High-Pressure Synthesis of New Aromatic Poly(diazetidinediones) by Cyclodimerization Polymerization of Aromatic Diisocyanates

Abstract

New aromatic poly(diazetidinediones) having a strained four-membered heterocyclic ring structure, which we were unable to obtain by the polymerization under atmospheric pressure, were synthesized for the first time by the cyclodimerization polymerization of aromatic diisocyanates under high pressure without use of solvent or catalyst. As shown by a model compound study, aromatic monoisocyanates cyclodimerized almost quantitatively, yielding 1,3-disubstituted l,3-diazetidine-2,4-diones at 180-200 °C under 400-800 MPa for 20-40 h. Aromatic diisocyanates were converted cleanly to poly-(diazetidinediones) through the cyclodimerization polymerization at 200 °C under 700 MPa for 20 h.The polymers formed were pale yellow, opaque, hard solids with high crystallinity and insoluble in any solvent. They depolymerize drastically at around 270 °C in nitrogen into the parent diisocyanates.

Building a Cocrystal by Using Supramolecular Synthons for Pressure‐Accelerated Heteromolecular Azide–Alkyne Cycloaddition

“…1 Ha nd 19 FNMR spectra were recorded on aB ruker-400 (400 MHz) spectrometer by using [D 6 ]DMSO as the solvent. 13 CNMR spectra were recorded on aB ruker-500 (500 MHz) spectrometer using [D 6 ]DMSO as the solvent. Chemical shifts are reported in parts per million (ppm) and coupling constants are reported in hertz (Hz).…”

“…Chemical shifts are reported in parts per million (ppm) and coupling constants are reported in hertz (Hz). 1 HNMR chemical shifts were referenced versus TMS (0 ppm), 13 CNMR chemical shifts were referenced versus [D 6 ]DMSO (40.45 ppm) and 19 FNMR chemical shifts were referenced versus aC F 3 CO 2 He xternal standard (0 ppm). Mass spectra were recorded on aV GZ AB-HS mass spectrometer.E lemental analysis was performed by using an Elementar VARIO EL elemental analyzer.I nfrared spectra were recorded in solid phase on aB io-Rad FTS-65A FT-IR spectrometer.S ingle-crystal X-ray diffraction data were collected with aN ONIUS Kappa CCD diffractometer for 1, 2,a nd 1·2,w ith graphite monochromator and Mo Ka radiation [l (MoKa) = 0.71073 ].…”

“…Another solution to control such reactions was the application of pressure to induce and accelerate the reactions in the solid state, in which the prearrangement of functional groups would be nearly remained. Recently, high pressure has been successfully employed in facilitating organic reactions, such as polymerization of butadiyne, acetylene, cyanoacetylene, and some other systems . Yet, the application of crystal engineering and pressure in a wider scope of reactions in the solid state is highly favorable to be explored.…”

Influence of the storage of reactive urethane quasi-prepolymers in their composition and adhesion properties

“…The most important bands are located at 3400 cm À1 (free N-H stretching), 3300 cm À1 (N-H hydrogen bonded stretching), 2250 cm À1 (free NCO stretching), 1722 cm À1 (free CQO stretching in urethane), 1600 cm À1 (N-H bending in urethane), 1525 cm À1 (C-N stretching and N-H bending from urethane group) and 1100 cm À1 (C-O-C stretching in aliphatic polyether from the polyol) [1]. At 1780 cm À1 the CQO stretching band in uretdione, the dimer of the isocyanate, was observed [7]. By comparing the areas under the band at 1780 cm À1 before and after storage of the quasi-prepolymer, an increase was found, indicating that uretdione was formed during storage in the tinplate container.…”

Advances in cycloaddition polymerizations

“…Isocyanates are isoelectronic with ketenes and can also form cyclic dimers (1,3-diazetidine-2,4-diones) and trimers (trisubstituted triazetidinediones) when basic conditions are used. Imai et al have investigated 21 this process in polymer synthesis. Under high pressure conditions (and without solvent or catalysts), cycloaddition processes are favoured when compared to linear homopolymerizations with concomitant loss of carbon dioxide gas.…”