Surface grafted high internal phase emulsion foams for chemical separations
A method of forming a high internal phase emulsion (HIPE) foam is provided. A nitroxide-containing monomer can be used in combination with other monomers that can then be used to make a high internal phase emulsion foam upon curing. The nitroxide group can subsequently be used to control the radical polymerization of many monomers, which can be grafted from the surface of the high internal phase emulsion foam. The resulting foam can be useful in performing separations of radioactive species, metals, metal ions, multi-element ions, metal complexes, halides, and organic chemical species in chemical process streams, clean-up operations, etc.
1. A method of forming a high internal phase emulsion foam, the method comprising:
forming a high internal phase emulsion comprising an oil phase and an aqueous phase, wherein the oil phase comprises a first monomer comprising a nitroxide-containing co-monomer, a second monomer comprising 4-vinylpyridine, and a crosslinking agent, wherein the oil phase comprises from about 5 wt. % to about 20 wt. % of the total weight of the high internal phase emulsion, wherein the nitroxide-containing co-monomer is present in the oil phase in an amount from about 15 wt. % to about 50 wt. % based on the total weight of the oil phase, and the aqueous phase comprises from about 80 wt. % to about 95 wt. % of the total weight of the high internal phase emulsion;
curing the high internal phase emulsion to form a high internal phase emulsion foam, the high internal phase emulsion foam including the first monomer in a backbone of the high internal phase emulsion foam; and
following formation of the high internal phase emulsion foam, polymerizing a plurality of the second monomer via graft polymerization from a surface of the high internal phase emulsion foam, wherein the first monomer controls the polymerization of the second monomer, resulting in the formation of polymer chains comprising the plurality of the second monomer grafted at the surface, the surface comprising pore walls of the high internal phase emulsion foam, such that the polymer chains extend into pores of the high internal phase emulsion foam.
2. The method of claim 1 , wherein forming the high internal phase emulsion comprises blending the oil phase with the aqueous phase.
3. The method of claim 1 , wherein the nitroxide-containing co-monomer has the following structure:
wherein R1 is H, CH 3 , CN, or short alkyl;
wherein R2 is methyl, ethyl, alkoxy, halide, or nitrile (cyano);
wherein R3 is H, CH 3 , CH 2 H 3 , short alkyl, phenyl, substituted phenyl, heteroaromatic, CN, or halide; and
wherein R4-R9 are each independently a straight chain alkyl, a branched chain alkyl, a cycloalkyl, an arenyl group, a heterocyclic group, H phosphate, or phosphate ester,
wherein each of R1-R9 are chosen to provide steric hindrance and weakening of the O—CR3 2 bond.
4. The method of claim 1 , wherein the nitroxide-containing co-monomer has the following structure:
5. The method of claim 1 , wherein the nitroxide-containing co-monomer has the following structure:
6. The method of claim 1 , wherein the nitroxide-containing co-monomer has the following structure:
7. The method of claim 1 , wherein the second monomer is selected from the following classes of monomers: styrenics, acrylates, methacrylates, dienes, acrylamides, methacrylamides, vinyl esters, and vinyl pyridines.
8. The method of claim 1 , wherein the cross-linking agent comprises divinyl benzene.
9. The method of claim 1 , wherein the oil phase further comprises a surfactant.
10. The method of claim 1 , wherein the oil phase further comprises an organic-soluble thermal initiator.
11. The method of claim 10 , wherein the organic-soluble thermal initiator comprises azobisisobutyronitrile.
12. The method of claim 1 , wherein the aqueous phase comprises water and a water-soluble thermal initiator.
13. The method of claim 12 , wherein the water-soluble thermal initiator comprises potassium persulfate.
14. The method of claim 1 , wherein the step of graft polymerizing the plurality of the second monomer from the surface of the high internal phase emulsion foam comprises soaking the high internal phase emulsion foam in a solution containing the second monomer and a solvent.
15. The method of claim 1 , wherein the second monomer comprises 4-vinylpyridine.
16. The method of claim 14 , wherein the solvent comprises butanol, methanol, ethanol, propanol, isopropanol, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), water, or a combination thereof.
17. The method of claim 2 , wherein the high internal phase emulsion is cured at a temperature below a temperature at which the nitroxide-containing co-monomer is activated.
18. The method of claim 1 , wherein the high internal phase emulsion foam is cured at a temperature less than 90° C. prior to the step of graft polymerizing the second monomer from the surface of the high internal phase emulsion foam, and wherein the step of graft polymerizing the monomer from the surface of the high internal phase emulsion foam is carried out at a temperature ranging from about 95° C. to about 160° C., which is a temperature above a temperature at which the nitroxide-containing co-monomer is activated.
19. The method of claim 1 , wherein the high internal phase emulsion foam adsorbs at least about 0.075 grams of metal ions or metal complexes per gram of the high internal phase emulsion foam.
20. A stationary phase for a liquid chromatography column, wherein the stationary phase comprises the high internal phase emulsion foam of claim 1 .
21. The stationary phase of claim 20 , wherein the second monomer is selected from the following classes of monomers: styrenics, acrylates, methacrylates, dienes, acrylamides, methacrylamides, vinyl esters, and vinyl pyridines.
22. A liquid chromatography column, the liquid chromatography column comprising:
a first connector;
a second connector;
a tube disposed between the first connector and the second connector; and
a stationary phase disposed within the tube, wherein the stationary phase comprises the high internal phase emulsion foam of claim 1 .