“…Another effective way to transparent PIs is to use monomers containing nonconjugated spacer such as diphenylether diamine [12] or triphenylmethylene diamine. [13] One of the most promising approach is to synthesize semi-aromatic PIs consisting of aromatic diamines and alicyclic dianhydrides, such as 1,2,3,4butanetetracarboxylic dianhydride (BT), [14] 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), [15] 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride (DM-CBDA), [16] 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), [17] 1S,2R,4S,5Rcyclohexanetetracarboxylic dianhydride (CHDA), [4,18] bicyclo-[2.2.2]oct-7-ene-2-exo,3-exo,5-exo,6-exo-2,3 : 5,6-dianhydride (BTA), [19] bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic 2,3 : 5,6-dianhydrides (H-BTA), [20] 3,3',4,4'-bicyclohexyltetracarboxylic dianhydride (H-BPDA), [21] 5-(2,5-Dioxytetrahydrofuryl)-3-methyl-3cyclohexene-1,2-dicarboxylic anhydride (CDA), [22,23] cyclopentanone bis-spironorbornanetetra carboxylic dianhydride (CpODA) [24] and 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride (TDA) [25] as show in Scheme 1. [4,18,26,27] Although these semi-aromatic PIs always have high optical transparency, good solubility and low CTE, they still suffer from the relatively low thermal stability.…”