In the 1940s polyimide early stage of development has been reported fat-containing polyimide unit. As the pyromellitic dianhydride with a diamine aliphatic polyimide. Due to the low thermal stability of these polymers, generally about 400 ℃ began to decompose. Simultaneous multi-crystalline polymers, the poor mechanical properties, it has not been developed. With respect may be dissolved in an organic solvent, and require low dielectric constant of the refractory material having optical properties becomes imperative. And since the insoluble aromatic polyimides, high dielectric constant and transparent communication within the wavelength range of light loss, usually with color and other reasons. Its use is limited, so in the early 1990s to study fat-containing polyimide unit becomes active again. Containing alicyclic polyimide because of its high transparency, low dielectric constant, good solubility characteristics can be obtained in the color filter, aligning agent, nonlinear optical materials, separation membranes, etc. application. The introduction of the spiro ring structure of the unit and can destroy the plane of the molecule chains, reduce load transfer, but also reduces the packing density of the molecular chain. For increasing the solubility, reduce the dielectric constant, increase transparency and the like are advantageous.
Typically the fat-containing polyimide unit into three categories: Aliphatic diamine and the aromatic dianhydride synthesized polyimide. From fatty dianhydride and aromatic diamine polyimide dianhydride and the fat and fatty diamine full fat polyimide.