Real Time Exfoliation Behavior of Clay Layers in Epoxy−Clay Nanocomposites

Exfoliation behavior of clay layers in epoxy−clay nanocomposites was studied with the electronegativities of aromatic diamine curing agents and curing temperatures. While faster gelation in the extragallery region accelerated by much more reactive aromatic diamine curing agents (1, 3-phenylendiamine (PDA) and 4, 4‘-methylenedianiline (MDA)) produced the intercalated structure (<10 nm of d spacing), a well-exfoliated nanostructure (>20 nm) was obtained from the slow curing rate of diglycidyl ether of bisphenol A (DGEBA)−4,4‘-diaminodiphenyl sulfone (DDS). The exfoliation trend of the clay layer has a unique S-shape pattern with increasing extent of conversion at any curing temperatures. A three-step increase of interlayer distance was found in real time small-angle X-ray diffraction patterns on a polymerizing DGEBA−DDS−C18 clay nanocomposite.