Synthesis and properties of novel alicyclic-functionalized polyimides prepared from natural-(D)-camphor

摘要

In this article, a new alicyclic-functionalized diamine, 1,3-bis(4-aminophenoxymethylene)-1,2,2-trimethylclopentane (BAMT) was successfully synthesized starting from natural - (D)-camphor through four reaction steps of oxidation to offer a dicaboxylic acid, reduction to offer a diol, nucleophilic substitution to give a dinitro compound and then reduction to give the final diamine. Two alicyclic-containing polyimides were prepared by polycondensing BAMT with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-oxydiphthalicanhydride (ODPA), respectively. For the studies of the structure-property relationships of the polyimides, one aromatic polyimide of 4, 4′-oxydianiline (ODA) polycondensed with ODPA was prepared in comparison. The alicyclic-containinig polyimides PI (BPDA-BAMT) and PI (ODPA-BAMT) maintain good thermal properties with glass transition temperatures (T_g) of 257°C and 240°C, and temperatures at 5% weight loss (T_5) of 443°C and 436°C in nitrogen, respectively. The alicyclic polyimides exhibit tensile strengths of 91.9-133 MPa, Young's moduli of 2.75 - 3.24 GPa, and elongations at break of 5.6-18%. Compared with the aromatic polyimide PI (ODPA-ODA), PI (ODPA-BAMT) shows improved transparency with the UV-Vis transmittance at 500 nm over 80%. In addition, PI (ODPA-BAMT) displays better solubility than PI (ODPA-ODA), which has been confirmed by the bigger d-spacing value of PI (ODPA-BAMT) than that of PI (ODPA-ODA) calculated from the Wide-angle X-ray Diffraction spectra. This study indicates that the renewable forestry compound, such as natural - (D)-camphor, could be a good origin for the structural designing and preparation of alicyclic-containing polyimides with outstanding combined features suitable for advanced microelectronic and optoelectronic applications.