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.
