多壁碳纳米管分散剂的制备及分散性能研究

Study on Preparation and Dispersion Properties of Multi-Walled Carbon Nanotube Dispersants

摘要:

由于碳纳米管（CNTs）自身较大的比表面积及碳管间强的作用力，使其在溶剂中不易分散，因此应用前需要进行分散处理，使其能够满足更多应用的需求。利用在淀粉上接枝丙烯酸（AA）或苯乙烯（St），分别制备了淀粉接枝丙烯酸聚合物（SAa）、苯乙烯聚合物（SSty）、丙烯酸-苯乙烯聚合物（SSA）新型分散剂，并研究在水中对多壁碳纳米管（MWCNTs）的分散性。结果表明：改性淀粉的分子量（M_w）由4.25×10⁵减小到3.92×10⁵、分子量分布系数（M_w/M_n）由3.01减小到了2.88，分子量分布较窄，聚合物的结构更加稳定；改性淀粉颗粒溶胀崩解，原有形貌发生改变，晶型受到破坏，尺寸变小更有利于分散；此外，对于0.10 g?L^-1的MWCNTs，使用SSA的MWCNTs分散效果最好，SSA分散MWCNTs 在20 d时的沉降率为30.6%。通过机理研究发现，SSA利用结构中接枝聚合的苯环与MWCNTs的p―p非共价键吸附在MWCNTs表面，通过静电斥力和空间位阻效应的协同作用对MWCNTs进行分散，因而SSA比SAa和SSty更能有效地降低水中MWCNTs的聚集趋势。

Abstract:

Carbon nanotubes （CNTs） are difficult to disperse in solvents because of their large specific surface area and strong interaction between carbon nanotubes. Therefore， it is necessary to disperse CNTs before their application， so that they can meet the needs of more applications. In this paper， starch was grafted with acrylic acid （AA） or styrene （St） to prepare starch grafted acrylic acid polymer （SAa）， styrene polymer （SSty） and acrylic acid-styrene polymer （SSA） respectively. A new dispersant was prepared， and its dispersibility in water for multi-walled carbon nanotubes （MWCNTs） was studied. The results showed that the molecular weight （Mw） of the modified starch decreased from 4.25×10⁵ to 3.92×10⁵， and the M_w/M_n ratio decreased from 3.01 to 2.88. The molecular weight distribution was narrow and the polymer structure was more stable. Moreover， the modified starch granules swelled and disintegrated， the original morphology changed， the crystal form was destroyed， and the size became smaller， which was more conducive to dispersion. In addition， for 0.10 g?L^-1MWCNTs， the dispersing effect of MWCNTs using SSA was the best， and the sedimentation rate of MWCNTs dispersed by SSA was 30.6% for 20 days. Through mechanism research， it is found that SSA adsorbed MWCNTs on the surface of MWCNTs by the non-covalent bond between the grafted benzene ring and the p―p of MWCNTs， and dispersed MWCNTs by the synergistic effect of electrostatic repulsion and steric effects. Therefore， SSA can effectively reduce the aggregation trend of MWCNTs in water than SAa and SSty.