熔融法制备金属离子配位的氧化石墨烯/聚甲基丙烯酸甲酯复合材料及其性能研究

Preparation of GO/PMMA Nanocomposites with Significantly Increased Properties through Metal Ion Coordination

通过金属离子(二价铜离子、三价铁离子)配位的方法,增强了氧化石墨烯(GO)与聚甲基丙烯酸甲酯(PMMA)之间基体-填料的相互作用,实现了GO/聚合物复合材料的抗拉伸性能和热稳定性的大幅提升.采用红外光谱对聚合物基体加入GO和金属离子前后的特征峰变化进行研究,观察配位键是否成功作用于基体与填料之间.使用拉曼光谱分析了GO的表面结构,结果表明金属离子的加入对GO表面缺陷情况的影响很小.采用直接熔融法和母料法2种方法制备了复合材料,并对其进行性能测试,发现母料法制备的样品的力学性能更好.用扫描电子显微镜(SEM)观察材料的断面,结果表明,使用母料法制备的样品,其内部纳米材料的分散均匀性优于直接熔融法的样品.母料法制备的GO/PMMA复合材料拥有优异的力学和热学性能,而在引入了金属离子进行配位之后,其杨氏模量进一步提升29.6%,抗拉强度提升31.8%,最大热失重温度提升26°C,表明配位键提供的微观强相互作用增强了材料的宏观性能.

Metal ion coordinated GO/PMMA composites have been prepared by melt method. The interfacial interaction between the nanofiller and the polymer matrix is significantly increased due to the coordination bonding. As a result, the mechanical and thermal properties of the composites are highly improved. To study the property variation with the change of metal ions and preparation methods, two different metal ions (Cu(II) and Fe(III)) were added into the GO/PMMA system, respectively, and the composites were prepared by two different methods-the direct-melt method and the master-batch method. Fourier transform infrared spectroscopy (FTIR), Raman spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), tensile test, and thermogravimetic analysis (TGA) were performed to study the structures and properties of the composites. The FTIR results showed that GO and PMMA are successfully bridged via coordination bonding, for the characteristic peaks showed obvious blue shifts. Raman spectra indicated that coordination causes no extra defect to the GO sheets. SEM images showed that the GO sheets could be homogeneously dispersed in PMMA through master-batch method, while a poor dispersion through direct-melt method. From the tensile test results, it could be seen that the composites prepared by master-batch method had a better mechanical performance than those prepared by directmelt method because of the different dispersion states. Fe(III)-coordinated composites have better mechanical performance than Cu(II)-coordinated composites do, due to the higher valence state of iron ions. The Young ’s modulus and tensile strength of Fe(III)-0.5 wt% GO/PMMA composite are 29.6% and 31.8%, respectively, higher than those of the composite with only GO, and 75.0% and 35.7%, respectively, higher than those of neat PMMA. The temperature of maximum weight loss of Fe(III)-0.5 wt% GO/PMMA is 26 °C higher than that of GO/PMMA, and 82 ℃ higher than that of neat PMMA. This metal ion coordination method is efficient and simple, and can easily bridge nanofillers and polymer matrixes containing polar groups. This approach opens up a new strategy for improving the performance of many kinds of nanocomposites.