Porous layer for nonaqueous electrolyte secondary battery

A nonaqueous electrolyte secondary battery porous layer comprising:

• a block copolymer;
• and
• a filler,
• the block copolymer having:
• a block A containing, as a main component, units each represented by the following Formula (1):
• —(NH—Ar1—NHCO—Ar2—CO)— Formula (1);
• and
• a block B containing, as a main component, units each represented by the following Formula (2):
• —(NH—Ar3—NHCO—Ar4—CO)— Formula (2),
• wherein:
• Ar1, Ar2, Ar3, and Ar4 may each vary from unit to unit;
• Ar1, Ar2, Ar3, and Ar4 are each independently a divalent group having one or more aromatic rings;
• not less than 50% of all Ar1 each have a structure in which two aromatic rings are connected by a sulfonyl bond;
• not more than 50% of all Ar3 each have a structure in which two aromatic rings are connected by a sulfonyl bond;
• 30% to 70% of all Ar1 and Ar3 each have a structure in which two aromatic rings are connected by a sulfonyl bond.