Zwitterionic copolymers for fouling resistant filtration membranes
A graft copolymer including zwitterionic repeat units and hydrophobic repeat units, in which the zwitterionic repeat units constitute 2-60 wt % of the graft copolymer and each of the hydrophobic repeat units is characterized in that a homopolymer formed thereof is miscible with polyvinylidene fluoride, polysulfone, poly ether sulfone, polyvinyl chloride, or polyacrylonitrile, each of the hydrophobic repeat units not being a repeat unit of polyvinylidene fluoride. Also disclosed is a filtration membrane containing such a graft copolymer or a statistical copolymer that includes the same composition of repeat units as the graft copolymer. Further disclosed are methods of preparing the graft copolymer and the filtration membrane.
1. A graft copolymer, comprising:
a hydrophobic backbone, comprising a plurality of hydrophobic repeat units and a plurality of zwitterionic repeat units, wherein the number of hydrophobic repeat units is greater than the number of zwitterionic repeat units; and
a plurality of 2-50 repeat side chains, comprising hydrophobic repeat units and zwitterionic repeat units, wherein each side chain comprises more zwitterionic repeat units than hydrophobic repeat units;
wherein
the zwitterionic repeat units constitute 2-60% by weight of the graft copolymer;
each of the hydrophobic repeat units, independently, is [—O-Ph-C(CH 3 ) 2 -Ph-O-Ph-SO 2 -Ph-], [-Ph-SO 2 Ph-O-Ph-Ph-O—], [-Ph-SO 2 -Ph-O-Ph-SO 2 -Ph-O—], [-Ph-SO 2 -Ph-O-Ph-O—], or a repeat unit formed from methyl methacrylate, N,N-dimethyl acrylamide, ethyl methacrylate, acetonyl methacrylate, trifluoroethyl methacrylate, acrylonitrile, vinyl pyridine, vinyl chloride, styrene, cyclohexyl methacrylate, or propyl acrylate;
the hydrophobic repeat units are capable of forming a homopolymer that is miscible with polyvinylidene fluoride, polysulfone, poly ether sulfone, polyvinyl chloride, or polyacrylonitrile; and
each of the hydrophobic repeat units being different from a repeat unit formed from vinylidene fluoride.
2. The graft copolymer of claim 1 , wherein
the zwitterionic repeat units each comprise independently sulfobetaine, carboxybetaine, phosphorylcholine, or pyridinium alkyl sulfonate; and
each of the hydrophobic repeat units, independently, is formed from methyl methacrylate, N,N-dimethyl acrylamide, ethyl methacrylate, acetonyl methacrylate, trifluoroethyl methacrylate, acrylonitrile, vinyl pyridine, vinyl chloride, styrene, cyclohexyl methacrylate, or propyl acrylate.
3. The graft copolymer of claim 2 , wherein the zwitterionic repeat units constitute 5-45% by weight of the graft copolymer and the graft copolymer has a molecular weight of 10,000 to 3,000,000 Dalton.
4. The graft copolymer of claim 3 , wherein the zwitterionic repeat units constitute 10-30% by weight of the graft copolymer and the graft copolymer has a molecular weight of 30,000 to 1,000,000 Dalton.
5. The graft copolymer of claim 2 , wherein the zwitterionic repeat units are each formed independently from sulfobetaine methacrylate, sulfobetaine-2-vinyl pyridine, sulfobetaine-4-vinyl pyridine, phosphorylcholine methacrylate, carboxybetaine methacrylate, or sulfobetaine acrylamide; and the hydrophobic repeat units are each formed from methyl methacrylate.
6. The graft copolymer of claim 5 , wherein the zwitterionic repeat units constitute 5-45% by weight of the graft copolymer and the graft copolymer has a molecular weight of 10,000 to 3,000,000 Dalton.
7. The graft copolymer of claim 2 , wherein the zwitterionic repeat units are each formed independently from sulfobetaine methacrylate, sulfobetaine-2-vinyl pyridine, sulfobetaine-4-vinyl pyridine, phosphorylcholine methacrylate, carboxybetaine methacrylate, or sulfobetaine acrylamide.
8. The graft copolymer of claim 7 , wherein the zwitterionic repeat units are each formed from sulfobetaine methacrylate.
9. The graft copolymer of claim 8 , wherein the hydrophobic repeat units are each formed from methyl methacrylate.
10. The graft copolymer of claim 7 , wherein the zwitterionic repeat units are each formed from sulfobetaine-2-vinyl pyridine.
11. The graft copolymer of claim 10 , wherein the hydrophobic repeat units are each formed from methyl methacrylate.
12. The graft copolymer of claim 7 , wherein the zwitterionic repeat units are each formed from sulfobetaine-4-vinyl pyridine.
