Advancing Dynamic Polymer Mechanochemistry through Molecular Gears

Harnessing mechanical force to modulate material properties and enhance biomechanical functions is essential for advancing smart materials and bioengineering. Polymer mechanochemistry provides an emerging toolkit to unlock unconventional chemical transformations and modulate molecular structures via mechanical force. One of the key challenges is developing innovative force-sensing mechanisms for precise, in situ force detection and quantification. This study addresses this challenge by introducing mDPAC, a mechanosensitive molecular gear with dynamic and sensitive mechanochromic properties. Its unique mechanoresponsive mechanism is based on the simultaneous configurational variation of its phenazine and phenyl moieties, facilitated by a worm-gear structure. We affirm mDPAC\u27s sensitive mechanochemical response and elucidate its force transduction mechanism through our experimental emission data and comprehensive DFT and MD simulations. The compatibility of mDPAC with hydrogels is particularly notable, highlighting its potential for applications in aqueous biological environments as a dynamic molecular force sensor and mapping tool. Moreover, mDPAC\u27s multicolored mechanochromism enables direct force sensing, visual detection, and real-time quantification, paving the way for integrating molecular gears into bulk materials for precise and instantaneous mechanical force sensing

Terpyridine-Based, Coordination-Driven, 2D and 3D Supramolecular Architectures

Utilization of \u3c tpy-MII-tpy \u3e (tpy = 2,2\u27:6\u27,2 -terpyridine; M = metal) connectivity to construct specific shaped supramolecular architectures has been recently well-developed. Many transition metals can readily coordinate to terpyridine providing a wide range of bonding strength and properties. A large number of stoichiometrically self-assembled, terpyridine-based, supramolecular architectures have been achieved by using ZnII and CdII ions, which are known as the labile-bonded metals in the \u3c tpy-MII-tpy \u3e connectivity family. In recent years, a series of supramolecular polygons, utilizing \u3c tpy-MII-tpy \u3e connectivity, as the edges, and bisterpyridine ligands, as the vertices, have been synthesized. To explore the formation of higher-ordered 2D- and 3D-supramolecular architectures, multitopic terpyridine ligands must be considered, since each vertex contains at least three branching arms. Multitopic terpyridine ligands, such as tristerpyridine and hexakisterpyridine possessing 60° or 120° directionality, have been successfully synthesized via Suzuki cross-coupling reaction. Various coordination-driven, supramolecular structures, from 2D-based centrally-bridged rhomboid and spoked wheel, to 3D-based tetrahedron and mandoline-shaped architecture, have been quantitatively formed via a facial stoichiometric self-assembly. These novel assemblies will be addressed and their related synthesis, characterization, and properties will also be considered

A Robust Oil-in-Oil Emulsion for the Nonaqueous Encapsulation of Hydrophilic Payloads

Compartmentalized structures widely exist in cellular systems (organelles) and perform essential functions in smart composite materials (microcapsules, vasculatures, and micelles) to provide localized functionality and enhance materials’ compatibility. An entirely water-free compartmentalization system is of significant value to the materials community as nonaqueous conditions are critical to packaging microcapsules with water-free hydrophilic payloads while avoiding energy-intensive drying steps. Few nonaqueous encapsulation techniques are known, especially when considering just the scalable processes that operate in batch mode. Herein, we report a robust oil-in-oil Pickering emulsion system that is compatible with nonaqueous interfacial reactions as required for encapsulation of hydrophilic payloads. A major conceptual advance of this work is the notion of the partitioning inhibitora chemical agent that greatly reduces the payload’s distribution between the emulsion’s two phases, thus providing appropriate conditions for emulsion-templated interfacial polymerization. As a specific example, an immiscible hydrocarbon–amine pair of liquids is emulsified by the incorporation of guanidinium chloride (GuHCl) as a partitioning inhibitor into the dispersed phase. Polyisobutylene (PIB) is added into the continuous phase as a viscosity modifier for suitable modification of interfacial polymerization kinetics. The combination of GuHCl and PIB is necessary to yield a robust emulsion with stable morphology for 3 weeks. Shell wall formation was accomplished by interfacial polymerization of isocyanates delivered through the continuous phase and polyamines from the droplet core. Diethylenetriamine (DETA)-loaded microcapsules were isolated in good yield, exhibiting high thermal and chemical stabilities with extended shelf-lives even when dispersed into a reactive epoxy resin. The polyamine phase is compatible with a variety of basic and hydrophilic actives, suggesting that this encapsulation technology is applicable to other hydrophilic payloads such as polyols, aromatic amines, and aromatic heterocyclic bases. Such payloads are important for the development of extended pot or shelf life systems and responsive coatings that report, protect, modify, and heal themselves without intervention

Probing a Hidden World of Molecular Self-Assembly: Concentration-Dependent, Three-Dimensional Supramolecular Interconversions

A terpyridine-based, concentration-dependent, facile self-assembly process is reported, resulting in two three-dimensional metallosupramolecular architectures, a bis-rhombus and a tetrahedron, which are formed using a two-dimensional, planar, tris-terpyridine ligand. The interconversion between these two structures is concentration-dependent: at a concentration higher than 12 mg mL(-1), only a bis-rhombus, composed of eight ligands and 12 Cd2+ ions, is formed; whereas a self-assembled tetrahedron, composed of four ligands and six Cd2+ ions, appears upon sufficient dilution of the tris-terpyridine-metal solution. At concentrations less than 0.5 mg mL(-1), only the tetrahedron possessing an S-4 symmetry axis is detected; upon attempted isolation, it quantitatively reverts to the bis-rhombus. This observation opens an unexpected door to unusual chemical pathways under high dilution conditions

Programmable Payload Release from Transient Polymer Microcapsules Triggered by a Specific Ion Coactivation Effect

