密封沉积处理对纤维素纳米晶体薄膜光学特性的调控

Regulation of the Optical Properties of Cellulose Nanocrystal Films by Sealed Deposition Treatment

纤维素纳米晶体(Cellulose nanocrystal,CNC)在特定浓度下可自组装排列,赋予体系独特的光学性能。为阐明CNC薄膜形成过程中CNC自组装行为机制,本文通过分析CNC薄膜在宏观颜色、紫外可见光谱、偏振光学、微观形貌以及晶体结构等方面的变化,探究了密封沉积时间和CNC浓度对自然蒸发干燥薄膜内部胆甾相液晶形成与排列的影响。结果表明,当密封沉积时间延长至48 h后,CNC薄膜的结构色显色范围、胆甾相结构的长程有序性均得到明显提升。随着浓度的升高,CNC颗粒间距减小,相邻颗粒间扭转角增大,螺距被压缩,从480 nm减小至344 nm。此外,密封沉积处理对高浓度CNC悬浮液形成长程有序性胆甾相结构具有明显优势。本研究结果表明,延长密封沉积时间和提高CNC浓度可以提高薄膜中长程有序性的提高,并促进胆甾相结构域的形成。这进一步完善了CNC基智能包装材料制备的科学基础,对于新型可视化食品包装和检测材料的开发具有积极作用。

Cellulose nanocrystal(CNC)can self-assemble and arrange at specific concentrations,imparting unique optical properties to the system.This paper investigated the effects of sealed deposition time and CNC concentration on the formation and alignment of cholesteric liquid crystals within the naturally dried films by analyzing the changes of CNC films in macroscopic color,UV-vis spectra,polarization optics,microscopic morphology,and crystal structure to elucidate the mechanism of CNC self-assembly behavior during the formation of CNC films.The results showed that when the sealed deposition time was extended to 48 h,the structural color development range and the long-range ordering of the cholesteric phase structure of CNC films were considerably enhanced.As the concentration increased,the CNC particle spacing decreased,the torsion angle between neighboring particles increased,and the pitch was compressed,decreasing from 480 nm to 344 nm.The results of polarized light microscopy analysis demonstrated that the sealed deposition treatment had a significant advantage in the formation of long-range ordered cholesteric phase structure in high-concentration CNC suspensions.The results of this research indicated that prolonging the sealed deposition time and increasing the CNC concentration could enhance the improvement of long-range orderliness in the films and promote the formation of cholesteric phase structural domains.This further improved the scientific basis for the preparation of CNC-based smart packaging materials and had a positive effect on the development of new visual food packaging and inspection materials.