Dispersed structure change of smectic clay/poly(methyl methacrylate) nanocomposites by copolymerization with polar comonomers

Abstract

Via in situ free-radical copolymerization of methyl methacrylate (MMA) with a small amount of polar comonomers such as N,N-dimethylaminopropyl acrylamide (PAA), N,N-dimethylaminoethyl acrylate (AEA) and acrylamide (AA), we synthesized clay/copolymer-based nanocomposites from lipophilized smectic clay (SPN). The degree of dispersion and the intercalation spacing of these nanocomposites were investigated by using a transmission electron microscope (TEM) and X-ray diffraction (XRD), respectively. The introduction of the polar comonomers affected the features of both aggregation and flocculation (edge–edge) interactions. On incorporation of the PAA comonomer, a much stronger flocculation took place owing to the edge–edge interaction of the silicate layers. In contrast, the AA comonomer played an important role in delaminating the layers. Especially in the PMMA-AA (1mol%)/SPN system, the ordered intercalated nanocomposite was formed as revealed by XRD and TEM. Each copolymer matrix nanocomposite showed a larger enhancement of moduli compared with the PMMA/SPN nanocomposite due to the large aspect ratio of the dispersed clay particles in the copolymer matrices.