Abstract
The degradation of polymers is described by mathematical models based on bond cleavage statistics including the decreasing probability of chain cuts with decreasing average chain length. We derive equations for the degradation of chains under a random chain cut and a chain end cut mechanism, which are compared to existing models. The results are used to predict the influence of internal molecular parameters. It is shown that both chain cut mechanisms lead to a similar shape of the mass or molecular mass loss curve. A characteristic time is derived, which can be used to extract the maximum length of soluble fragments l of the polymer. We show that the complete description is needed to extract the degradation rate constant k from the molecular mass loss curve and that l can be used to design polymers that lose less mechanical stability before entering the mass loss phase.Graphical abstract
Highlights
The design of degradable polymers often relies on cleavable functional groups in the main chain [1–4]
The polymer contains chains with RU(0) repeating units and NE(0) chain ends at the beginning of the degradation
The probability to have a chain cut between two repeating units is independent of the position of these repeating units within the chain
Summary
The design of degradable polymers often relies on cleavable functional groups in the main chain [1–4]. The availability of water in relevant system environments such as the human body or nature created a special interest in hydrolysable bonds, such as ester, anhydride or orthoester bonds. Macromolecules are split into two smaller fragments in each hydrolysis step. If these polymer fragments are small enough, they become water soluble and the mass of the polymer material decreases depending on the diffusibility of these molecular fragments through the amorphous domains of the partially degraded material. The diffusion of water in the polymer plays an important role. Bulk erosion occurs homogenously in the entire polymer if water diffusion is fast in comparison to the kinetics of hydrolysis
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