Core-shell silica/polystyrene composite

As an example of composite core/shell submicron particles, we made colloidal spheres with a polystyrene core and a silica shell. The polar vapors preferentially affect the silica shell of the composite nanospheres by sorbing into the mesoscale pores of the shell surface. This vapor sorption follows two mechanisms physical adsorption and capillary condensation of condensable vapors17. Similar vapor adsorption mechanisms have been observed in porous silicon20 and colloidal crystal films fabricated from silica submicron particles32, however, with lack of selectivity in vapor response. The nonpolar vapors preferentially affect the properties of the polystyrene core. Sorption of vapors of good solvents for a glassy polymer leads to the increase in polymer free volume and polymer plasticization32. 

Fig. 4.2 TEM images of fabricated nanoparticles, (a) Isolated composite core/shell submicron particles, (b) Hollow silica submicron particles prepared by removing the polystyrene core to demonstrate the high quality of the formed sol gel shell of the composite nanospheres employed to prepare sensing colloidal crystal films...

Thin films of blended deuterated polystyrene (dPS) and poly(vinyl methyl ether) (PVME) were imaged as a fimction of the dPS PVME ratio. Near the critical composition of 35% dPS, an imdulating, spinodal-like structure was observed, whereas for compositions away from the critical mixture ratio, regular mounds or holes (< dPS < < crit and < dPS > (pent, respectively) were present. These variations were assigned to surface tension effects (120). Blends of PBD, SBR, isobutylene-brominated p-methylstyrene, PP, PE, natural rubber, and isoprene-styrene-isoprene block rubbers were imaged (Fig. 18). Stiff, styrenic phases and rubbery core-shell phases were evident as the authors utilized force-modulated afm to determine detailed microstructure of blends, including those with fillers such as carbon-black and silica (121). 

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