Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada.
Department of Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, British Columbia V6T 1Z3, Canada.
ACS Appl Mater Interfaces. 2023 Feb 15;15(6):8406-8414. doi: 10.1021/acsami.2c21870. Epub 2023 Jan 31.
Gels are useful materials for drug delivery, wound dressings, tissue engineering, and 3D printing. These various applications require gels with different mechanical properties that can be easily tuned, also preferably excluding the use of chemical additives, which can be toxic or harmful to the body or environment. Here, we report a novel strategy to synthesize cellulose nanocrystal (CNC) gels with tunable mechanical properties. Sequential freeze-thaw cycling and hydrothermal treatments were applied to CNC suspensions in different orders to give a series of pristine CNC hydrogels. Freeze-drying of the hydrogels also afforded a series of lightweight CNC aerogels. The mechanical properties of the hydrogels and aerogels were studied by rheological measurements and compression strength tests, respectively. Specifically, the complex modulus of CNC hydrogels ranged from 160 to 32,000 Pa among eight different hydrogels, while Young's modulus of CNC aerogels was tuned from 0.114 to 3.98 MPa across five different aerogels. The microstructures of aerogels were also investigated by scanning electron microscopy and X-ray microtomography, which revealed remarkable differences between the materials. Solvent sorption-desorption tests showed that the reinforced networks have excellent stability over the basic CNC aerogels in ethanol, demonstrating a material enhancement from the preparation strategies we developed. Thermal conductivity and thermal stability for these materials were also investigated, and it was found that the lowest thermal conductivity was 0.030 W/m K, and all of the aerogels are generally stable below 280 °C. These characteristics also expand the potential applications of this family of CNC gels to lightweight supporting materials and thermal insulators.
凝胶是药物输送、伤口敷料、组织工程和 3D 打印等领域的有用材料。这些不同的应用需要具有不同机械性能的凝胶，这些性能可以很容易地进行调整，并且最好不使用化学添加剂，因为这些添加剂可能对身体或环境有毒或有害。在这里，我们报告了一种合成具有可调机械性能的纤维素纳米晶体（CNC）凝胶的新策略。顺序冷冻-解冻循环和水热处理被应用于不同顺序的 CNC 悬浮液中，以获得一系列原始的 CNC 水凝胶。水凝胶的冷冻干燥也得到了一系列的轻量级 CNC 气凝胶。通过流变学测量和压缩强度测试分别研究了水凝胶和气凝胶的机械性能。具体而言，在八种不同的水凝胶中，CNC 水凝胶的复模量范围为 160 至 32,000 Pa，而 CNC 气凝胶的杨氏模量在五种不同的气凝胶中从 0.114 至 3.98 MPa 可调。气凝胶的微观结构也通过扫描电子显微镜和 X 射线微断层扫描进行了研究，结果表明这些材料之间存在显著差异。溶剂吸附-解吸测试表明，在乙醇中，增强网络相对于基本的 CNC 气凝胶具有优异的稳定性，证明了我们开发的制备策略带来了材料增强。还研究了这些材料的热导率和热稳定性，发现最低热导率为 0.030 W/m K，所有气凝胶在 280°C 以下通常都是稳定的。这些特性还将这种 CNC 凝胶家族的潜在应用扩展到了轻质支撑材料和热绝缘体。
