TY - JOUR
T1 - Vesicle-to-micelle transformation in systems containing dimeric surfactants
AU - Danino, Dganit
AU - Talmon, Yeshayahu
AU - Zana, Raoul
N1 - Funding Information:
We thank Professor David Andelman and Professor Sam Safran for useful comments, and Ms. Berta Shdemati and Ms. Judith Schmidt for expert technical help. R.Z. thanks the Direction des Relations Internationales of the CNRS for partially supporting his stay at the Technion. The work done at the Technion was supported in part by grants from the United States– Israel Binational Science Foundation (BSF), Jerusalem, Israel, and from the Fund for the Promotion of Research at the Technion.
PY - 1997/1/1
Y1 - 1997/1/1
N2 - The vesicle-to-micelle transformation has been investigated thus far in lipid + surfactant systems where the vesicle-forming lipid is chemically very different from the micelle-forming surfactant. The dimeric surfactants, alkanediyl-α, ω-bis(dimethyldodecylammonium bromide), are known to form vesicles when the alkanediyl spacer is long enough (for instance, spacer = eicosanediyl, referred to as 12-20-12) and spheroidal micelles for shorter spacers (spacer = decanediyl, referred to as 12-10-12). These surfactants together with the conventional surfactant dodecyltrimethylammonium bromide (DTAB) permitted us to study the transformation of the 12-20-12 vesicles into micelles on addition of the chemically similar micelle-forming DTAB and 12-20-12. Spectrophotometry (light absorbance measurements), video-enhanced light microscopy, and transmission electron microscopy at cryogenic temperatures (cryo-TEM) were used to study the transformation at different scales of aggregate size. Electrical conductivity, which probes the system at the atomic scale (free counterions), was also used. Absorbance measurements showed the transformation to occur between 1.8 and 2.8 wt% added surfactant at a constant 12-20-12 concentration of 1.4 wt%. Light microscopy showed the progressive solubilization of the larger vesicles. Cryo-TEM showed that the initial effect of DTAB addition was to reduce the size of the vesicles, whereas 12-10-12 addition resulted in the formation of multilamellar vesicles. Further additions of either surfactant reduced the size of the vesicles, then brought about the formation of spheroidal micelles until complete solubilization of the vesicles. The giant threadlike micelles seen in previous studies of vesicle-to-micelle transformation in lipid/surfactant systems were never observed with the systems investigated. The conductivity results also revealed differences in behavior on additions of DTAB and 12-10-12.
AB - The vesicle-to-micelle transformation has been investigated thus far in lipid + surfactant systems where the vesicle-forming lipid is chemically very different from the micelle-forming surfactant. The dimeric surfactants, alkanediyl-α, ω-bis(dimethyldodecylammonium bromide), are known to form vesicles when the alkanediyl spacer is long enough (for instance, spacer = eicosanediyl, referred to as 12-20-12) and spheroidal micelles for shorter spacers (spacer = decanediyl, referred to as 12-10-12). These surfactants together with the conventional surfactant dodecyltrimethylammonium bromide (DTAB) permitted us to study the transformation of the 12-20-12 vesicles into micelles on addition of the chemically similar micelle-forming DTAB and 12-20-12. Spectrophotometry (light absorbance measurements), video-enhanced light microscopy, and transmission electron microscopy at cryogenic temperatures (cryo-TEM) were used to study the transformation at different scales of aggregate size. Electrical conductivity, which probes the system at the atomic scale (free counterions), was also used. Absorbance measurements showed the transformation to occur between 1.8 and 2.8 wt% added surfactant at a constant 12-20-12 concentration of 1.4 wt%. Light microscopy showed the progressive solubilization of the larger vesicles. Cryo-TEM showed that the initial effect of DTAB addition was to reduce the size of the vesicles, whereas 12-10-12 addition resulted in the formation of multilamellar vesicles. Further additions of either surfactant reduced the size of the vesicles, then brought about the formation of spheroidal micelles until complete solubilization of the vesicles. The giant threadlike micelles seen in previous studies of vesicle-to-micelle transformation in lipid/surfactant systems were never observed with the systems investigated. The conductivity results also revealed differences in behavior on additions of DTAB and 12-10-12.
KW - Cryo-TEM
KW - Electrical conductivity
KW - Light absorbance
KW - Micelles
KW - Solubilization
KW - Vesicles
UR - http://www.scopus.com/inward/record.url?scp=0030782657&partnerID=8YFLogxK
U2 - 10.1006/jcis.1996.4545
DO - 10.1006/jcis.1996.4545
M3 - 文章
AN - SCOPUS:0030782657
SN - 0021-9797
VL - 185
SP - 84
EP - 93
JO - Journal of Colloid and Interface Science
JF - Journal of Colloid and Interface Science
IS - 1
ER -