Singlet Oxygen Responsive Small Molecules and Polymers.
Abstract: Abstract Conjugated polymers are widely used in applications for
developing sensory materials. The binding of a single analyte to one of the receptors in
conjugated polymer results in an amplified response due to the migration of the exciton on
the polymer chain. This amplification of the signal makes the conjugated polymers more
advantageous relative to small molecule sensors. This ... read morethesis describes the use of
conjugated polymers as well as non-conjugated polymers, mimicking the light harvesting
behavior of conjugated polymers, that response to photogenerated singlet oxygen in both
organic solvent and aqueous environment. Chapter 2 describes conjugated
poly(fluorene-co-phenylene)s (PFs) with 2,5-diarylfuran moieties as nonconjugated pendants
that respond to singlet oxygen by fluorescence quenching. By oxidizing the diarylfurans to
more electron-poor moieties, singlet oxygen causes poly(fluorene-co-phenylene) conjugated
backbones to donate excited electrons to the oxidized pendants, resulting in quenching of
up to 93% of the initial fluorescence of the polymer. Chapter 3 describes two-dimensional
conjugated poly(phenylene-ethynylene)s (PPEs) linked to singlet oxygen-reactive
diethynyltetracene units through phenylene-ethynylene (PE) bridges. Small molecule models
of the polymers showed ratiometric responses of fluorescence upon exposure to singlet
oxygen. The fluorescent responses of the tetracene-linked PPEs, however, were remarkably
different: i) upon exposure to singlet oxygen, fluorescence intensity and fluorescence
lifetime of the side-chain tetracenes was increased initially, indicating an
analyte-induced slowing of self-quenching due to high local acene concentration, and ii)
ratiometric blue-shifted response did not occur until approximately 75% of pendant acenes
were oxidized, which highlights the potential utility of analyte-induced removal of traps
in light-harvesting fluorescent materials. Chapter 4 describes the design of a system that
respond singlet oxygen in water for potential use in bioanalytical applications such as
protein sensing. The designed system mimics the light harvesting behavior of CPs, but is
prepared with an acrylic polymer formulation that is easier to make water-soluble. The
signal transduction mechanism uses 1O2 to communicate the presence of dye-labeled protein
to the responsive non-conjugated polymer and prevents proteins from directly interacting
with the polymer.
Thesis (Ph.D.)--Tufts University, 2015.
Submitted to the Dept. of Chemistry.
Advisor: Samuel Thomas III.
Committee: Clay Bennett, Arthur Utz, and Shawn Burdette.
Keywords: Chemistry, Organic chemistry, and Polymer chemistry.read less