Nanostructured article and method of making the same

A method of making nanostructured polymeric film comprising:

• providing a tool having a porous anodized aluminum surface or a metallic replica thereof, wherein the average depth of the pores is in a range of from about 0.1 micrometer to about 5 micrometers and the average pore width is in a range of from about 10 to about 500 nanometers;
• forming a continuous layer of thermoplastic polymer on at least a portion of the surface of the tool such that the continuous layer extends into the pores of the porous surface, wherein the thermoplastic polymer is selected from cellulose esters, poly alpha-olefins, and combinations thereof;
• and
• separating the continuous layer from the tool as a film having first and second opposed major surfaces with nanofibrils formed on the first major surface, wherein during formation of the nanofibrils they extend from the first major surface to the porous surface and are stretched in length until they finally are released from the porous surface, the nanofibrils having an average width of from 5 to 200 nm and an aspect ratio of at least 10, wherein the nanofibrils are bonded to one another at points where they contact each other, and arc generally disposed parallel to the first surface of the film, and wherein the continuous layer comprises a fluorocarbon melt additive.