Two series of alicyclic polyimides composed of cis- and trans-dicyclohexyl-3,3′,4,4′-tetracarboxylic dianhydrides (DCDAs) and aromatic diamines were prepared. All cis-polymers could be readily prepared both in a one-step method and a two-step method. However, a two-step method is preferably applied in the preparation of trans-polymers, because in a one-step method the trans-configuration is partially lost at higher temperatures. These polyimide solutions could be cast into tough and flexible films, which were characterized by inherent viscosity, GPC, DSC, TGA measurements, and UV-vis spectroscopy. The glass transition temperatures (Tg's) of the polymers were in the range of 210–270°C and the 5% weight loss temperatures were around 480°C for all PIs prepared. The optical transmittances of these films were more than 80% at 350 nm for ca. 15 μm thickness.
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Shiotani et al. (2001) studied this question.