pH responsive MWCNT-star terpolymer nanohybrids
pH responsive MWCNT-star terpolymer nanohybrids
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DOI：
10.1039/c2sm27211c
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发表时间：
2013-01-01
期刊：
影响因子：
3.4
通讯作者：
Tsitsilianis, Constantinos
中科院分区：
文献类型：
--
作者：
Iatridi, Zacharoula;Tsitsilianis, Constantinos
我们提出了一种独特的多嵌段、杂臂星形嵌段共聚物，可以作为多壁碳纳米管在水介质中的有效分散剂。(polystyrene)(22)(poly(2-vinylpyridine)-b-poly(acrylic酸)(22)，PS22(P2VP-b-PAA)(22)，星形三元共聚物由于其两嵌段共聚臂的两性性质，在水溶液中表现出pH响应性的自组装行为。根据介质的pH值，观察到两种不同的自组装。在低pH(pH=2)条件下，形成了具有疏水PS核和壳层中的P2VP、PAA链段的核壳单分子胶束以及多核大分子复合胶束。在pH=8.5时，星体由双亲水转变为双疏水状态，形成网络状的胶束间组装。这种星形三元共聚物能够通过非共价相互作用分散多壁碳纳米管，从而在水中形成稳定的多壁碳纳米管-星形纳米杂化材料。更重要的是，所得到的MWCNT-STAR纳米杂化材料采用了物理吸附的STAR的“智能”pH响应特性，即纳米杂化材料可以在低pH和高pH下分别带正电荷或负电荷，而在中等pH窗口，由于相反电荷片段的中和而发生相分离。
We present a unique multisegmented, heteroarm star block terpolymer that can be used as an effective dispersing agent for multiwalled carbon nanotubes in aqueous media. The (polystyrene)(22)(poly(2-vinylpyridine)-b-poly(acrylic acid))(22), PS22(P2VP-b-PAA)(22), star terpolymer exhibits a pH responsive self-assembly behavior in aqueous solution, due to the ampholytic nature of its diblock copolymer arms. Depending on the pH of the medium, two different self-assemblies were observed. At a low pH (pH 2), core-shell unimolecular micelles, with a hydrophobic PS core and P2VP, PAA segments in the shell, as well as multicore large compound micelles were formed. At pH 8.5, the star was transformed from a bis-hydrophilic into a bis-hydrophobic state, leading to a network-like intermicellar assembly. This star terpolymer was capable of dispersing MWCNTs, through non-covalent interactions, thus leading to stable MWCNT-star nanohybrids in water. More importantly, the resulted MWCNT-star nanohybrids adopted the "smart" pH responsive properties of the physisorbed stars, i.e. the nanohybrids can be positively or negatively charged at low and high pH respectively, while at an intermediate pH window, phase separation occurs due to neutralization of the oppositely charged segments.