| 摘要 |
PROBLEM TO BE SOLVED: To obtain a linear polyimide having a specific recurring unit, of which molecular terminals are blocked by a norbornene-based dicarboxylic acid anhydride having a carbon-carbon double bond, and having an extremely excellent heat resistance. SOLUTION: This linear polyimide is expressed by formula I [(m) is 100-70 mol.%; (n) is 0-30 mol.%; (l) is 1-100 degree of polymerization]. The logarithmic viscosity (measured by using N,N-dimethylacetamide as a solvent, 0.5 g/dl concentration and at 35 deg.C) of a linear polyamic acid of formula II as a precursor of the above linear polyimide is preferably 0.05-1.0 dl/g. The linear polyimide can be obtained by using 1,3-bis(4-aminophenoxy)benzene and 3,3',4,4'- biphenyltetracarboxylic acid as indispensable monomers and mixing pyromellitic acid dianhydride with these monomers. Also, the molar ratio of the aromatic tetracarboxylic acid dianhydride component to the aromatic diamine component is preferably 0.7-1.0.
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