CMDITR Review of Undergraduate Research - Pluto - University of ...

Alternating Polymerization of EZ-FTC and Bis-(3,5)-
dibenzyloxybenzyl Alcohol to Improve Site Isolation of NLO
Material
Cyrus Anderson, University of Washington
Yi Liao, Bruce Robinson, and Larry Dalton
Dalton Lab, Dept. of Chemistry, University of Washington
Objective/Thesis
Foremost among research being conducted
in the Dalton group is investigation into the
synthesis of novel organic nonlinear optical
(NLO) material for use in electro-optic devices.
The anticipated superior bandwidth, low drive
voltages and decreased manufacture costs of
electro-optic (EO) devices utilizing novel
organic NLO material relative to those using
conventional material lend the new devices to
exclusive use in a broad range of new
applications in several major industries including
military and telecommunication. 1 The realization
of suitable organic NLO material for use in
communication devices is by no means a simple
task as material must have unique properties at
both the microscopic and macroscopic level.
Microscopic properties required for organic NLO
material include high first order
hyperpolarizability (β), noncentrosymmetric
structure, and an absorption spectrum which
does not overlap communication wavelengths.
Requirements on the macroscopic level include a
noncentrosymmetric spatial arrangement of
charge transfer chromophores present in organic
NLO material, or bulk order, as well as excellent
photo, thermal, and thermodynamic stability,
while also being soluble in common solvents
allowing simple processing. 1, 2
Bulk order is induced in an organic NLO
material by means of heating the material above
its glass transition temperature (T g ) and applying
an electric field to align the large dipole
moments of chromophores in the material. 2
Presently, material performance is primarily
limited by the amount of bulk order induced by
the electric field; chief among the limiting
factors are intermolecular interactions. 1 Two
closely related methods of reducing
intermolecular interactions are thought possible:
synthesizing “spherical” chromophores by
adding bulky dendrimer groups which limit the
closest approach of nearby chromophores, 1 and
application of site isolation principles 3 to
encapsulate chromophores from environmental
interaction. 4
Figure 1. An alternating chromophoredendrimer
polymer system.
Chromophores are represented by ovals
and dendrimers by triangles.
Research Methods
Several approaches to improving this site
isolation have been previously explored, for
example, adding bulky groups to chromophores
doped in a polymer and random grafting of
chromophores and dendrimers to a polymer. 5 An
alternative method is investigated here by
synthesizing an alternating chromophoredendrimer
copolymer (Figure 1) which can be
spin - coated without being doped in a host
polymer. In the above arrangement dendrimer
units provide a means to control the distance one
chromophore is allowed to approach another
chromophore. If the dendrimer is large enough,
the distance between chromophores will be such
as to render intermolecular interactions between
chromophores sufficiently weak thereby
decreasing resistance to chromophore
rearrangement under an applied poling field. An
additional aim of this method is to synthesize a
copolymer which achieves the maximum
theoretical loading density of the active
chromophore. Materials containing the
maximum amount of chromophore 6 have the
potential to exhibit improved EO properties as
both quantities are directly related. The
combined effects of higher loading density and
site “isolated” chromophores are anticipated to
improve the bulk order generated by the poling
field and thus improve the EO property of the
material.
12 CMDITR Review of Undergraduate Research Vol. 1 No. 1 Summer 2004