Biomacromolecules. 2020 Feb 10;21(2):545-555. doi: 10.1021/acs.biomac.9b01268. Epub 2019 Dec 5.
Chitin nanofibers (ChNFs) and cellulose nanocrystals (CNCs) have been proposed as materials for renewable packaging with low O transmission that protect food, medicine, and electronics. A challenge in biomass-derived functional materials is tuning both barrier and mechanical properties, while minimizing process steps. A concept that merits additional study in this field is tuning of the barrier and mechanical properties by use of oppositely charged biomass-derived fibers, through interactions that support dense film formation. We report free-standing films formed by solution casting of blends of aqueous suspensions of CNCs and ChNFs with either low degree of acetylation (LChNFs, higher charge) or high degree of acetylation (HChNFs, lower charge). While neat CNC films had the highest O permeability (OP), the OP was lowered by 91% by addition of at least 25 wt % LChNFs to CNCs to an OP value near 1.7 cm μm/m/d/kPa. Interestingly, blends of CNCs with less highly charged, larger HChNFs had equivalently lower OP as with LChNFs. The tensile strength and strain at break of blended ChNF/CNC films was optimal compared to neat cellulose or chitin when at least 50 wt % LChNFs or HChNFs were blended with CNCs. We show that the ability to tune properties of ChNF/CNC blends was coincident with the formation of aggregates of chitin and cellulose nanomaterials, which appear to support formation of dense layers of tortuous fiber networks.
壳聚糖纳米纤维（ChNFs）和纤维素纳米晶体（CNCs）已被提议作为具有低氧气传输率的可再生包装材料，可保护食品、药品和电子产品。在生物质衍生功能材料中，面临的挑战是调整阻隔性能和机械性能，同时尽量减少工艺步骤。在该领域，一个值得进一步研究的概念是通过使用带相反电荷的生物质衍生纤维相互作用，支持致密膜形成，从而调整阻隔性能和机械性能。我们报告了通过将 CNCs 的水悬浮液与具有低乙酰化度（LChNFs，更高电荷）或高乙酰化度（HChNFs，更低电荷）的 ChNFs 的水溶液共混物进行溶液浇铸而形成的独立膜。虽然纯 CNC 膜具有最高的氧气透过率（OP），但通过向 CNCs 中添加至少 25wt%的 LChNFs，OP 降低了 91%，达到了接近 1.7cmμm/m/d/kPa 的 OP 值。有趣的是，与 LChNFs 相比，与电荷较低、尺寸较大的 HChNFs 混合的 CNCs 的 OP 同样较低。与纯纤维素或壳聚糖相比，当至少 50wt%的 LChNFs 或 HChNFs 与 CNCs 混合时，共混的 ChNF/CNC 膜的拉伸强度和断裂伸长率达到最佳。我们表明，调整 ChNF/CNC 共混物性能的能力与壳聚糖和纤维素纳米材料的聚集能力一致，这似乎支持了致密的曲折纤维网络层的形成。
