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The directional deformation of liquid crystalline elastomers (LCEs) is predicated on alignment, enforced by various processing techniques. Specifically, surface-aligned LCEs can exhibit higher temperature thermomechanical responses and weakened strain−temperature coupling in comparison to LCEs subjected to mechanical or rheological alignment. Recently, we reported enhanced stimuli response of mechanically aligned LCEs containing supramolecular liquid crystals. Here, we prepare supramolecular LCEs via surface-enforced alignment to study the impact of the supramolecular bond strength and intermolecular forces. This was evaluated using oxybenzoic acid (OBA) derivatives with and without pendant methyl groups as well as via oxybenzoic acid-pyridine complexes. Increased incorporation of supramolecular mesogens reduces the isotropic transition temperature and generally increases the strain−temperature coupling. The number of elastically active strands per unit volume, hydrogen bond conformations, and network morphology are affected by the supramolecular mesogens and influence the observed stimuli response. Overall, reduced intermolecular interactions correlate with more desirable actuation properties, demonstrating the influence of the supramolecular mesogen’s structure. 

Liquid crystalline elastomers (LCEs) are soft materials which disorder upon heating through the isotropic transition temperature. The order-disorder phase transition of LCEs results in a contraction of up to ∼50% along the aligned axis. Motivated by this distinctive stimuli-response, LCEs are increasingly considered as low-density actuators. Generally, LCEs are composed entirely of covalent bonds. Recently, we have prepared LCEs with intramesogenic supramolecular bonds from dimerized oxybenzoic acid derivatives and documented distinctive thermomechanical response in these supramolecular LCEs. Here, we report a detailed investigation of phase transitions in supramolecular LCEs by systematically varying the composition to affect the strength of the intermolecular interactions in the polymer network. The order-disorder phase transition is shown to be influenced by the conformation and dissociation of supramolecular dimers. Distinctly, this report isolates and details an LCE composition which undergoes an intermediate transition to an incommensurate phase at lower temperatures than the order-disorder transition. 

Magic-sized clusters (MSCs) are kinetically stable, atomically precise intermediates along the quantum dot (QD) reaction potential energy surface. Literature precedent establishes two classes of cadmium selenide MSCs with QD-like inorganic cores: one class is proposed to be cation-rich with a zincblende crystal structure, while the other is proposed to be stoichiometric with a “wurtzite-like” core. However, the wide range of synthetic protocols used to access MSCs has made direct comparisons of their structure and surface chemistry difficult. Furthermore, the physical and chemical relationships between MSC polymorphs are yet to be established. Here, we demonstrate that both cation-rich and stoichiometric CdSe MSCs can be synthesized from identical reagents and can be interconverted through the addition of either excess cadmium or selenium precursor. The structural and compositional differences between these two polymorphs are contrasted using a combination of 1H NMR spectroscopy, X-ray diffraction (XRD), pair distribution function (PDF) analysis, inductively coupled plasma optical emission spectroscopy, and UV–vis transient absorption spectroscopy. The subsequent polymorph interconversion reactions are monitored by UV–vis absorption spectroscopy, with evidence for an altered cluster atomic structure observed by powder XRD and PDF analysis. This work helps to simplify the complex picture of the CdSe nanocrystal landscape and provides a method to explore structure–property relationships in colloidal semiconductors through atomically precise synthesis. 

Self-discharge and chemically induced mechanical effects degrade calendar and cycle life in intercalation-based electrochromic and electrochemical energy storage devices. In rechargeable lithium-ion batteries, self-discharge in cathodes causes voltage and capacity loss over time. The prevailing self-discharge model centers on the diffusion of lithium ions from the electrolyte into the cathode. We demonstrate an alternative pathway, where hydrogenation of layered transition metal oxide cathodes induces self-discharge through hydrogen transfer from carbonate solvents to delithiated oxides. In self-discharged cathodes, we further observe opposing proton and lithium ion concentration gradients, which contribute to chemical and structural heterogeneities within delithiated cathodes, accelerating degradation. Hydrogenation occurring in delithiated cathodes may affect the chemo-mechanical coupling of layered cathodes as well as the calendar life of lithium-ion batteries.