Synthesis and characterization of carbosilane dendrimer–sodium montmorillonite clay nanocomposites. Experimental and theoretical studies

Abstract

Novel organic/inorganic hybrid materials with carbosilane fillers were developed. New carbosilane dendrimers of the first (Dm1) and second (Dm2) generations bearing four and eight cationic ammonium groups on their periphery were synthesized first. Their structure was elucidated by NMR spectroscopy and ESI-HRMS whereas their thermal stability was confirmed by TGA. Both dendrimers were used as organic components in the preparation of organoclays. A series of nanocomposites Dm1Mt and Dm2Mt with varied contents of dendrimers were prepared and characterized by a wide variety of analytical techniques. The analytical data show that the structure of organoclays and the ability of dendrimers to effectively interact with montmorillonite are strongly affected by their generation. Both species Dm1 and Dm2 intercalated into the interlayer space of montmorillonite increase correspondingly the basal spacing of Mt. In contrast to Dm2, increased loadings of Dm1 in suspension during the intercalation process have a negligible effect on d-spacing in the studied concentration range, as confirmed by XRD analysis. Besides unmodified Mt we also studied the interactions of dendrimers with plasma treated Mt and the results are presented. Computer modelling based mainly on Molecular Dynamics has shown the non-linear dependence of the d-spacing on the amount of dendrimers in the interlayer space within the studied dendrimer/montmorillonite mass ratio interval. The filling capacity of plasma unmodified montmorillonite with respect to both dendrimers was estimated using a combination of experimental and theoretical results.