壳聚糖/笼型倍半硅氧烷纳米复合膜的阻湿特性与机理研究

Membranes based on polysaccharides such as chitosan which are biodegradable and biocompatible are potential candidates to replace synthetic plastics in many fields such as packaging. However, their applications are largely limited by their poor water barrier properties due to high water affinity. Incorporating nano-particles to construct nanocomposite membranes may open new possibilities for improving these properties. Preliminary studies revealed that polyhedral oligosilsesquioxane(POSS) as a novel of unique nanostructured organic/inorganic hybrid molecules were able to decrease the water permeability of chitosan membranes with the effectiveness depending on R groups of POSS. Therefore, in this study, we will incorporate three kinds of POSS with different R groups into chitosan, respectively, to prepare different nanocomposite membranes. The transport behaviors of water molecules in these membranes will be fully studied. Combining with the inter-molecular interactions between POSS and chitosan, as well as the microstructures of these membranes, the reinforcement mechanisms of POSS on the water vapor barrier properties of membranes will be proposed. Therefore, this study may provide new sight for performance improving of natural polysaccharides membranes taking advantage of the interactions between nanoparticles and polymers. It may also advance the industrial applications of natural polysaccharides membranes.

壳聚糖等多糖类天然高分子制得的薄膜具有可生物降解、生物相容性好等特性，在包装等众多领域具有取代塑料薄膜的巨大潜力。但这类高分子的强亲水性导致薄膜阻湿性差，大大限制了其应用范围。引入纳米粒子构建复合膜是对此进行改善并提高薄膜综合性能的重要途径。前期研究发现笼型倍半硅氧烷（POSS）作为一种具有独特纳米结构的有机/无机杂化分子，可有效降低水分子在壳聚糖膜中的透过率，且效果与POSS中R基结构有关。基于此，本项目拟利用不同结构特征的POSS与壳聚糖复合成膜，重点研究POSS结构对水分子在膜中的传质过程的影响，结合POSS-壳聚糖分子间作用力以及复合膜微观结构研究，揭示POSS增强壳聚糖膜阻湿性的分子机制。该研究可为利用纳米粒子与膜基材间的相互作用对多糖类天然高分子进行性能调控提供新的视角；为进一步提升多糖基高分子膜的工业化应用性能提供重要参考价值。

为提高壳聚糖等多糖类天然高分子薄膜的阻湿性，纳米粒子被添加到其中制备成复合膜。本项目将三种不同结构的笼型倍半硅氧烷（POSS）引入壳聚糖中制备成复合膜，并从以下方面探讨了POSS对复合膜阻湿性的影响机制：（1）对复合膜的水分子等温吸附曲线进行GAB拟合，结合表面接触角、溶胀度和溶解度测定结果，说明POSS的引入一方面减少了水分子在其表面的吸附，另一方面降低了其在膜中的扩散速率；（2）观察复合膜的微观形貌，发现POSSD的分散最为良好；（3）从机械性能的结果来看，POSSD对复合膜的杨氏模量和抗拉强度的提高最为显著，说明POSSD粒子与壳聚糖之间具有较强的界面结合，可进行有效的应力传递。以上三方面的研究表明，POSS对复合膜阻湿性提高的机理主要在于提高表面疏水性以抑制吸附，同时在复合膜中形成水分子的扩散障碍，以降低扩散速率。而要达到上述目的，则需要POSS分子与壳聚糖之间具有较强的结合力，一方面使其在膜中达到良好分散以发挥最大作用，同时与壳聚糖之间形成良好的界面结合，以防止缺陷的产生。.在此基础上，我们进行了以下研究进一步明确其机制：（1）采用湿法球磨方法促进POSSD在复合膜中的分散，发现制备的复合膜具有更高的表面疏水性、更佳的阻湿性和更好的强度；（2）利用湿法球磨手段将氧化石墨烯（GO）与POSSD混合分散后同时加入复合膜，发现片层状GO的加入对复合膜阻湿性的提高效果不如POSSD显著，进一步说明复合膜阻湿性的提高主要是由于表面疏水性的提高；（3）利用湿法球磨手段将POSS和多壁碳纳米管（MWNTs）混合后，加入羧甲基纤维素钠中制备复合膜，发现它们对复合膜的阻湿性和机械性能的改善效果要好于单一的纳米粒子。.综上所述，本研究在一定程度上揭示了POSS对壳聚糖复合膜阻湿性的增强机制，并探索了不同维度的纳米粒子对复合膜性能的协同作用，为促进多糖类高分子膜的工业化应用起到了积极促进作用。