Preparation And Properties Of Photocatalytic Polyimide/Titanium Dioxide Hybrid Film

Polyimide(PI)is now widely used in aerospace,electronics and electric appliance as well as microelectronics due to its excellent comprehensive properties.PI/TiO₂ nanohybrid materials have attracted more and more attention because of the great advantages of TiO₂ nanoparticles in enhancing heat resistance of PI and possessing special photoelectric properties.However,there are few reports on PI/TiO₂ nanohybrid materials with photocatalytic function.In this paper,PI/TiO₂ nanohybrid films were prepared by mixing two PI precursors,polyamic acid and polyamic acid salt,and soluble polyimide with nano-TiO₂followed by the study of their component,structure,morphology and properties,especially photocatalytic performance.The main work is as follows:1.The polyamic acid solution was prepared from pyromellitic dianhydride(PMDA)and diphenyl ether diamine(ODA).Further,it was mixed with titanium dioxide(TiO₂)hydrosol,and the PI/TiO₂ nano-hybrid films with TiO₂content of 1,3 and 5wt%were obtained by the formation of casting film followed by thermal imidization.The component,structure and morphology of PI/TiO₂ nanohybrid films were characterized by FT-IR,EDS and TEM.The results show that TiO₂has been successfully introduced into the PI matrix and is evenly distributed in nanometer size.The photocatalytic degradation of methylene blue showed that pure PI and three PI/TiO₂ nanohybrid films degraded13.67,43.11,53.62 and 70.00%of methylene blue in 180 min.The photocatalytic degradation of resazurin showed that the time required for the complete degradation of resazurin by the three PI/TiO₂ nano-hybrid films was 390,330 and 270 min,respectively,while the pure PI did not degrade resazurin.The results indicate that the PI/TiO₂ nanohybrid film has significant photocatalytic activity.In addition,TGA,tensile and electric breakdown were conducted to measure the thermal,mechanical and electric properties of PI/TiO₂ nanohybrid films.The results showed that the increase of TiO₂enhanced the thermal stability,mechanical and electric properties of PI film.2.The polyamic acid(PAS)salt solution was prepared by reacting polyamic acid(PMDA-ODA)with trimethylamine.Then,it was mixed with titanium dioxide(TiO₂)hydrosol,and the PI/TiO₂ nano-hybrid films with TiO₂content of 1,3 and 5wt%were obtained by the thermal imidization after casting film formation.The component,structure and morphology of PI/TiO₂ nanohybrid films were characterized by FT-IR,EDS and TEM.The results showed that TiO₂has been successfully introduced into the PI matrix and is evenly distributed in nanometer size.The photocatalytic degradation of methylene blue showed that pure PI and three PI/TiO₂ nanohybrid membranes degraded13.50,41.47,52.38 and 65.15%methylene blue in 180 min.The photocatalytic degradation of resazurin experiments showed that the time required for the complete degradation of resazurin by the three PI/TiO₂ nanohybrid membranes was 480,420 and330 min,respectively,while the pure PI did not degrade resazurin.The results indicated that the PI/TiO₂ nanohybrid film had significant photocatalytic activity.In addition,TGA,tensile and electric breakdown were conducted to measure the thermal,mechanical and electric properties of PI/TiO₂ nanohybrid films.The results showed that the increase of TiO₂enhanced the mechanical and electric properties of PI/TiO₂ nanohybrid films of PI film,wile maintained thermal stability of PI film.3.The soluble PI(KPI)was synthesized by the copolymerization of 2,3,3',4'-biphenyltetracarboxylic dianhydride with 2,2'-bistrifluoromethyl-4,4'-biphenylene diamine and m-phenylene diamine.Then,the soluble PI solution was blended with the TiO₂hydrosol,and the PI/TiO₂ nano-hybrid films with TiO₂content of 1wt%,3wt%and5wt%were obtained by the thermal imidization after casting film formation.Further,the component,structure and morphology of PI/TiO₂ nanohybrid films were characterized by FT-IR,EDS and TEM.The results showed that TiO₂has been successfully introduced into the PI matrix and is evenly distributed in nanometer size.The photocatalytic degradation of methylene blue showed that pure PI and three PI/TiO₂ nano-hybrid membranes degraded 10.75,41.44,53.06 and 70.30%methylene blue solution in 180 min.The photocatalytic degradation of resazurin experiments showed that the time required for the complete degradation of resazurin by three PI/TiO₂ nano-hybrid membranes was420,330 and 270 min,respectively,while the pure PI did not degrade resazurin.The results showed that the PI/TiO₂ nanohybrid film had significant photocatalytic activity.In addition,TGA,tensile and UV-Vis spectra were conducted to measure the thermal,mechanical and optical properties of PI/TiO₂ nanohybrid films.The results showed that the increase of TiO₂enhanced the thermal stability and mechanical properties of PI film,wile maintained optical properties of PI film.In summary,PI/TiO₂ nanohybrid films prepared by blending polyamic acid,polyamic acid salt and soluble polyimide with nano-TiO₂(?5wt%)all showed remarkable photocatalytic properties.Moreover,compared with pure PI,the thermal stability and mechanical properties of PI/TiO₂ nanohybrid films are all improved to a certain degree.In addition,the PI/TiO₂ nanohybrid film prepared from polyamic acid has the best mechanical properties;the thermal stability of the PI/TiO₂ nanohybrid film from soluble PI is optimal;the photocatalytic activity of the PI/TiO₂ nanohybrid film from soluble PI/TiO₂and polyamic acid is higher than that of polyamic acid salt prepared by PI/TiO₂.