The Degradation of Polyglycolide in Water and Deuterium Oxide. Part II: Nuclear Reaction Analysis and Magnetic Resonance Imaging of Water Distribution

Magnetic resonance imaging (MRI) and scanning microbeam nuclear reaction analysis (NRA) were used to monitor changes of water ingress into polyglycolide (PGA) disks with degradation time. MRI detects H2O, whereas NRA is sensitive to D2O. The acid-catalysed hydrolysis of the ester is significantly slower in D2O than H2O because of the kinetic isotope effect. This behaviour was investigated in Part I. In this paper, NRA was used to investigate PGA hydration in buffers made from D2O, and NRA and MRI experiments were performed on samples degraded buffers made from a 50% mixture of D2O and H2O (D2O/H2O 50:50) to allow a comparison between the two techniques. The NRA and MRI results provide direct evidence in support of the four-stage reaction–erosion model reported in previous literature, and show that this model applies to polymer degradation in heavy water and in a buffer made from D2O/H2O 50:50. It is believed that this is the first time that NRA and MRI have been compared for the same hydrating system.