Method for improving the properties of amphiphile particles
The present invention provides a method for forming a dispersion comprising non-lamellar amphiphile particles having improved phase behavior, particle size distribution and/or storage stability, said method comprising forming a dispersion of lamellar and optionally non-lamellar particles comprising at least one structuring agent in a polar solvent, heating said particles to an elevated temperature, followed by cooling, wherein said heating is to a temperature and for a period sufficient to provide, after cooling, a measurable improvement in phase behavior, particle size distribution and/or storage stability.
1. A method for the conversion in an single heat cycle of at least 50% of lamellar particles in a dispersion of lamellar and optionally non-lamellar amphiphile particles to non-lamellar form, said method comprising
forming a dispersion of lamellar and optionally non-lamellar particles comprising 0.5 to 20 wt % at least one amphiphilic structuring agent in an aqueous solution,
heating said particles to a temperature between 80 and 150° C. and maintaining the temperature for a time of one minute to four hours,
followed by cooling, wherein said non-lamellar particles have an internal region comprising a reversed cubic or hexagonal phase, L3 phase, or mixture thereof;
wherein said lamellar particles have a solvent core region; and
wherein, after cooling, at least 50% of said originally lamellar particles are converted to non-lamellar form.
2. A method as claimed in claim 1 wherein said heating and maintaining is to a temperature of between 80 to 150° C. and for a period of one minute to four hours, wherein said heating and maintaining is sufficient to provide a narrowing of said particle size distribution, after cooling, such that after cooling less than 1% of particles have a range outside of 0.05 to 1.5 μm.
3. A method as claimed in claim 1 wherein said heating and maintaining is to a temperature of between 80 to 150° C. and for a period of one minute to four hours, wherein said heating is sufficient to provide stabilization of said particle size distribution after cooling, such that the mean particle size after cooling increases no more than two-fold after at least 10 days at room temperature.
4. A method as claimed in claim 1 wherein said particles are colloidal.
5. A method as claimed claim 1 wherein said particles comprise at least 50% of a structure forming amphiphilic component “a”, up to 40% of at least one structure swelling agent “b” and up to 20% of a dispersion stabilizing polymeric agent “c”, wherein all parts are by weight relative to the total weight of a+b+c.
6. A method as claimed in claim 1 wherein said heating and maintaining is to a temperature of between 80 to 150° C. at which the equilibrium form of the particles is not non-lamellar.
7. A method as claimed in claim 6 wherein said heating and maintaining is to a temperature of between 80 to 150° C. at which the equilibrium form of the particles is L2 phase.
8. A method as claimed in claim 1 wherein said heating and maintaining is to a temperature of between 80 to 150° C. at which the equilibrium form of the particles is not liquid crystalline.
9. A method as claimed claim 1 wherein said dispersion of lamellar and/or non-lamellar particles is formed by sonication and/or extrusion.
10. A method as claimed in claim 1 further comprising drying the resultant non-lamellar particles formed after the cooling step, followed by resuspension/hydration of said particles.
11. A method as claimed in claim 1 , wherein the duration of heating at a temperature of between 80 to 150° C. is for a period of from 2 to 30 minutes.