Ice-binding proteins
(IBPs) from extremophile organisms can modulate
ice formation and growth. There are many (bio)technological applications
of IBPs, from cryopreservation to mitigating freeze–thaw damage
in concrete to frozen food texture modifiers. Extraction or expression
of IBPs can be challenging to scale up, and hence polymeric biomimetics
have emerged. It is, however, desirable to use biosourced monomers
and heteroatom-containing backbones in polymers forin vivoor environmental applications to allow degradation. Here we investigate
high molecular weight polyproline as an ice recrystallization inhibitor
(IRI). Low molecular weight polyproline is known to be a weak IRI.
Its activity is hypothesized to be due to the unique PPI helix it
adopts, but it has not been thoroughly investigated. Here an open-to-air
aqueousN-carboxyanhydride polymerization is employed
to obtain polyproline with molecular weights of up to 50000 g mol–1. These polymers were found to have IRI activity down
to 5 mg mL–1, unlike a control peptide of polysarcosine,
which did not inhibit all ice growth at up to 40 mg mL–1. The polyprolines exhibited lower critical solution temperature
behavior and assembly/aggregation observed at room temperature, which
may contribute to its activity. Single ice crystal assays with polyproline
led to faceting, consistent with specific ice-face binding. This work
shows that non-vinyl-based polymers can be designed to inhibit ice
recrystallization and may offer a more sustainable or environmentally
acceptable, while synthetically scalable, route to large-scale applications.