Shape Memory Supramolecular Polyurea with Adjustable Toughness and Ultrahigh Energy Density

Abstract

As typical stimulus-responsive materials, shape memory polymers (SMPs) have potential for many advanced applications owing to their controllable and programmable shape-changing properties. However, the combination of high toughness and tailorable strength remains a challenge to overcome for SMPs. Here, we engineered meticulously a supramolecular structure with quadruple and double hydrogen bonding arrays to achieve shape memory polyurea elastomers with adjustable strength and toughness. The polyurea with a supramolecular structure had the highest tensile strength of 47 MPa and ultrahigh toughness up to 256 MJ m −3 . Meanwhile, the polyurea was also adjustable to a small tensile strength of 0.87 MPa matching the tensile strength of biological soft tissue (≈1 MPa). The reversible hydrogen bonding arrays endowed polyurea with a shape memory effect as well as excellent selfhealing properties. More importantly, the prestretched polyurea could raise a 500 g weight, which is over 3968 times its own mass, up to 18 mm, because of a high energy density of 75 MJ m −3 , which was higher than the energy density of most SMPs (generally <1 MJ m −3 ).

Immiscible Polymer Blends Compatibilized through Noncovalent Forces: Construction of a “Quasi-Block/Graft Copolymer” by Interfacial Stereocomplex Crystallites

“…Besides covalent bonds, there are many noncovalent bond forces, − such as Van der Waals forces, , π–π interaction forces, , hydrogen bonds, , and ionic bond forces. , Compared with covalent bonds, the interaction energy of noncovalent bond forces is slightly lower, , which provides us the possibility of using covalent bond forces to construct “block” or “graft” copolymers. − We hope that we can find a suitable noncovalent interaction to realize the transformation from a covalently linked diblock copolymer to a noncovalently linked block copolymer.…”

Humidity-Responsive Shape Memory Polyurea with a High Energy Output Based on Reversible Cross-Linked Networks

“…The characteristic peak positions of the three PUs are basically the same, which indicates that they have the same groups. In detail, 3333 and 1630–1689 cm –1 are ascribed to the N–H and CO groups of the urea group, proving the formation of PUs . Further, the peak of O–H is possible to overlap with the peak of N–H at 3333 cm –1 .…”

“…In detail, 3333 and 1630−1689 cm −1 are ascribed to the N−H and C�O groups of the urea group, proving the formation of PUs. 28 Further, the peak of O−H is possible to overlap with the peak of N−H at 3333 cm −1 . Particularly, the peaks of C�O groups of PU -IPDI and PU -HMDI appearing at 1630 cm −1 and that of PU -MDI appearing at 1650 cm −1 are different because the degree of Hbonding association leads to different stretching vibrations, impacting the peak position of C�O.…”

Multifunctional properties optimization and stimuli‐responsivity of shape memory polymeric nanoarchitectures and applications

“…Because of even heating as well as elevated speed of recovery, electroactivated SMP nanoarchitectures display great benefit over thermally responsive SMP. [62,63] Specifically, the escalating quest to eliminate externally heating sources with the incremental interest in self-isolatable actuative gadgets has geared researches in direction of electroresponsive nanoarchitectures. From this perspective, electroresponsive nanoarchitectures have undergone fabrication through the synergy of thermoresponsive SMPs with an electrically conductive part.…”

“…Because of even heating as well as elevated speed of recovery, electroactivated SMP nanoarchitectures display great benefit over thermally responsive SMP. [ 62,63 ]…”