不同表面基团的纤维素纳米晶体薄膜在不同磁场下的光学特性响应

本文探究了磁场对不同表面基团的纤维素纳米晶体(Cellulose Nanocrystal,CNC)薄膜光学特性的影响。以硫酸化纤维素纳米晶体(S-CNC)为原料,通过2,2,6,6-四甲基哌啶-1-氧基自由基(TEMPO)氧化制备表面带有羧基的纳米纤维素(T-CNC),并采用傅里叶红外光谱、扫描电子显微镜和Zeta电位对其基本结构进行表征。并在无磁场、垂直磁场、倾斜磁场、水平磁场四种模式下观察磁场对不同表面电荷CNC薄膜的影响。结果表明,T-CNC表面带有羧基,S-CNC表面带有硫酸酯基。由于表面电荷不同,使得T-CNC电位绝对值低于S-CNC。两种CNC由于表面电荷差异表现出不同的自组装模式,其中T-CNC为同心自组装,S-CNC为手性向列自组装,且自组装模式的差异不因磁场而改变。但T-CNC与S-CNC在自组装过程中的排列均受到磁场影响。随着磁场取向的不同,两种薄膜的颜色因CNC的排列发生变化而受到影响,其中垂直磁场对两种CNC薄膜的影响最为显著,能使薄膜中CNC的排列更加均匀紧密,从而提升薄膜颜色的均匀性。不同表面基团CNC的自组装薄膜在不同磁场下的颜色响应研究为后续对CNC虹彩...

Effect of Magnetic Field on Optical Properties of CNC Films with Different Surface Groups

In this paper, the effect of the magnetic field on the optical properties of cellulose nanocrystal (CNC) films with different surface groups was investigated. T-CNC with carboxyl groups on its surface was prepared from cellulose sulfate nanocrystals (S-CNC) by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) oxidation. Its basic structure was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and zeta potential. The effects of magnetic field on CNC films with different surface charges were observed in four modes: no magnetic field, vertical magnetic field, inclined magnetic field, and horizontal magnetic field. The results showed that T-CNC had carboxyl groups on its surface and S-CNC had sulfate groups on its surface. The absolute value of T-CNC potential was lower than that of S-CNC due to the different surface charges. The two kinds of CNC exhibited different self-assembly modes due to the difference in surface charges, in which T-CNC was concentric self-assembly and S-CNC was chiral nematic self-assembly, and the difference in self-assembly modes was not changed by the magnetic field. However, the arrangement of T-CNC and S-CNC in self-assembly process was affected by the magnetic field. With the different orientations of the magnetic field, the color of the two films was affected by the change in the arrangement of CNC. Among them, the vertical magnetic field had the most significant effect on the two kinds of CNC films, which could make the arrangement of CNC in the films more uniform and closer, thus improving the uniformity of film color. The color response of CNC self-assembled films with different surface groups under different magnetic fields lays a foundation for the subsequent regulation of CNC iridescent films and their application in the field of packaging.