Transparent polymer substrates for flexible perovskite solar cells and foldable displays must offer high transparency, thermal stability, and active deformability. With the rapid development of intelligent and adaptive flexible electronics, shape memory functionality has emerged as a key requirement for next-generation devices to enable smart behaviors such as self-deployment or morphing. However, although conventional colorless transparent polyimides exhibit outstanding transparency and thermal resistance, they tend to lack shape memory functionality, making it difficult to meet the demands of next-generation intelligent flexible devices such as self-deployable structures. We designed a molecular system using two dianhydrides, one containing a hexafluoroisopropylidene group and one containing ether linkages, and three fluorinated diamines with different rigidities. The hexafluoroisopropylidene and ether units suppress charge-transfer complex formation to enhance optical transparency, while the ether linkages also improve chain flexibility. The varying diamine rigidity enables tuning of thermal properties. Based on this design, colorless shape memory polyimide (co-CSMPI) films were prepared via quaternary copolymerization. The results demonstrate that co-CSMPIs exhibit excellent overall performance. A representative co-CSMPI possesses a glass transition temperature (Tg) of 241 °C, satisfying the requirements for high-temperature processing; a transmittance of 88.0% at 500 nm, indicating good optical transparency. Furthermore, it exhibits excellent shape memory performance, with shape fixity ratios (Rf) of 99.4% and shape recovery ratios (Rr) of 98.9%. The colorless shape memory polyimide films enable lighter device designs, holding great promise for flexible perovskite solar cell substrates and foldable display covers.

Shuting Jiang, Kong Deyan, Kang Yu Kang, Xinli Xiao, Xiaofei Wang, Jinsong Leng, Yanju Liu

Colorless shape memory polyimide films for flexible optoelectronics.pdf