Polymer-functionalised Polymer Nanoparticles and their Behaviour in Suspensions
Soft polymer nanoparticles can be functionalised with end-tethered polymer chains to control their solvent compatibility and stability. Controlling and understanding the behaviour of such functionalised latex suspensions is critical for their comprehensive applications. To investigate the effect of the nanoparticles architecture on their rheological behaviour, a library of polystyrene nanoparticles functionalised with a canopy of end-tethered poly(methyl acrylate) chains with different degrees of polymerisation and grafting densities was prepared. When the end-tethered polymer chains were long enough, the suspensions of polymer-functionalised nanoparticles underwent a liquid to gel transition when the concentration of nanoparticles was increased. The architecture of the polymer canopy was the determining factor for the mechanical properties of the resulting gels, nanoparticles with moderate grafting density where the polymer chains adopt a relax polymer brush conformation led to the formation of the strongest and most robust gels. In comparison to suspensions made with polymer functionalised nanoparticles particles with a soft and swollen core formed gels with higher yield stress at lower solid content.