In analogy to the synthesis of polycarbonates, poly(Bisphenol A N-phenyliminocarbonate) (7) (Mw = 85 000, by GPC relative to polystyrene standards), was synthesized from the disodium salt of Bisphenol A and phenyliminophosgene. 7 formed transparent, amorphous, mechanically strong films (tensile strength, 550 kg/cm2; tensile modulus, 23 500 kg/cm2; elongation at break, 2.8%). Upon heating to about 300–350 °C, 7 spontaneously rearranged to poly(Bisphenol A N-phenylurethane) (4). The rearrangement was a first-order reaction with an activation energy of 180 kJ/mol. The transformation of 7 to 4 was followed by FT-IR. Analysis of the polymer before and after heat treatment by gel permeation chromatography and low-angle laser light scattering indicated that the rearrangement proceeded without detectable backbone cleavage. The chemical structure of 4 was confirmed by 1H and 13C NMR. This polymer formed transparent, amorphous, and mechanically strong films (tensile strength, 567 kg/cm2; tensile modulus, 23,800 kg/cm2; elongation at break, 5.5%). Contrary to unsubstituted polyurethanes, 4 was thermally very stable. The onset of the decomposition exotherm was observed at 475 °C (DSC, in air, open pan), and the polymer started to lose weight at 504 °C (TGA, in air). Since N-substituted polyurethanes cannot be readily obtained by conventional polymerization reactions, the exceptionally clean, thermal rearrangement of 7 to 4 represents a rare case of a synthetically useful, polymeric backbone rearrangement.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry