A method of forming a pattern comprises diffusing an acid, generated by irradiating a portion of a photosensitive layer, into an underlayer comprising an acid sensitive copolymer comprising an acid decomposable group and an attachment group, to form an interpolymer crosslink and/or covalently bonded to the surface of the substrate. Diffusing comprises heating the underlayer and photosensitive layer. The acid sensitive group reacts with the diffused acid to form a polar region at the surface, in the shape of the pattern. The photosensitive layer is removed to forming a self-assembling layer comprising a block copolymer having a block with an affinity for the polar region, and a block having less affinity than the first. The first block forms a domain aligned to the polar region, and the second block forms a domain aligned to the first. Removing either the first or second domain exposes a portion of the underlayer.