Homostructured Mixed Inorganic−Organic Ion Clays: A New Approach to Epoxy Polymer−Exfoliated Clay Nanocomposites with a Reduced Organic Modifier Content

Abstract

A new approach to the preparation of epoxy−clay nanocomposites is reported based on the intercalation and exfoliation of homostructured mixed inorganic/organic cation exchanged forms of a commercially available montmorillonite (PGW) and a synthetic fluorohectorite (FH) clay. In these mixed-ion homostructures both the organic onium ions and the inorganic exchange ions co-occupy the gallery surfaces of the clay, thereby dramatically reducing the amount of organic modifier needed to access the galleries for nanocomposite formation. The homostructures were prepared by ion exchanging the inorganic H+ and Li+ forms of the smectite clays with diprotonated primary α,ω-diamines of the type H2NCH(CH3)CH2[OCH2CH(CH3)]xNH2 (denoted Jeffamine D2000 with x = 33.1). Varying the ratio of inorganic cations to onium ions afforded homostructured mixed-ion intercalates with basal spacings ranging from ∼17 A (25% onium ion exchange) to ∼46 A (65% onium ion exchange), indicating the Jeffamine D2000 modifier adopted extended ch...