Halogen-bonded shape memory polymers

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.publishedVersionPeer reviewe

NMR and Quantum-Chemical Studies of Electrostatically Stabilized 1-(N,N-Substituted-aminiomethyl)spirobi [3-oxo(2,5-dioxa-1-silacyclopentan)]ates (ES-Silanates)

1-(N,N-substituted-aminiomethyl)spirobi[3-oxo(2,5-dioxa-1-silacyclopentan)]ates were investigated using NMR, X-ray, and quantum-chemical methods. The free activation parameters for the inversion of “ammonium-amine nitrogen” and the chirality change at the pentacoordinated silicon were determined by dynamic NMR spectroscopy. The latter proceeds via the dissociation of Si[BOND]O bonds. The results were confirmed by quantum-chemical calculations, the experimental observation of cross-peaks in 2D-EXSY NMR spectra, and the spirocycle exchange reactions. Transition pathways between the different diastereomers in solution were analyzed

J Biomol NMR

Solid-state NMR spectroscopy is a powerful technique to study insoluble and non-crystalline proteins and protein complexes at atomic resolution. The development of proton (1H) detection at fast magic-angle spinning (MAS) has considerably increased the analytical capabilities of the technique, enabling the acquisition of 1H-detected fingerprint experiments in few hours. Here an approach based on double-quantum (DQ) 13C spectroscopy, detected on 1H, is proposed for fast MAS regime (> 60 kHz) to perform the sequential assignment of insoluble proteins of small size, without any specific deuteration requirement. By combining two three-dimensional 1H detected experiments correlating a 13C DQ dimension respectively to its intra-residue and sequential 15 N-1H pairs, a sequential walk through DQ (Ca + CO) resonance is obtained. The approach takes advantage of fast MAS to achieve an efficient sensitivity and the addition of a DQ dimension provides spectral features useful for the resonance assignment process

Direct amide 15N to 13C transfers for solid-state assignment experiments in deuterated proteins

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