An in situ IR-spectroscopic study of the solid-state formation reaction of polyglycolide - Thermal elimination of NaCl from sodium chloroacetate

The thermal elimination of NaCl from sodium chloroacetate, a polymerization reaction that takes place between 150 and 200 degrees C in the solid state, leads quantitatively to the simplest polyester, polyglycolide. By in situ IR-spectroscopy, we have shown that the reaction proceeds smoothly and directly without intermediates or by-products. The endgroups of the polymeric product - ionised carboxylate groups (-COONa) and hydrogen-bonded alcohol groups (-COH) - are clearly detectable. It is therefore concluded that the polymer forms extended chains, not rings, during the course of this solid-state reaction. That corresponds well with the idea of a polymerization reaction in the solid state. However, this experiment does not exclude the formation of polyglycolide rings as further product because they do not contain any terminating groups.