Preparation of Nanocomposite Based on Exfoliation of Montmorillonite in Acrylamide Thermosensitive Polymer

Poly(N-isopropylacrylamide) (PNIPAM) was synthesized in the presence of AIBN as radical initiator. The structure of polymer was elucidated using IR, 1H NMR, and 13C NMR spectroscopies and TGA thermogram. Exfoliated nanocomposite based on thermosensitive polymer (PNIPAM) was prepared utilizing montmorillonite (MMT) by solution blending. Its dispersion characteristics were investigated using SEM, X-ray diffraction, and particle size analysis. XRD showed exfoliation of MMT in polymer matrix above lower critical solution temperature (LCST). SEM indicated that polymer chains were dispersed among the layers of MMT. Particle size analysis showed two distinctive regions at 311 (31/5%) and 1160 (68/5%) nm. 1. Introduction The production of clay-polymer nanocomposites is an active area of research which benefits from the high surface area ratio of nanoclay particles to greatly improve the thermomechanical properties of the polymer matrix, even with low filler contents [1]. The success in the development of clay-polymer nanocomposites requires two key conditions: first, achieving a correct dispersion of nanoparticles in the matrix in order to obtain a high fraction of interfacial clay-polymer region within the material, and second, controlling the interfacial interactions between silicate particles and the polymer matrix, so that highly interacting polymer chains can either intercalate between the silicate layers or even break the stacking of the basal planes to induce exfoliation [2–4]. The ultimate goal for the preparation of nanocomposites is to achieve a very high degree of dispersion (exfoliation) of the aggregates of layered silicates. However, perfect exfoliation of the aggregates of layered silicates is very difficult to be achieved, if not impossible [5]. There are three ways of preparing nanocomposites, namely, (1) in situ polymerization of a monomer using an initiator tethered to the silicate surface or copolymerization of monomers by a silicate-anchored bifunctional initiator, (2) solution blending, and (3) melt blending [2]. It is well established that layered silicates (e.g., montmorillonite (MMT)) are hydrophilic [6, 7]. Therefore, they do not have chemical affinity with hydrophobic organic polymers and thus the two are incompatible. Thermosensitive polymers [8], such as poly(N-isopropylacrylamide) (PNIPAM) [9–11], exhibit a volume phase transition at a critical temperature, which causes a sudden change in the solvation state. Such polymers, which become insoluble and hydrophobic upon heating, have a lower critical solution temperature (LCST) [11].