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"Hydrogen bonding."
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Incorporation of hydrogen‐bonding units into polymeric semiconductors toward boosting charge mobility, intrinsic stretchability, and self‐healing ability
The soft nature has endowed conjugated polymers with promising applications in a wide range of field‐effect transistor (FET) based flexible electronics. With unremitting efforts on revealing the molecular structure–property relationships, numerous novel conjugated polymers with high mobility and excellent mechanical property have been developed in the past decades. Incorporating hydrogen‐bonding (H‐bonding) units into semiconducting polymers is one of the most successful strategies for designing high‐performance semiconducting materials. In this review, we aim to highlight the roles of H‐bonding units in the performances of polymeric FETs from three aspects. These include (i) charge mobility enhancement for semiconducting polymers after incorporation of H‐bonding units into the side chains, (ii) the effects of H‐bonding units on the stretchability of conjugated polymers, and (iii) the improvement of self‐healing properties of conjugated polymers containing dynamic hydrogen bonds due to the H‐bonding units in the side chains or conjugated backbones. In this review, the effects of H‐bonding units on the interchain packing order, semiconducting performance, stretchability and self‐healing property of conjugated polymers have been summarized and discussed.
Journal Article
Hydrogen-bonding regulated supramolecular chirality with controllable biostability
The regulation of natural helical nanostructures is principally supported and actuated by hydrogen bonds (H-bonds) formed from hydrogen-bonding groups (peptide bonds and base pairs) to realize biological activities and specific biofunctional transformations. However, studying the role of H-bonding patterns on the handedness of supramolecular assemblies is still challenging, since supramolecular assemblies will be disassembled or destabilized with slightly varying H-bonding groups for most supramolecules. To circumvent this issue, herein, two types of self-assembled C
2
-symmetric phenylalanine derivatives differed by a single H-bonding group (ester or amide) are systematically designed for deciphering the role of H-bonding pattern on the chirality of supramolecular assemblies and their related biostability. Opposite handedness nanofibrous structures with tailorable diameter and helical pitch are achieved with the transition from ester to amide groups in the gelators. Experimental and theoretical evidence suggests that helical orientation of ester-containing gelators ascribes to intermolecular H-bonds. In contrast, the helical direction for the amide-counterparts is mainly due to intra- and intermolecular H-bonds. Moreover, these H-bonding groups greatly influence their stability, as revealed by
in vitro
and
in vivo
degradation experiments and the left-handed assemblies are more stable than the right-handed ones. Thus, the study offers a feasible model to have valuable insight into understanding the role of H-bonding patterns in biological folding.
Journal Article
Skeletal Muscle Fibers Inspired Polymeric Actuator by Assembly of Triblock Polymers
Inspired by the striated structure of skeletal muscle fibers, a polymeric actuator by assembling two symmetric triblock copolymers, namely, polystyrene‐b‐poly(acrylic acid)‐b‐polystyrene (SAS) and polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene (SES) is developed. Owing to the microphase separation of the triblock copolymers and hydrogen‐bonding complexation of their middle segments, the SAS/SES assembly forms a lamellar structure with alternating vitrified S and hydrogen‐bonded A/E association layers. The SAS/SES strip can be actuated and operate in response to environmental pH. The contraction ratio and working density of the SAS/SES actuator are approximately 50% and 90 kJ m−3, respectively; these values are higher than those of skeletal muscle fibers. In addition, the SAS/SES actuator shows a “catch‐state”, that is, it can maintain force without energy consumption, which is a feature of mollusc muscle but not skeletal muscle. This study provides a biomimetic approach for the development of artificial polymeric actuators with outstanding performance. A actuator with striated structure like skeletal muscle sarcomeres is fabricated by assembly of two triblock copolymers, polystyrene‐b‐poly(acrylic acid)‐b‐polystyrene (SAS) and polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene (SES). The actuator presents the “catch‐state” that maintains force while without energy consumption, and has high contraction ratio and working density compared with human skeletal muscle.
Journal Article
Dissecting the THz spectrum of liquid water from first principles via correlations in time and space
Solvation of molecules in water is at the heart of a myriad of molecular phenomena and of crucial importance to understanding such diverse issues as chemical reactivity or biomolecular function. Complementing well-established approaches, it has been shown that laser spectroscopy in the THz frequency domain offers new insights into hydration from small solutes to proteins. Upon introducing spatially-resolved analyses of the absorption cross section by simulations, the sensitivity of THz spectroscopy is traced back to characteristic distance-dependent modulations of absorption intensities for bulk water. The prominent peak at≈200 cm⁻¹ is dominated by first-shell dynamics, whereas a concerted motion involving the second solvation shell contributes most significantly to the absorption at about 80 cm⁻¹ ≈2.4 THz. The latter can be understood in terms of an umbrella-like motion of two hydrogen-bonded tetrahedra along the connecting hydrogen bond axis. Thus, a modification of the hydrogen bond network, e.g., due to the presence of a solute, is expected to affect vibrational motion and THz absorption intensity at least on a length scale that corresponds to two layers of solvating water molecules. This result provides a molecular mechanism explaining the experimentally determined sensitivity of absorption changes in the THz domain in terms of distinct, solute-induced dynamical properties in solvation shells of (bio)molecules—even in the absence of well-defined resonances.
