title: Degradation mechanisms of bioresorbable polyesters. Part 1. Effects of random scission, end scission and autocatalysis.
abstract: A mathematical model was developed to relate the degradation trend of bioresorbable polymers to different underlying hydrolysis mechanisms, including noncatalytic random scission, autocatalytic random scission, noncatalytic end scission or autocatalytic end scission. The effect of each mechanism on molecular weight degradation and potential mass loss was analysed. A simple scheme was developed to identify the most likely hydrolysis mechanism based on experimental data. The scheme was first demonstrated using case studies, then used to evaluate data collected from 31 publications in the literature to identify the dominant hydrolysis mechanisms for typical biodegradable polymers. The analysis showed that most of the experimental data indicates autocatalytic hydrolysis, as expected. However, the study shows that the existing understanding on whether random or end scission controls degradation is inappropriate. It was revealed that pure end scission cannot explain the observed trend in molecular weight reduction because end scission would be too slow to reduce the average molecular weight. On the other hand, pure random scission cannot explain the observed trend in mass loss because too few oligomers would be available to diffuse out of a device. It is concluded that the chain ends are more susceptible to cleavage, which produces most of the oligomers leading to mass loss. However, it is random scission that dominates the reduction in molecular weight.
authors.affiliation: Institute for Advanced Manufacturing, Faculty of Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Gleadall
authors.affiliation: Department of Engineering, University of Leicester, Leicester LE1 7RH, UK. Electronic address: jp165@le.ac.uk.
authors.forename: Jingzhe
authors.initials: J
authors.lastname: Pan
authors.affiliation: Purac Biomaterials, P.O. Box 21, 4200 AA Gorinchem, The Netherlands.
authors.forename: Marc-Anton
authors.initials: MA
authors.lastname: Kruft
authors.affiliation: BioMediTech and Department of Electronics and Communications Engineering, P.O. Box 692, 33101 Tampere, Finland.
authors.forename: Minna
authors.initials: M
authors.lastname: Kellomäki
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D002384:Catalysis; D003198:Computer Simulation; D006868:Hydrolysis; D008962:Models, Theoretical; D008970:Molecular Weight; D011091:Polyesters / Q000737:chemistry*; D013997:Time Factors
chemical_list: D001672:Biocompatible Materials; D011091:Polyesters
keywords: Biodegradable polymers; Biodegradation; End scission; Modelling; Random scission