Self-assembly of surface-active powder at the interfaces of selective liquids. 2: Behavior of an organic-crystalline powder

A ternary system consisting of a surface-active organic-crystalline powder (fluorinated calcium N-lauroyl taurate powder), fluorinated oil (perfluoropolymethylisopropyl ether, PFPE), and silicone oil (dimethylpolysiloxane, DMS) has been studied to examine the self-assembling behavior of the powder. Mixed states of the ternary system were classified into eight regions: W network-structured state, (ii) ON emulsion state (O/F emulsion means DMS-in-PFPE type emulsion), (iii) O/F emulsion state with excess PFPE and DMS phases, (iv) separated state, (v) powdery state, (vi) granular state, (vii) powder dispersion state with excess PFPE and DMS phases, and (viii) dispersion state of powder and PFPE. The separated state, in which a transparent DMS phase was separated from a milky white phase containing the powder and PFPE, was observed first in this system. The O/F emulsion was able to contain a larger amount of DMS oil than the ternary system having a spherical surface-active resin powder reported in our previous paper [Langmuir 2002, 18, 10163]. Shear-stress curve and contact angle measurements as well as theoretical analysis indicated that these interesting observations originated from the plate-type shape of the organic-crystalline powder and its characteristic network in the fluorinated oil.