synthesis and polymerization of vinylcyclopropanes

Abstract

Polyglycolide (polyglycolic acid, PGA) was prepared by thermally induced solid-state polycondensation from sodium chloroacetate. This reaction leads to a composite of PGA with NaCl, out of which the latter can be extracted by washing with water. A highly porous polymer remains. The course of the reaction was followed by differential scanning calorimetry (crystallinity), X-ray diffraction, NMR spectroscopy and viscosimetry (degree of polymerization), and the polymer was also analyzed by mass spectrometry and mercury porosimetry. The polymer chains grow during the reaction, but prolonged heating leads to a subsequent decrease in chain length due to thermal degradation. The formed NaCl crystals are increasing in size during the reaction. PGA from solid-state reaction is identical with PGA conventionally prepared by ring-opening polymerization, but the molecular weight is smaller (ca. 2 000). No oligomers (like diglycolide) were detected.