13. The graft copolymer of claim 12 , wherein the hydrophobic repeat units are each formed from methyl methacrylate.
14. The graft copolymer of claim 7 , wherein the zwitterionic repeat units are each formed from phosphorylcholine methacrylate.
15. The graft copolymer of claim 14 , wherein the hydrophobic repeat units are each formed from methyl methacrylate.
16. The graft copolymer of claim 7 , wherein the zwitterionic repeat units are each formed from carboxybetaine methacrylate.
17. The graft copolymer of claim 16 , wherein the hydrophobic repeat units are each formed from methyl methacrylate.
18. The graft copolymer of claim 7 , wherein the zwitterionic repeat units are each formed from sulfobetaine acrylamide.
19. The graft copolymer of claim 18 , wherein the hydrophobic repeat units are each formed from methyl methacrylate.
20. The graft copolymer of claim 1 , wherein the zwitterionic repeat units constitute 5-45% by weight of the graft copolymer and the graft copolymer has a molecular weight of 10,000 to 3,000,000 Dalton.
21. The graft copolymer of claim 20 , wherein the zwitterionic repeat units constitute 10-30% by weight of the graft copolymer and the graft copolymer has a molecular weight of 30,000 to 1,000,000 Dalton.
22. A filtration membrane comprising:
a base polymer, and
a zwitterion-containing copolymer,
wherein
the base polymer is polyvinylidene fluoride, polysulfone, poly ether sulfone, polyvinyl chloride, or polyacrylonitrile;
the zwitterion-containing copolymer comprises zwitterionic repeat units and hydrophobic repeat units, in which the zwitterionic repeat units constitute 2-60% by weight of the copolymer and the hydrophobic repeat units are capable of forming a homopolymer that is miscible with the base polymer, each of the hydrophobic repeat units being different from a repeat unit of polyvinylidene fluoride; and
the zwitterion-containing copolymer is insoluble in water, wherein the zwitterion-containing copolymer is a graft copolymer including a hydrophobic backbone, comprising a plurality of hydrophobic repeat units and a plurality of zwitterionic repeat units, wherein the number of hydrophobic repeat units is greater than the number of zwitterionic repeat units, and a plurality of 2-50 repeat side chains, each of which comprises more zwitterionic repeat units than hydrophobic units; wherein
the zwitterionic repeat units constitute 2-60% by weight of the graft copolymer;
the zwitterionic repeat units each comprises independently sulfobetaine, carboxybetaine, phosphorylchloline, or pyridinium alkyl sulfonate;
each of the hydrophobic repeat units, independently, is [—O-Ph-C(CH 3 ) 2 -Ph-O-Ph-SO 2 -Ph-], [-Ph-SO 2 Ph-O-Ph-Ph-O—], [-Ph-SO 2 -Ph-O-Ph-SO 2 -Ph-O—], [-Ph-SO 2 -Ph-O-Ph-O—], or a repeat unit formed from methyl methacrylate, N,N-dimethyl acrylamide, ethyl methacrylate, acetonyl methacrylate, trifluoroethyl methacrylate, acrylonitrile, vinyl pyridine, vinyl chloride, styrene, cyclohexyl methacrylate, or propyl acrylate;
the hydrophobic repeat units are capable of forming a homopolymer that is miscible with polyvinylidene fluoride, polysulfone, poly ether sulfone, polyvinyl chloride, or polyacrylonitrile; and
each of the hydrophobic repeat units being different from a repeat unit formed from vinylidene fluoride.
23. The filtration membrane of claim 22 , wherein the membrane is an ultrafiltration membrane or a microfiltration membrane.
24. The filtration membrane of claim 22 , wherein each of the hydrophobic repeat units is different from a repeat unit of polyacrylonitrile; and the zwitterion-containing copolymer constitutes less than 50 wt % of a mixture of the base polymer and the zwitterion-containing copolymer.
25. The filtration membrane of claim 22 , wherein the zwitterionic repeat units are each formed independently from sulfobetaine methacrylate, sulfobetaine-2-vinyl pyridine, sulfobetaine-4-vinyl pyridine, phosphorylcholine methacrylate, carboxybetaine methacrylate, or sulfobetaine acrylamide; and each of the hydrophobic repeat units, independently, is formed from methyl methacrylate, N,N-dimethyl acrylamide, ethyl methacrylate, acetonyl methacrylate, trifluoroethyl methacrylate, acrylonitrile, vinyl pyridine, vinyl chloride, styrene, cyclohexyl methacrylate, or propyl acrylate.
26. The filtration membrane of claim 22 , wherein the zwitterionic repeat units constitute 5-45% by weight of the graft copolymer and the graft copolymer has a molecular weight of 10,000 to 3,000,000 Dalton.
27. The filtration membrane of claim 22 , wherein the membrane is a flat sheet membrane or a hollow fiber membrane.