Study on nanodispersion of PI/clay nanocomposite by temporal analyses

The detail of nanoscaled dispersive behavior for layered clay in polyimide was first illustrated using temporal analyses. The layered structure of pristine clay remained in the poly(amic acid) and polyimide matrixes almost throughout curing process. However, the clay was mutilated by polymer chain motion during the process (cluster size reduced from ∼700 to ∼298 nm). On the other hand, organo-clay modified with octadecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride initially exfoliated in the poly(amic acid) solution (d-spacing >42 nm). At room temperature ∼200 °C, the layered structure of the clay recovered due to loss of solvent and poly(amic acid) chains intercalating into the organo-clay interlayer (d ∼ 3.49 nm). After polyimide fully formed at 350 °C, organo-clay d-spacing decreased to ∼2.27 nm. The reduction of d-spacing was ascribed to some of the polyimide molecular chains being squeezed out of the organo-clay interlayer since hydrogen bonds between the organo-clay and poly(amic acid) molecules diminished. The change in organo-clay cluster size behaved like pristine clay, finally decreasing to ∼367 nm after polyimide formed completely. The relatively large size of the organo-clay clusters in polyimide was ascribed to the confinement effect of polymer chain motion by organo-clay since the chains were frozen in the organo-clay interlayer.