Methods for preparing core-shell composites having cross-linked shells and core-shell composites resulting therefrom

1. A method of preparing a core-shell composite comprising a polymeric core component and a crosslinked polymeric shell component, the method comprising

preparing a first phase comprising a polymeric core component and a shell polymer in a first liquid, the shell polymer being substantially dissolved in the first liquid, comprising

hydrating the core component in the first liquid, the first liquid being an aqueous solution, the core component comprising a hydrophilic core polymer,

dissolving the shell polymer in the aqueous solution, the shell polymer being a hydrophilic shell polymer,

allowing the shell polymer to interact with a surface of the hydrated core component to form a hydrated core-shell intermediate,

preparing a second phase comprising a crosslinking agent in a second liquid, the second liquid being substantially immiscible with the first liquid,

combining the first phase and the second phase to form a heterogeneous multiphase media,

crosslinking the shell polymer with the crosslinking agent on a surface of the core component to form the core-shell composite in the multiphase media, and

removing at least a portion of the first liquid from the heterogeneous multiphase media during crosslinking;

wherein the core component comprises a cation exchange polymer and the shell polymer comprises a net positively charged crosslinked amine polymer comprising amine moieties and the core-shell particle has a size of 1 μm to 500 μm and a binding capacity for potassium of at least 1.5 mmol/g at a pH greater than 5.5.

2. The method of preparing a core-shell composite of claim 1 , the method further comprising

concurrently (i) contacting the hydrated core-shell intermediate with the crosslinking agent under crosslinking conditions, such that the core-shell composite is formed, and (ii) removing water from the aqueous solution.

3. The method of claim 1 , wherein the removing step is a dehydrating step.

4. A method of preparing a core-shell composite comprising a polymeric core component and a crosslinked polymeric shell component, the method comprising

hydrating the core component in a first aqueous phase, the core component comprising a hydrophilic polymer,

dissolving a shell polymer in the first aqueous phase,

mixing the first aqueous phase with a second phase, the second phase comprising a crosslinking agent and being substantially immiscible with the first aqueous phase, to form a heterogeneous multiphase media,

crosslinking the shell polymer with the crosslinking agent on a surface of the core component to form the core-shell composite, and

dehydrating the heterogeneous multiphase media during crosslinking;

wherein the core component comprises a cation exchange polymer and the shell polymer comprises a net positively charged crosslinked amine polymer comprising amine moieties and the core-shell particle has a size of 1 μm to 500 μm and a binding capacity for potassium of at least 1.5 mmol/g at a pH greater than 5.5.

5. The method of claim 1 further comprising controlling a pH of the first liquid phase.

6. The method of claim 4 wherein at least 2% of the amine moieties of the shell polymer are quaternary ammonium.

7. The method of claim 4 wherein the amine moieties are substituted by an alkyl, (alk)heterocyclic moiety having the formula —(CH 2 ) m -HET-(R x ) t or an (alk)aryl moiety having the formula —(CH 2 ) m —Ar—(R x ) t , wherein m is 0-10, t is 0-5, HET is a heterocyclic moiety, Ar is an aryl moiety, and R x is hydrocarbyl or substituted hydrocarbyl.

8. The method of claim 4 wherein the crosslinked amine polymer comprises alkyleneimine repeat units.

9. The method of claim 8 wherein the crosslinked amine polymer comprises ethyleneimine repeat units and the alkyleneimine repeat units are substituted by an alkyl, (alk)heterocyclic moiety having the formula —(CH 2 ) m -HET-(R x ) t or an (alk)aryl moiety having the formula —(CH 2 ) m —Ar—(R x ) t , wherein m is 0-10, t is 0-5, HET is a heterocyclic moiety, Ar is an aryl moiety, and R x is hydrocarbyl or substituted hydrocarbyl.

10. The method of claim 4 wherein the crosslinked amine polymer comprises a vinylic repeat unit represented by Formula I:

or a copolymer thereof,

wherein n is at least 4,

R 1 and R 2 are independently hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted phenyl, substituted or unsubstituted aryl, or substituted or unsubstituted heterocyclic, and

A is a covalent bond between the N atom and the C atom of the polymer backbone, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted heterocyclic, carboxyalkyl wherein the alkyl group is substituted or unsubstituted, carboxamidoalkyl wherein the alkyl group is substituted or unsubstituted, or aminoalkyl wherein the alkyl group is substituted or unsubstituted.

11. The method of claim 10 wherein R 1 or R 2 have the formula —(CH 2 ) m —Ar—(R x ) t wherein m is 0-10, t is 0-5, Ar is an aryl moiety, and R x is hydrocarbyl or substituted hydrocarbyl.

12. The method of claim 11 wherein R x is C 1 -C 18 alkyl or C 1 -C 18 alkylene.

13. The method of claim 10 wherein R 1 or R 2 have the formula

wherein

m is 0 to 10;

R x is linear or branched C 1 -C 18 alkyl, C 1 -C 18 alkenyl, C 1 -C 18 alkynyl, or C 1 -C 20 aryl; and

t is 0 to 5.

14. The method of claim 13 wherein m is 1-3 and t is 1.

15. The method of claim 4 further comprising controlling a pH of the first liquid phase.