The Friedel-Crafts homopolycondensations of 3-(4-biphenylyl)-3-chlorophthalide (1 a), 3-(2fluorenyl)-3-chlorophthalide (1 b), 3-(4-phenoxyphenyl)-3-chlorophthalide (1 c), 3-(4-phenylthiophenyl)-3-~hlorophthalide (1 d) were studied. The homopolycondensation of 1 a was found to give linear, fully soluble polymers. A gelation, depending on reaction parameters, can occur in the reactions of l b -l d . The methylene group of l b was shown to be reactive in the course of synthesis, giving cross-links. Using the NMR pulsed gradient spin echo method, it was found, that degradations of macromolecular chains in the homopolycondensation of l c is followed by gelation. A proposed mechanism of gelation is based on the transformations of intermediate acyloxonium complexes. Similar transformations of acyl-sulfonium complexes are suggested to occur in the course of the homopolycondensation of 1 d.
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