Synthesis of Poly(tartar amides) as Bio‐Inspired Antifreeze Additives

Abstract

Summary: Multifunctional poly(tartar amides) have been synthesized and used as bio‐inspired antifreeze additives. It is shown that these polymers strongly interfere with the crystallization process of water in comparison to commercially available commodity polymers. While the addition of the poly(tartar amides) results in minor freezing point depression, as is shown by differential scanning calorimetry, a strong change in the ice crystal morphology is evident. Wide‐angle X‐ray scattering and optical microscopy indicate that the hexagonal structure of undisturbed ice‐crystals is oriented and partly deformed.Light microscopy image of ice crystals at 223 K after a freezing assay with poly(tartar amides) shown at a polymer concentration of 2 wt.‐%.imageLight microscopy image of ice crystals at 223 K after a freezing assay with poly(tartar amides) shown at a polymer concentration of 2 wt.‐%.

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“…Although this observation was deduced to signal a change in ice crystal morphology, it may also reflect preferred orientations of the ice crystals such that the (002) planes are not parallel to the sample stage. In a related investigation, the (002) peak was absent for ice crystals grown in the presence of a poly(tartar amide) with glycol side chains, and the (101) intensity was substantially reduced (27). This study also revealed that the (002) reflection was negligible when ice crystals were grown in the presence of poly(ethylene glycol), specifically PEG-6 (average M n = 5,900).…”

“…This study also revealed that the (002) reflection was negligible when ice crystals were grown in the presence of poly(ethylene glycol), specifically PEG-6 (average M n = 5,900). This study was attributed to an earlier postulate that macromolecules can block the c-directional growth of ice crystals (51), producing ice nanoplatelets interleaved with polymers such that the diffraction intensity would be diminished (27). Whereas ) at −1.0 ± 0.1°C.…”

“…Other research groups have investigated the effect of macromolecular additives on ice crystal properties using powder X-ray diffraction (XRD) (26,27) of frozen macromolecule-ice mixtures. For example, some broadening of the (100) and (101) diffraction peaks for hexagonal ice formed in the presence of a poly(ethylene oxide)-polyethyleneimine block copolymer with polyglycidol side chains was surmised to be evidence of smaller crystals compared with ice crystals formed in the absence of this macromolecule (26).…”

“…Noncolligative antifreeze activity has been reported for a limited number of synthetic molecules, including oligopeptides (22)(23)(24)(25) and bulk polymers (26)(27)(28). Synthetic oligomers that can mimic the structures and functions of natural polypeptides (29) present an opportunity for the exploration of antifreeze activity paralleling that observed in natural systems.…”

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“…It is also shown that hyper-branched polyglycidol influences of the crystallization kinetics of ice (slowing down) and leads to changes in the ice crystal morphology. Recently Yagci et al 177 showed that multifunctional poly (tartar amides) polymers can strongly interfere with the crystallization process of water in comparison with commercially available commodity polymers. While the addition of the poly(tartar amides) results in a minor freezing point depression, as is shown by differential scanning calorimetry, a strong change in the ice crystal morphology is evident.…”