Interaction Between Polymer Chains Covalently Fixed to Single‐Walled Carbon Nanotubes
Interaction Between Polymer Chains Covalently Fixed to Single‐Walled Carbon Nanotubes
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DOI：
10.1002/macp.200600040
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发表时间：
2006-05
影响因子：
2.5
通讯作者：
H. Kitano;Kazutaka Tachimoto;Makoto Gemmei-Ide;N. Tsubaki
中科院分区：
文献类型：
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作者：
H. Kitano;Kazutaka Tachimoto;Makoto Gemmei-Ide;N. Tsubaki
将单壁碳纳米管（SWNT）用硝酸和硫酸的混合物氧化，在其末端提供极性基团，与携带葡聚糖（DEX）、聚（乙二醇）（PEG）或聚（N-乙烯基吡咯烷酮）（PVPy）链的偶氮型大分子引发剂在70°C下孵育。类似地，将氧化的 SWNT 与 2,2'-偶氮异丁腈和丙烯酸 (HAA) 或 N-乙烯基吡咯烷酮在 70°C 下孵育。由于SWNT具有较大的自由基捕获能力，对应于偶大分子引发剂（PEG、DEX或PVPy）的聚合物链和增长聚合物链（聚丙烯酸（HPAA）或PVPy）被共价固定到SWNT的表面。亲水聚合物修饰的SWNTs可以稳定地分散在水中。此外，用PEG和DEX修饰的SWNT分别在游离DEX和PEG存在下沉淀，而在同种游离聚合物存在下，PEG-和DEX修饰的SWNT没有沉淀。这似乎与水溶性DEX和PEG体系中由PEG和DEX分子之间的排斥相互作用引起的相分离现象有关。然而，两种聚合物修饰的单壁碳纳米管（PEG-SWNT 和 DEX-SWNT）的混合物没有表现出明显的相分离，这可能是由于固定在巨大的单壁碳纳米管上而产生的有效排斥聚合物-聚合物相互作用的空间位阻。此外，将HPAA-SWNT和PEG-SWNT或PVPy-SWNT的分散体混合后，分散体的浊度逐渐增加，而在二甲基亚砜存在下，没有观察到分散体混合物的浊度增加，这表明HPAA与SWNT表面的PEG或PVPy链之间存在氢键。这项工作中研究的修饰方法有望赋予单壁碳纳米管各种功能。
A single-walled carbon nanotube (SWNT), which had been oxidized with a mixture of nitric acid and sulfuric acid to afford polar groups at its ends, was incubated with an azo-type macroinitiator carrying dextran (DEX), poly(ethylene glycol) (PEG) or poly(N-vinylpyrrolidone) (PVPy) chains at 70 °C. Similarly, the oxidized SWNT was incubated with 2,2'-azoisobutyronitrile and acrylic acid (HAA) or N-vinylpyrrolidone at 70°C. Due to the large radical trapping ability of SWNT, the polymer chains corresponding to the cloven macroinitiator (PEG, DEX or PVPy) and the propagating polymer chains (poly(acrylic acid) (HPAA) or PVPy) were covalently fixed to the surface of the SWNTs. The hydrophilic polymer-modified SWNTs could be stably dispersed in water. Furthermore, the SWNTs modified with PEG and DEX sedimented in the presence of free DEX and PEG, respectively, whereas there was no precipitation of the PEG- and DEX-modified SWNTs in the presence of the same kind of free polymer. This seemed to be related to the phase separation phenomena in water soluble DEX and PEG systems induced by the repulsive interaction between PEG and DEX molecules. However, the mixture of two kinds of polymer-modified SWNTs (PEG-SWNT and DEX-SWNT) did not show noticeable phase separation, probably due to steric hindrance for the efficient repulsive polymer-polymer interaction by fixation to the gigantic SWNTs. Furthermore, upon mixing the dispersions of HPAA-SWNT and PEG-SWNT or PVPy-SWNT, the turbidity of the dispersions gradually increased, while no increase in turbidity of the dispersion mixture was observed in the presence of dimethyl sulfoxide, indicating hydrogen bonding between the HPAA and PEG or PVPy chains on the surface of the SWNTs. The modification methods examined in this work would be promising to give various functions to SWNT.