A series of sustainable aliphatic polyester thermoplastic elastomers (APTPEs) consisting of multi-arm star polymers with arms of poly(l-lactide)-b-poly(γ-methyl-ϵ-caprolactone) were investigated and compared to analogous linear poly(l-lactide)-b-poly(γ-methyl-ϵ-caprolactone)-b-poly(l-lactide) triblock polymers. Linear analogues with comparable arm molar mass and comparable overall molar mass were synthesized to distinguish architectural and molar mass effects. Overall, the star block polymers significantly outperformed their linear analogues with respect to ultimate tensile strength and tensile toughness, exhibiting more pronounced strain hardening than corresponding linear APTPEs. The stars exhibited high ultimate tensile strengths (∼33 MPa) and large elongations at break (∼1400%), outperforming commercially relevant, petroleum-derived, and non-degradable styrenic TPEs. The star polymers also exhibited superior recovery characteristics during cyclic strain cycles and reduced stress relaxation compared to the linear APTPEs, highlighting the impact of architecture on improved TPE mechanical properties. Dynamic mechanical thermal analysis suggests that the star architecture increases the usage temperature range and does not negatively influence processability, an important feature for future applications. Overall, this work illustrates that simple and convenient changes in the macromolecular architecture in sustainable APTPEs result in materials with greatly enhanced mechanical properties. A comprehensive understanding of the relationship between polymer architecture and mechanical properties can be capitalized on to develop property-specific and industrially relevant sustainable materials.
|Original language||English (US)|
|Number of pages||14|
|State||Published - Oct 26 2021|
Bibliographical noteFunding Information:
We would like to acknowledge Daphne Wui Yarn Chan, Steven Weigand, and Gabriela Diaz Gorbea for collecting SAXS data as well as Farihah Haque, Colin Peterson, Jay Weber, Annabelle Watts, Mahesh Mahanthappa, and Elizabeth Feinberg for many helpful discussions. We thank Ortec, Inc. for generously providing lactide used in these studies. SAXS experiments were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by the Northwestern University, E.I. DuPont de Nemours & Co., and Dow Chemical Company. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science user facility operated for the U.S. DOE Office of Science by the Argonne National Laboratory under contract no. DE-AC02-06CH11357. Graphics creation was assisted by John Beumer with the NSF Center for Sustainable Polymers. We also acknowledge the funding for this work, which was provided by the NSF Center for Sustainable Polymers (CHE-1901635) at the University of Minnesota.
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