The synthesis of a foldable viologen-functionalized peptide–polymer conjugate is presented.
The ABA-type triblock conjugate with a PEG polymer was capped with a FHFHF pentapeptide
sequence and further modified with a viologen building block at both chain ends. The
pH-responsive peptide domains fold into an intermediate structure inducing close proximity
of the viologen units, which upon a reduction step form π-dimers of the radical cation.
Overall the intramolecular folding and intermolecular self-assembly process leads
to the formation of supramolecular nanorods. Mixing of viologen-peptide–polymer conjugates
with unfunctionalized conjugates leads to crosslinking of the nanorods and hydrogels
with a tunable content of viologen end groups. π-Dimerization in the gels induces
a deep purple color, which is used as an optical probe to monitor the diffusion of
molecular oxygen through the hydrogel matrix.
Key words
supramolecular materials - stimuli-responsive polymers - electrochromism - peptide
conjugation - hydrogel