Abstract
Optically transparent polyimides with excellent thermal stability and shape memory effect have potential applications in optoelectronic devices and aerospace industries. A series of optically transparent shape memory polyimide hybrid films are synthesized from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2′-bis-(trifluoromethyl)biphenyl-4,4′-diamine (TFMB) with various polyhedral oligomeric silsesquioxane (POSS) contents and then subjected to thermal imidization. The hybrid films show good optical transparency (>80% at 400 nm and >95% at 500 nm) with cutoff wavelengths ranging from 318 to 336 nm. Following the incorporation of the inorganic POSS structure, the hybrid films exhibit excellent thermal stability with glass transition temperature (Tg) ranging from 351 to 372 °C. The hybrid films possess the highest Tg compared with the previously-reported shape memory polymers. These findings show that POSS is successfully utilized to develop transparent polyimides with excellent thermal stability and shape memory effect.
Highlights
IntroductionPolyimide (PI) is widely used in the microelectronics and aerospace industries because of its excellent thermal stability, chemical resistance and suitability for advanced manufacturing [1,2,3]
Polyimide (PI) is widely used in the microelectronics and aerospace industries because of its excellent thermal stability, chemical resistance and suitability for advanced manufacturing [1,2,3].Optically transparent PIs with high thermal resistance have drawn great attention due to their extensive applications as transparent flexible substrates of optoelectronic devices, such as image displays, organic photovoltaics, printing circuit boards, and touch panels [4]
The glass transition temperature of the PI-polyhedral oligomeric silsesquioxane (POSS) hybrid film with different OAPS concentrations was evaluated by Dynamic mechanical analysis (DMA) and Differential scanning calorimetry (DSC) (Figure 1a,b and Table 1)
Summary
Polyimide (PI) is widely used in the microelectronics and aerospace industries because of its excellent thermal stability, chemical resistance and suitability for advanced manufacturing [1,2,3]. Improving the optical properties of PI has been attempted by introducing highly electronegative fluorine groups [22,23], alicyclic moieties [24,25], asymmetric segments [26,27], and bulky substituents [28,29,30]. These methods diminish the thermal stability in many cases. We obtain a series of thermoset PI-POSS hybrid films with good transparency, excellent thermal stability and shape memory effect by copolymerizing of octa(aminophenyl)-silsesquioxane (OAPS) and fluorinated monomers (6FDA/TFMB). To the best of our knowledge, the resulted films possess the highest Tg compared with the reported shape memory polymers (SMPs)
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