A method of forming a membrane comprising the steps of forming a film from a composition comprising a polyurethane component and a solvent, and evaporating the solvent thereby forming a membrane, wherein the composition comprises from 0.5 wt% to 10 wt% of the polyurethane component and from 90 to 99.5 wt% of the solvent, the polyurethane component comprising a blend of from 5 wt% to 95 wt%, based on the total weight of the polyurethane component, of an amphiphilic polyurethane, and from 5 wt% to 95 wt%, based on the total weight of the polyurethane component, of a hydrophobic polyurethane, wherein the amphiphilic polyurethane comprises a first amphiphilic polyurethane or a second amphiphilic polyurethane, and a. the first amphiphilic polyurethane comprises the reaction product of: i. an aliphatic diisocyanate; ii. a hydrophilic polymer diol; iii. a hydrophobic poly(alkylene oxide) diol; and iv. a chain extender; b. the second amphiphilic polyurethane comprises the reaction product of: i. an aliphatic diisocyanate; ii. a copolymer diol comprising a hydrophilic polymer and a hydrophobic poly(alkylene oxide); and iii. a chain extender; c. the hydrophobic polyurethane comprises the reaction product of: i. an aliphatic diisocyanate; ii. a hydrophobic poly(alkylene oxide) diol; and iii. a chain extender; wherein the amphiphilic polyurethane and the hydrophobic polyurethane are substantially devoid of siloxane moieties, wherein the solvent comprises tetrahydrofuran, methyl-tetrahydrofuran (methyl-THF), or a mixture thereof, and wherein the membrane has a residual solvent content of less than 50 ppm after drying the membrane in a convection oven at 50 °C for 16 hours after forming the membrane. wherein the composition comprises from 0.5 wt% to 10 wt% of the polyurethane component and from 90 to 99.5 wt% of the solvent, the polyurethane component comprising a blend of from 5 wt% to 95 wt%, based on the total weight of the polyurethane component, of an amphiphilic polyurethane, and from 5 wt% to 95 wt%, based on the total weight of the polyurethane component, of a hydrophobic polyurethane, wherein the amphiphilic polyurethane comprises a first amphiphilic polyurethane or a second amphiphilic polyurethane, and a. the first amphiphilic polyurethane comprises the reaction product of: i. an aliphatic diisocyanate; ii. a hydrophilic polymer diol; iii. a hydrophobic poly(alkylene oxide) diol; and iv. a chain extender; b. the second amphiphilic polyurethane comprises the reaction product of: i. an aliphatic diisocyanate; ii. a copolymer diol comprising a hydrophilic polymer and a hydrophobic poly(alkylene oxide); and iii. a chain extender; c. the hydrophobic polyurethane comprises the reaction product of: i. an aliphatic diisocyanate; ii. a hydrophobic poly(alkylene oxide) diol; and iii. a chain extender; a. the first amphiphilic polyurethane comprises the reaction product of: i. an aliphatic diisocyanate; ii. a hydrophilic polymer diol; iii. a hydrophobic poly(alkylene oxide) diol; and iv. a chain extender; i. an aliphatic diisocyanate; ii. a hydrophilic polymer diol; iii. a hydrophobic poly(alkylene oxide) diol; and iv. a chain extender; b. the second amphiphilic polyurethane comprises the reaction product of: i. an aliphatic diisocyanate; ii. a copolymer diol comprising a hydrophilic polymer and a hydrophobic poly(alkylene oxide); and iii. a chain extender; i. an aliphatic diisocyanate; ii. a copolymer diol comprising a hydrophilic polymer and a hydrophobic poly(alkylene oxide); and iii. a chain extender; c. the hydrophobic polyurethane comprises the reaction product of: i. an aliphatic diisocyanate; ii. a hydrophobic poly(alkylene oxide) diol; and iii. a chain extender; i. an aliphatic diisocyanate; ii. a hydrophobic poly(alkylene oxide) diol; and iii. a chain extender; wherein the amphiphilic polyurethane and the hydrophobic polyurethane are substantially devoid of siloxane moieties, wherein the solvent comprises tetrahydrofuran, methyl-tetrahydrofuran (methyl-THF), or a mixture thereof, and wherein the membrane has a residual solvent content of less than 50 ppm after drying the membrane in a convection oven at 50 °C for 16 hours after forming the membrane.