Core-Shell Polymer Nanoparticles for Baroplastic Processing

Core-shell polymer nanoparticles consisting of a low glass transition temperature (Tg)core of poly(n-butyl acrylate)or poly(2-ethylhexyl acrylate)and a glassy polystyrene shell were synthesized by two-stage emulsion polymerization. The obtained materials exhibit pressure-induced mixing of their components and could be processed at low temperatures (25-50 °C)by compression molding or extrusion. Nanoparticles of varying PS content and particle size were investigated to determine parametric effects on processing and mechanical properties. Transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and small-angle neutron scattering (SANS)measurements performed before and after processing indicate the partial release of the soft component from the nanoparticle cores and subsequent intermixing with shells of adjacent particles under the application of pressure. The processed materials range from rigid plastics to elastomers with mechanical properties omparable to conventional styrenic thermoplastic elastomers (TPEs). Pressure-enhanced mixing is shown to play a crucial role in generating strong interfaces between the nanophase domains.