Poly(ferulic acid-<i>co</i>-tyrosine): Effect
of the Regiochemistry on the Photophysical and Physical Properties
en Route to Biomedical Applications
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Abstract
The photophysical and mechanical
properties of novel poly(carbonate-amide)s
derived from two biorenewable resources, ferulic acid (FA) and l-tyrosine ethyl ester, were evaluated in detail. From these
two bio-based precursors, a series of four monomers were generated
(having amide and/or carbonate coupling units with remaining functionalities
to allow for carbonate formation) and transformed to a series of four
poly(carbonate-amide)s. The simplest monomer, which was biphenolic
and was obtained in a single amidation synthetic step, displayed bright,
visible fluorescence that was twice brighter than FA. Multidimensional
fluorescence spectroscopy of the polymers in solution highlighted
the strong influence that regioselectivity and the degree of polymerization
have on their photophysical properties. The regiochemistry of the
system had little effect on the wettability, surface free energy,
and Young’s modulus (ca. 2.5 GPa) in the solid state. Confocal
imaging of solvent-cast films of each polymer revealed microscopically
flat surfaces with fluorescent emission deep into the visible region.
Fortuitously, one of the two regiorandom polymers (obtainable from
the biphenolic monomer in only an overall two synthetic steps from
FA and l-tyrosine ethyl ester) displayed the most promising
fluorescent properties both in the solid state and in solution, allowing
for the possibility of translating this system as a self-reporting
or imaging agent in future applications. To further evaluate the potential
of this polymer as a biodegradable material, hydrolytic degradation
studies at different pH values and temperatures were investigated.
Additionally, the antioxidant properties of the degradation products
of this polymer were compared with its biphenolic monomer and FA