Polymer-stabilized gold nanoparticles and their incorporation into polymer matrices
Polymer-stabilized gold nanoparticles and their incorporation into polymer matrices
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DOI：
10.1021/ja0166287
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发表时间：
2001-10-24
影响因子：
15
通讯作者：
Lennox, RB
中科院分区：
文献类型：
--
作者：
Corbierre, MK;Cameron, NS;Lennox, RB
功能化金属纳米颗粒在生物医学、电子和光学材料方面的潜在应用引起了人们的极大兴趣。在过去的十年中，随着合成技术的进步，这些体系得到了广泛的研究。在聚合物基质中加入纳米颗粒是材料工程和纳米颗粒-基质相互作用研究的一个特别感兴趣的领域。虽然配体稳定纳米颗粒的例子很多，但聚合物稳定金属纳米颗粒的例子很少，其中聚合物是线性的，并且有一个明确的附着点。已经有各种各样的尝试来实现纳米颗粒聚合物复合材料。总的来说，我们注意到迄今为止使用的两种不同方法。第一种技术包括在基质中原位制备纳米颗粒。这要么是由于溶解在聚合物基体中的金属盐的减少，要么是由于加热的聚合物表面上金属的蒸发。第二种不太常见的技术是在纳米颗粒周围聚合基质。一种理想的方法是将预制的纳米颗粒混合到预合成的聚合物中。这提供了对纳米颗粒和基质的全面合成控制，并有可能产生各种各样的复合材料。我们实验室对烷硫醇修饰金纳米颗粒的初步研究表明，这些纳米颗粒很难分散到各种聚合物基质中，如聚苯乙烯（PS）和聚二甲基硅氧烷（PDMS）。金纳米颗粒聚集体通常在聚合物基体中形成，其尺寸约为几百纳米。为了克服这些困难，我们认为有必要设计纳米颗粒的涂层，使其与聚合物基体兼容。我们推测，聚合物配体与基质在化学上相同的金纳米颗粒在热力学上更有利于它们的结合。在这篇文章中，我们描述了用共价结合的巯基聚苯乙烯大分子（PS- sh）修饰的新型金纳米颗粒（PS- au）的合成，以及它们在PS基质中的成功分散。之所以选择聚苯乙烯，是因为它的玻璃化转变温度高（Tg≈100℃），可以在室温下形成坚固的薄膜。采用阴离子聚合法制备了PS-SH大分子。聚苯乙烯阴离子用一个单位的硫化丙烯滴定生成巯基。13C核磁共振证实了巯基的存在。凝胶渗透色谱法（GPC）测定了其数量、平均分子量和多分散性指数（Mn 13 300 g/mol, PI 1.7）。采用改进的Ulman反应条件11，以1/3.5的硫醇/HAuCl4试剂比例，三乙基硼氢化锂（超氢化锂，Aldrich）为还原剂制备了PS-Au纳米颗粒。PS-Au溶液的紫外-可见光谱在523 nm处证实了等离子体带的存在，这是链烷硫醇包覆金纳米颗粒的特征区域。这些纳米颗粒被分离并在溶剂（如氯仿）中多次再溶解，这些溶剂也是PS配体的溶剂。通过透射电子显微镜（TEM）测定了金芯直径，显示出中等程度的多分散性（6.2 (1.7 nm)）。大多数纳米颗粒呈球对称。然而，一些较大的纳米颗粒似乎不是特别球形。PS- au加入到PS基质（Mn 46 400 g/mol, PI 1.05）中。
Functionalized metal nanoparticles are of great interest in terms of their potential applications in biomedical, electronic, and optical materials. 1 Such systems have been extensively studied over the past decade following synthetic advances. 2 Incorporation of nanoparticles in polymer matrices is a field of particular interest for materials engineering and the study of nanoparticle-matrix interactions. 3 Although there are many examples of ligandstabilization of nanoparticles, there are few examples of polymerstabilized metal nanoparticles where the polymer is linear and has one well-defined point of attachment. 4 There have been a variety of attempts to achieve nanoparticlepolymer composites. Overall, we note two different approaches used to date. The first technique consists of the in situ preparation of the nanoparticles in the matrix. This is effected either by the reduction of metal salts dissolved in the polymer matrix5 or by the evaporation of metals on the heated polymer surface. 6 A second, less common technique, involves polymerizing the matrix around the nanoparticles. 7 A desirable approach would involve the blending of pre-made nanoparticles into pre-synthesized polymer. This provides full synthetic control over both the nanoparticles and the matrix, and has the potential for generating a wide variety of composite materials. Preliminary work in our laboratory with alkanethiol-decorated gold nanoparticles demonstrated difficulty in dispersing these nanoparticles into a variety of polymer matrices, such as polystyrene (PS) and poly (dimethylsiloxane)(PDMS). Gold nanoparticle aggregates were always formed in the polymer matrices, with dimensions on the order of several hundreds of nanometers. 8 To overcome these difficulties, we reasoned that it is necessary to design the coating of the nanoparticles to make them compatible with the polymer matrix. We speculated that gold nanoparticles whose polymer ligand is chemically the same as the matrix would be more thermodynamically favorable to their incorporation. 9 In this communication we describe the synthesis of novel gold nanoparticles (PS-Au) decorated with covalently bound thiolcapped polystyrene macromolecules (PS-SH), and their successful dispersion in a PS matrix. Polystyrene was chosen because its high glass-transition temperature (Tg≈ 100 C) allows for the formation of robust films at room temperature. The PS-SH macromolecules were synthesized by anionic polymerization. 10 The polystyrene anion was titrated with one unit of propylene sulfide to generate the thiol end group. The presence of the thiol end group was confirmed by 13C NMR. Gel permeation chromatography (GPC) provided the number average molecular weight and the polydispersity index (Mn 13 300 g/mol, PI 1.7). The PS-Au nanoparticles were prepared following modified Ulman reaction conditions, 11 using a 1/3.5 thiol/HAuCl4 reagent ratio and lithium triethylborohydride (Superhydride, Aldrich) as the reducing agent. UV-vis spectroscopy of a PS-Au solution in toluene confirmed the presence of the plasmon band at 523 nm, which is in the region characteristic of alkanethiol-capped gold nanoparticles. 12 The nanoparticles were isolated and redissolved several times in solvents (eg, chloroform) that are also solvents for the PS ligand. The Au core diameters were determined from transmission electron micrographs (TEM) and exhibit a moderate degree of polydispersity (6.2 (1.7 nm). Most of the nanoparticles appear to be spherically symmetric. However, several of the larger nanoparticles appear to be not particularly spherical.Incorporation of PS-Au into the PS matrix (Mn 46 400 g/mol, PI 1.05) was effected …