Geometric Confinement Controls Stiffness, Strength, Extensibility, and Toughness in Poly(urethane–urea) Copolymers - Université de Lille Accéder directement au contenu
Article Dans Une Revue Macromolecules Année : 2021

Geometric Confinement Controls Stiffness, Strength, Extensibility, and Toughness in Poly(urethane–urea) Copolymers

Résumé

Achieving a unique combination of stiffness, strength, extensibility and toughness in sol-cast poly(urethane-urea) (PU) copolymer films is a challenge since these properties are -in general- mutually exclusive. Here we demonstrate that geometric confinement of the basic building blocks controls stiffness, strength, extensibility and toughness in PU films. Our results suggest that the severity of geometric confinement can be tuned by adjusting (i) soft segment molecular weight (SSMW) and (ii) drying temperature (DT) thanks to their effects on the structure formation via micro-phase separation and/or (confined and/or bulk) crystallization. It is therefore possible to produce (i) soft (no notable confinement) and (ii) stiff, strong, extensible and tough (severe confinement) materials without changing any other parameter except SSMW and DT. The former has a typical physically cross-linked network and shows a well-defined elastomeric behavior with elastic modulus (E) of 5–20 MPa, tensile strength ( smax) of 30–35 MPa, extensibility ( e) of 1000–1300% and toughness (W) of 90–180 MJm-3. The latter, on the other hand, possesses an elegant hierarchical structure containing tightly packed secondary structures (72-helix, 41-helix and antiparallel b-sheets) and displays an elasto-plastic behavior with E of 400– 700 MPa, smax of 45–55 MPa, e of 650–850% and W of 200–250 MJm-3. Hence, our findings may be of interest in designing advanced materials containing synthetic replica of the secondary structures found in protein based materials. The structure formation in the materials with this structural hierarchy is driven by the confined crystallization of helical poly(ethylene oxide) (PEO) chains in subnanometer urea channels, which –to the best of our knowledge– is a new phenomenon has not yet reported in PU literature, and complemented by the “bulk” crystallization of PEO and/or the micro-phase separation.

Domaines

Matériaux
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Dates et versions

hal-04413964 , version 1 (24-01-2024)

Identifiants

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Oguzhan Oguz, Nicolas Candau, Gregory Stoclet, Eren Simsek, Cagla Kosak Soz, et al.. Geometric Confinement Controls Stiffness, Strength, Extensibility, and Toughness in Poly(urethane–urea) Copolymers. Macromolecules, 2021, Macromolecules, 54 (10), pp.4704-4725. ⟨10.1021/acs.macromol.1c00596⟩. ⟨hal-04413964⟩
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