单壁碳纳米管与热可逆嵌段共聚物及表征功能化小角度中子散射
Summary
A method for the functionalization of carbon nanotubes with structure-tunable polymeric encapsulation layers and structural characterization using small-angle neutron scattering is presented.
Abstract
We demonstrate a protocol for single-walled carbon nanotube functionalization using thermo-sensitive PEO-PPO-PEO triblock copolymers in an aqueous solution. In a carbon nanotube/PEO105-PPO70-PEO105 (poloxamer 407) aqueous solution, the amphiphilic poloxamer 407 adsorbs onto the carbon nanotube surfaces and self-assembles into continuous layers, driven by intermolecular interactions between constituent molecules. The addition of 5-methylsalicylic acid changes the self-assembled structure from spherical-micellar to a cylindrical morphology. The fabricated poloxamer 407/carbon nanotube hybrid particles exhibit thermo-responsive structural features so that the density and thickness of poloxamer 407 layers are also reversibly controllable by varying temperature. The detailed structural properties of the poloxamer 407/carbon nanotube particles in suspension can be characterized by small-angle neutron scattering experiments and model fit analyses. The distinct curve shapes of the scattering intensities depending on temperature control or addition of aromatic additives are well described by a modified core-shell cylinder model consisting of a carbon nanotube core cylinder, a hydrophobic shell, and a hydrated polymer layer. This method can provide a simple but efficient way for the fabrication and in-situ characterization of carbon nanotube-based nano particles with a structure-tunable encapsulation.
Introduction
碳纳米管（CNT）是通过轧制微米级石墨片成纳米管形成的中空圆筒状的纳米颗粒。因为他们的非凡的机械，热和电性能的，碳纳米管已经被广泛1-3调查作为一个新的候选用于治疗和生物传感应用，以及在自组装的纳米复合材料的纳米填料官能纳米粒子。然而，它们的溶解性差并有志于做出常用的有机和水性溶剂束强烈的偏好阻碍生物应用方便，环保的处理以及进步。因此，各种官能化的方法，例如超声处理，表面化学改性，并通过使用表面活性剂和嵌段共聚物的非共价官能化，4-9已经开发来修改在CNT表面和提高其分散性在广泛的溶剂。非共价泛函基于物理的表面处理补肾中药方法，特别是，被认为是一个有希望的和健壮的策略，因为在固有的CNT特性的任何表面改性诱导抑制可以最小化。10迄今为止，已经有不少努力提高分散效率的通过采用各种类型的分散剂，包括基本的表面活性剂（ 如，SDS CTAB，NaDDBS），7,11两亲嵌段共聚物，8生物材料（ 如 DNA），12,13和合成的官能聚合物的非共价官能化的方法（ 例如 ，共轭聚合物，芳族聚合物）。14,15
PEO-PPO-PEO聚合物，一种由两个亲水聚（环氧乙烷）的三嵌段共聚物（PEO）在两条链末端共价结合到一个疏水聚（环氧丙烷）在中心处（PPO）链，可以延长电势非共价键的官能化碳纳米管的应用我2N水溶液。这些聚合物提供接口，这不仅是为了在CNT表面，但也向水介质和其它聚合物基质并且表现出巨大的生物相容性友好由于PEO链的毒性最小。这在一个宽的范围内分散的环境中，以及在生物医学应用的聚合物涂覆的CNT的利用率便于更容易处理。12,16-17此外，这些聚合物的基于其对外部刺激敏感反应的富热力学相行为使在其中内和粒子间结构可以可逆地和精确地控制智能嵌段共聚物的CNT混合纳米结构的制造。18-21在这里，我们提出了一个协议，用于基于CNT的混合纳米粒子具有的可调谐封装层的制造PEO105-PPO70-PEO105（泊洛沙姆407）。所得到的结构的特征在于通过小角中子散射（SANS）。这项工作预计将introducË智能功能构建块的概念，并帮助非专业人士轻松地准备嵌段共聚物功能化的碳纳米管悬浮液和使用SANS在橡树岭国家实验室的详细特征。
Protocol
Representative Results
Discussion
SANS和AFM测量表明，单壁碳纳米管已成功解捆绑并单独使用泊洛沙姆407三嵌段共聚物分散在水溶液中。在此样品的制备方法，超声波处理并离心过程是确定最终悬浮液的特征的关键步骤。的单壁碳纳米管间的强相互作用，这迫使未涂覆的SWNT在溶液中捆绑在一起，必须克服与嵌段共聚物稳定的各个单壁碳纳米管。提供足够的能量，适当长的时间使聚合物克服能垒，并成功地稳定了单壁碳纳米管。然?…
Divulgations
The authors have nothing to disclose.
Acknowledgements
The Research at Oak Ridge National Laboratory’s Spallation Neutron Source and Center for Nanophase Materials Sciences was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The author, Zhe Zhang, gratefully acknowledges the financial support from Jülich Center for Neutron Science, Research center Jülich.
Materials
| HiPco Single-walled carbon nanotubes | Unidym | P2771 | |
| Pluronic F127 | BASF | 9003-11-6 | Mw = 12.6 kg/mol |
| 5-methylsalicylic acid | TCI America | C0410 | |
| Ultrasonic processor | Cole-Parmer | ML-04714-52 | |
| Sorvall 6 plus centrifuge | Thermo Scientific | 46910 | |
| Innova AFM | Bruker | ||
| Si-wafer | Silicon Quest International | 150 mm in diameter ; N type <1-1-1> cut ; 1-10 Ohm/cm ; Single-side polyshed (675 +- 25 um) ; Diced (12 mm x 12 mm) |
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