Quantitative Mapping of Molecular Substituents to Macroscopic Properties Enables Predictive Design of Oligoethylene Glycol-Based Lithium Electrolytes.

Molecular details often dictate the macroscopic properties of materials, yet due to their vastly different length scales, relationships between molecular structure and bulk properties can be difficult to predict a priori, requiring Edisonian optimizations and preventing rational design. Here, we introduce an easy-to-execute strategy based on linear free energy relationships (LFERs) that enables quantitative correlation and prediction of how molecular modifications, i.e., substituents, impact the ensemble properties of materials. First, we developed substituent parameters based on inexpensive, DFT-computed energetics of elementary pairwise interactions between a given substituent and other constant components of the material. These substituent parameters were then used as inputs to regression analyses of experimentally measured bulk properties, generating a predictive statistical model. We applied this approach to a widely studied class of electrolyte materials: oligo-ethylene glycol (OEG)-LiTFSI mixtures; the resulting model enables elucidation of fundamental physical principles that govern the properties of these electrolytes and also enables prediction of the properties of novel, improved OEG-LiTFSI-based electrolytes. The framework presented here for using context-specific substituent parameters will potentially enhance the throughput of screening new molecular designs for next-generation energy storage devices and other materials-oriented contexts where classical substituent parameters (e.g., Hammett parameters) may not be available or effective.

Jumping Crystals of Pyrene Tweezers: Crystal-to-Crystal Transition Involving π/π-to-CH/π Assembly Mode Switching.

Crystals of pyrene tweezers 1 with interdigitating pyrenyl blades jump vigorously at around 160 °C. Single-crystal X-ray diffraction analysis before jumping revealed the presence of a "pyrene tetrad" in the crystal lattice, where four pyrenyl blades are π-stacked on top of each other. Upon heating the crystal to induce the jumping event, inner two pyrenyl blades in the "pyrene tetrad" probably rotate to switch off their π-stacking interaction with the neighboring outer pyrenyl blades and form new CH-π bonds. Different from reported salient crystals, our crystal jumps with the release of CHCl3 as inclusion solvent.

Mikto-Brush-Arm Star Polymers via Cross-Linking of Dissimilar Bottlebrushes: Synthesis and Solution Morphologies.

A convergent brush-first ring-opening metathesis polymerization (ROMP) approach for the synthesis of mikto-brush-arm star polymers (MBASPs) via cross-linking of dissimilar bottlebrush polymers is reported. Living bottlebrush polymers prepared via ROMP of norbornene-terminated poly(ethylene glycol) (PEG) or polystyrene (PS) macromonomers (MMs) were mixed together in a desired ratio and exposed to a bis-norbornene cross-linker to yield MBASPs with narrow size distributions. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed that the solution morphologies of MBASPs depended on the feed ratio of the PEG and PS bottlebrush polymers at the cross-linking stage. This work provides a robust and modular strategy for the synthesis of a new type of miktoarm star polymer wherein the star arms are bottlebrush polymers.