State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou, 510070, China; Department of Biological System Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
Department of Biological System Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
Carbohydr Polym. 2018 Nov 15;200:115-121. doi: 10.1016/j.carbpol.2018.07.062. Epub 2018 Jul 19.
The use of chitosan natural polymers to replace synthetic polymers is of interest as part of the green materials movement. However, a major challenge of using chitosan material is its rigid and brittle nature associated primarily with its intra- and inter-molecular hydrogen bonds creating a hydrogen bond network. Plasticizers are able to make chitosan flexible, hypothetically by destroying its hydrogen bond networks. Herein, we showed the importance and complicated nature of the chitosan's hydrogen bond network with respect to its flexibility, through a comparative study of glycerol and ionic liquids plasticizers. The results demonstrated that glycerol's hydrogen bonding was able to disrupt the chitosan's hydrogen bond network resulting in a flexible film, but ionic liquids, even with their very strong hydrogen bonding, were not able to plasticize chitosan. This result suggested that the plasticization phenomenon was more complicated than hydrogen bond disruption. A molecular level study by quantum chemistry calculation showed that the efficiency of glycerol as chitosan plasticizer was due to its single hydrogen bonding site, which breaks down the chitosan hydrogen bonding networks, and leave hydrophobic C-H ending groups to limit the formation of inter molecular hydrogen bonds.
将壳聚糖等天然聚合物替代合成聚合物，是绿色材料运动的一个关注点。然而，使用壳聚糖材料的一个主要挑战是其刚性和脆性，这主要与其分子内和分子间氢键有关，形成氢键网络。增塑剂能够使壳聚糖具有柔韧性，这是通过破坏其氢键网络来实现的。在本文中，我们通过对比甘油和离子液体增塑剂，展示了壳聚糖氢键网络对其柔韧性的重要性和复杂性。结果表明，甘油的氢键能够破坏壳聚糖的氢键网络，从而形成柔性薄膜，但离子液体即使具有很强的氢键，也不能增塑壳聚糖。这一结果表明，增塑现象比氢键破坏更为复杂。量子化学计算的分子水平研究表明，甘油作为壳聚糖增塑剂的效率归因于其单一的氢键结合位点，该位点破坏了壳聚糖的氢键网络，并留下疏水性 C-H 末端基团，以限制分子间氢键的形成。
