High Axial Ratio Nanochitins for Ultrastrong and Shape-Recoverable Hydrogels and Cryogels via Ice Templating

Liang Liu, Long Bai, Anurodh Tripathi, Juan Yu, Zhiguo Wang, Maryam Borghei, Yimin Fan*, Orlando J. Rojas

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

18 Citations (Scopus)
216 Downloads (Pure)


High yield (>85%) and low-energy deconstruction of never-dried residual marine biomass is proposed following partial deacetylation and microfluidization. This process results in chitin nanofibrils (nanochitin, NCh) of ultrahigh axial size (aspect ratios of up to 500), one of the largest for bioderived nanomaterials. The nanochitins are colloidally stable in water (ζ-potential = +95 mV) and produce highly entangled networks upon pH shift. Viscoelastic and strong hydrogels are formed by ice templating upon freezing and thawing with simultaneous cross-linking. Slow supercooling and ice nucleation at -20 °C make ice crystals grow slowly and exclude nanochitin and cross-linkers, becoming spatially confined at the interface. At a nanochitin concentration as low as 0.4 wt %, highly viscoelastic hydrogels are formed, with a storage modulus of ∼16 kPa, at least an order of magnitude larger compared to those measured for the strongest chitin-derived hydrogels reported so far. Moreover, the water absorption capacity of the hydrogels reaches a value of 466 g g -1 . Lyophilization is effective in producing cryogels with a density that can be tailored in a wide range of values, from 0.89 to 10.83 mg·cm -3 , and corresponding porosity, between 99.24 and 99.94%. Nitrogen adsorption results indicate reversible adsorption and desorption cycles of macroporous structures. A fast shape recovery is registered from compressive stress-strain hysteresis loops. After 80% compressive strain, the cryogels recovered fast and completely upon load release. The extreme values in these and other physical properties have not been achieved before for neither chitin nor nanocellulosic cryogels. They are explained to be the result of (a) the ultrahigh axial ratio of the fibrils and strong covalent interactions; (b) the avoidance of drying before and during processing, a subtle but critical aspect in nanomanufacturing with biobased materials; and (c) ice templating, which makes the hydrogels and cryogels suitable for advanced biobased materials.

Original languageEnglish
Pages (from-to)2927-2935
Number of pages9
JournalACS Nano
Issue number3
Publication statusPublished - 26 Mar 2019
MoE publication typeA1 Journal article-refereed


  • chemical cross-linking
  • cryogels
  • hydrogels
  • ice templating
  • nanochitin
  • shape recovery
  • ultrahigh axial size

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