“…It is an effective way to reduce the dielectric constant of the polymer by decreasing the molar polarizability or increasing the molar volume of the molecules. Hence, the dielectric constants of polyimides could be reduced by introducing fluorine [ 5 , 6 , 7 , 8 ], aliphatic/alicyclic structure [ 9 , 10 , 11 ], large side groups [ 12 , 13 , 14 , 15 , 16 ] or air [ 17 , 18 , 19 , 20 ] into polymer backbones. Zhi et al [ 21 ] synthesized a series of semi-aromatic polyimide sheets, which were derived from the copolymerization of an alicyclic tetrahedral dianhydride (HBPDA) and an aromatic diamine mixture containing three flexible diamines.…”