Light-Activated Replication of Block Copolymer Fingerprint
Patterns
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Abstract
A strategy to replicate fingerprint
patterns formed by the self-assembly
of lamella-forming block copolymer (BCP) was investigated. To accomplish
this, liquid conformal layers were placed between the surfaces of
a “master” BCP film and a transparent “replica”
substrate that solidified and covalently bonded to the BCP upon exposure
to light. The benzophenone-containing conformal layer enabled pattern
replication over areas limited only by the size of the samples and
exposure field. The replication step is light activated, occurs below
the glass transition of the BCP, and takes less than 1 h. This demonstration
used a poly(styrene-<i>b</i>-methyl methacrylate) BCP with
a bulk domain periodicity of 42 nm, but it is possible that the chemistry
may be generalized to many other BCPs. Control experiments conducted
with alternative conformal layer compositions indicate that interfacial
photosensitization of the BCP by excited benzophenone, followed by
propagation to residual acrylate groups present in the conformal layer,
is the primary mechanism by which pattern replication takes place