Polyimide-based composite films with high thermal conductivity,good mechanical property and electrical insulating performance are urgently needed in the electronics and microelectronics fields.As one of the key techni...Polyimide-based composite films with high thermal conductivity,good mechanical property and electrical insulating performance are urgently needed in the electronics and microelectronics fields.As one of the key technical challenges to be solved,interfacial compatibility between filler and matrix plays an important role for composite film.Herein,boron nitride was modified by grafting polyimide brushes via a twostep method,and a series of thermally conductive polyimide/boron nitride composite films were prepared.Both characterization and performance results proved that the interfacial interaction and compatibility was greatly enhanced,resulting in a significant reduction in defects and interfacial thermal resistance.The interphase width of transition zone between two phases was also efficiently enlarged due to polyimide brushes grafted on filler surface.As a result,composite films based on polyimide-grafted boron nitride exhibited significantly improved properties compared with those based on pristine filler.Tensile strength can reach up to 80 MPa even if the filler content is as high as 50 wt%.The out-of-plane and in-plane thermal conductivity of composite film increased to 0.841 and 0.850 W·m^(-1)·K^(-1),respectively.In addition,thermal and dielectric properties of composite films were also enhanced to some extent.The above results indicate that surface modification by chemically grafting polymer brushes is an effective method to improve two-phase interfacial compatibility so as to prepare composite film with enhanced properties.展开更多
The mesoscopic simulation technique was applied to describe the phase separation behavior ofpolyimide blends and used for design of immiscible polyimide/BN blend films with enhanced thermal conductivity. The simulatio...The mesoscopic simulation technique was applied to describe the phase separation behavior ofpolyimide blends and used for design of immiscible polyimide/BN blend films with enhanced thermal conductivity. The simulation equilibrium morphologies of different poly（amic acid） （PAA） blend systems were investigated and compared with optical images of corresponding polyimide blend films obtained by experiment. The immiscible polyimide blend fihns containing nano-/micro-sized BN with vertical double percolation structure were prepared. The result indicated that the thermal conductivity of polyimide blend film with 25 wt% nano-sized BN reached 1,16 W/（m·K）, which was 236% increment compared with that of the homogenous film containing the same BN ratio. The significant enhancement in thermal conductivity was attributed to the good phase separation of polyimide matrix, which made the inorganic fillers selectively localized in one continuous phase with high packing density, consequently, forming the effective thermal conductive pathway.展开更多
A series of novel poly(amide-imide)(PAl)films with different amide contents were prepared from pyromellitic dianhydride and four amide-containing diamines.These PAl films exhibited excellent mechanical and thermal pro...A series of novel poly(amide-imide)(PAl)films with different amide contents were prepared from pyromellitic dianhydride and four amide-containing diamines.These PAl films exhibited excellent mechanical and thermal properties with tensile strength of 203.7-297.4 MPa and Tg above 407℃.The rigid backbone structures combined with strong intermolecular interactions provided PAl films with ultralow in-plane CTE values from-4.17 ppm/℃to-0.39 ppm/℃in the temperature range of 30-300℃.The correlation between thermal expansion behavior and aggregation structures of PAl film was investigated.The results suggested that hydrogen bonding interactions could be maintained even at high temperature,thus resulting in good dimension reversibility of films in multiple heating-cooling cycles.It is demonstrated that dimensional stabilities of PAl films are determined by the rigidity,orientation,and packing of molecular chains.Heat-resistant PAl films with ultralow CTE can be developed as flexible substrates by regulating backbones and aggregation structures for optoelectronic application.展开更多
Polyimide films derived from representative PMDA/ODA were prepared with thickness ranging from 5 μm to 25 μm,and the effect of aggregation structure on thermal expansion behavior along different directions was studi...Polyimide films derived from representative PMDA/ODA were prepared with thickness ranging from 5 μm to 25 μm,and the effect of aggregation structure on thermal expansion behavior along different directions was studied.Both in-plane and out-of-plane linear thermal expansion(CTEand CTE) were respectively characterized by thermal mechanical analysis and FT-near-IR interference method.Volumetric and anisotropic behavior of thermal expan sion were also investigated.With increasing film thickness,CTEgradually increased from 32.2 ppm/℃ to46.1 ppm/℃ while CTEdecreased from 149.7 ppm/℃ to 128.2 ppm/℃.Volumetric thermal expansion of polyimide films was less sensitive to the va ried thickness,but anisotropy of thermal expansion was reduced.Polyimide film of 5 μm thickness showed large birefringence,indicating more considerable in-plane chain orientation anisotropy.Besides,molecular chains were more densely packed along in-plane direction when film thickness increased,while became loosely stacked in the out-of-plane direction.In contrast to the enhanced lateral chain packing for thicker film s,higher vertical chain packing order was found in thinner films.The variation of aggregation structure during thermal expansion procedure was analyzed by temperature-dependent WAXD.It is proved that thermal expansion behavior of thinner films could be largely attributed to molecular chain packing,whereas that may be influenced by many factors for thicker films in addition to the effect of chain packing.The results revealed that thermal expansion of films with thickness variation is closely related to molecular chain orientation and packing,which is associated with both chemistry and morphological structure of polyimide.展开更多
基金financially supported by the Natural Science Foundation of Beijing(No.2202068)the National Natural Science Foundation of China(No.51803221)National Key Research and Development Program(No.2022YFB3603105).
