Zhao Junchai, Zhao Yujing, Wang Zhao, Peng Zheng
School of Materials Science and Engineering, Shijiazhuang Tiedao University, 050043, Shijiazhuang, China.
Eur Phys J E Soft Matter. 2016 Dec;39(12):118. doi: 10.1140/epje/i2016-16118-2. Epub 2016 Dec 9.
Cellulose nanocrystals (CNCs) with different polymorphs CNC I and II were fabricated from native and mercerized microcrystalline cellulose (MCC) by sulfuric acid hydrolysis. CNC I and II were successfully acetylated by a "green" method, which was performed in an ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF). X-ray diffraction (XRD) proved that the crystal structure of CNC I and II was maintained after acetylation. Transmission electron microscopy (TEM) showed the rod-like structure for acetylated CNC I and spherical crystal morphologies for acetylated CNC II. Thermogravimetric analysis (TGA) revealed that the thermal stability of CNC I and II was enhanced after acetylation. The effect of CNC polymorphs on the crystallization behavior and thermal stability of poly(lactic acid)/acetylated CNC (PLA/ACN) composites was investigated by differential scanning calorimetry (DSC) and TGA, respectively. It was found that compared to ACN I, ACN II was better able to promote the cold crystallization of PLA-based composites, and PLA/ ACN II possessed higher thermal stability.
通过硫酸水解法，以天然微晶纤维素（MCC）和丝光处理微晶纤维素为原料制备了具有不同晶型（I型和II型）的纤维素纳米晶体（CNC）。采用“绿色”方法，即在1-丁基-3-甲基咪唑四氟硼酸盐（[BMIM]BF）离子液体中对I型和II型CNC进行了成功的乙酰化。X射线衍射（XRD）证明乙酰化后I型和II型CNC的晶体结构得以保持。透射电子显微镜（TEM）显示乙酰化I型CNC呈棒状结构，乙酰化II型CNC呈球形晶体形态。热重分析（TGA）表明乙酰化后I型和II型CNC的热稳定性增强。分别通过差示扫描量热法（DSC）和TGA研究了CNC晶型对聚乳酸/乙酰化CNC（PLA/ACN）复合材料结晶行为和热稳定性的影响。结果发现，与ACN I相比，ACN II更能促进基于PLA的复合材料的冷结晶，且PLA/ACN II具有更高的热稳定性。
