ORDERED POLY(P-PHENYLENEVINYLENE) MATRIX NANOCOMPOSITES VIA LYOTROPIC LIQUID-CRYSTALLINE MONOMERS
ORDERED POLY(P-PHENYLENEVINYLENE) MATRIX NANOCOMPOSITES VIA LYOTROPIC LIQUID-CRYSTALLINE MONOMERS
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DOI：
10.1021/ja963837w
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发表时间：
1997-04
影响因子：
15
通讯作者：
Ryan C. Smith;W. Fischer;D. Gin
中科院分区：
文献类型：
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作者：
Ryan C. Smith;W. Fischer;D. Gin
在过去的十年中，合成纳米复合材料1、2、3以及具有纳米尺度结构域的材料4、5的构建受到了极大的关注。这项工作的主要推动力是合成生物材料的类似物，由于其复杂的纳米结构，生物材料具有独特的性质。6这一研究领域正在解决的主要问题之一是，如果能够用现代工程部件实现纳米级的建筑控制，是否可以制造出具有独特或优异性能的材料。在制造散装人造材料时，传统的加工技术无法达到这种程度的控制。6A在这里，我们报道了一种新的策略，利用基于溶致(即，两亲性)液晶(LCS)7的自组织单体来构建具有明确结构的高度有序的聚合物基纳米复合材料(方案1)。可聚合溶致液晶被用来在含有反应剂的水溶液周围自发形成有序的反六方液晶基质。随后的光聚合以锁定基质结构，8随后在所产生的亲水结构域内引发化学反应，产生最终的材料。为了证明这种方法可以用来合成具有良好结构的聚合物纳米复合材料，我们构建了一种高度有序的聚对苯乙炔(PPV)复合材料。PPV被选为本次演示的“填充物”是因为(1)它是由一种水溶性前体9形成的，以及(2)PPV及其衍生物最近被用于制造聚合物基发光二极管10和激光材料。11因此，PPV是研究纳米级工程对材料光学性质影响的极佳平台。PPV前驱体聚(对二甲基二甲基氯化硫)9，12与1的水溶液和自由基光引发剂(2-羟基-2-甲基丙酮)的有机溶液最初混合形成了六方有序的PPV纳米复合材料，以建立所需的LC相。单体1是一种可聚合的两亲性丙烯酸酯类似物，最初由Percec和其同事开发的一类锥形热致液晶，在没有水的情况下呈现柱状盘状LC相。将没食子酸甲酯与3当量的11-溴十二烷-1-醇偶联，形成两亲分子的基本平台，合成了13个单体1。13酯的皂化，然后端羟基的丙烯酸化，生成1的酸形式。用NaOH中和得到59%的总收率。为了制备PPV纳米复合材料，使用0.4wt%的聚(对二甲基二甲基氯化)水溶液15作为形成相的亲水组分。自由基光引发剂以20wt%的对二甲苯溶液的形式引入相中。通常，由8：1：1(w/w/w)纯1/水PPV前驱体溶液/2-羟基-2-甲基苯丙酮溶液组成的混合物在常温(19℃)下提供定义明确、稳定的反六方相。当样品在常温下简单地混合各组分时，它在交叉偏振器下显示出类似于气溶胶OT(一种商业表面活性剂)在反六方相中的光学织构。7B，16小角X射线衍射仪得到了1，1/3，1/4…比率(D100、D110、D200...)六方相的特征(图1a)。在含…的LC单体混合物中，上述PPV前驱体水溶液的总重量可达20%
The construction of synthetic nanocomposites1, 2, 3 and materials with nanometer-scale domains4, 5 has received considerable attention over the past decade. The impetus for much of this work has been to synthesize analogs to biological materials, which possess unique properties as a result of their sophisticated nanoarchitectures. 6 One of the principal questions being addressed in this area of research is whether materials with unique or superior properties could be manufactured if nanometer-scale architectural control could be achieved with modern engineering components. Conventional processing techniques are unable to achieve this level of control in the fabrication of bulk, manmade materials. 6a Herein, we report a novel strategy for constructing highly ordered, polymer-based nanocomposites with well-defined architectures using self-organizing monomers based on lyotropic (ie, amphiphilic) liquid crystals (LCs) 7 (Scheme 1). Polymerizable lyotropic LCs are used to form spontaneously an ordered inverse hexagonal LC matrix around aqueous solutions containing reactive agents. Subsequent photopolymerization to lock-in the matrix architecture, 8 followed by the initiation of chemistry within the resulting hydrophilic domains, yields the final material. In order to demonstrate that this approach can be used to synthesize well-defined polymerpolymer nanocomposites, a highly ordered poly (p-phenylenevinylene)(PPV) composite was constructed. PPV was chosen as the “filler” in this demonstration because (1) it is formed from a water-soluble precursor9 and (2) PPV and its derivatives have recently been used to make polymer-based light-emitting diodes10 and lasing materials. 11 Consequently, PPV is an excellent platform for investigating the effects of nanometerscale engineering on the optical properties of a material. The hexagonally ordered PPV nanocomposite was formed by initially mixing an aqueous solution of the PPV precursor, poly (p-xylylenedimethylsulfonium chloride), 9, 12 with 1 and an organic solution of a radical photoinitiator (2-hydroxy-2-methylpropiophenone) to establish the desired LC phase. Monomer 1 is a polymerizable, amphiphilic, acrylate analog of a class of tapered thermotropic LCs originally developed by Percec and co-workers that exhibit columnar discotic LC phases in the absence of water. 13 Monomer 1 is synthesized by coupling methyl gallate with 3 equiv of 11-bromoundecan-1-ol to form the basic platform of the amphiphile. 13 Saponification of the ester, followed by acrylation14 of the terminal hydroxy groups, generates the acid form of 1. Neutralization with NaOH affords 1 in 59% overall yield.In order to generate the PPV nanocomposite, a 0.4 wt% aqueous solution15 of poly (p-xylylenedimethylsulfonium chloride) was used as the hydrophilic component in the formation of the phase. The radical photoinitiator was introduced into the phase as a 20 wt% solution in p-xylene. Typically, a mixture consisting of 8: 1: 1 (w/w/w) pure 1/aqueous PPV precursor solution/2-hydroxy-2-methylpropiophenone solution affords a well-defined, stable, inverse hexagonal phase at ambient temperature (19 C). When the sample is prepared by simply mixing the components at ambient temperature, it displays an optical texture under crossed polarizers similar to that of Aerosol OT (a commercial surfactant) in the inverse hexagonal phase. 7b, 16 Low-angle X-ray diffraction yielded d spacings with the 1, 1/3, 1/4... ratio (d100, d110, d200...) characteristic of a hexagonal phase (Figure 1a). 7b The aforementioned aqueous PPV precursor solution can be accommodated up to 20% by total weight in the LC monomer mixture with …