文摘Polyimide-based composite films with high thermal conductivity,good mechanical property and electrical insulating performance are urgently needed in the electronics and microelectronics fields.As one of the key technical challenges to be solved,interfacial compatibility between filler and matrix plays an important role for composite film.Herein,boron nitride was modified by grafting polyimide brushes via a twostep method,and a series of thermally conductive polyimide/boron nitride composite films were prepared.Both characterization and performance results proved that the interfacial interaction and compatibility was greatly enhanced,resulting in a significant reduction in defects and interfacial thermal resistance.The interphase width of transition zone between two phases was also efficiently enlarged due to polyimide brushes grafted on filler surface.As a result,composite films based on polyimide-grafted boron nitride exhibited significantly improved properties compared with those based on pristine filler.Tensile strength can reach up to 80 MPa even if the filler content is as high as 50 wt%.The out-of-plane and in-plane thermal conductivity of composite film increased to 0.841 and 0.850 W·m^(-1)·K^(-1),respectively.In addition,thermal and dielectric properties of composite films were also enhanced to some extent.The above results indicate that surface modification by chemically grafting polymer brushes is an effective method to improve two-phase interfacial compatibility so as to prepare composite film with enhanced properties.
文摘The mesoscopic simulation technique was applied to describe the phase separation behavior ofpolyimide blends and used for design of immiscible polyimide/BN blend films with enhanced thermal conductivity. The simulation equilibrium morphologies of different poly（amic acid） （PAA） blend systems were investigated and compared with optical images of corresponding polyimide blend films obtained by experiment. The immiscible polyimide blend fihns containing nano-/micro-sized BN with vertical double percolation structure were prepared. The result indicated that the thermal conductivity of polyimide blend film with 25 wt% nano-sized BN reached 1,16 W/（m·K）, which was 236% increment compared with that of the homogenous film containing the same BN ratio. The significant enhancement in thermal conductivity was attributed to the good phase separation of polyimide matrix, which made the inorganic fillers selectively localized in one continuous phase with high packing density, consequently, forming the effective thermal conductive pathway.
基金This work was financially supported by the National Natural Science Foundation of China(No.51803221).
文摘A series of novel poly(amide-imide)(PAl)films with different amide contents were prepared from pyromellitic dianhydride and four amide-containing diamines.These PAl films exhibited excellent mechanical and thermal properties with tensile strength of 203.7-297.4 MPa and Tg above 407℃.The rigid backbone structures combined with strong intermolecular interactions provided PAl films with ultralow in-plane CTE values from-4.17 ppm/℃to-0.39 ppm/℃in the temperature range of 30-300℃.The correlation between thermal expansion behavior and aggregation structures of PAl film was investigated.The results suggested that hydrogen bonding interactions could be maintained even at high temperature,thus resulting in good dimension reversibility of films in multiple heating-cooling cycles.It is demonstrated that dimensional stabilities of PAl films are determined by the rigidity,orientation,and packing of molecular chains.Heat-resistant PAl films with ultralow CTE can be developed as flexible substrates by regulating backbones and aggregation structures for optoelectronic application.
基金financially supported by the National Natural Science Foundation of China (No.51803221)。
文摘Polyimide films derived from representative PMDA/ODA were prepared with thickness ranging from 5 μm to 25 μm,and the effect of aggregation structure on thermal expansion behavior along different directions was studied.Both in-plane and out-of-plane linear thermal expansion(CTEand CTE) were respectively characterized by thermal mechanical analysis and FT-near-IR interference method.Volumetric and anisotropic behavior of thermal expan sion were also investigated.With increasing film thickness,CTEgradually increased from 32.2 ppm/℃ to46.1 ppm/℃ while CTEdecreased from 149.7 ppm/℃ to 128.2 ppm/℃.Volumetric thermal expansion of polyimide films was less sensitive to the va ried thickness,but anisotropy of thermal expansion was reduced.Polyimide film of 5 μm thickness showed large birefringence,indicating more considerable in-plane chain orientation anisotropy.Besides,molecular chains were more densely packed along in-plane direction when film thickness increased,while became loosely stacked in the out-of-plane direction.In contrast to the enhanced lateral chain packing for thicker film s,higher vertical chain packing order was found in thinner films.The variation of aggregation structure during thermal expansion procedure was analyzed by temperature-dependent WAXD.It is proved that thermal expansion behavior of thinner films could be largely attributed to molecular chain packing,whereas that may be influenced by many factors for thicker films in addition to the effect of chain packing.The results revealed that thermal expansion of films with thickness variation is closely related to molecular chain orientation and packing,which is associated with both chemistry and morphological structure of polyimide.
