Nanocomposites from Layered Silicates: Graft Polymerization with Intercalated Ammonium Peroxides

Abstract

Nanocomposites were prepared by butyl acrylate graft polymerization from montmorillonite‐type layered silicates. Successful polymer grafting required novel dialkyl peroxides comprising two cationic ammonium groups, which were intercalated in the layered silicate by cation exchange. Thermal cleavage of the peroxide functionality in the presence of butyl acrylate as monomer initiated polymerization and hence exfoliation of the layers. Detailed examination of this process shows that the polymerization cannot be controlled by external nitroxides. magnified image

Polymer nanotechnology: Nanocomposites

“…Nanocomposites can, in principle, be formed from clays and organoclays in a number of ways including various in situ polymerization [4,6,[62][63][64][65][66][67][68], solution [51,53], and latex [69,70] methods. However, the greatest interest has involved melt processing because this is generally considered more economical, more flexible for formulation, and involves compounding and fabrication facilities commonly used in commercial practice.…”

Physical adsorption of organic molecules on the surface of layered silicate clay platelets: A thermogravimetric study

“…This system is more like a kinetic entrapment of the polymer chains along with clay platelets after cooling the melt in which clay platelets were exfoliated by shear rather than a thermodynamic process of filler exfoliation; however, it has been reported to be stable even after several cycles of processing of the composite material at high temperature [12,19]. The various techniques reported in the literature include modification of the clay platelets with ammonium ions of longer chain lengths [12], grafting of oligomeric chains "to" or "from" the clay surface [20][21][22][23][24][25][26][27][28][29], and chemical reactions on the clay surface with reactive surface modifications [30][31][32][33][34][35][36][37]. These routes lead to increased basal plane spacing of the clay platelets and reduced surface energy, thus making them susceptible to exfoliation when sheared along with the polymer matrix.…”

Polymer chains grafted “to” and “from” layered silicate clay platelets

“…Polymerization to and from the surface has been extensively studied for generating chemically attached polymer chains to the clay surface [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Polymerization to the surface is generally achieved by ionically exchanging on the clay surface an ammonium ion with a terminal acrylic or methacrylic monomer moiety followed by its free radical polymerization with the external monomer and initiator, whereas polymerization from the surface is carried out by polymerizing the external monomer with the initiator ionically bound on the clay surface.…”