A method of forming a patterned chemical epitaxy template, for orientation of a self-assemblable block copolymer including first and second polymer blocks, on a surface of a substrate, the method including applying a primer layer of a primer composition to the surface, the primer composition including a first polymer moiety having a chemical affinity with the first polymer blocks and a second polymer moiety having a chemical affinity with the second polymer blocks, selectively exposing the surface, the primer layer and any overlying layer to actinic radiation to provide exposed and unexposed regions, to render labile the first polymer moiety in the exposed region, and removing the labile first polymer moiety from the exposed region to deplete the primer layer surface in the exposed region of first polymer moiety to form the patterned chemical epitaxy template.