Stimuli-responsive materials activated by a pair of molecular or ionic species are of interest in the design of chemical logic gates and signal amplification schemes. There are relatively few materials whose coactivated response has been well-characterized. Here, we demonstrate a specific ion coactivation (SICA) effect at the interfaces of transient polymer solids and liquid solutions. We found that depolymerization of the transient polymer, cyclic poly­(phthalaldehyde) (cPPA), exhibited a SICA effect when the cPPA core–shell microcapsules were suspended in ion-containing acidic methanol solutions. Significant acceleration in cPPA depolymerization rate is triggered by the combination of acid and ion coactivators. Intriguingly, the SICA effect is related to the Hofmeister behavior. The SICA effect is primarily determined by anions, and cations exhibit a secondary effect that modulates the coactivation strength. Based on these observations, we developed cPPA programmable microcapsules whose payload release rates depend on the composition and concentration of the salt/acidic-methanol solutions

Water/Alcohol Soluble Neutral Fullerene Derivative to Reengineer the Surface of the Electron Extraction Layer for High Efficiency Inverted Polymer Solar Cells

Dipole induced vacuum level shift has been demonstrated to be responsible for the enhanced efficiency in polymer solar cells (PSCs), as the modified energy level alignment could reduce the energy barrier and facilitate charge transport, hence result in enhanced efficiency of PSCs. Herein, we report a new mechanism towards enhanced efficiency by using a water/alcohol-soluble neutral fullerene derivative to reengineer the surface of zinc oxide (ZnO) electron extraction layer (EEL) in PSCs with an inverted device structure. Due to neutral property of fullerene derivatives, a negligible change in open circuit voltage is observed from the inverted PSCs with neutral fullerene derivative layer. The neutral fullerene derivative layer greatly increased the surface electrical conductivity of ZnO EEL, suppressed the surface charge recombination, and increased the short circuit current and fill factor, resulting in more than 30% enhanced efficiency from the inverted PSCs. These results demonstrated that the surface electrical conductivity of EEL plays an important role in high performance inverted PSCs

Interfacial Engineering for High Performance Inverted Polymer Solar Cells

Bulk heterojunction (BHJ) polymer solar cells (PSCs) that can be fabricated by solution processing techniques are under intense investigation in both academic and industrial sectors because of their potential to enable mass production of flexible and cost-effective alternative of silicon-based solar cells. A combination of novel polymer development, nanoscale morphology control and processing optimization has led to over 9% of power conversion efficiencies (PCEs) for BHJ PSCs with a conventional device structure. Attempts to develop PSCs with an inverted device structure as required for achieving high PECs and good stability have, however, met with limited success. Here, we report interfacial engineering for high performance inverted polymer solar cells. Our review include: (1) solution-processed zinc oxide (ZnO) thin film as an electron extraction layer for inverted polymer solar cells. Operated at room temperature, no obviously degradation was observed from the PSCs with ZnO layer after continuously illuminating the devices for 4 hours. However, a significantly degradation was observed from the PSCs without ZnO buffer layer after illuminating the devices only for 1 hour. Furthermore, PSCs with ZnO buffer layer also show very good shelf stability; only 10 % degradation observed in PCEs after 6 months; (2) a high PCE of 8.4% under AM1.5G irradiation was achieved for BHJ PSCs with an inverted device structure. This high efficiency was obtained through interfacial engineering of solution-processed electron extraction layer, ZnO, leading to facilitated electron transport and suppressed bimolecular recombination; (3) Further study of the effect on a novel water/alcohol-soluble neutral fullerene derivative (PC60BM-G2 ) layer on the device performance of the inverted PSCs is investigated. An over 30% enhancement in PCE was observed from the inverted PSCs with PC60BM-G2 layer to reengineer the surface of the ZnO EEL, when compared with those without PC60BM-G2 layers. All these results provided an important progress for solution-processed PSCs, and demonstrate that PSCs with an inverted device structure are comparable to PSCs with the conventional device structure

Probing a Hidden World of Molecular Self-Assembly: Concentration-Dependent, Three-Dimensional Supramolecular Interconversions

A terpyridine-based, concentration-dependent, facile self-assembly process is reported, resulting in two three-dimensional metallosupramolecular architectures, a bis-rhombus and a tetrahedron, which are formed using a two-dimensional, planar, tris-terpyridine ligand. The interconversion between these two structures is concentration-dependent: at a concentration higher than 12 mg mL^–1, only a bis-rhombus, composed of eight ligands and 12 Cd²⁺ ions, is formed; whereas a self-assembled tetrahedron, composed of four ligands and six Cd²⁺ ions, appears upon sufficient dilution of the tris-terpyridine-metal solution. At concentrations less than 0.5 mg mL^–1, only the tetrahedron possessing an <i>S</i>₄ symmetry axis is detected; upon attempted isolation, it quantitatively reverts to the bis-rhombus. This observation opens an unexpected door to unusual chemical pathways under high dilution conditions

One Ligand in Dual Roles: Self-Assembly of a Bis-Rhomboidal-Shaped, Three-Dimensional Molecular Wheel

A facile high yield, self-assembly process that leads to a terpyridine-based, three-dimensional, bis-rhomboidal-shaped, molecular wheel is reported. The desired coordination-driven supramolecular wheel involves eight structurally distorted tristerpyridine (tpy) ligands possessing a 608 angle between the adjacent tpy units and twelve Zn2+ ions. The tpy ligand plays dual roles in the self-assembly process: two are staggered at 1808 to create the internal hub, while six produce the external rim. The wheel can be readily generated by mixing the tpy ligand and Zn2+ in a stoichiometric ratio of 2: 3; full characterization is provided by ESI-MS, NMR spectroscopy, and TEM imaging