Structural effect of emulsifiers on the emulsion stability of a water/benzene mixture

Core–shell‐type microspheres with microphase‐separated shells of polystyrene (PS) and poly(ethylene glycol) (PEG) (microsphere_block: molar ratio: PS/PEG 49.1/45.9 mol %; M_w: PS chain: 1.07 × 10⁴, PEG chain 1.0 × 10⁴; the ratio of arm numbers of PEG to PS: 1.0; microsphere_graft: molar ratio: PS/PEG 33.8/55.9 mol %; M_w: PS chain: 1.54 × 10⁴, PEG chain 1.0 × 10⁴, the ratio of arm numbers of PEG to PS: 2.55) were synthesized by crosslinking of spherical domains of poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly(4‐vinyl pyridine) (P4VP) of the microphase‐separated films of poly(ethylene glycol)‐block‐poly(2‐hydroxyethyl methacrylate)‐block‐polystyrene triblock terpolymer (M_n: 2.18 × 10⁴; molar ratio: PS 49.1 mol %, PHEMA 5.0 mol %, PEG 45.9 mol %) and polystyrene‐block‐[poly(4‐vinyl pyridine)‐graft‐poly(ethylene glycol)] block–graft copolymer (M_n: 4.56 × 10⁴; molar ratio: PS 33.8 mol %, P4VP 10.3 mol %, PEG 55.9 mol %; branch number of PEG: 2.55), respectively. The structures of microphase‐separated films were investigated by transmission electron microscopy and small‐angle X‐ray scattering. The effects of the arm number ratio of PS to PEG and the total arm number on the stability of the water/benzene emulsion were investigated. The emulsion stability of oil in water was improved by using the microsphere synthesized with the microsphere_graft. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 321–331, 2004