| 摘要 |
The present invention provides a process for producing polyamic acids and polyimides having a controllable molecular weight and molecular weight distribution without the need to utilize end-capping agents in the polymerization process and without the need to stoichiometrically vary monomer ratios. The process of this invention involves subjecting a mixture of aromatic dianhydride and aromatic diamine monomers, at least one of which contains the group (CF3 - ? - R) linking two aromatic moieties, wherein R is CF3 or phenyl, to a low temperature, substantially isothermal solution polymerization process wherein the content of the mixed monomers in solvent is maintained within the range of from about 8 to about 12% by weight solids concentration during the polymerization process. The process is conducted for a sufficient length of time and uniformity of temperature, generally below about 35.degree.C, to achieve a weight average polyimide polymer molecular weight within the range of about 80,000 to about 135,000, more preferably of about 90,000 to about 125,000, a polyimide inherent viscosity within the range of from about 0.45 to about 0.70, and a polydispersity with the range of from about 1.7 to about 2.6.
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