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Ag(i)-mediated self-assembly of anisotropic rods and plates in the surfactant mixture of CTAB and Pluronics

机译:Ag(i)介导的CTAB和Pluronics表面活性剂混合物中的各向异性棒和板的自组装

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One-dimensional (1D) metallogels are commonly observed in metal-coordinated complexes, but there are not many examples of soft crystalline solids which are generated by the self-assembly of metal–polymer complexation in a non-gel state. In a continued effort to obtain 1D materials by utilizing the tendency of Pluronic triblock copolymers to be micellized anisotropically at an elevated temperature, we investigate Ag( I )-mediated self-assembly of the surfactant mixture of Pluronic copolymers and cetyltrimethylammonium bromide (CTAB). At sufficiently high temperature, Pluronic copolymers are known to organize into many crystalline mesophases, such as body-centered-cubic, hexagonal, and lamellar phases. Four Pluronics of L-31, L-64, P-123, and F-108 were studied, and at the concentration of 17.9%, macroscale 1D rods with the aspect ratios ranging from 3.07 to 12.8 are obtained. At the concentration of 35.7%, anisotropic two dimensional (2D) planar plates are observed. These planar structures were believed to be generated from 2D lamellar mesophases, which is consistent with the general phase diagram of Pluronic copolymers that shows lamellar phase with the highest concentration. In the absence of ascorbic acid, rods and plates of larger size are produced. Rather than as a reductant, ascorbic acid is thought to play the roles of an agent to increase the hydrophilicity, and as a mediator to determine the dimension of rods and plates by hindering the long range self-assembly of alkyl chains. Dehydration by the addition of AgNO _(3) , and the increase of hydrophobicity enable self-assembly of alkyl groups of CTAB and Pluronics and promote the formation of crystalline soft solids.
机译:一维(1D)金属元素通常在金属配位的配合物中观察到,但没有许多通过非聚合物态的金属-聚合物配合物的自组装而生成的软晶体固体的例子。为了继续利用一维Pluronic三嵌段共聚物在高温下各向异性胶束化的趋势来获得一维材料,我们研究了Ag(I)介导的Pluronic共聚物和十六烷基三甲基溴化铵(CTAB)的表面活性剂混合物的自组装。在足够高的温度下,已知Pluronic共聚物会组织成许多结晶中间相,例如体心立方,六方和层状相。研究了L-31,L-64,P-123和F-108的四种Pluronic,并在17.9%的浓度下获得了纵横比从3.07到12.8的大型一维棒。在35.7%的浓度下,观察到各向异性的二维(2D)平板。据信这些平面结构是由2D层状中间相产生的,这与Pluronic共聚物的一般相图一致,后者显示了最高浓度的层状相。在不存在抗坏血酸的情况下,会产生较大尺寸的棒和板。认为抗坏血酸不是还原剂,而是起增加亲水性的作用,并通过阻碍烷基链的长距离自组装而起决定棒和板尺寸的作用。通过添加AgNO_(3)进行脱水,以及增加疏水性,可以使CTAB和Pluronics的烷基自组装并促进结晶性软固体的形成。

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