Ceramic encapsulation with controlled layering by use of prehydrolyzed functionalized silanes
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. In the method, an emulsion is prepared including a continuous phase that is polar or non-polar, and a dispersed phase comprising droplets including (i) a polar active ingredient when the continuous phase is non-polar or (ii) a non-polar active ingredient when the continuous phase is polar; and a prehydrolyzed silica precursor is added to the emulsion such that the silica precursor can be emulsion templated on the droplets to form 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 polar or non-polar, and a dispersed phase comprising droplets including (i) a polar active ingredient when the continuous phase is non-polar or (ii) a non-polar active ingredient when the continuous phase is polar; and
(b) adding a prehydrolyzed silica precursor to the emulsion such that the silica precursor can be emulsion templated on the droplets to form hollow silica-based particles, wherein the prehydrolyzed silica precursor is formed in water at pH below 7 and before hydrolysis the 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, substituted and unsubstituted aryl, alcohols, amines, amides, aldehydes, acids, esters, and functional groups having an unsaturated carbon-carbon bond, R 2 is an alkyl group, x+y=4, and y=1, 2 or 3, and after formation of the prehydrolyzed silica precursor, alcohol is removed before adding the prehydrolyzed silica precursor to the emulsion.
2. The method of claim 1 further comprising:
(c) adding a second silica precursor to the emulsion such that the second silica precursor can be emulsion templated on the droplets or deposited on the hollow silica-based particles to form hollow silica-based particles.
3. The method of claim 2 wherein:
wherein 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, substituted and unsubstituted aryl, alcohols, amines, amides, aldehydes, acids, esters, and functional groups having an unsaturated carbon-carbon bond, R 4 is an alkyl group, m+n=4, and m=0, 1, 2 or 3.
4. The method of claim 3 further comprising:
(d) adding a third silica precursor to the emulsion such that the third silica precursor can be emulsion templated on the droplets or deposited on the hollow silica-based particles to form hollow silica-based particles,
wherein the third silica precursor has the general formula (III):
R 5 a —Si—(OR 6 ) b (III)
wherein R 5 is selected from substituted and unsubstituted alkyl, substituted and unsubstituted aryl, alcohols, amines, amides, aldehydes, acids, esters, and functional groups having an unsaturated carbon-carbon bond, R 6 is an alkyl group, a+b=4, and a=0, 1, 2 or 3.
5. The method of claim 2 wherein:
the silica particle is modified from a continuously formed shell to a partially formed hollow shell by adjusting a ratio of the prehydrolyzed silica precursor and the second silica precursor in the emulsion.
6. The method of claim 2 wherein:
the prehydrolyzed silica precursor leaves a first shell thickness of 1 nanometer to 500 nanometers for the particle when the prehydrolyzed silica precursor and the second silica precursor are templated on a droplet, and
the second silica precursor bonds to the first shell to create an outer layer such that the first shell and the outer layer together have a thickness in the range of 1 nanometer to 1 micron.
7. The method of claim 1 wherein:
step (a) further comprises adding a charged polymer to the emulsion, wherein the charged polymer is cationic.
8. The method of claim 1 wherein:
the R 1 groups are capable of attaching a coating by covalent bonding, non-covalent bonding, ionic bonding, electrostatic attraction, or any other attachment mechanism which allows for coating proximity within sub-nanometer ranges to 500 microns.
9. The method of claim 8 wherein:
the coating comprises a polymeric material.
10. The method of claim 1 wherein:
R 1 is phenyl.
11. The method of claim 1 wherein:
R 1 is C 12 -C 24 alkyl.
12. The method of claim 1 wherein:
R 1 is substituted or unsubstituted acrylic acid.
13. The method of claim 1 wherein:
R 1 is polyethylene glycol.
14. The method of claim 1 wherein:
R 1 is alkylamine.
15. The method of claim 1 wherein:
R 1 is alkyl carboxylate.
16. The method of claim 1 wherein:
R 1 is alkyl quaternary amine.
17. 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.
18. The method of claim 1 wherein:
the emulsion templating is undertaken at a pH above 7.