In this work, we report highly transparent flexible polyimide/silica hybrids with low coefficient of thermal expansion (CTE) comparable to that of a glass, low optical birefringence and high thermal stability over 400 degrees C. We started from the polyimide system based on 2,2'-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA)/2,2'-bis-(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB), which has high optical transparency for aromatic polyimides, utilized well-known simple strategy of using silane end-capped oligomeric polyamic acid and silica sol-gel reaction to increase the miscibility between PI and silica, and finely tuned the property by control of molecular weight and processing condition. The resulting hybrid film showed homogeneous surface after oxide deposition and annealing, and passed the repeated folding/unfolding test with more than 200,000 cycles. These finely tuned hybrid films are promising candidate for flexible transparent substrate especially for high temperature (>400 degrees C) electronic and optoelectronic manufacturing processes. (C) 2016 Elsevier Ltd. All rights reserved.