Thermal expansion of clay polymer nanocomposites as a function of aspect ratio and filler content

Comparative analysis of the properties of colorless and transparent polyimide nanocomposites with and without fluorine substitution

Two types of polyamic acids (PAAs) were synthesized using 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydro-naphthalene-1,2-dicarboxylic anhydride and two diamines, 2,2-bis[4-(4-aminophenoxy)phenyl] propane and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. Colorless and transparent polyimide (CPI) hybrid films were synthesized by dispersing various amounts (1-4 wt%) of Cloisite 30B (CS30B) into a PAA matrix using a solution intercalation method. The thermomechanical properties, clay dispersion morphology, optical transparency, and solubility of the two types of CPI hybrid films synthesized using different monomer structures were evaluated at various CS30B concentrations, and the results were compared. An increase in the thermomechanical properties of the CPI hybrid films was observed with only a small amount of organoclay dispersion, and the maximum enhancement in the physical properties occurred at a specific, critical clay content. Electron microscopy revealed that at low concentrations, the clay was uniformly dispersed throughout the polymer matrix at the nanoscale level but aggregated when added beyond a critical level. Structural changes in the CPI monomers and variations in CS30B content significantly influenced the physical properties of the CPI hybrid films. This study also highlighted the structure of an eco-friendly CPI designed to exhibit desirable physical properties without halogen elements, such as fluorine, which are environmentally regulated substances.