Halogen-bonded shape memory polymers

Abstract

Halogen bonding (XB), a non-covalent interaction between an electron-deficient halogen atom and a Lewis base, is widely adopted in organic synthesis and supramolecular crystal engineering. However, the roadmap towards materials applications is hindered by the challenges in harnessing this relatively weak intermolecular interaction to devise human-commanded stimuli-responsive soft materials. Here, we report a liquid crystalline network comprising permanent covalent crosslinks and dynamic halogen bond crosslinks, which possess reversible thermo-responsive shape memory behaviour. Our findings suggest that I···N halogen bond, a paradigmatic motif in crystal engineering studies, enables temporary shape fixation at room temperature and subsequent shape recovery in response to human body temperature. We demonstrate versatile shape programming of the halogen-bonded polymer networks through human-hand operation and propose a micro-robotic injection model for complex 1D to 3D shape morphing in aqueous media at 37 °C. Through systematic structure-property-performance studies, we show the necessity of the I···N crosslinks in driving the shape memory effect. The halogen-bonded shape memory polymers expand the toolbox for the preparation of smart supramolecular constructs with tailored mechanical properties and thermoresponsive behaviour, for the needs of, e.g., future medical devices.

Iodine(I) and Silver(I) Complexes Incorporating 3-Substituted Pyridines

“…1−3 The incorporation of halogen bond donors into polymers has led to the development of topochemical polymerization, molecularly-imprinted polymers, functional-/stimuli-responsive polymeric materials, 1,2,4 and, most recently, shape-memory polymers. 5 A main advantage of halogen bonding is its highly directional nature, owing to its electronic origin as a σ−hole interaction (i.e., the tightly confined electropositive region along the axis of the halogen bond donor's R−X bond), 6 which has found great utility in the construction of a variety of supramolecular architectures. 7−14 The epitome of halogen bonding is the linear halogen(I) (also termed halonium) complexes, 15,16 which comprise a halenium ion (X + ; X = Cl, Br, and I) and a pair of stabilizing Lewis bases (L; commonly nitrogen-based aromatic ligands such as pyridine), [L−X−L] + .…”

“…Halogen bonding enjoys being one of the most studied types of intermolecular interactions after hydrogen bonding, and as such has been deftly employed to construct a myriad of magnetic, porous, phosphorescent, and liquid-crystalline materials toward applications such as biomolecular engineering, chemical separations, and ion-pair recognition. − The incorporation of halogen bond donors into polymers has led to the development of topochemical polymerization, molecularly-imprinted polymers, functional-/stimuli-responsive polymeric materials, ,, and, most recently, shape-memory polymers . A main advantage of halogen bonding is its highly directional nature, owing to its electronic origin as a σ–hole interaction ( i.e.…”

Halogen Bonding Channels for Magnetic Exchange in Cu(II) Complexes with 2,5‐Di(methylthio)‐1,3,4‐thiadiazole

“…The number of investigations concerning halogen bonding can be compared with the solar‐cells “big boom”. A lot of recent research data can be easily found in the literature [13–18] . In Russia such studies are actively being developed by the leading research groups of Prof. V. Yu.…”

“…A lot of recent research data can be easily found in the literature. [13][14][15][16][17][18] In Russia such studies are actively being developed by the leading research groups of Prof. V. Yu. Kukushkin and Prof. S. A. Adonin.…”

Role of halogen atoms in the mechanical properties of para-substituted benzaldehyde oximes

“…17 Guo has pointed out the necessity of halogen bonds for the shape memory effect in organic polymers. 18…”