原位氨基化氧化石墨烯/聚酰亚胺复合材料的制备及性能

以1，4-双（4-氨基-2-三氟甲基苯氧基）苯（6FAPB）和3，3'，4，4'-二苯醚四酸二酐（ODPA）为合成聚酰亚胺（PI）的单体，首先采用原位氨基化方法使氧化石墨烯（GO）与6FAPB反应转变为原位氨基化GO，再与ODPA和剩余的6FAPB发生聚合反应得到原位氨基化GO/聚酰胺酸（PAA）溶液。涂膜后，经热酰亚胺化制备出GO质量分数分别为0.05wt%、0.1wt%、0.3wt%、0.5wt%和1.0wt%的原位氨基化GO/PI复合材料膜。利用FTIR、XPS、XRD、UV-vis、TGA、TMA、SEM、拉伸性能测试及接触角测试对原位氨基化GO/PI复合材料的结构和性能进行表征。结果表明，原位氨基化使GO以化学键与PI大分子链连接，有利于GO在复合材料基体中的稳定和均匀分散。XRD结果表明，所得到的原位氨基化GO/PI复合材料膜均为无定型结构。随GO质量分数增加，原位氨基化GO/PI复合材料薄膜的光学透明性急剧降低，但力学性能和热稳定性有一定提高。当GO的质量分数为1.0wt%时，原位氨基化GO/PI复合材料的拉伸强度由64 MPa增加到83 MPa，杨氏模量由1.67 GPa提高到2.10 GPa，10%热失重温度由593℃增加到597℃，玻璃化转变温度变化不大。由于热酰亚胺化后GO表面的大部分含氧官能团消失，原位氨基化GO/PI复合材料膜的吸水率由0.86%降低至0.58%，水接触角由72.5°增加到77.8°。

Preparation and properties of in-situ aminated graphene oxide/polyimide composites

1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) and 3,3',4,4'-oxydiphthalic dianhydride (ODPA) were used as the monomers of polyimide (PI). Using the in-situ amination method, the graphene oxide (GO) was firstly reacted with 6FAPB to obtain the in-situ aminated GO. Then, the in-situ aminated GO was polymerized with ODPA and 6FAPB to obtain the in-situ aminated GO/poly(amic acid) (PAA) solution. After coating of the GO/PAA solution on a clean glass substrate, the in-situ aminated GO/PI composites containing 0.05wt%, 0.1wt%, 0.3wt%, 0.5wt% and 1.0wt% GO (mass fraction) were successfully prepared by thermal imidization. By means of FTIR, XPS, XRD, UV-vis, TGA, TMA, SEM, tension tester and contact angle measurement, the structure and properties of the in-situ aminated GO/PI composites were characterized. These experimental results show that the in-situ aminated GO connects with PI macromolecular chains with chemical bonds, which is helpful for improving the dispersion uniformity of GO in PI matrix and the interaction between GO and PI molecular. The XRD results show that the in-situ aminated GO/PI composites are amorphous. The optical properties of the in-situ aminated GO/PI composite films show a sharp downward trend, while the mechanical and thermal properties increase with the increase of GO loading. When the mass fraction of GO is 1.0wt%, the tensile strength of the in-situ aminated GO/PI composites increases from 64 MPa to 83 MPa, the Young's modulus improves from 1.67 GPa to 2.10 GPa, furthermore, the 10% thermal decomposition temperature also increases from 593℃ to 597℃. However, the glass transition temperature (T_g) of the in-situ aminated GO/PI composites changes slightly. As a result of thermal imidization, most of the oxygen functional groups on the surface of GO disappear, the water uptake of the in-situ aminated GO/PI composites decreases from 0.86% to 0.58%, and the water contact angle enhances from 72.5°of pure PI film to 77.8° of 1.0%GO/PI film.