Affiliation:
1. Department of Chemistry Life Sciences and Environmental Sustainability and INSTM UdR Parma University of Parma Parco Area delle Scienze 17/A 43124 Parma Italy
2. Department of Engineering & Architecture University of Parma Parco Area delle Scienze 181/A 43124 Parma Italy
3. IMEM‐CNR Institute of Materials for Electronics and Magnetism Trento unit, Via alla Cascata 56/C – 318123 Trento Italy
Abstract
AbstractAuxetics are materials characterized by a negative Poisson's ratio (NPR), an uncommon mechanical behavior corresponding to a transversal deformation tendency opposite to the traditional materials. Here, the first example of a synthetic molecular auxetic polymer obtained by embedding a conformationally expandable cavitand as a crosslinker into a rigid polymer of intrinsic microporosity (PIM) is presented. The rigidity and microporosity of the polymeric matrix are pivotal to maximizing the expansion effect of the cavitand that, under mechanical stress, can assume two different conformations: a compact vase one and an extended kite form. The auxetic behavior and the corresponding NPR of the proposed material is predicted by a specific micromechanical model that considers the cavitand volume expansion ratio, the fraction of the cavitand crosslinker in the polymer, and the mechanical characteristics of the polymer backbone. The reversible auxetic behavior of the material is experimentally verified via the digital image correlation technique performed during the mechanical tests on films obtained by blending the auxetic crosslinked polymer with pristine PIM. Two specific control experiments prove that the mechanically driven conformational expansion of the cavitand crosslinker is the sole responsible for the observed NPR of the polymer.
Subject
Electrochemistry,Condensed Matter Physics,Biomaterials,Electronic, Optical and Magnetic Materials
Cited by
4 articles.
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