Synthesis
of Well-Defined Polymer Structures:
One of the goals of synthetic chemists
is to acquire control over all degrees of structural
complexity. One phase of our research utilizes organometallic
catalysts to prepare well defined polymer structures.
Molecular topology is one of the most difficult degrees
of freedom to control. We are developing synthetic methodologies
for the preparation of macrocyclic polymers that will
utilize structured catalysts and incorporate the principle
of topological control. Extensions of this methodology
will lead to the preparation of macrocyclic catenanes
and polymers with knotted topologies. These molecule
will mimic topologies previously seen only in DNA.
We are also using these catalysts to
produce structured surfaces. Organometallic catalysts
are bound to a surface through an initiator group and
polymerization is initiated directly from the surface.
Current efforts involve the preparation of block copolymer
brushes on gold surfaces and nanoparticles. Functionalization
of the polymer endgroup and control of the helix sense
for liquid crystalline isocyanate polymers pave the
way for the preparation of a range of surfaces with
molecular recognition and biocompatibility as properties
we plan to control for a variety of applications in
the biomedical industry.
Polymer Dynamics and Macromolecular
Associations:
Our second research thrust involves
physical studies of the structure and dynamics of polymer
molecules in solution and on surfaces. We are particularly
interested in how these are modified by specific, strong
interactions between molecules. We apply techniques
of static and dynamic light scattering, fluorescence
recovery after photobleaching and transient electric
birefringence to solutions of polymers with interacting
pendant groups. These interactions result from a range
of forces that include hydrogen bonds, electrostatic
repulsions, Van der Waals attractions and hydrophobic
effects.
The polymer systems of interest include:
interacting protein fragments that have been implicated
in the pathogenesis of Alzheimer's disease; model solutions
of polystyrene sulfonate in solvents of extremely high
dielectric constant; conducting polymers that aggregate
in solution hampering their processibility; and a respiratory
enzyme associating with its cofactor during turnover.
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