A fiber tow and methods for separating a fiber tow are disclosed. The fiber tow may include adjacent filaments and a polymer coating covering at least a portion of the adjacent filaments. The polymer coating may include a polymer that is configured to contract in a direction generally parallel to the adjacent filaments and expand in a direction generally perpendicular to the adjacent filaments. The polymer coating may contract/expand in response to an energy source, such as heat or a UV light source. The methods may include coating at least a portion of a plurality of filaments with a polymer, bundling the filaments into a fiber tow, and exposing the fiber tow to an energy source to contract the polymer in a direction generally parallel to the filaments and to expand the polymer in a direction generally perpendicular to the filaments. The filaments may be carbon fiber filaments.