms of physical and mechanical characteristics.POSS molecules are uniformly porous in nanometer-range size,and pure nanoporous POSS macromolecules have been shown to have a very low dielectric constant(2.1-2.7).In the work, Octa(maleimidophenyl)silsesquioxane(OMPS)was synthesized.DSC and FT-IR were used to investigate the curing behavior of BCE and BT resins incorporated with OMPS.The results show that OMPS catalyze the curing reaction of BCE,which may due to that OMPS accelerate the formation of imidocarbonate(the first step of cyclotrimerization),it also can be found that there is no evidence demonstrated the co-reaction between maleimide and cyanate ester.The thermal properties of BT,BTA, and BTE resins with different contents of OMPS were detected by DMTA and TG,the results show that OMPS has a slight effect on the thermal properties of these resins,and the BT,BTA,and BTE resins containing 1wt%of OMPS exhibit enhanced thermal properties in comparison with pristine BT0,BTA0,and BTE0 resins,while more content of OMPS may slightly impair the thermal properties of the polymer matrix.The dielectric constant of BT,BTA,and BTE resins were also measured,it can be found that OMPS distinctly decrease the dielectric constant of these hybrid materials,however,overmuch content of OMPS are disadvantageous for dielectric constant of these hybrid materials due to the aggregation of OMPS.