| Polyimide(PI)is a kind of polymer material synthesized by polymerization of diamine and dianhydride monomer.It has excellent thermal stability,chemical stability and other excellent properties.Widely used in aerospace,microelectronics,military and other fields,and its types and forms are diverse.Now,it is one of the organic polymer materials with the best comprehensive performance.However,due to the characteristics of molecular structure,such polymers have some limitat ions in the application.It is mainly manifested in two aspects:1,poor solubility;2,difficult to melt and not easy to thermoplastic molding.To solve the shortcom ings,this thesis provides a new method for the synthesis of soluble and meltable polyimides by using the good solubility of imidazole ionic liquids.Mainly using 4,5-dimethanol-2-phenyl-1H-imidazole(PDHmI),1-butyl bromide,Lauryl Brom ide etc.as the main raw materials,the imidazole ionic liquid structure was intro duced by design to synthesize four kind of diamine monomers(NH2-PDHmI);th en,different ratios of polyimide were prepared by thermal imidization with p-Ph enylenediamine(PDA)and pyromellitic dianhydride(PMDA).The physical and chemical properties of the monomers and polyimides were studied systematically.The mainconclusions are obtained as follows:(1)At room temperature,NH2-PDHmI exhibits an amorphous structure.Both have good thermal stability,show a lower glass transition temperature,and the th ermal decomposition temperature is above 270℃.(2)When the addition amount of NH2-PDHmI was 100%,the XRD results indicated that PI was an amorphous polymer.With the decrease of NH2-PDHmI and the increase of PDA content,PI gradually showed partial crystallization.And,with good thermal stability,the thermal decomposition temperature improved sign ificantly after polymerization,which is greater than 300℃.Viscous flow temperat ure is not higher than 250℃,and it is easy to be thermoformed.(3)TEM analysis showed that the microstructure of PI macromolecules was dendritic.EPMA results of PI showed that NH2-PDHmI and PMDA were evenly distributed.The XPS results of PI indicate that there are specific elements such as C,N,O,F and B in PI,and the types of chemical bonds in the molecule are determined by the binding energy.(4)PI exhibits good solubility properties.At room temperature,it can be sol uble in common high boiling polar solvents such as DMAC,and is also can be soluble in low boiling solvents such as THF.When the amount of NH2-PDHmI added is 100%,the solubility is optimal.The contact angle test results showed that the contact angle increased with the decreases of NH2-PDHmI addition ratio,and the material exhibited hydrophobicity.(5)The ionic conductivity of PI increases with the rise of temperature,and 4-75-PI-BF4 has the highest conductivity(4.59×10-4Scm-1)at 80℃.The electroc hemical stability window of most PI reaches 3-4V.(6)The antibacterial activity of PI showed that polyimide had certain antiba cterial effect on Escherichia coli. |
