Developments in liquid-crystalline dimers and oligomers

ABSTRACT

Liquid-crystalline dimers and bimesogens have attracted much attention due to their propensity to exhibit the spontaneously chiral twist-bend mesophase (N_TB), most often by dimers with methylene spacers. Despite their relative ease of synthesis, the number of ether-linked twist-bend materials significantly lags behind those of methylene-linked compounds. In this work, we have prepared and studied a range of ether-linked bimesogens homologous in structure to the FFO9OCB; as with methylene-linked systems, it appears that it is molecular topology and the gross molecular shape that are the primary drivers for the formation of this phase of matter. Dimers and bimesogens are well studied within the context of the twist-bend phase; however, present understanding of this mesophase in oligomeric systems lags far behind. We report our recent efforts to prepare further examples of oligomeric twist-bend nematogens, including further examples of our ‘n+1’ methodology, which may allow the synthesis of high-purity, monodisperse materials of any given length to be prepared. We have observed that there is a tendency for these materials to exhibit highly ordered soft-crystalline mesophases as opposed to the twist-bend phase.     

带有羧酸基侧臂的十元环大环三胺衍生物及其金属配合物的合成和结构表征

合成了侧壁带有羧酸基的十元环大环三胺衍生物配体1,4,7-三氮杂环癸烷-N,N′N″-三羧酸(L)及它的4种过渡金属配合物[ML]·1/2[M(H2O)6]·[ClO4]·nH2O(M=Co2+,Cu2+,Ni2+,Zn2+),利用元素分析,红外光谱以及热重分析等手段对它们的结构进行了表征,并测定了配合物[NiL]·1/2[Ni(H2O)6]·[ClO4]·3H2O(1)的晶体结构。结果表明这4种配合物具有类似的结构。     

多面体齐聚倍半硅氧烷的合成及应用研究进展

多面体齐聚倍半硅氧烷(Polyhedral Oligomeric Silasesquioxane,POSS)本身作为一种分子水平上的纳米有机/无机杂化体,由于几乎能够改性所有传统材料而引起人们的极大关注。这种杂化体可以通过多种合成方法得到,为新型杂化材料的设计提供了便利。本文综述了近年来有关POSS的合成方法、POSS基聚合物的研究及其在电子材料、航空航天材料、多孔材料、发光材料等方面的应用研究进展并对其发展前景予以展望。     

乳香大环二萜类化学成分研究

采用硅胶柱层析,制备薄层层析等色谱方法,从乳香CO_2超临界提取物中分得7个大环二萜类化合物,经波谱方法鉴定为incensole acetate(1),incensole(2),incensole oxide acetate(3),isoincensole acetate(4),incensole oxide(5),isoincensoleoxide(6),isoincensolol(7),其中,化合物7为新化合物,化合物4为首次从该属植物中分离得到.采用四甲基偶氮唑蓝(MTT)法观察化合物对肿瘤细胞的抑制增殖作用.     

Complexes of tri- and tetra-protonated forms of 1,4,8,12-tetraazacyclopentadecane with chloride,nitrate, iodate,and sulfate ions in aqueous media: II. Analysis of the underlying experimental and theoretical assumptions

In a previous paper [1] the complexation behavior of 1,4,8,12-tetraazacyclopentadecane with various anions was studied. This analysis depended on various assumptions involving the accuracy and the interpretation of the experimental data. In this paper these assumptions are examined using pH potentiometry,¹³C NMR, and conductometric techniques. The validity of each of the assumptions was confirmed.