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Significance Statement
Poly(ether-block-amide)s (PEBAs) are biocompatible thermoplastic elastomers that are currently used in manufacturing a variety of biomedical devices due to their nontoxicity, long-term chemical stability and characteristic mechanical properties. Renewable PEBAs show good mechanical performances and affordable cost and are thus particularly appealing for the replacement of non-renewable polymers.
The polymer chemistry and biomechanics research groups at the Centre for Mechanics of Biological Materials at University of Padova have extensively studied the physicochemical properties of several block copolymers for different applications, also considering their durability in use conditions (S. Todros, A. N. Natali, M. Piga, G. A. Giffin, G. Pace, V. Di Noto, Polym. Degrad. Stabil. 2013, 98, 1126–1137; S. Todros, A. N. Natali, G. Pace, V. Di Noto, Macromol. Chem. Phys. 2013, 214, 2061–2072; S. Todros, C. Venturato, A. N. Natali, G. Pace, V. Di Noto, J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1337-1346).
In this work, a study is reported about the effect of steam sterilization on the chemical and mechanical properties of two renewable PEBAs. Whereas PEBAs are used in-vivo, it is mandatory to predict their degradation behavior, as polymers undergo modifications of their physical and mechanical properties due to water, high temperature, bio-agents and radiation. In particular, a possible degradation process of biomedical device materials is due to sterilization before use. Autoclaving can modify the chemical or crystalline structure of a polymer, inducing a degradation in mechanical properties. The effect of steam on renewable PEBA is studied correlating the modification of their micro-domain crystalline structure with phenomenological mechanical properties. The investigation provides a basis for a better understanding of the functional response of biomedical polymers, with regard to reliability and durability, in clinical applications.
Figure Legend: Steam elicits an increase of polyamide (PA) crystallinity in PEBA with longer PA blocks, while induces an increase of random PA domains and the formation of a more extended hydrogen bonding network in PEBA with longer polyether (PE) blocks.
Journal Reference
Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 409–418. Silvia Todros1,2, Arturo N. Natali1,2, Giuseppe Pace3,4 , Vito Di Noto2,4,*
- Department of Industrial Engineering, University of Padova, Padova, Italy and
- Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy and
- CNR—IENI, Padova, Italy and
- Department of Chemical Sciences, University of Padova, Padova, Italy.
Abstract
The effect of steam on chemical structure and mechanical properties of renewable poly(ether-block-amide)s (PEBAs) is investigated by different characterization techniques, i.e. FT-IR, TGA, DSC, DMA, and BES. Steam sterilization is a mandatory process for materials used in medical applications. This process employed during clinical practice and replicated in this study, affects polymer structure and morphology. Steam induces an increase of polyamide (PA) crystallinity in PEBAs with a majority of PA domains, due to the conformational transition from {Alpha}-helix to parallel and anti-parallel {Beta}-sheet, with stronger hydrogen bonding. In PEBAs with longer polyether (PE) blocks, steam induces an increase of random PA domains and the formation of a more extended hydrogen bonding network between ether and amide moieties of the two segments. As a consequence of these microdomain conformational variations, relevant changes occur in molecular relaxations as demonstrated by DMA and BES results.
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