Interlamellar Complex Formation between Various Ion Forms of Montmorillonite and Poly(ethylene oxide) or Polyacrylamide

Abstract

Effect of exchangeable cations on the interlamellar complex formation between montmorillonite and poly (ethylene oxide) (PEO) or polyacrylamide (PAA) has been studied by treating homoionic bentonite (Na-, K-, Mg-, Ca-, or Ba-bentonite) suspension (1%) with PEO or PAA solution (0.2%).
X-ray diffraction patterns of PEO or PAA-treated bentonites revealed that interlamellar complexes containing one layer of the polymers in the interlamellar region of montmorillonite were formed except the case when K-montmorillonite was treated with PAA. The polymers adsorbed in the interlamellar region of alkali metal ion forms of montmorillonite were relatively easily desorbed by washing with water, whereas the polymers adsorbed in the same region of alkaline earth metal ion forms of montmorillonite were not desorbed. Differential thermal analysis indicated that the polyethylene oxides adsorbed on the alkaline earth metal ion forms of montmorillonite were thermally more stable than those adsorbed on the alkali metal ion forms of montmorillonite.
From the results obtained, the formation of interlamellar complexes between PEO or PAA and the alkaline earth metal ion forms of montmorillonite, which swell less easily than the alkali metal ion forms, may be explained by assuming the following adsorption process of the polymers onto montmorillonite from their aqueous solutions: considerably stable chelate polymers are first formed by the coordination of ether or amide groups of the polymers with exchangeable alkaline earth metal ions of montmorillonite, and then penetrate into the interlamellar region of montmorillonite in the form of a cationic polymer.