Colloidal Silica/Poly(Methacrylsiloxane) Nanocomposite Particles: Synthesis, Characterization, and Application in Toners
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Colloidal Silica/Poly(Methacrylsiloxane) Nanocomposite Particles: Synthesis, Characterization, and Application in Toners. Dmitry Fomitchev,1 Russell Lewis,1 Hairuo Tu,1 Li Cheng,1 Hajime Kambara,1 and Geoffrey Moeser1 1
Cabot Corporation, 157 Concord Road Billerica, MA 01821, U.S.A. ABSTRACT We report on a new class of materials for laser printer toner applications. These materials were prepared from methacrysilane-in-water emulsions stabilized with colloidal silica particles. In this elegant system, the colloidal silica particles reside at the water/oil interface helping to emulsify the oil droplet, self-organizing into a raspberry-like morphology. The emulsion formation is followed by free-radical polymerization, hydrophobic treatment, and drying steps. This one pot synthesis in water affords a hydrophobic material with a particle size in the range of 80 to 300 nm. The particle size could be fine-tuned by changing the oil-to-silica mass ratio or by using colloidal silica particles of different sizes. Results of material characterization by solidstate NMR, electron microscopy, and particle size measurements methods will be presented. Examples of possible extensions of the synthesis towards materials with methacrylsilane partially substituted with other methacrylates will be provided. Application of the new material in toners will be described as will the comparison of its performance with the incumbent material - hydrophobic colloidal silica. INTRODUCTION Controlled self-assembly at nanometer scale is a powerful tool for creating new materials with useful properties [1, 2]. Hybrid nanoparticles combining an inorganic oxide and an organic polymer phases are one of the new prominent classes of such materials. A large number of synthetic methods and strategies for producing hybrid particles have been proposed within last 15 years. One resent example is a spontaneous emulsification of methacryloxypropyltrimethoxysilane (MPS) induced by various inorganic colloids followed by formation of hybrid particles with raspberry-like morphology which was reported by the group from the Utrecht University in the Netherlands [3, 4]. We extended this synthetic method and developed a flexible process for synthesis of hybrid composite particles suitable for application in a new generation of toners for laser printers. These new particles are from 80 to 300 nm in diameter and have a raspberry-like structure where colloidal silica protrudes from the particle surface, while the methacryloxypropysiloxane polymer forms the Figure 1. TEM image of colloidal composite particles. Colloidal silica particle core (Figure 1). particles are seen as dark spots. Scale bar is 100 nm.
These particles are designed to be used as external additives for toner, which are typically dry mixed with the toner at the last stage of toner formulation process. The primary function of external additives is to act as spacers and improve what is called toner durability – the rate at which properties of the toner like electrostatic charge and free flow decay as a fun
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