Stability and rheology of W/Si/W multiple emulsions with polydimethylsiloxane

• The polydimethylsiloxane was used to prepare W/Si/W multiple emulsion.
• The W/Si/W multiple emulsion was prepared by single-step emulsification.
• The relationship to stability of multiple structures in emulsion with the oil/aqueous rate, MgSO4 and xanthan gum was studied.
• The rheology properties of W/Si/W multiple emulsion and simple emulsion were compared.

W/Si/W multiple emulsions were prepared with polydimethylsiloxane (PDMS), PEG/PPG-18/18 dimethicone in cyclopentasiloxane and Bis-PEG/PPG-20/5 PEG/PPG-20/5 dimethicone and methoxy PEG/PPG-25/4 dimethicone by single-step emulsification. The formulation factors, including oil/aqueous rate, magnesium sulfate and xanthan gum, were examined. The stability and rheological analysis of multiple emulsions were implemented. An excellent multiple structure occurred with the weight rate between oil and aqueous phase of 1:8, stabilized by 0.005 mol/L magnesium sulfate in external aqueous phase, 0.03 g xanthan gum in internal aqueous phase. W/Si/W multiple emulsions showed shear-thinning behavior, consisting with simple emulsion, except exhibiting a stress yield and steady viscosity area. Both the storage modulus (G′) and the loss modulus (G″) of multiple emulsion were slightly higher than that of simple emulsions, implying the existence of multiple structure. Tan (delta) of multiple emulsions had with a same trend but slightly higher than that of simple emulsion when strain increased, showed that multiple emulsions had resistance with the stress in converting viscoelastic character into elastic character.

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