Regina F. Nogueira

Carbon-13 NMR study of poly(alpha–methylstyrene)

Abstract Nuclear magnetic resonance spectroscopy (NMR) in solution and solid state was applied to obtain response of the chemical behaviour of commercial poly(alpha–methylstyrene) (PAMS). From solution measurements it was possible to determine the microstructure of this amorphous homopolymer. The solid state NMR investigation showed that the CPMAS 13 C routine spectrum allowed us to obtain information on the polymer microstructure and also evaluate the domain mobilities. The variation contact time and the proton spin-lattice relaxation time were determinant factors to evaluate the dynamic molecular motion.

Carbon-13 Solid State NMR Study of Polypropylene/Clay Nanocomposite

As it is known there are at least three ways to prepare a nanocomposite: solution casting, polymerization in situ and melting extrusion. In this work we have chosen to prepare the hybrids nanocomposite of polypropylene with brazilian clay (montmorillonite) using two types of blending mixers: one was a rheometer mix and the other one an extrusion process with the polypropylene/clay (PP/clay) proportion 95/5 w/w. The conditions of blending processing were: temperature 180 °C for 10 minutes. The objective of this work is to evaluate the characteristics of both types of nanocomposites obtained, employing solid state nuclear magnetic resonance (NMR). The C and Al NMR techniques were employed to obtain the nanocomposites homogeneity and dispersion of nanocomposite components. A comparison of the carbon-13 CPMAS NMR spectra of polypropylene and their nanocomposites prepared in Haake and extruder, revealed changes in the chains packing and ordination. Changes in both chemical and line width of Al NMR spectra indicates the formation of nanocomposite. To confirm these results, X-ray diffraction pattern was also registered. When the sample was prepared in the Haake only a composite was formed, but when the blend was performed in the extruder an exfoliated and dispersed nanocomposite was obtained.

Preparation and Characterization of Amorphous Silica Organofunctionalised with 2-Mercaptobenzimidazole

Organofunctionalised silica materials are of great interest once they combine a high surface area and a narrow pore size distribution with the advantage of owing organic ligand properties. This paper describes the organofunctionalisation of an amorphous silica with 2-mercaptobenzimidazole. The characterization of such material was performed by elemental analysis (EA), IR spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC) and solid state 13C and 29Si NMR spectroscopy.