Superabsorbent polymers based on copolymers of charged monomers and neutral monomers

1 . A superabsorbent polymer comprising

a copolymer comprising

a major portion of charged monomers;

a minor portion of alkyl or aryl end-capped neutral and hydrophilic monomers; and

optionally a crosslinker;

wherein the alkyl or aryl end-capped neutral and hydrophilic monomers lack free hydroxyl groups and have a water solubility of at least 200 mg/mL;

wherein the major portion is present in an amount greater than about 50 mol % of the copolymer and the minor portion is present in an amount more than about 5 mol % and less than about 50 mol % of the copolymer;

wherein the minor portion comprises an alkyl or aryl end-capped neutral and hydrophilic monomer having a molecular weight less than 1000 g/mol;

wherein the copolymer lacks structured ordering of the charged monomers and the alkyl or aryl end-capped neutral and hydrophilic monomers;

wherein the charged monomers are selected from the group consisting of salts of acrylic acids, vinyl sulfonic acids, vinyl phosphoric acids, partially hydrolyzed maleic anhydrides; and

wherein the alkyl or aryl end-capped neutral and hydrophilic monomers are selected from the group consisting of polyethylene glycol monomethylether monomethacrylate, methoxy ethyl acrylate, compounds according to Formula I:

wherein n is a number in the range of 1-50 and R 1 and R 2 are each independently selected from the group consisting of hydrogen, linear or branched C 1 -C 6 alkyl groups, and combinations thereof.

2 . The superabsorbent polymer of claim 1 , wherein the major portion is present in an amount greater than about 65 mol % of the copolymer and the minor portion is present in an amount less than about 35 mol % of the copolymer.

3 . The superabsorbent polymer of claim 1 , wherein the superabsorbent polymer is in a form selected from the group consisting of a particle, a gel, a fiber, a bead, a liquid, a solid, a paste, and combinations thereof.

4 . The superabsorbent polymer of claim 1 , wherein the superabsorbent polymer is in the form of a particle with a diameter in the range of about 100 μm to about 1000 μm.

5 . The superabsorbent polymer of claim 1 , wherein the superabsorbent polymer is surface-crosslinked.

6 . The superabsorbent polymer of claim 1 , wherein the crosslinker density is in the range of about 0.05 wt % to about 1 wt %.

7 . The superabsorbent polymer of claim 1 , wherein the minor portion of alkyl or aryl end-capped neutral and hydrophilic monomers comprises an alkyl or aryl end-capped neutral and hydrophilic monomer having a water solubility in the range of about 200 mg/mL to about 500 mg/mL.

8 . A method of making a superabsorbent polymer comprising

a copolymer comprising

a major portion of charged monomers;

a minor portion of alkyl or aryl end-capped neutral and hydrophilic monomers; and

optionally a crosslinker;

wherein the alkyl or aryl end-capped neutral and hydrophilic monomers lack free hydroxyl groups and have a water solubility of at least 200 mg/mL, wherein the major portion is present in an amount greater than about 50 mol % of the copolymer and the minor portion is present in an amount more than 5 mol % and less than about 50 mol % of the copolymer, wherein the minor portion comprises an alkyl or aryl end-capped neutral and hydrophilic monomer having a molecular weight less than 1000 g/mol; wherein the copolymer lacks structured ordering of the charged monomers and the alkyl or aryl end-capped neutral and hydrophilic monomers, wherein the charged monomers are selected from the group consisting of salts of acrylic acids, vinyl sulfonic acids, vinyl phosphoric acids, and partially hydrolyzed maleic anhydrides; and

wherein the alkyl or aryl end-capped neutral and hydrophilic monomers are selected from the group consisting of polyethylene glycol, monomethylether monomethacrylate, methoxy ethyl acrylate, compounds according to Formula I:

wherein n is a number in the range of 1-50 and R 1 and R 2 are each independently selected from the group consisting of hydrogen, linear or branched C 1 -C 6 alkyl groups, and combinations thereof, the method comprising

forming a mixture comprising

a solvent

a charged monomer;

an alkyl or aryl end-capped neutral and hydrophilic monomer; and

optionally a crosslinker

initiating a reaction; and

reacting the mixture.

9 . The method of claim 8 , wherein the method step of initiating a reaction comprises adding to the mixture an initiator, an accelerator, or a combination thereof.

10 . The method of claim 8 , wherein the method step of reacting the mixture comprises reacting the mixture in an inert atmosphere.

11 . The method of claim 8 , wherein the method step of reacting the mixture comprises heating the mixture.

12 . The method of claim 8 , wherein the method further comprises drying the produced superabsorbent polymer.

13 . The method of claim 8 , wherein the method further comprises grinding the produced superabsorbent polymer.

14 . A method of using a superabsorbent polymer comprising

a copolymer comprising

a major portion of charged monomers;

a minor portion of alkyl or aryl end-capped neutral and hydrophilic monomers; and

optionally a crosslinker;

wherein the alkyl or aryl end-capped neutral and hydrophilic monomers lack free hydroxyl groups and have a water solubility of at least 200 mg/mL, wherein the major portion is present in an amount greater than about 50 mol % of the copolymer and the minor portion is present in an amount more than about 5 mol % and less than about 50 mol % of the copolymer, wherein the minor portion comprises an alkyl or aryl end-capped neutral and hydrophilic monomer having a molecular weight less than 1000 g/mol, wherein the copolymer lacks structured ordering of the charged monomers and the alkyl or aryl end-capped neutral and hydrophilic monomers, wherein the charged monomers are selected from the group consisting of salts of acrylic acids, vinyl sulfonic acids, vinyl phosphoric acids, partially hydrolyzed maleic anhydrides, wherein the alkyl or aryl end-capped neutral and hydrophilic monomers are selected from the group consisting of polyethylene glycol, monomethylether monomethacrylate, methoxy ethyl acrylate, compounds according to Formula I:

wherein n is a number in the range of 1-50 and R 1 and R 2 are each independently selected from the group consisting of hydrogen, linear or branched C 1 -C 6 alkyl groups, and combinations thereof, the method comprising using the superabsorbent polymer in a consumer product.

15 . The method of claim 14 , wherein the superabsorbent polymer is in the form of a particle with a diameter in the range of about 100 μm to about 1000 μm.

16 . The method of claim 14 , wherein the consumer product is selected from the group consisting of cloth products, diapers, feminine napkins, and disposable bed liners.