Stability grafted silica dispersions

Preparation and Stability of Polymer-Grafted Silica Dispersions... 

Steric stabilization is another well-established method of stabilizing colloidal suspensions of submicron to micron size [23]. The particles are coated with a layer of adsorbed or grafted polymer chains that provides a steric repulsion of entropie origin and helps disperse the particles by counterbalancing van der Waals attraction (Fig. la). The polymeric nature of the adsorbed or grafted layer softens the interparticle interactions and makes the particles intrinsically deformable. Many polymer chain/particle combinations have been synthesized and studied, and are described in the literature. Several popular colloidal systems consist of silica particles covered with various polymers such as polydimethylsiloxane [24], stearyl alcohol [25], alkyl chains [26], and polyethylene oxide [27]. Polymethylmethacrylate and polystyrene particles grafted with polymer chains have also been used extensively. For a review on the impressive literature on the subject we refer the interested reader to Vlassopoulos and Fytas [2]. 

This phenomenon can be observed with many systems, for example, with aqueous electrostatically stabilized particles [126], with aqueous latexes containing particles with grafted polyoxyethylene chains [127] and with non-aqueous dispersions of coated silica particles [128] and sterically stabilized poly(methyl methacrylate) particles [129],... 

Guo et al. synthesized a series of block-type amphiphilic copolymers via copolymerization of methacrylate end-capped oligo-urethane and MPS via the sol-gel process [167]. After hydrolysis and condensation of the copolymer precursors (self-assembled in the form of spherical micelles), polyurethane-silica hybrid materials with excellent thermal stability and mechanical properties were obtained. Etmimi et al. synthesized PS-GO nanocomposites via surface RAFT-mediated miniemulsion polymerization [155]. The molar mass and dispersity of PS in the nanocomposites were dependent on the amount of RAFT-grafted GO in the system. The PS-GO nanocomposites were of exfoliated morphology, and their thermal stability and mechanical properties were dependent on the modified GO content and better than those of neat PS polymer. Salami-Kalajahi et al. studied the effect of pristine nanoparticle loading on the properties of PMMA-silica nanocomposites prepared... 

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