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1. Non-solvating, side-chain polymer electrolytes as lithium single-ion conductors: synthesis and ion transport characterization

   https://doi.org/10.1039/c9py01035a  

   Liu, Jiacheng; Pickett, Phillip D.; Park, Bumjun; Upadhyay, Sunil P.; Orski, Sara V.; Schaefer, Jennifer L. (January 2020, Polymer Chemistry)

   Solid-state single-ion conducting polymer electrolytes have drawn considerable interest for secondary lithium batteries due to their potential for high electrochemical stability and safety, but applications are limited by their low ionic conductivities. Specifically, poly(ethylene oxide) (PEO) based electrolytes have the highest reported Li + conductivities for these materials; however, their potential is limited due to the ion transport mechanism being coupled to segmental relaxations of the cation solvating polymer chain. To investigate the potential of single-ion conducting polymer electrolytes lacking polar matrices, we synthesized three para -polyphenylene-based, side-chain polymer electrolytes with various pendent anion chemistries (–SO 3 − , –PSI − , and –TFSI − ) with differing binding affinities to Li + . Compared with the previously reported lithium poly(4-styrenesulfonyl(trifluoromethylsulfonyl)imide) (LiPSTFSI), the side-chain polymers showed at least 3 orders of magnitude higher conductivity with the same –TFSI − anion (6.7 × 10 −6 S cm −1 compared with 1.2 × 10 −10 S cm −1 at 150 °C). We found that the side-chain electrolyte showed a dielectric relaxation dominated transport mechanism through use of dielectric spectroscopy analysis. The conductivity is highly dependent on the charge delocalization and size of the pendent anion, which provides a pathway forward for the engineering of polymeric ion conductors for electrochemical applications. 

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2. The function of peptide-mimetic anionic groups and salt bridges in the antimicrobial activity and conformation of cationic amphiphilic copolymers

   https://doi.org/10.1039/D1RA02730A  

   Bhat, Rajani; Foster, Leanna L.; Rani, Garima; Vemparala, Satyavani; Kuroda, Kenichi (June 2021, RSC Advances)

   Herein we report the synthesis of ternary statistical methacrylate copolymers comprising cationic ammonium (amino-ethyl methacrylate: AEMA), carboxylic acid (propanoic acid methacrylate: PAMA) and hydrophobic (ethyl methacrylate: EMA) side chain monomers, to study the functional role of anionic groups on their antimicrobial and hemolytic activities as well as the conformation of polymer chains. The hydrophobic monomer EMA was maintained at 40 mol% in all the polymers, with different percentages of cationic ammonium (AEMA) and anionic carboxylate (PAMA) side chains, resulting in different total net charge for the polymers. The antimicrobial and hemolytic activities of the copolymer were determined by the net charge of +3 or larger, suggesting that there was no distinct effect of the anionic carboxylate groups on the antimicrobial and hemolytic activities of the copolymers. However, the pH titration and atomic molecular dynamics simulations suggest that anionic groups may play a strong role in controlling the polymer conformation. This was achieved via formation of salt bridges between cationic and anionic groups, transiently crosslinking the polymer chain allowing dynamic switching between compact and extended conformations. These results suggest that inclusion of functional groups in general, other than the canonical hydrophobic and cationic groups in antimicrobial agents, may have broader implications in acquiring functional structures required for adequate antimicrobial activity. In order to explain the implications, we propose a molecular model in which formation of intra-chain, transient salt bridges, due to the presence of both anionic and cationic groups along the polymer, may function as “adhesives” which facilitate compact packing of the polymer chain to enable functional group interaction but without rigidly locking down the overall polymer structure, which may adversely affect their functional roles. 

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3. Highly Conductive Polyoxanorbornene‐Based Polymer Electrolyte for Lithium‐Metal Batteries

   https://doi.org/10.1002/advs.202302932  

   An, So_Young; Wu, Xinsheng; Zhao, Yuqi; Liu, Tong; Yin, Rongguan; Ahn, Jung_Hyun; Walker, Lynn_M; Whitacre, Jay_F; Matyjaszewski, Krzysztof (July 2023, Advanced Science)

   Abstract This present study illustrates the synthesis and preparation of polyoxanorbornene‐based bottlebrush polymers with poly(ethylene oxide) (PEO) side chains by ring‐opening metathesis polymerization for solid polymer electrolytes (SPE). In addition to the conductive PEO side chains, the polyoxanorbornene backbones may act as another ion conductor to further promote Li‐ion movement within the SPE matrix. These results suggest that these bottlebrush polymer electrolytes provide impressively high ionic conductivity of 7.12 × 10⁻⁴S cm⁻¹at room temperature and excellent electrochemical performance, including high‐rate capabilities and cycling stability when paired with a Li metal anode and a LiFePO₄cathode. The new design paradigm, which has dual ionic conductive pathways, provides an unexplored avenue for inventing new SPEs and emphasizes the importance of molecular engineering to develop highly stable and conductive polymer electrolytes for lithium‐metal batteries (LMB). 

