Synthesis And Properties Of Catechol-Bearing Polybenzoxazines

Catechol groups have many outstanding properties such as adhesion property,coordination ability,and redox property.Catechol-bearing polymers have been widely studied in many academic fields such as adhesives,surface modification,self-healing materials,and electrode materials owing to the functional diversity of catechol groups.The reported catechol-bearing polymers mainly include polyethers,polyolefins,polyesters,and polypeptides.Up to now,catechol-bearing polybenzoxazines have not been systematically studied.As a new type of phenolic resin,the polybenzoxazine has many characteristics such as flexible molecular design,low moisture absorption,flame retardancy,and excellent thermal properties.The thesis aim is to introduce catechol groups into the polybenzoxazine skeleton,and to study the characteristics of catechol-bearing polybenzoxazines.For this purpose,we have carried out the following five researches.1.Catechol-bearing monofunctional benzoxazine resinA catechol-bearing monofunctional benzoxazine resin was synthesized based on the superior adhesion property of catechol groups.Firstly,the monofunctional benzoxazine monomers(BZ-ca)were synthesized successfully using catechol as raw material.Secondly,the catechol-bearing polybenzoxazine adhesive(PBZ-ca)was obtained by ring-opening polymerization.As the control experiments,other three monofunctional benzoxazine monomers were synthesized using phenol,resorcinol,and hydroquinone as raw materials.The molecular structures of target compounds were characterized by NMR and FTIR.The DSC results show that the polymerization temperature of BZ-ca is reduced to 149℃ due to the self-catalysis effect.The adhesion tests confirm that the adhesion property of PBZ-ca is improved by 53%due to the introduction of catechol groups.The work provides a new method for improving the adhesion performance of polybenzoxazine adhesives2.Tannic acid-benzoxazine copolymerThe biomass catechol-bearing polybenzoxazine adhesive was synthesized based on the excellent adhesion properties of catechol groups.Firstly,two kinds of biomass monofunctional and difunctional benzoxazine monomers(BZmo and BZdi)were synthesized.Secondly,the catechol-bearing polybenzoxazine adhesives(PBZmo-TA and PBZdi-TA)were obtained through copolymerizing with tannic acid.The molecular structures of target compounds were characterized by NMR and FTIR.The DSC results show that the polymerization temperatures of BZmo and BZdi are decreased to 155 and 150℃ owing to the introduction of tannic acid,respectively The adhesion tests confirm that the adhesion properties of PBZmo-TA and PBZdi-TA are improved by 217%and 154%due to the introduction of catechol groups.The work provides a concise and efficient method for producing new biomass adhesives3.Polybenzoxazine surface modifier containing catechol,sulfonic acid,and sulfobetaine groupsBased on the oxidative self-polymerization of catechol groups,a polybenzoxazine surface modifier of PBZ-CA/SA/SB with catechol,sulfonic acid,and sulfobetaine groups on the side groups was synthesized.Subsquently,PBZ-CA/SA/SB was used for the surface hydrophilic modification of the PTFE membranes.The molecular structures of target compounds were characterized by NMR and FTIR.A coating on the surface of the PTFE membrane was formed by the oxidative polymerization of catechol groups,and then the two hydrophilic groups of sulfonic acid and sulfobetaine were fixed onto the surface of the PTFE membrane.The results of contact angle,XPS and SEM confirm that the surface hydrophilic modification of the PTFE membranes is successful.The water contact angle of modified PTFE membrane is as low as 0°,indicating a super-hydrophilicity.Emulsion oil-water separation experiments show that the modified PTFE membrane has an excellent oil-water separation ability and good recycling performance.The work provides a new method for the surface hydrophilic modification of PTFE membranes.In addition,PBZ-CA/SA/SB also has potential application value for the surface hydrophilic modification of other materials.4.The reprocessable polybenzoxazine crosslinked by catechol-Fe3+ coordination bondsBased on the coordination ability of catechol groups with Fe3+,a reprocessable polybenzoxazine with catechol-Fe3+ dynamic crosslinked network was prepared.Firstly,a polybenzoxazine with catechol pendant groups was synthesized.Secondly,the polybenzoxazine with catechol-Fe3+reversible cross-linked network was obtained by catechol groups coordinating with Fe3+.The successful synthesis of the target molecules was proved by NMR and FTIR.The formation of the catechol-Fe3+dynamic cross-linking network was monitored by UV-Vis.The reprocessing tests confirm that PBZ-dopa45-Fe3+ has excellent reprocessing property.In three reprocessing procedures,the mechanical property recovery rates of PBZ-dopa45-Fe3+were 89%,83%,and 76%,respectively.The PBZ-dopa45-Fe3+ also maintains good heat resistance and thermal stability.The work provides a new method for preparing reprocessable cross-linked polymers with good thermal properties.5.AgNPs/graphite/polybenzoxazine conductive composite based on catechol reduction reactionBased on the reduction properties of catechol,silver ions were reduced to AgNPs in situ,and then the AgNPs/graphite/polybenzoxazine conductive composite was prepared.Firstly,a catechol group-containing benzoxazine monomer(BZ-py)was synthesized using pyrogallol as raw material.Secondly,the silver ions dispersed in the graphite/benzoxazine system were reduced to AgNPs in situ.The successful synthesis of the target molecule was proved by NMR and FTIR.DSC results show that the polymerization temperature of benzoxazines is reduced to 165℃ because of catalytic ring-opening effect.XRD and SEM results show that AgNPs are successfully generated in the composite and uniformly filled into graphite layers.The electrical conductivity tests show that the electrical conductivity of composite is igraproved by 58.6%due to the uniformly dispersed AgNPs.In addition,the AgNPs/graphite/polybenzoxazine composite also has good heat resistance and thermal stability.The work provides a new method for improving the conductivity of the polybenzoxazine composite,and also provides an effective method for solving the problem of the dispersion of metal nanoparticles in the polybenzoxazine matrix.