水解时间对纤维素纳米晶体性质及其连续相分离行为的影响

Effect of Hydrolysis Time on the Properties of Cellulose Nanocrystals and Their Continuous Phase Separation Behavior

关键词:  纤维素纳米晶体  细菌纤维素  自组装  相分离  分级

Key Words:cellulose nanocrystals  bacterial cellulose  self-assembly  phase separation  grading

摘要:本研究采用硫酸水解法制备了一系列细菌纤维素纳米晶体（BCNC），并考察了酸水解时间对BCNC性能及其连续相分离行为的影响。结果表明，随着酸水解时间的延长，BCNC的长度、直径和长径比均逐渐减小。当不同酸水解时间制备的BCNC悬浮液的质量分数均调整到5.00%时，仅酸水解60 min制备的BCNC悬浮液出现连续相分离现象，且第2次相分离得到的各向异性相（BCNC_60-2b）的体积分数明显小于第1次相分离得到的各向异性相（BCNC_60-1b）的体积分数。各向同性相和各向异性相BCNC级分的性质存在明显差异，其中各向异性相BCNC的长度、直径、长径比、Zeta电位绝对值和结晶度，均大于相应各向同性相BCNC。因此，多分散的BCNC粒子的自组装不是随机发生的，不同的BCNC粒子具有不同的自组装优先级，而连续相分离行为可用于BCNC的分级。

Abstract:In this study， a series of bacterial cellulose nanocrystals （BCNC） were prepared by sulphuric acid hydrolysis， and the effects of acid hydrolysis time on the properties of BCNC and their continuous phase separation behaviour were investigated. The results showed that the length， diameter， and aspect ratio of the BCNC decreased gradually with the increase of acid hydrolysis time. When the mass fractions of the BCNC suspensions prepared at different acid hydrolysis time were all adjusted to 5.00%， the continuous phase separation only occurred in the BCNC suspension prepared by acid hydrolysis for 60 min. Meanwhile， the volume fraction of the anisotropic phase obtained from the second phase separation （BCNC_60-2b） was significantly less than that of the anisotropic phase obtained from the first phase separation （BCNC_60-1b）. The properties of the BCNC fractions from isotropic and anisotropic phases differed significantly， with the length， diameter， aspect ratio， Zeta potential absolute value， and crystallinity of the anisotropic phase BCNC being greater than those of the corresponding isotropic phase BCNC. Therefore， the self-assembly of the polydispersed BCNC particles was not random， but rather had different priorities， whereas the continuous phase separation could be used for BCNC grading.