A method of producing microporous membranes includes stretching a multi-layer layer extrudate having first and second layers, the first layer including a first polyolefin and a first diluent, and the second layer including a second polyolefin and a second diluent, the second polyolefin including polypropylene in an amount of 1.0 wt. % to 40.0 wt. %, the polypropylene having an Mw>0.9×106 and a ΔHm≧100.0 J/g; removing at least a portion of the diluents to produce a dried membrane having a first length and a first width; stretching the membrane by a first magnification factor of 1.1 to 1.5 and stretching the membrane by a second magnification factor of 1.1 to 1.3; and reducing the width.