Order Development in Polymer-Clay Nanocomposites: from Aqueous Gels to Multilayered Films
E.A. Stefanescu, C. Stefanescu, W.H. Daly, I.I. Negulescu
Virginia Commonwealth University, US
Keywords: gel, film, PEO, montmorillonite
Abstract:When passing a material through a semihyperbolic convergent die in an elongational rheometer, high degrees of order are induced in the material, and the entropy changes, indicative of orientation, can be calculated. The aim of the present contribution is to determine the extent of internal orientation developed in salt containing montmorillonite (CNA)-poly(ethylene oxide) dispersions subjected to elongational deformations. Furthermore, we correlate the findings with the high degrees of anisotropy observed in multilayered films prepared from the tested precursor gels. The extent of order developed in the salt containing nanocomposite gels is investigated combining shear and elongational rheology methods. Entropic changes indicate that the strength of the transient network present in each gel affects the orientational ability of clay particles and polymer chains. We found that an increased Hencky strain of the hyperbolic die, used by the elongational rheometer, leads to a higher variation of the calculated entropy of the material. The extent of anisotropy developed in the multilayered films was studied by means of small-angle X-ray scattering. SAXS measurements showed that at the nanoscale the polymer-covered clay platelets in the films are highly structured and oriented preferentially with the surface parallel to the plane of the film.