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4. Characterization of Micelle Formation by the Single Amino Acid-Based Surfactants Undecanoic L-Isoleucine and Undecanoic L-Norleucine in the Presence of Diamine Counterions with Varying Chain Lengths

   https://doi.org/10.3390/colloids7020028  

   Maynard-Benson, Amber; Alekisch, Mariya; Wall, Alyssa; Billiot, Eugene J.; Billiot, Fereshteh H.; Morris, Kevin F. (June 2023, Colloids and Interfaces)

   The binding of linear diamine counterions with different methylene chain lengths to the amino-acid-based surfactants undecanoic L-isoleucine (und-IL) and undecanoic L-norleucine (und-NL) was investigated with NMR spectroscopy. The counterions studied were 1,2-ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, and 1,6-diaminohexane. These counterions were all linear diamines with varying spacer chain lengths between the two amine functional groups. The sodium counterion was studied as well. Results showed that when the length of the counterion methylene chain was increased, the surfactants’ critical micelle concentrations (CMC) decreased. This decrease was attributed to diamines with longer methylene chains binding to multiple surfactant monomers below the CMC and thus acting as templating agents for the formation of micelles. The entropic hydrophobic effect and differences in diamine counterion charge also contributed to the size of the micelles and the surfactants’ CMCs in the solution. NMR diffusion measurements showed that the micelles formed by both surfactants were largest when 1,4-diaminobutane counterions were present in the solution. This amine also had the largest mole fraction of micelle-bound counterions. Finally, the und-NL micelles were larger than the und-IL micelles when 1,4-diaminobutane counterions were bound to the micelle surface. A model was proposed in which this surfactant formed non-spherical aggregates with both the surfactant molecules’ hydrocarbon chains and n-butyl amino acid side chains pointing toward the micelle core. The und-IL micelles, in contrast, were smaller and likely spherically shaped. 

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5. pH- and chaotropic anion-induced conformational changes of tertiary amine-containing binary heterografted star molecular bottlebrushes in aqueous solution

   https://doi.org/10.1039/D0PY01466D  

   Kent, Ethan W.; Lewoczko, Evan M.; Zhao, Bin (January 2021, Polymer Chemistry)

   null (Ed.)

   This article reports on the conformational behavior of binary heterografted three-arm star molecular bottlebrushes composed of poly(ethylene oxide) (PEO) and either poly(2-( N , N -dimethylamino)ethyl methacrylate) (PDMAEMA, the brushes denoted as SMB-1) or poly(2-( N , N -diethylamino)ethyl methacrylate) (PDEAEMA, the brushes denoted as SMB-2) side chains in aqueous solutions in response to pH changes and addition of salts containing chaotropic anions (CAs). PEO was introduced into the brushes as a stabilizer when the tertiary amine-containing side chains collapsed. While a small size decrease of SMB-1 was observed with increasing pH from acidic to basic, SMB-2 exhibited a large and abrupt size transition caused by the pH-induced solubility change of PDEAEMA. Atomic force microscopy imaging revealed a star-to-globule shape transition of SMB-2 upon increasing pH across the p K a ; in contrast, SMB-1 stayed in the starlike state at both low and high pH values. Intriguingly, both SMB-1 and -2 displayed star-to-globule shape transitions in acidic solutions upon addition of salts containing sufficiently strong CAs such as ClO 4 − , with SMB-2 showing a greater sensitivity to moderate CAs than SMB-1. Moreover, superchaotropic anions ( e.g. , Fe(CN) 6 3− and S 2 O 8 2− ) were significantly more efficient in inducing shape changing than common CAs. The CA-induced shape transitions resulted from the ion pairing of CAs and protonated tertiary amine groups and the high propensity of CAs to associate with hydrophobic moieties in the brushes, which decreased the solubility of the tertiary amine-containing side chains and caused the brushes to collapse. The findings reported here may enable potential applications of molecular bottlebrushes in, e.g. , encapsulation and release of ionic substances. 

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