Hollow fiber membranes with polydiorganosiloxane polyoxamide copolymer skin layer and methods of making and using the same

A method of making an asymmetric hollow fiber membrane comprising:

• providing a substrate resin and a skin layer resin,
• the substrate resin comprising at least one semi-crystalline thermoplastic polyolefin (co)polymer, and the skin layer resin comprising at least one polydiorganosiloxane polyoxamide copolymer comprising at least two repeat units of Formula I:
• wherein:
• each R1 is independently an alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo;
• each Y is independently an alkylene, aralkylene, or a combination thereof;
• G is a divalent residue equal to a diamine of formula R3HN-G-NHR3 minus the two —NHR3 groups;
• R3 is hydrogen or alkyl or R3 taken together with G and to the nitrogen to which they are both attached form a heterocyclic group;
• n is independently an integer of 1 to 1500;
• p is an integer of 1 to 10;
• and
• q is an integer of 1 or greater, wherein n, p and q are selected so that the polydiorganosiloxane block comprises at least 50 mass percent of the polydiorganosiloxane polyoxamide copolymer;
• co-extruding the substrate resin and the skin layer resin to form an asymmetric hollow fiber membrane precursor;
• and
• stretching the asymmetric hollow fiber membrane precursor to form the asymmetric hollow fiber membrane comprising a barrier layer surrounding an internal lumen, wherein the barrier layer comprises a nonporous skin layer comprised of the skin layer resin overlaying a porous substrate comprised of the substrate resin, wherein the porous substrate comprises a plurality of pores.