Division of Applied Chemistry, Department of Chemistry and Chemical Engineering , Chalmers University of Technology , Gothenburg 41296 , Sweden.
Department of Natural and Microbial Products Chemistry , National Research Centre , Dokki, Giza , Egypt 12622.
Biomacromolecules. 2018 Mar 12;19(3):973-979. doi: 10.1021/acs.biomac.7b01751. Epub 2018 Feb 22.
Nanocellulose-based self-standing films are becoming a substrate for flexible electronics, diagnostics, and sensors. Strength and surface chemistry are vital variables for these film-based endeavors, the former is one of the assets of nanocellulose. To contribute to the latter, nanocellulose films are tuned with a side-specific functionalization, having an aldehyde and a carboxyl side. The functionalities were obtained combining premodification of the film components by periodate oxidation with ozone post-treatment. Periodate oxidation of cellulose nanocrystals results in film components that interact through intra- and intermolecular hemiacetals and lead to films with an elastic modulus of 11 GPa. The ozone treatment of one film side induces conversion of the aldehyde into carboxyl functionalities. The ozone treatment on individual crystals was largely destructive. Remarkably, such degradation is not observed for the self-standing film, and the film strength at break is preserved. Preserving a physically intact film despite ozone treatment is a credit to using the dry film structure held together by interparticle covalent linkages. Additionally, gas-phase post-treatment avoids disintegration that could result from immersion into solvents. The crystalline cellulose "Janus" film is suggested as an interfacial component in biomaterial engineering, separation technology, or in layered composite materials for tunable affinity between the layers.
基于纳米纤维素的自支撑膜正成为柔性电子、诊断和传感器的基底。强度和表面化学是这些基于薄膜的努力的关键变量，前者是纳米纤维素的优势之一。为了改进后者，纳米纤维素膜通过侧特异性功能化进行调整，具有醛基和羧基侧。通过对膜成分进行高碘酸盐氧化的预修饰，并结合臭氧后处理，获得了这些功能。纤维素纳米晶体的高碘酸盐氧化导致通过分子内和分子间半缩醛相互作用的膜成分相互作用，从而得到弹性模量为 11 GPa 的薄膜。对一侧膜进行臭氧处理会将醛基转化为羧基官能团。对单个晶体的臭氧处理在很大程度上是破坏性的。值得注意的是，这种降解在自支撑膜中没有观察到，并且断裂时的膜强度得以保留。尽管进行了臭氧处理，但仍能保持物理完整的膜，这要归功于由颗粒间共价键连接在一起的干燥膜结构。此外，气相后处理避免了因浸入溶剂而导致的崩解。建议将结晶纤维素"两面神"膜用作生物材料工程、分离技术中的界面组件，或用于层状复合材料中，以调节层间的亲和力。
