Polystyrene nanoparticles with tunable interfaces and softness

Polystyrene nanoparticles, cross-linked with divinylbenzene (PS-(DVB)x) and having radii, Rp ≤ 10 nm, have been synthesized using batch and semi-batch radical microemulsion polymerizations. The nanoparticles were characterized thoroughly using 1H NMR, size exclusion chromatography, differential scanning calorimetry, and various small-angle scattering techniques (light, X-rays, and neutrons). Control over network and interface morphologies of the PS-(DVB)x nanoparticles is readily achieved by varying the concentration of divinylbenzene and the polymerization technique (batch vs. semi-batch). Small-angle neutron scattering (SANS) allowed us to identify three distinct nanoparticle morphologies: (i) fuzzy soft gels with flexible chain-segments tethered/looped at the interface of a homogeneous core, (ii) smooth soft gels without a fuzzy interfacial layer, and (iii) dendritic glassy gels exhibiting an inhomogeneous core with an ill-defined interface. Atomic force microscopy imaging supports the morphologies and the softness of the nanoparticles as indicated by SANS.