Acknowledgements

Thus, it is shown that star-shaped oligo- and polyimides with narrow MWD (Mw/Mn = 1.1–1.2) can be synthesized by polycondensation under these conditions. To confirm the presence of reactive amino groups in SOI molecule, the following experiments were performed. In Figure 22a, the IR spectrum is shown of acetyl derivative SOI-ac10 obtained by the treatment of SOI 10 with acetic anhydride. The reaction of SOI with acetic anhydride leads to the disappearance absorption band of the amino group at 3480 cm<sup>1</sup> and the appearance of a new band at 1538 cm<sup>1</sup>

H spectra (b) of SOI 10 (1) and SOI-ac10 (2).

5.4 ppm (NH2) and 6.3–6.4 ppm (aromatic protons of terminal moiety) disappear, and new signals appear at 10.1 ppm (▬NH▬C=O)and 2.0 ppm (CH3▬C=O), in

Presently, two novel tetrafunctional amines and corresponding tetra-arm starshaped oligomers with Mw/Mn < 1.6 were also synthesized via B4 + AB scheme, where AB is 2-APPA and B4 is the product of direct condensation of di-N-BOCprotected 3,5-diaminobenzoic acid with aromatic diamines (ODA, AFL) [34] in the

1. The one-pot high-temperature catalytic polycondensation of diamines and tetracarboxylic acids dianhydrides in molten benzoic acid at 140–160°C is a new effective, technologically simple, and ecologically friendly method for obtaining polyimides and copolyimides of different chemical structures and topologies including linear polyimides from low reactive monomers, polyimides based on AB monomers, random and multiblock copolyimides, hyperbranched polyimides, star-shaped oligomers with narrow MMD and

2. Kinetics and mechanism of this method were investigated in detail. Due to catalysis of the first stage of the process—transient polyamic acid formation,

3. Imidization reaction at the conditions of polyimide synthesis at 140–160° C in molten benzoic acid in open system with slow inert gas flow behaves like

combined with its low equilibrium constant—this stage is kinetically

insignificant, and imidization becomes the limiting reaction.

H spectrum of the SOI-ac10 (Figure 22b), the signals at

(amide II). In the NMR <sup>1</sup>

Figure 22.

IR spectra (a) and NMR <sup>1</sup>

Solvents, Ionic Liquids and Solvent Effects

7. Conclusions

60

full correspondence with our expectations.

presence of triphenyl phosphate-pyridine.

controlled arm length, etc.

The work is supported by the Russian Foundation of Basic Research, Grant #19-03-00820, and the Ministry of High Education and Science of Russian Federation.
