The surface of silica nanoparticles is modifi ed using the "grafting from" technique. A multi-step reaction is conducted to modify their surface properties. (3-glycidoxypropyl) trimethoxysilane (GPS) is used as the coupling agent for the fi xation of atom transfer radical polymerization (ATRP) initiator. The grafting effi ciency of GPS mixed with aqueous suspension of silica nanoparticles is studied, followed by the coupling effi ciency towards ATRP initiator. The bromide concentration of ATRP initiator is kept constant for comparative kinetic studies of styrene and MMA polymerizations. The consequences at high conversions and the particle size distribution are studied. The behaviour of the glass transition temperature of either polymer-modifi ed particles and the nature of dispersion of polymer-coated silica particles are analyzed.

In this study, the influence of rheological and morphological properties on the foaming behaviour of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymers and their composites with PMMA modified silica nanoparticles is discussed. The blowing agent was carbon dioxide. Cylindrical and lamellar types of PS-b-PMMA diblock copolymers with different molecular weights were chosen in order to elucidate the influence of morphology and molecular weight on the foaming behaviour. The microphase-separated morphology of the diblock copolymers was studied by small-angle x-ray scattering and microscopic investigations. The rheological behaviour of the materials under shear was analyzed using linear viscoelastic shear oscillations and creep experiments in order to probe the microstructure at different time scales. High pressure differential scanning calorimetry measurements indicate that the blowing agent carbon dioxide was dissolved in the PS and in the PMMA domains. Generally, the diblock copolymers of our study with a cylindrical morphology led to foams with a lower density than the ones with a lamellar morphology. This effect indicates that large stresses are necessary to deform lamellar structures during nucleation and expansion of foam cells. The diblock copolymer with a cylindrical morphology and polystyrene as the matrix was associated with an ω-independent plateau at low frequencies of the shear oscillations. After foaming, the cell walls and the surface of the foamed PS-b-PMMA diblock copolymer with the polystyrene matrix depicted the cylindrical morphology of the microphase-separated structure.

Silica nanoparticles with an average diameter of 12 nm are grafted with PBMA‐b‐PMMA double shells through typical sequential ATRP from bromoisobutyrate initiators anchored at the silica surface using an epoxysilane. A commercially available PMMA homopolymer is used for the preparation of composites with unmodified, silane‐modified and double‐shell‐modified silica particles. Good mechanical properties are obtained for silica double shell containing systems. The silica content in double shell particle systems is varied from 0 to 2.5 wt%. A significant improvement in impact properties is observed. The surface‐modified silica particles are characterized by ATR‐FTIR, NMR, GPC, and thermal analyses. TEM analysis is used to analyze the nature of dispersion of particles in the composites.

The grafting of polymeric chains to inorganic (as well as organic) particle interfaces has become an indispensable tool to engineer the physicochemical and/ or biochemical properties of material interfaces. For example, polymer grafting is ubiquitously being used to compatibilize particles to polymer matrices to augment the properties of polymers in applications such as biomedical devices, lightweight aircraft wings, energy generation and storage, and for separation and environmental remediation to name a few. The recent emergence of surface-initiated controlled radical polymerization has further expanded the scope of polymer-grafted particulate materials, as the precise control of the structure of the polymer grafts offers new opportunities to tailor the properties of polymer-grafted particle systems. This chapter summarizes recent developments in synthesis of polymer-tethered nanoparticle interfaces that have afforded this fine control in the structure and properties of the resultant composite. Particular emphasis is given to the concept of "one-component hybrid materials"-that is the ability to synthesize multifunctional nanocomposite materials by the self-assembly of polymer-tethered particle systems. The role of polymer-graft modification on the interaction, dynamics, and assembly of particle brush materials is discussed to provide the context to showcase studies that have demonstrated the opportunity to harness the precision-engineered polymergrafted particle systems for the fabrication of innovative nanocomposite material technologies.