Dizon Glenieliz C, Atkinson George, Argent Stephen P, Santu Lea T, Amabilino David B
School of Chemistry, University of Nottingham, University Park, NG7 2RD, UK.
Soft Matter. 2020 May 21;16(19):4640-4654. doi: 10.1039/d0sm00343c.
During the development of soft material systems inspired by green chemistry, we show that naturally occurring starting materials can be used to prepare mono- and di-benzylidene sorbitol derivatives. These compounds gelate a range of organic, aqueous (including with mono and divalent metal salt solutions) and ethanolic (ethanol-water) solutions, with the equimolar mixture of two of the gelators gelling all compositions from 100% ethanol to 100% water (something neither of the individual components do). We explored the influence of modifications to the acetal substituents on the formation of the compounds as well as the impact of steric bulk on self-assembly properties of the gelators. The effect of solvent on the self-assembly, morphology, and rheology of the 1,3:2,4-di(4-isopropylbenzylidene)-d-sorbitol (DBS-iPr), 2,4(4-isopropylbenzylidene)-d-sorbitol (MBS-iPr) and the equimolar multicomponent (DBS-MBS-iPr) gels have been investigated. DBS-iPr gelates polar solvents to form smooth flat fibres, whereas in non-polar solvents such as cyclohexane helical fibres grow where the chirality is determined by the stereochemistry of the sugar. Oscillatory rheology revealed that MBS-iPr gels have appreciable strength and elasticity, in comparison to DBS-iPr gels, regardless of the solvent medium employed. Powder X-ray diffraction was used to probe the arrangement of the gelators in the xerogels they form, and two single crystal X-ray structures of related MBS derivatives give the first precise structural information concerning layering and hydrogen bonding in the monobenzylidene compounds. This kind of layering could explain the apparent self-sorting behaviour of the DBS-MBS-iPr multicomponent gels. The combination of sorbitol-derived gelators reported in this work could find potential applications as multicomponent systems, for example, in soft materials for personal care products, polymer nucleation/clarification, and energy technology.
在受绿色化学启发的软材料系统开发过程中，我们表明天然存在的起始原料可用于制备单苄叉山梨醇和二苄叉山梨醇衍生物。这些化合物能使一系列有机溶液、水性溶液（包括与单价和二价金属盐溶液）以及乙醇（乙醇 - 水）溶液凝胶化，两种凝胶剂的等摩尔混合物能使从100%乙醇到100%水的所有组合物凝胶化（单个组分都无法做到这一点）。我们研究了缩醛取代基的修饰对化合物形成的影响以及空间位阻对凝胶剂自组装性质的影响。研究了溶剂对1,3:2,4 - 二(4 - 异丙基苄叉基)-d - 山梨醇（DBS - iPr）、2,4(4 - 异丙基苄叉基)-d - 山梨醇（MBS - iPr）以及等摩尔多组分（DBS - MBS - iPr）凝胶的自组装、形态和流变学的影响。DBS - iPr能使极性溶剂凝胶化形成光滑的扁平纤维，而在非极性溶剂如环己烷中则生长出螺旋纤维，其手性由糖的立体化学决定。振荡流变学表明，无论使用何种溶剂介质，与DBS - iPr凝胶相比，MBS - iPr凝胶都具有相当的强度和弹性。粉末X射线衍射用于探测凝胶剂在它们形成的干凝胶中的排列，相关MBS衍生物的两个单晶X射线结构给出了关于单苄叉基化合物中分层和氢键的首个精确结构信息。这种分层可以解释DBS - MBS - iPr多组分凝胶明显的自分类行为。本文报道的山梨醇衍生凝胶剂的组合作为多组分系统可能具有潜在应用，例如，用于个人护理产品的软材料、聚合物成核/澄清以及能源技术。
