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Optically transparent and heat‐resistant polymer films are useful in the field of organic glasses usable for electric insulators for panels, windows, optical devices, etc. A series of biopolyimides having non‐π‐conjugated backbones prepared using a renewable diamine, 4,4′‐diaminotruxillic acid dimethyl esters, and various dianhydride monomers were prepared and cast onto substrates to form transparent films with high heat resistances and good electric resistance. The second order orientation coefficients (P200) of the biopolyimide films were evaluated by polarized attenuated total reflection Fourier‐transform infrared spectroscopy, and the P200 values for the C−N stretching vibrations at a wavenumber of 1365 cm−1 displayed a good correlation with that for the aromatic C−C stretching at 1510 cm−1, regardless of the dianhydride structure. The in‐plane/out‐of‐plane birefringence and coefficients of linear thermal expansion exhibited strong correlations with P200 except for those of a few samples. Most of the biopolyimide films exhibited good transparencies with low birefringence and high electric resistance, which are applicable to flexible substrates with a low coefficient of thermal expansion for panel displays. [ABSTRACT FROM AUTHOR]