超分子胶体的合成与表征
Summary
A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.
Abstract
Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.
Introduction
介孔胶体材料发现在科学和技术的广泛应用，如用在原子和分子的物质1,2-基础研究的模型系统，因为光子材料3,4，作为药物递送系统5,6，用作涂料7和光刻表面图案形成8,9。由于疏液胶体，最终不可逆地聚集由于无所不在范德华相互作用亚稳材料，其操作成特定的靶结构是非常困难的。许多策略已经被开发，以控制胶体自组装包括使用添加剂以调整静电10,11或耗竭的相互作用12,13，或外部触发，如磁14或电动15字段。一个成熟的替代策略，以实现对结构的控制，这些系统的动力学和力学及其功能的机智^ h分子通过特定和定向力的相互作用。超分子化学提供小分子呈现位点特异性，定向性强但可逆的相互作用，其可以在强度由溶剂的极性，温度和光16进行调制的综合工具箱。因为它们的性能进行了散装和溶液中广泛的研究，这些分子是有吸引力的候选构造软材料进外来阶段以可预测的方式。尽管有这样的综合方法的潜在明确通过超分子化学编排胶体组装，这些学科很少接口裁缝介孔胶体材料17,18的属性。
超分子的胶体一个坚实的平台必须满足三个主要需求。首先，超分子结构部分的耦合应该温和条件下进行，以防止降解。其次，表面力在separati组件不是直接接触大应该由栓系基序，这意味着未涂覆胶体应当几乎完全通过排除容积相互作用相互作用支配。因此，该胶体的物理 – 化学特性应适合于抑制在胶体体系，如范德华力或静电引力固有的其他相互作用。第三，表征应该允许大会的明确归属的超分子部分的存在。为了满足这些三个前提，超分子胶体健壮两步合成被开发（ 图1a）。在第一步骤中，疏水NVOC官能化的二氧化硅颗粒是在环己烷中分散的准备。该NVOC组能够容易地切割，从而产生胺官能化的颗粒。胺的反应性高可进行直接的后官能化，使用范围广的温和的反应条件所需的超分子结构部分。在此，我们公关通过用硬脂醇和苯-1,3,5- tricarboxamide（BTA）衍生物20的硅石珠粒官能epare超分子胶体。十八烷醇几个起着重要的作用：它使胶体亲有机并介绍这有助于降低胶体21,22之间的非特异性相互作用短程立体排斥。范德华力，因为胶体的折射率和溶剂23之间的紧密匹配的进一步降低。光及温敏短程吸引力表面力被保护双边贸易20的邻硝基掺入产生的。 邻硝基苄基部分是一个光可切割组块的相邻双边贸易间的氢键时在discotics酰胺掺入形成（ 图1b）。经紫外光光切割的BTA溶液中能够识别并具有相同的BTA分子相互作用通过3倍ħydrogen债券阵，与强烈依赖于温度17粘结强度。由于范德华吸引力是最小为环己烷硬脂涂覆的二氧化硅粒子以及轻型和温度无关，所观察到的刺激响应胶体组件必须BTA-介导的。
这种详细的视频演示了如何合成和表征超分子胶体以及如何通过共聚焦显微镜，研究在紫外线照射他们的自我组装。此外，简单图像分析协议从聚集胶体区分胶体汗衫及确定每簇报道胶体的量。的合成策略的多功能性允许容易地变化的粒径，表面覆盖率以及引入的结合部分，这对于一个大家族介孔高级材料的胶态积木的发展开辟了新的途径。
Protocol
Representative Results
Discussion
当环己烷，具有1.426的折射率，被用作溶剂以分散BTA-胶体，范德华相互作用非常弱，由于胶体的折射率和溶剂几乎相同。注意，相比于在水中的裸二氧化硅胶体用于在环己烷中的SLS实验官能胶体的浓度要高得多。这是必要的，以获得足够强的散射，由于低对比度的折射率几乎匹配。立即检测出的环己烷样品中的痕量的水，尽管是间接地通过不可忽略的聚类由于毛细管力。因此，它是最重要的，以?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
作者承认提供的财政支持荷兰科学研究组织（NWO ECHO-STIP格兰特717.013.005，NWO VIDI格兰特723.014.006）。
Materials
| APTES | Sigma-Aldrich | ||
| FTIC | Sigma-Aldrich | ||
| TEOS | Sigma-Aldrich | ||
| LUDOX AS-40 | Sigma-Aldrich | Silica particles of 13 nm in radius | |
| MilliQ | — | — | 18.2 MΩ·cm at 25 °C |
| Ethanol | SolvaChrom | — | |
| Ammonia (25% in water) | Sigma-Aldrich | — | |
| Chloroform | SolvaChrom | — | |
| Cyclohexane | Sigma-Aldrich | — | |
| Dimethylformamide (DMF) | Sigma-Aldrich | — | |
| Stearyl alcohol | Sigma-Aldrich | — | |
| N,N-Diisopropylethylamine (DIPEA) | Sigma-Aldrich | — | |
| Benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate (PyBOP) | Sigma-Aldrich | — | |
| Succinimidyl 3-(2-pyridyldithio)propionate (SPDP) | Sigma-Aldrich | — | |
| Dithiothreitol (DTT) | Sigma-Aldrich | — | |
| NVOC-C11-OH | Synthesized | — | I. de Feijter, 2014 Responsive materials from adaptive supramolecular constructs, Doctoral thesis, Technical University of Eindhoven, The Netherlands |
| BTA | Synthesized | — | I. de Feijter, 2014 Responsive materials from adaptive supramolecular constructs, Doctoral thesis, Technical University of Eindhoven, The Netherlands |
| Centrifuge | Thermo Scientific | Heraeus Megafuge 1.0 | |
| Ultrasound bath | VWR | Ultrasonic cleaner | |
| Peristaltic pumps | Harvard Apparatus | PHD Ultra Syringe Pump | |
| UV-oven | Luzchem | LZC-a V UV reactor equipped with 8×8 UVA light bulbs (λmax=354 nm) | |
| Stirrer-heating plate | Heidolph | MR-Hei Standard | |
| Light Scattering | ALV | CGS-3 MD-4 compact goniometer system, equipped with a Multiple Tau digital real time correlator (ALV-7004) and a solid-state laser (λ=532 nm, 40 mW) | |
| UV-Vis spectrophotometer | Thermo Scientific | NanoDrop 1000 Spectrophotometer | |
| Confocal microscope | Nikon | Ti Eclipse with an argon laser with λexcitation=488 nm | |
| Slide spacers | Sigma-Aldrich | Grace BioLabs Secure seal imaging spacer (1 well, diam. × thickness 13 mm × 0.12 mm) | |
| Syringes | BD Plastipak | 20 mL syringe | |
| Plastic tubing | SCI | BB31695-PE/5 | Ethylene oxide gas sterilizable micro medical tubing |
| Pulsating vortex mixer | VWR | Electrical: 120V, 50/60Hz, 150W Speed Range: 500–3000 rpm |
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