Ceramic Encapsulation By Use of One or More Silanes To Template Water Soluble Actives In A Water-In-Oil Emulsion
This invention relates to a method for forming hollow silica-based particles suitable for containing one or more active ingredients or for containing other smaller particles which may include one or more active ingredients. The emulsion templated particles can be formed from two or more silanes. The emulsion templated particles can also be formed from a silane and a compound that attaches a polymer on the shell of the hollow silica-based particles.
1 . A method for forming hollow silica-based particles, the method comprising:
(a) preparing an emulsion including a continuous phase that is non-polar, and a dispersed phase comprising droplets including a polar active ingredient;
(b) adding a first silica precursor to the emulsion such that the first silica precursor is emulsion templated on the droplets to form hollow silica-based particles having a shell and a core including the polar active ingredient,
wherein the first silica precursor has the general formula (I):
R 1 x —Si—(OR 2 ) y (I)
wherein R 1 is selected from substituted and unsubstituted alkyl, aryl, alcohols, amines, amides, aldehydes, acids, esters, and functional groups having an unsaturated carbon-carbon bond, wherein R 2 is an alkyl group, wherein x+y=4, and wherein x=0 or 1 or 2; and
(c) adding a second precursor to the emulsion such that a coating can be deposited on at least part of the shell of the hollow silica-based particles.
2 . The method of claim 1 wherein:
the second precursor is a second silica precursor,
the coating is a coating including silica, and
the second silica precursor has the general formula (II):
R 3 m —Si—(OR 4 ) n (II)
wherein R 3 is selected from substituted and unsubstituted alkyl, aryl, alcohols, amines, amides, aldehydes, acids, esters, and functional groups having an unsaturated carbon-carbon bond, and aminofunctional groups, wherein R 4 is an alkyl group, wherein m+n=4, and wherein m=0, 1, or 2.
3 . The method of claim 1 wherein:
step (a) comprises adding a surfactant selected from cationic, anionic, nonionic and amphoteric surfactants to a first material comprising the continuous phase and a second material comprising the dispersed phase to form the emulsion.
4 . The method of claim 3 wherein:
the surfactant is introduced to the emulsion below a critical micelle concentration of the surfactant for precursor interface interaction.
5 . The method of claim 3 wherein:
the surfactant introduced to the emulsion above a critical micelle concentration of the surfactant.
6 . The method of claim 3 wherein:
the surfactant has a charge to help speed up the reaction at interfaces between the droplets and the continuous phase by targeting and directing precursor formation at interfaces between the droplets and the continuous phase.
7 . The method of claim 2 wherein:
at least one of R 1 of the first silica precursor and R 3 of the second silica precursor has a net charge to attract towards an opposite charge of a surfactant at interfaces between the droplets and the continuous phase.
8 . The method of claim 2 wherein:
at least one of R 1 of the first silica precursor and R 3 of the second silica precursor prevents or limits aggregation of the hollow silica-based particles.
9 . The method of claim 2 wherein:
at least one of R 1 of the first silica precursor and R 3 of the second silica precursor allows for attachment of a polymer or other molecular complex to a surface of the particles by covalent linking.
10 . The method of claim 2 wherein:
step (c) comprises adjusting a ratio of the first silica precursor and the second silica precursor to modify the hollow silica-based silica particle from a continuously formed shell to a partially formed hollow shell.
11 . The method of claim 2 wherein:
the first silica precursor leaves a thickness of the shell of 1 nanometer to 500 nanometers for the hollow silica-based particles, and
the second silica precursor bonds to the shell to create an outer layer such that the shell and the outer layer together have a thickness in the range of 1 nanometer to 1 micron.
12 . The method of claim 1 wherein:
the second precursor is a water soluble polymeric compound or an unsaturated compound, and
the coating includes a polymer.
13 . The method of claim 12 wherein:
step (a) comprises adding a surfactant selected from cationic, anionic, nonionic and amphoteric surfactants to a first material comprising the continuous phase and a second material comprising the dispersed phase to form the emulsion.
14 . The method of claim 13 wherein:
the surfactant is introduced to the emulsion below a critical micelle concentration of the surfactant for precursor interface interaction.
15 . The method of claim 13 wherein:
the surfactant introduced to the emulsion above a critical micelle concentration of the surfactant.
16 . The method of claim 12 wherein:
the second precursor is a water soluble polymeric compound.
17 . The method of claim 12 wherein:
R 1 of the first silica precursor allows for attachment of the water soluble polymeric compound or the unsaturated compound to a surface of the particles by covalent linking.
18 . The method of claim 1 further comprising:
washing the hollow silica-based particles such that the active ingredient remains in the shell of the hollow silica-based particles after being washed.
19 . The method of claim 1 wherein:
the first silica precursor leaves a thickness of the shell of 1 nanometer to 250 microns for the hollow silica-based particles.
20 . The method of claim 1 wherein:
the hollow silica-based particles have a Zeta potential range from 0 mV to 150 mV.