Inimer-containing random copolymers and crosslinked copolymer films for dense polymer brush growth

A method of forming a self-assembled block copolymer film using a crosslinked copolymer film on a substrate surface, the crosslinked copolymer film comprising crosslinked random copolymer chains, wherein the random copolymer is a copolymer of a first monomer comprising an alkyl halide functional group that is capable of acting as an ATRP initiator, and a second monomer, and further wherein the alkyl halide functional groups are pendant groups on the backbone of the random copolymer chains and the crosslinks between the random copolymer chains are formed between crosslinkable functional groups on the second monomers, the method comprising:

• patterning the crosslinked copolymer film to provide a plurality of regions comprising the alkyl halide functional groups that are capable of acting as ATRP initiators and a plurality of regions that do not have ATRP initiating functional groups;
• exposing the crosslinked copolymer film to a solution comprising polymerizable monomers and a transition metal complex under reaction conditions in which the alkyl halide functional groups initiate the polymerization of the polymerizable monomers into a polymer brush via atom transfer radical polymerization to provide a patterned polymer brush layer;
• and
• depositing a block copolymer film over the patterned polymer brush layer, wherein the patterned polymer brush layer induces the block copolymer to self-assemble into patterned domains;
• wherein the first monomer is selected from acrylate monomers having an alkyl halide functional group, methacrylate monomers having an alkyl halide functional group, styrene monomers having an alkyl halide functional group, or combinations thereof, and
• wherein the crosslinked copolymer film has a halogen atom density of at least 1.5 atoms/nm3.