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Free, publicly-accessible full text available May 7, 2026
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Understanding structure-mechanical activity relationships (SMARs) in polymer mechanochemistry is essential for the rational design of mechanophores with desired properties, yet SMARs in noncovalent mechanical transformations remain relatively underexplored. In this study, we designed a subset of diarylethene mechanophores based on a lever-arm hypothesis and systematically investigated their mechanical activity toward a noncovalent-yet-chemical conversion of atro-pisomer stereochemistry. Results from DFT calculations, single-molecule force spectroscopy (SMFS) measurements, and ultrasonication experiments collectively support the lever-arm hypothesis and confirm the exceptional sensitivity of chemo-mechanical coupling in these atropisomers. Notably, the transition force for the diarylethene M3 featuring extended 5-phenylbenzo[b]thiophene aryl groups is determined to be 131 pN ± 4 pN by SMFS. This value is lower than typically recorded for other mechanically induced chemical processes, highlighting its exceptional sensitivity to low-magnitude forces. This work contributes a fundamental understanding of chemo-mechanical coupling in atropisomeric configurational mechanophores and paves the way for designing highly sensitive mechanochemical processes that could facilitate the study of nanoscale mechanical behaviors across scientific disciplines.more » « lessFree, publicly-accessible full text available November 21, 2025
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When multiple reaction steps occur before thermal equilibration, kinetic energy from one reaction step can influence overall product distributions in ways that are not well predicted by transition state theory. An understanding of how the structural features of mechanophores, such as substitutions, affects reactivity, product distribution, and the extent of dynamic effects in the mechanochemical manifolds is necessary for designing chemical reactions and responsive materials. We synthesized two tetrafluorinated [4]-ladderanes with fluorination on different rungs and found that the fluorination pattern influenced the force sensitivity and stereochemical distribution of products in the mechanochemistry of these fluorinated ladderanes. The threshold forces for mechanochemical unzipping of ladderane were decreased by alpha-fluorination and increased by gamma-fluorination; these changes correlated to the different stabilizing or destabilizing effects of fluorination patterns on the first transition state. Using ab initio steered molecular dynamics (AISMD), we compared the product distributions of synthesized and hypothetical ladderanes with different substitution patterns. These calculations suggest that fluorination on the first two bonds of ladderane gives rise to a larger fraction of dynamic trajectories and a larger fraction of E alkene prod-uct through a mechanism resulting from larger momentum because of the greater atomic mass of fluorine. Fluorination on the third and fourth rungs instead gives a larger fraction of E alkene product primarily due to electronic effects. These com-bined experimental and computational studies of the mechanochemical unzipping of fluorinated ladderanes provide an example of how relatively simple substituents can affect the extent of non-statistical dynamics, and thus mechanochemical outcomes.more » « lessFree, publicly-accessible full text available November 27, 2025
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Plant virus-like particles (VLPs) are biocompatible, non-infectious nanomaterials with promising applications as immunotherapeutics and vaccines. However, slow-release VLP formulations are needed to achieve long-term efficacy without repeated administration. VLP hydrogels allow the encapsulation and sustained delivery of VLPs, but the particles must covalently bind the hydrogel polymers to avoid premature loss. This has been achieved so far by in situ VLP polymerization, which requires high viral concentrations (5–10 mg/mL, 0.5–1 wt%) to form stable hybrid VLP–hydrogel networks and this complicates scalability and clinical translation. Here, we developed a novel swell-and-click method that led to successful VLP scaffold formation regardless of the viral load used. As a result, VLP-functionalized hydrogels were fabricated with viral concentrations as low as 0.1–1 mg/mL (0.01–0.1 % wt%) without compromising the scaffold stability on the process. The hydrogels incorporate VLPs during swelling, followed by copper-free click chemistry reactions that bind the particles covalently to the polymer. The swell-and-click method also resulted in more than a two-fold enhancement in VLP uptake into the hydrogels and it provides a means of combined burst release and prolonged sustained release, desired traits for cancer immunotherapy treatment. The present work introduces a novel methodology for the design of VLP-based hydrogels, which could facilitate the scalability of the fabrication process and move a significant step forward towards clinical translation of long-term VLP vaccination in cancer disease.more » « less
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Abstract Thermoset toughness and deconstructability are often opposing features; simultaneously improving both without sacrificing other mechanical properties (e.g., stiffness and tensile strength) is difficult, but, if achieved, could enhance the usage lifetime and end‐of‐life options for these materials. Here, a strategy that addresses this challenge in the context of photopolymer resins commonly used for 3D printing of glassy, acrylic thermosets is introduced. It is shown that incorporating bis‐acrylate “transferinkers,” which are cross‐linkers capable of undergoing degenerative chain transfer and new strand growth, as additives (5–25 mol%) into homemade or commercially available photopolymer resins leads to photopolymer thermosets with substantially improved tensile toughness and triggered chemical deconstructability with minimal impacts on Young's moduli, tensile strengths, and glass transition temperatures. These properties result from a transferinker‐driven topological transition in network structure from the densely cross‐linked long, heterogeneous primary strands of traditional photopolymer networks to more uniform, star‐like networks with few dangling ends; the latter structure more effectively bear stress yet is also more easily depercolated via solvolysis. Thus, transferinkers represent a simple and effective strategy for improving the mechanical properties of photopolymer thermosets and providing a mechanism for their triggered deconstructability.more » « lessFree, publicly-accessible full text available September 11, 2025
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Mechanical force drives distinct chemical reactions; yet, its vectoral nature results in complicated coupling with reaction trajectories. Here, we utilize a physical organic model inspired by the classical Morse potential and its differential forms to identify effective force constant (keff) and reaction energy (ΔE) as key molecular features that govern mechanochemical kinetics. Through a comprehensive experimental and computational investigation with four norborn-2-en-7-one (NEO) mechanophores, we establish the relationship between these features and the force-dependent energetic changes along the reaction pathways. We show that the complex kinetic behavior of the tensioned bonds is generally and quantitatively predicted by a simple multivariate linear regression based on the two easily computed features with a straightforward workflow. These results demonstrate a general mechanistic framework for mechanochemical reactions under tensile force and provide a highly accessible tool for the large-scale computational screening in the design of mechanophores.more » « less