Improvements on the synthesis and properties of fluorinated polyimide–clay nanocomposites by using double-swelling agents

Abstract

Polyimide (6FBpA–6FDA)–montmorillonite nanocomposites (PiCN) were synthesized from modified montmorillonite (MMT) and poly(amic acid), using single- and double-swelling agents. The silicate layers of clay in the matrix of 6FBpA–6FDA were intercalated and became more exfoliated when double (DAETPB–ODA) swelling agents were used to modify the montmorillonite. Structures of exfoliation were confirmed by wide-angle X-ray diffraction (WAXRD) and transmission electron microscopy (TEM). The improved exfoliation of nanocomposites by the double-swelling agents resulted in enhanced thermal and mechanical properties. In particular, the maximum increase in Td, Tg, and storage modulus of these nanocomposites was found to be those with addition of 5.0wt% DAETPB–ODA modified-MMT. The moisture absorption of these nanocomposites was also reduced by the addition of double-swelling agent-modified MMT. The dielectric properties of PiCN in the form of film with MMT loading from 1.0 to 5.0wt% were measured under frequencies of 100Hz–1MHz at 35–150°C. Reduced dielectric constants were observed for these fluorinated polyimide–clay nanocomposites.