Brief Description of Project:
Major advances in the synthesis of polymers have yielded
unprecedented control over macromolecular composition, molecular
weight, and polydispersity to enable the preparation of
extremely well-defined polymeric materials. The combination of
these highly controlled methods of polymerization with the
self-assembly of molecules at surfaces has the potential to
provide uniquely “thick” molecular coatings that present a dense
sheet of surface functionality, exhibit unprecedented
stabilities, enable Angstrom-level control over film thickness,
and possess useful side functionalities for target
applications. In this summer project, we will synthesize and
assemble new classes of thiol adsorbates that bridge the
thickness gap between self-assembled monolayers (SAMs) (< 3 nm)
and successful polymer films (> 10 nm). These adsorbates
consist of straight-chained molecules as well as adsorbates with
controlled extents of functional side groups. The adsorbates
will be prepared by the innovative polymerization known as
polyhomologation, in which end-functionalized homopolymers and
copolymers can be synthesized at extremely low polydispersity
through insertion and addition of each repeat unit. The degree
of polymerization will be controlled to achieve adsorbates with
maximal thicknesses that should span the range between 3 and 10
nm. The average number of side groups per chain will also be
controlled based on the ratio of monomers. Assembly of these
precisely crafted adsorbates onto metal surfaces should yield
thick, densely packed monolayer films that have potential
applications as nanoscale capacitors, electron-tunneling
barriers, corrosion-resistant coatings, ultra-low friction
surfaces, and highly blocking, bioinert interfaces. Since the
stability and barrier properties of SAMs generally scale with
the chain length of the alkyl tether, the proposed adsorbates
should yield a step change in improved stability and in
protection of the underlying substrate.
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