Synthesis, characterization and catalytic application of clay-sulphonated PVA based composite materials

Abstract

A series of clay-sulfonated polyvinyl alcohol (SPVA) composite materials were synthesized by insertion of the polymeric component inside the clay interlayer. The sulfonated polyvinyl alcohol was synthesized by sulfonation of PVA using chlorosulfonic acid as sulfonating agent. In order to facilitate proper intercalation of the polymeric component a low molecular weight polymer sample was chosen for this purpose. The sulfonated polymer was intercalated inside the interlayer of the parent clay as well as that of Zr-pillared clay. The Zr-pillared clay was synthesized by intercalation of zirconium oxyhydroxy clusters inside the clay interlayer. The synthesized materials were characterized using XRD, IR, UV-Vis, and FESEM techniques. XRD study indicated an expansion of the interlayer space of the clay material as a result of pillaring with Zr-polycation. Upon intercalation of the SPVA, it was observed that the parent clay was ineffective for well dispersion of the polymer. A fraction of the clay material display interlayer space similar to the parent clay. The pillared clay on the other hand due to enhanced basal spacing was quite effective for the dispersion of the polymeric component. The FTIR and the UV-Vis study indicated the structural integrity of the clay structure as well as the SPVA species in the composite material. SEM study indicated considerable disturbance in the stacking arrangement of the clay sheet in case of the clay-SPVA composite material. The Zr-pillared clay-SPVA composites were used as an efficient heterogeneous catalyst for the environmentally benign synthesis of hexahydropyrimidines by multicomponent one pot condensation of formaldehyde, substituted anilines and ƒÒ-dicarbonyl compounds. The Zr-pillared clay-SPVA composites were found to be highly active for the multicomponent condensation reaction yielding a variety of hexahydropyrimidines in high yield and purity.