酸解时间对纳米晶纤维素胆甾相液晶的影响

Effect of Acid Hydrolysis Time on Cholesteric Liquid Crystalof Cellulose Nanocrystal

研究了酸解时间对纳米晶纤维素薄膜颜色和螺距的影响。以棉短绒为原料,采用硫酸酸解法,以酸解时间为影响因素,制备了三种纳米晶纤维素(CNC)悬浮液,再将三种悬浮液放入烘箱干燥,制成具有不同颜色的纳米晶纤维素薄膜。采用Zeta电位及纳米粒度分析仪对CNC悬浮液的Zeta电位和粒径进行表征。采用紫外可见近红外分光光度计(UV-vis-NIR)、全反射傅里叶红外光谱仪(FT-IR)、X-射线衍射仪(XRD)、扫描电子显微镜(SEM)以及偏光显微镜(POM)对薄膜进行表征进而研究了酸解时间对纳米晶纤维素胆甾相液晶螺距的影响。结果表明,随着酸解时间增长,CNC的粒径减小,引入的磺酸酯增多,表面负电荷增大,颗粒之间静电斥力增大,最终导致螺距增大,薄膜的反射波长红移,薄膜的颜色从蓝色逐渐转向红色。

The effect of acid hydrolysis time on the pitch and color of nanocrystalline cellulose(CNC)films was studied.In order to study its influence,the CNC suspension was prepared by sulfuric acid hydrolysis from cotton linter and three kinds of CNC suspensions were prepared with difference acid hydrolysis time. Then suspensionswere dried in an oven at 45℃. Finally CNC films with different colors were prepared. The Zeta potential andparticle size of CNC suspension were investigated by ZetaPALS. Ultraviolet-visible near-infrared spectrophotometer(UV-vis-NIR), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electronmicroscope (SEM), and polarizing optical microscope (POM) were used to characterize the film to study effect ofacid hydrolysis time on the pitch of cholesteric liquid crystal of cellulose nanocrystal. The results showed that theparticle size of CNC decreased, as well as the Zeta potential changed from -21 mV to -59 mV, and thereflectance spectra increased with the increase of acid hydrolysis time. The increase of negative charge andsulfonate leads to the increase of intermolecular electrostatic repulsion. Eventually these phenomena caused thepitch of CNC films to increaseand the color of the CNC films to change from blue to red gradually. Overall, a newand facile method for the preparation of CNC films with the difference colors is demonstrated, offering excellentprospects foroptoelectronics and anti-counterfeiting applications.