Copolymer microstructure, nanocomposite morphology and aqueous solution viscosity of styrene-modified polyacrylamides in situ synthesized in presence of clay mineral

Abstract

Free-radical copolymerization of acrylamide (AM) with styrene (St) as a hydrophobic comonomer was carried out in the aqueous solution by potassium persulfate as an initiator in the presence of clay mineral. To investigate the influence of two kinds of clay minerals on the copolymer microstructure and nanocomposite morphology; hydrophilic Cloisite Na+ and hydrophobic Cloisite 30B were used in this work. Aqueous solution viscosity of the purified copolymers was also studied. Microstructural parameters were studied using 1H NMR spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy (TEM), aqueous solution viscosity, molecular weight measurements and solubility. Results showed that a mechanism almost similar to the heterogeneous mechanism can be considered for the St/AM copolymerization with both Cloisite Na+ and Cloisite 30B. Nanocomposite morphology studies showed that copolymer chains intercalated significantly into the clay mineral interlayers only with Cloisite Na+. In the case of Cloisite Na+, some exfoliation of the clay mineral interlayers was also observed from TEM micrographs. The formation of St interchain aggregations and physical network was confirmed by DLS and aqueous solution viscosity in the various salt and temperature conditions.