Graft copolymers of dextran and polyacrylamide and methods of making and using same

A graft copolymer comprising:

• dextran, wherein the dextran is a backbone polymer comprising about 70 wt % to about 82 wt % of the graft copolymer, based on the total weight of the graft copolymer;
• and
• polyacrylamide, wherein the polyacrylamide is a side chain polymer comprising about 18 wt % to about 30 wt % of the graft copolymer, based on the total weight of the graft copolymer, wherein the graft copolymer has a weight-average molecular weight from about 1,000,000 g/mol to about 1,500,000 g/mol.

A graft copolymer comprising:

• dextran, wherein the dextran is a backbone polymer comprises about 15 wt % to about 25 wt % of the graft copolymer, based on the total weight of the graft copolymer;
• and
• polyacrylamide, wherein the polyacrylamide is a side chain polymer comprises about 75 wt % to about 85 wt % of the graft copolymer, based on the total weight of the graft copolymer, wherein the graft copolymer has a weight-average molecular weight from about 1,000,000 g/mol to about 1,500,000 g/mol.