1 research outputs found
Hydrolysis-Induced Morphology Evolution of Linear and Bottlebrush Block Copolymers in Thin Films with Acid Vapor or Photoacid Generators
The
self-assembly of high-χ low-N block
copolymers (BCPs) can give patterns with sub-10 nm full pitch, serving
as a promising alternative to photolithographic methods. In this work,
we synthesized poly(solketal methacrylate)-block-polystyrene
copolymers, PSM-b-PS, with various volume ratios
of the two blocks. After hydrolysis of the PSM block into poly(glycerol
monomethacrylate), PGM, the BCPs had both lamellar and cylindrical
microdomain morphologies in the bulk phase and in thin films. In addition
to our previously developed solid-state hydrolysis strategy involving
trifluoroacetic acid vapor, we developed a new photoinduced solid-state
hydrolysis using photoacid generators, PAGs, embedded within the polymer
films. After exposure to UV followed by a postexposure baking or solvent
vapor annealing, the BCPs transitioned from the disordered, phase-mixed
state into laterally ordered cylindrical patterns. In comparison to
linear BCPs that rely on a random copolymer layer to modify interfacial
interactions with the substrate to promote an orientation of the microdomains
normal to the interface, we found that the microdomains in bottlebrush
multiblock copolymers oriented normal to the interface absent substrate
modification due to the chain architecture