Journal Article
Microscopic insights into the protein-stabilizing effect of trimethylamine N-oxide (TMAO)
Although it is widely known that trimethylamine N-oxide (TMAO), an osmolyte used by nature, stabilizes the folded state of proteins, the underlying mechanism of action is not entirely understood. To gain further insight into this important biological phenomenon, we use the C≡N stretching vibration of an unnatural amino acid, p -cyano-phenylalanine, to directly probe how TMAO affects the hydration and conformational dynamics of a model peptide and a small protein. By assessing how the lineshape and spectral diffusion properties of this vibration change with cosolvent conditions, we are able to show that TMAO achieves its protein-stabilizing ability through the combination of (at least) two mechanisms: (i) It decreases the hydrogen bonding ability of water and hence the stability of the unfolded state, and (ii) it acts as a molecular crowder, as suggested by a recent computational study, that can increase the stability of the folded state via the excluded volume effect.
Journal Article
A Theoretical Study on Terpene‐Based Natural Deep Eutectic Solvent: Relationship between Viscosity and Hydrogen‐Bonding Interactions
The aim of this work is to shed light on the origins of unique properties by studying the relationship between viscosity and hydrogen‐bonding interactions of terpene‐based natural deep eutectic solvents (NADES). Five systems including camphor/formic acid, menthol/acetic acid, menthol/β‐citronellol, menthol/lactic acid, and thymol/β‐citronellol are prepared (molar ratio 1:1). Their structures and nature of the associated hydrogen bonds are investigated through multiple methods and theories. The viscosity of NADES is consistent with the product of hydrogen‐bond number and lifetime. Through visualization of non‐covalent interactions, terpene‐acid‐based NADES with single sites show the lowest viscosity among the studied systems because of weak and unstable hydrogen bonding. Inversely, multi‐site terpene‐acid‐based NADES possess relatively high viscosity. Owing to the stability of hydrogen bonds in the network, the terpene‐terpene‐based system is in the middle level of viscosity. In‐depth analysis of these hydrogen bonds shows that they can be classified as “weak to medium” and are mainly derived from electrostatic interactions. Moreover, there is an obvious connection between viscosity and hydrogen‐bonding strength (integrated core‐valence bifurcation index) in the networks. The discovery of intrinsic rules between viscosity and hydrogen‐bonding interactions is beneficial for the design of novel low‐viscosity NADES in the future. The structures and inner nature of the hydrogen‐bond network of different systems are studied by multiple methods. The discovery of intrinsic rules between viscosity and hydrogen‐bonding interactions is beneficial for the rational and effective design of novel low‐viscosity natural deep eutectic solvents.
Journal Article
Continuous water-water hydrogen bonding network across the rim of carbon nanotubes facilitating water transport for desalination
The development of membranes featuring carbon nanotubes (CNTs) have provided possibilities of next-generation solar desalination technologies. For solar desalination, the microstructures and interactions between the filter membrane and seawater play a crucial role in desalination performance. Understanding the mechanisms of water evaporation and ion rejection in confined pores or channels is necessary to optimize the desalting process. Here, using non-equilibrium molecular dynamics simulations, we found that continuous water-water hydrogen bonding network across the rims of CNTs is the key factor in facilitating water transport through CNTs. With the continuous hydrogen bonding network, the water flux is two times of that without the continuous hydrogen bonding network. In CNT arrays, each CNT transports water molecules and rejects salt ions independently. Based on these observations, using CNT arrays consisted with densely packed thin CNTs is the most advisable strategy for evaporation desalination, possessing high transport flux as well as maintaining high salt rejection.
Journal Article
Supramolecular Annihilator with DPA Parallelly Arranged by Multiple Hydrogen-Bonding Interactions for Enhanced Triplet–Triplet Annihilation Upconversion
The triplet annihilator is a critical component for triplet–triplet annihilation upconversion (TTA-UC); both the photophysical properties of the annihilator and the intermolecular orientation have pivotal effects on the overall efficiency of TTA-UC. Herein, we synthesized two supramolecular annihilators A-1 and A-2 by grafting 9,10-diphenylanthracene (DPA) fragments, which have been widely used as triplet annihilators for TTA-UC, on a macrocyclic host—pillar[5]arenes. In A-1, the orientation of the two DPA units was random, while, in A-2, the two DPA units were pushed to a parallel arrangement by intramolecular hydrogen-bonding interactions. The two compounds showed very similar photophysical properties and host–guest binding affinities toward electron-deficient guests, but showed totally different TTA-UC emissions. The UC quantum yield of A-2 could be optimized to 13.7% when an alkyl ammonia chain-attaching sensitizer S-2 was used, while, for A-1, only 5.1% was achieved. Destroying the hydrogen-bonding interactions by adding MeOH to A-2 significantly decreased the UC emissions, demonstrating that the parallel orientations of the two DPA units contributed greatly to the TTA-UC emissions. These results should be beneficial for annihilator designs and provide a new promising strategy for enhancing TTA-UC emissions.
Journal Article