高轴比纳米几丁质<i>通过</i>冰模板用于超强和可恢复形状的水凝胶和冰晶,ACS Nano

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高轴比纳米几丁质通过冰模板用于超强和可恢复形状的水凝胶和冰晶
ACS Nano ( IF 15.8 ) Pub Date : 2019-01-28 00:00:00 , DOI: 10.1021/acsnano.8b07235
Liang Liu ₁ , Long Bai , Anurodh Tripathi , Juan Yu ₁ , Zhiguo Wang ₁ , Maryam Borghei , Yimin Fan ₁ , Orlando J. Rojas

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在部分脱乙酰化和微流化之后，提出了从未干燥的残留海洋生物质的高产率（> 85％）和低能解构的方法。此过程导致了几丁质纳米纤维（纳米壳素，NCh）具有超高的轴向尺寸（长宽比高达500），是生物衍生纳米材料中最大的一种。纳米几丁质在水中胶体稳定（ζ电位= +95 mV），并在pH值变化时产生高度纠缠的网络。粘弹性和坚固的水凝胶是通过在冷冻和解冻时同时进行交联的冰进行模板化而形成的。缓慢的过冷和-20°C的冰核作用使冰晶缓慢生长，并排除了纳米几丁质和交联剂，使其空间受限于界面。纳米甲壳素的浓度低至0.4 wt％时，会形成高粘弹性水凝胶，其储能模量约为16 kPa，与迄今为止报道的最强的几丁质衍生水凝胶相比，至少大一个数量级。此外，水凝胶的吸水量达到466 gg^–1。冻干可有效生产密度可在0.89至10.83 mg·cm ^–3的宽范围内定制的冷冻凝胶，相应的孔隙率在99.24和99.94％之间。氮吸附结果表明大孔结构可逆的吸附和解吸循环。压缩应力-应变磁滞回线记录了快速的形状恢复。经过80％的压缩应变后，冷冻凝胶在释放负荷后快速，完全恢复。几丁质和纳米纤维素冷冻凝胶都没有达到这些和其他物理性能的极限值。它们被解释为（a）原纤维的超高轴向比率和强共价相互作用的结果；（b）避免在加工之前和加工过程中干燥，这是生物基材料纳米制造中一个微妙但关键的方面；（c）冰模板，使水凝胶和冰凝胶适合于先进的生物基材料。

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

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.

更新日期：2019-01-28

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