Insights into Design of Biomimetic Glycerol-Grafted Polyol-Based Polymers for Ice Nucleation/Recrystallization Inhibition and Thermal Hysteresis Activity.

Many species living in colder regions of the world have adapted to the extreme climate by producing antifreeze (glycol) proteins (AF(G)P) which exhibit ice recrystallization inhibition (IRI), thermal hysteresis activity (THA), as well as other interactions with the freezing process of water. Although several synthetic approaches for the exploitation of these proteins have been investigated, challenges remain in the synthetic design of biomimetic polymers. Similar to biological antifreezes, poly(vinyl alcohol) (PVA) has potent IRI activity; however, by comparison, PVA has very little THA. In this study, we explored structural variations to polyol-based polymers to contrast with PVA as a control and identified several key structural elements for performance in IRI, THA, as well as in ice nucleation inhibition (INI). These structural features are bioinspired by the typical ice-binding plane of AFPs yet are surprisingly simple to produce with potency approaching that of typical AFPs. Key to the performance is positioning small organic functionalities with known antifreeze properties (such as ethylene glycol) pendent to a host polymer chain with consideration of their conformational freedom. To build systematic variations into both the backbone and side-chain structures, we used poly(vinyl alcohol), poly(isopropenyl acetate), poly(acrylic acid), and poly(methacrylic acid) parent polymers for such pendent modifications. One structure in particular, glycerol-grafted-PVA (G-g-PVA), shows potency rivaling that of AFPs at similar micromolar concentration. The findings in this study help guide the rational design of synthetic antifreeze polymers useful for applications such as anti-icing coatings through to cryopreservation methods for organ transport and cell preservation.