ABSTRACT Alicyclic polyimides were prepared from the monomers with a polyalicyclic structure using a two-step method. The poly(amic acid)s of semi-aromatic polyimides possessed a inherent viscosity range of 1.0-0.5, and formed tough polyimide films after being cured. In the case of full-aliphatic polyimides, the poly (amic acid) solutions had somewhat low viscosities, but gave the polyimides as free standing films. Semi-aromatic polyimides were soluble in aprotic polar solvents like DMAc, whereas all the full-aliphatic polyimide films were insoluble except sulfuric acid. The alicyclic polyimide films had no absorption in visible area (400-780 nm) and the transparencies were over 85%. The transparency at room temperature was maintained up to 200 oC when cured in air. However, the transparencies both before and after being cured at 400 oC in N2 were almost the same. The semi-aromatic polyimide films had an average refractive index (nAV) range of 1.599-1.617. The decreasing aromatic character of the polyimide diminished the refractive index. The nAV of a full-aliphatic polyimide was 1.522, which translates into a dielectric constant of 2.55 according to a modified Maxwell’s equation . The birefringencies were nearly zero. All the alicyclic polyimides had the 5% weight loss temperatures over 450 oC in nitrogen, and over 400 o C in air. They possessed Tg’s over 280 oC. The alicyclic polyimide films had a tensile modulus range of 3.0-1.3 GPa, and a tensile strength range of 145-38 MPa. Semi-aromatic polyimide films displayed high strength and had an elongation at break range of 30-5%.
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