Synthesis And Properties Of Novel Degradable Polyimide Containing Acetal,Trifluoromethyl And Pyridine Ring Structure

Polyimide(PI)is a kind of polymer material with excellent performance in all aspects.It has good chemical and physical properties,heat resistance,chemical resistance and mechanical properties.However,with the progress of science and technology and the development of high-tech,various industries for the performance of polyimide put forward higher requirements,the shortcomings of traditional polyimide slowly revealed,such as poor optical transmission,poor solubility,Processing difficulties and other shortcomings,thus the structural modification of polyimide is very necessary.Polyimide is synthesize by diamine and dianhydride monomer,we designed and changed diamine or dianhydride monomer structure,to achieve the purpose of changing the performance of polyimide materials.With people's growing awareness of environmental protection,as well as the growing pollution and the shortage of natural resources,people demand for degradable materials is more and more urgent,while supported by national policy researchers for biodegradable materials research is also has a high heat,biodegradable materials is also the majority of consumers attention,but also the implementation of sustainable development strategies to alleviate the increasing emphasis on resources and environmental contradictions an important way.Today,for the vast number of consumers,the real good material in addition to its excellent performance,if the material is degradable will not bring pollution to the environment,it is undoubtedly the best choice.First of all,we consider the degradation,usually our polyimide can only be carried out under the conditions of alkaline degradation,and the need for high temperature alkali conditions for degradation,the conditions are very limited,so The acetal structure was added to the diamine monomer.: the use of cheap and available pentaerythritol and p-hydroxybenzaldehyde as a raw material in the structure of diamines introduced diacetal structure,acetal structure can be degraded under acidic conditions and conditions are more moderate.In the introduction of the diacetal structure,we introduced four ether bond and hydrocarbon segments in the structure of the polyimide,which will affect the thermal properties of the polyimide structure to some extent.We have introduced a pyridine ring structure,pyridine ring is a rigid aromatic heterocyclic structure,pyridine ring polymer has good thermal stability and chemical stability.In addition to this,there is a drawback that polyimide is difficult to dissolve and process difficult.For this reason,we introduce fluorine-containing groups into the structure of polyimide to make the solubility and machinability of polyimide Can be reduced due to the introduction of fluorine atoms can reduce the overall polarizability of polyimide material,can destroy the regularity of molecules,reduce the force between molecules,increasing the free volume within the molecule,increase the polyimide molecules The flexibility of the chain increases the solubility of the polyimide and the higher electronegativity of the fluorine atom can effectively affect the conjugation effect the conjugation of the electron cloud on the benzene ring attached to it in the PI structure,The optical properties of polyimides are improved.The main innovations of this paper are summarized as follows:From the design of the molecule,Based on the introduction of the structure of acetal structure,the divalent monosilane containing diacetal structure was prepared by nucleophilic addition of quaternary tetrakisol and p-hydroxybenzaldehyde under the catalysis of p-toluenesulfonic acid:p-hydroxy-2,4,8,10-oxo(5,5)undecane.Two diamines were prepared as the starting materials: 3,9-[4-(4-amino-2-pyridyloxy)phenyl]-2,4,8,10-oxo(5,5)undecane,3,9-[4-(2-trifluoromethyl-4-amino-phenoxy)phenyl]-2,4,8,10-undecane,the acetal structure was introduced into the molecular structure of polyimide,and the accuracy of the chemical structure of the product was characterized by infrared,hydrogen and carbon spectroscopy.Two newly prepared diacetal diamine monomers containing fluorine-containing groups and pyridine ring structures were used in combination with two commercially available dianhydride monomers(3,3,4,4-diphenyl Ketone tetracarboxylic dianhydride(BTDA)and 4,4-oxobisodiphenyl anhydride(ODPA))were prepared by thermal imidization and chemical imidization of polyimide polymer materials,and the same method was used to prepare a group of commercial diamines 4,4'-diaminodiphenyl ether(ODA)were prepared with BTDA and ODPA two dianhydride monomers to prepare a set of polymer materials for comparison with the previously prepared two groups of materials.he And the physical and chemical properties of each group of polymer materials: thermodynamic properties,optical properties,degradation and other were measured and comparative analysis.The results show that The introduction of acetal structure makes the polyimide material which can only be degraded under alkaline conditions can be under acidic conditions and the reaction conditions are relatively mild(reaction temperature is 20-40?)in the case of degradation.In the introduction of the acetal structure,we also introduced the fluorine-containing groups and the pyridine ring structure in the new diamine monomer respectively.The results show that the introduction of the fluorinecontaining structure can improve the solubility of the polymer material and make the The optical properties can be improved while the hygroscopicity of the polymer material can be reduced.At the same time,the pyridine ring structure can improve the thermodynamic properties of the polymer material.