Nonflocculating and chiral-nematic self-ordering of cellulose microcrystals suspensions in nonpolar solvents
Nonflocculating and chiral-nematic self-ordering of cellulose microcrystals suspensions in nonpolar solvents
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DOI：
10.1021/la9913957
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发表时间：
2000-10-17
期刊：
影响因子：
3.9
通讯作者：
Bonini, C
中科院分区：
文献类型：
--
作者：
Heux, L;Chauve, G;Bonini, C
纤维素是由许多有生命的物种以细长且几乎无穷无尽的杆状形式生物合成的，称为微纤维。根据它们的来源，这些元素的横向大小不同，直径从2到20纳米不等。在强酸的作用下，这些微纤维分解成短晶棒或“纤维素微晶”，其直径与母纤维相同，但长度更短，从几百纳米到几微米不等。1959年，Marchessault et al.1报道了这些纤维素微晶在酸处理后形成双折射水凝胶。这些悬浮液的稳定性是离子物种(硫酸盐、磷酸盐等)接枝的结果。在酸处理过程中。最近，Revol等人。结果表明，漂白硫酸盐木浆悬浮液中的微晶在临界浓度以上可以自发分离成手性向列型液晶相。这种组织类似于自然界中螺旋面的结构组织。从木材或棉花中提取的纤维素微晶可以观察到这种自组织，浓度范围从2%w/w到10%w/w，具体取决于实验过程。Onsager3预测了在高纵横比杆悬挂的一般情况下的这种液晶行为。棒自组织的临界浓度取决于它们的长径比和静电斥力，如果有的话是4。对于其他棒状颗粒也观察到了这一总体趋势，无论是有机的(甲壳素，5个烟草花叶病毒，6个DNA片段7，8)或无机来源的(氧化钒，9个薄水铝石棒10)，无论是手性向列型还是向列型。以纤维素为例，已广泛研究了制备条件、离子强度12或反离子13的影响。纤维素微晶形成稳定的水悬浮液的能力可能会导致一些潜在的应用。例如，纤维素微晶来自于
Cellulose is biosynthesized by numerous living species in the form of slender and nearly endless rods called microfibrils. Depending on their origin, these elements differ in lateral size, with diameter ranging from 2 to 20 nm. Upon the action of strong acids, these microfibrils break down into short crystalline rods or “cellulose microcrystals” whose diameter is the same as the parent microfibrils, but having shorter lengths, ranging from a few hundreds of nanometers to a few microns. In 1959, Marchessault et al. 1 reported the formation of birefringent aqueous gels of these cellulose microcrystals after an acidic treatment. The stability of these suspensions resulted from the grafting of ionic species (sulfate, phosphate,...) during the acidic treatment.More recently, Revol et al. 2 showed that microcrystals from bleached kraft wood pulp suspensions could spontaneously separate into a chiral-nematic liquid crystalline phase above a critical concentration. This organization is analogous to the structural organization of helicoids in nature. This self-organization has been observed with cellulose microcrystals extracted from wood or from cotton, in a concentration ranging from 2% w/w to 10% w/w, depending on the experimental procedure. Onsager3 has predicted this liquid crystalline behavior in the general case of suspension of rods with a high aspect ratio. The critical concentration at which the rods self-organize depends on their aspect ratio and on the electrostatic repulsion, 4 if any. This general trend is also observed for other rodlike particles both organic (chitin, 5 tobacco mosaic virus, 6 DNA fragments7, 8) or inorganic origin (vanadium oxide, 9 boehmite rods10) with either chiral-nematic or nematic order. In the case of cellulose, the effects of preparation conditions, 11 ionic strength12 or counterions13 have been extensively studied. The ability of cellulose microcrystals to form stable aqueous suspension may lead to a number of potential applications. For instance, cellulose microcrystals from