Degradation mechanisms of bioresorbable polyesters. Part 2. Effects of initial molecular weight and residual monomer.
This paper presents an understanding of how initial molecular weight and initial monomer fraction affect the degradation of bioresorbable polymers in terms of the underlying hydrolysis mechanisms. A mathematical model was used to analyse the effects of initial molecular weight for various hydrolysis mechanisms including noncatalytic random scission, autocatalytic random scission, noncatalytic end scission or autocatalytic end scission. Different behaviours were identified to relate initial molecular weight to the molecular weight half-life and to the time until the onset of mass loss. The behaviours were validated by fitting the model to experimental data for molecular weight reduction and mass loss of samples with different initial molecular weights. Several publications that consider initial molecular weight were reviewed. The effect of residual monomer on degradation was also analysed, and shown to accelerate the reduction of molecular weight and mass loss. An inverse square root law relationship was found between molecular weight half-life and initial monomer fraction for autocatalytic hydrolysis. The relationship was tested by fitting the model to experimental data with various residual monomer contents.
Department of Engineering, University of Leicester, Leicester LE1 7RH, UK.
Andrew
A
Gleadall
Department of Engineering, University of Leicester, Leicester LE1 7RH, UK. Electronic address: jp165@le.ac.uk.
Jingzhe
J
Pan
Purac Biomaterials, PO Box 21, 4200 AA Gorinchem, The Netherlands.
Marc-Anton
MA
Kruft
BioMediTech and Department of Electronics and Communications Engineering, PO Box 692, 33101 Tampere, Finland.
Minna
M
Kellomäki
D001672:Biocompatible Materials / Q000737:chemistry*; D003198:Computer Simulation; D008962:Models, Theoretical; D008970:Molecular Weight; D011091:Polyesters / Q000737:chemistry*
D001672:Biocompatible Materials; D011091:Polyesters
Biodegradable polymers; End scission; Initial molecular weight; Random scission; Residual monomer