The interplay between network morphology and degradation kinetics of polymers: Theoretical and experimental analysis by
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.457
The interplay between network morphology and degradation kinetics of polymers: Theoretical and experimental analysis by means of a 2D model system Rainhard Machatschek1, Shivam Saretia1,2, Andreas Lendlein1,2* 1
Institute of Biomaterial Science, Helmholtz-Zentrum Geesthacht and Berlin-Brandenburg Center for Regenerative Therapies, Kantstraße 55, 14513 Teltow, Germany 2 Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Straße 24-25, 14469 Potsdam, Germany *Correspondence to: Andreas Lendlein E-mail: [email protected]
ABSTRACT
Network formation by cross-linking is a common method to incorporate functions like elastic deformability, shape-memory capability or hydrogel formation into polymer materials for medical applications. Since these materials are often intended to degrade, their design would benefit from a quantitative prediction of the interdependence between network architecture and degradation behavior. Here, we introduce a quantitative description of the degradation behavior of polymer networks. A simplified model was developed under the assumption of having an ideal network, where all network strands are terminated by network nodes and each node is connected to the same number of strands. To describe the degradation of real networks, the model was modified by allowing for a varying connectivity of network nodes, which also included free chain-ends. The models were validated by comparison with Langmuir monolayer degradation data from 2D networks formed by cross-linking oligo(εcaprolactone)diols with dialdehydes. We found that both the ideal network hypothesis and the real network model were in excellent agreement with the experimental data, with the ideal network hypothesis requiring longer network strands than the real network to result in the same degradation behavior. The models were further used to calculate the degradation curves of the corresponding, non cross-linked molecules. By comparison, it was found that the network formation increases the time required to reach 50% degradation of oligo(εcaprolactone)diols by only 20%. This difference mainly arises from attaching free chain ends to network points.
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INTRODUCTION Improving the state of the art of treatments in regenerative medicine demands for materials that are capable of accomplishing multiple tasks [1]. For example, a material could be designed to maintain a temporary shape, allowing for insertion through a small incision and then to unfold to provide mechanical support [2]. The material would further be directed to release a drug that helps with the patient’s recovery and finally to vanish from the body [3, 4]. Such highly multifunctional materials require distinctly integrated functions. This can be achieved by tai
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