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1. Empirical Model of Solvophobic Interactions in Organic Solvents

   https://doi.org/10.1002/anie.202314962  

   Manzewitsch, Alexander_N; Liu, Hao; Lin, Binzhou; Li, Ping; Pellechia, Perry_J; Shimizu, Ken_D (December 2023, Angewandte Chemie International Edition)

   Abstract An empirical model was developed to predict organic solvophobic effects usingN‐phenylimide molecular balances functionalized with non‐polar alkyl groups. Solution studies and X‐ray crystallography confirmed intramolecular alkyl‐alkyl interactions in theirfoldedconformers. The structural modularity of the balances allowed systematic variation of alkyl group lengths. Control balances were instrumental in isolating weak organic solvophobic effects by eliminating framework solvent‐solute effects. A¹⁹F NMR label enabled analysis across 46 deuterated and non‐deuterated solvent systems. Linear correlations were observed between organic solvophobic effects and solvent cohesive energy density (ced) as well as changes in solvent‐accessible surface areas (SASA). Using these empirical relationships, a model was constructed to predict organic solvophobic interaction energy per unit area for any organic solvent with knowncedvalues. The predicted interaction energies aligned with recent organic solvophobic measurements and literature values for the hydrophobic effect on non‐polar surfaces confirmed the model‘s accuracy and utility. 

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2. Molecular Geometry‐Directed Self‐Recognition in the Self‐Assembly of Giant Amphiphiles

   https://doi.org/10.1002/marc.202200216  

   Zhou, Yifan; Luo, Jiancheng; Liu, Tong; Wen, Tao; Williams‐Pavlantos, Kayla; Wesdemiotis, Chrys; Cheng, Stephen Z. D.; Liu, Tianbo (May 2022, Macromolecular Rapid Communications)

   Abstract Three sets of polyoxometalate (POM)‐based amphiphilic hybrid macromolecules with different rigidity in their organic tails are used as models to understand the effect of molecular rigidity on their possible self‐recognition feature during self‐assembly processes. Self‐recognition is achieved in the mixed solution of two structurally similar, sphere‐rigid T‐shape‐linked oligofluorene(TOF₄) rod amphiphiles, with the hydrophilic clusters being Anderson (Anderson‐TOF₄) and Dawson (Dawson‐TOF₄), respectively. Anderson‐TOF₄is observed to self‐assemble into onion‐like multilayer structures and Dawson‐TOF₄forms multilayer vesicles. The self‐assembly is controlled by the interdigitation of hydrophobic rods and the counterion‐mediated attraction among charged hydrophilic inorganic clusters. When the hydrophobic blocks are less rigid, e.g., partially rigid polystyrene and fully flexible alkyl chains, self‐recognition is not observed, attributing to the flexible conformation of hydrophobic molecules in the solvophobic domain. This study reveals that the self‐recognition among amphiphiles can be achieved by the geometrical limitation of the supramolecular structure due to the rigidity of solvophobic domains. 

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3. Intramolecularly enhanced molecular tweezers with unusually strong binding for aromatic guests in unfavorable solvents

   https://doi.org/10.1039/C8OB00786A  

   Xing, Xiaoyu; Zhao, Yan (January 2018, Organic & Biomolecular Chemistry)

   Molecular tweezers using aromatic interactions for binding normally work best in polar instead of nonpolar solvents due to the strong solvophobic effect in the binding. Inspired by biological receptors that utilize “delocalized binding interactions” remote from the binding interface to strengthen guest-binding, we constructed molecular tweezers that have a reversed solvent effect. As the direct aromatic binding interactions were weakened by nonpolar solvent, guest-triggered intrahost interactions between two strategically placed carboxylic acids became stronger and contributed to the binding. 

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4. Sequence dependence of critical properties for two-letter chains

   https://doi.org/10.1063/5.0215700  

   Panagiotopoulos, Athanassios Z (June 2024, The Journal of Chemical Physics)

   Histogram-reweighting grand canonical Monte Carlo simulations are used to obtain the critical properties of lattice chains composed of solvophilic and solvophobic monomers. The model is a modification of one proposed by Larson et al. [J. Chem. Phys. 83, 2411 (1985)], lowering the “contrast” between beads of different types to prevent aggregation into finite-size micelles that would mask true phase separation between bulk high- and low-density phases. Oligomeric chains of lengths between 5 and 24 beads are studied. Mixed-field finite-size scaling methods are used to obtain the critical properties with typical relative accuracies of better than 10−4 for the critical temperature and 10−3 for the critical volume fraction. Diblock chains are found to have lower critical temperatures and volume fractions relative to the corresponding homopolymers. The addition of solvophilic blocks of increasing length to a fixed-length solvophobic segment results in a decrease of both the critical temperature and the critical volume fraction, with an eventual slow asymptotic approach to the long-chain limiting behavior. Moving a single solvophobic or solvophilic bead along a chain leads to a minimum or maximum in the critical temperature, with no change in the critical volume fraction. Chains of identical length and composition have a significant spread in their critical properties, depending on their precise sequence. The present study has implications for understanding biomolecular phase separation and for developing design rules for synthetic polymers with specific phase separation properties. It also provides data potentially useful for the further development of theoretical models for polymer and surfactant phase behavior. 

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5. Hybrid Photoiniferter and Ring‐Opening Polymerization Yields One‐Pot Anisotropic Nanorods

   https://doi.org/10.1002/marc.202400100  

   Hurst, Paul Joshua; Yoon, Junsik; Singh, Riya; Abouchaleh, Mohammed Faris; Stewart, Kevin A.; Sumerlin, Brent S.; Patterson, Joseph P. (April 2024, Macromolecular Rapid Communications)

   Abstract Polymerization‐induced self‐assembly (PISA) has emerged as a scalable one‐pot technique to prepare block copolymer (BCP) nanoparticles. Recently, a PISA process, that results in poly(l‐lactide)‐b‐poly(ethylene glycol) BCP nanoparticles coined ring‐opening polymerization (ROP)‐induced crystallization‐driven self‐assembly (ROPI‐CDSA), was developed. The resulting nanorods demonstrate a strong propensity for aggregation, resulting in the formation of 2D sheets and 3D networks. This article reports the synthesis of poly(N,N‐dimethyl acrylamide)‐b‐poly(l)‐lactide BCP nanoparticles by ROPI‐CDSA, utilizing a two‐step, one‐pot approach. A dual‐functionalized photoiniferter is first used for controlled radical polymerization of the acrylamido‐based monomer, and the resulting polymer serves as a macroinitiator for organocatalyzed ROP to form the solvophobic polyester block. The resulting nanorods are highly stable and display anisotropy at higher molecular weights (>12k Da) and concentrations (>20% solids) than the previous report. This development expands the chemical scope of ROPI‐CDSA BCPs and provides readily accessible nanorods made with biocompatible materials. 

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