Designing Zwitterionic Bottlebrush Polymers to Enable Long-Cycling Quasi-Solid-State Lithium Metal Batteries

Ionogel polymer electrolyte (IPE), incorporating ionic liquid (IL) within a polymer matrix, presents a promising avenue for safe quasi-solid-state lithium metal batteries. However, sluggish Li+ kinetics, resulting from the formation of [Li(anion)n]-(n-1) clusters and the occupation of Li+ transport sites by organic cations, limit their practical applications. In this study, we have developed zwitterionic bottlebrush polymers-based IPE with promoted Li+ conduction by employing poly(sulfobetaine methacrylate)-grafted poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVC-g-PSBMA) bottlebrushes as matrices of IL. The grafted zwitterionic side chains greatly facilitate the dissociation of [Li(anion)n]-(n-1) clusters to produce more movable Li+. Moreover, the positively charged -NR4 + groups in zwitterionic side chains effectively restrain anions migration, while the negatively charged -SO3 - groups immobilize IL cations, preventing them from occupying Li+ hopping sites and reducing the energy barrier for Li+ migration. These synergistic effects contribute to a notable ionic conductivity (7.5×10-4 S cm-1) and Li+ transference number (0.62) of PVC-g-PSBMA IPE at 25 °C. As a result, PVC-g-PSBMA IPE enables ultralong-term (over 6500 h) reversible and stable Li plating/stripping in Li||Li symmetric cells. Remarkably, the assembled Li||LiFePO4 full batteries demonstrate unprecedented cycling stability of more than 2000 cycles with a superior capacity retention of 93.7 %.

Zwitterionic nanospheres engineered co-polymer composite membrane for precise protein-protein separation via dynamic self-assembly micelle deposition

The accurate protein-protein separation is important but technically challenging. Achieving such a precise separation using membrane requires the selective channels with appropriate pore geometry structure and high anti-fouling property. In this study, polyethersulfone-b-poly(sulfobetaine methyl methacrylate) (PES-b-PSBMA) was synthesized and engineered onto polysulfone (PSF) ultrafiltration (UF) membrane to fabricate zwitterionic nanospheres engineered co-polymer (ZN-e-CoP) composite membrane via dynamic self-assembly micelle deposition. On the one hand, self-assembly zwitterionic nanospheres were used as blocks to construct hydrophilic layers with size-dependent sieving channels, endowing ZN-e-CoP composite membranes with enhanced permselectivity and protein-protein separation abilities, meanwhile zwitterionic groups from nanospheres reinforced the structure stability of nanospheres/nanospheres and nanospheres/membrane via multiple intermolecular interactions. On the other hand, zwitterionic nanospheres can induce to produce the hydration layer enveloping themselves by binding water molecules, where hydration layer acts as a protective barrier on the membrane surface, impeding the protein adhesion. Hence, ZN-e-CoP_1a composite membrane exhibited superior separation properties with Lysozyme/Bovine Serum Albumin (BSA) separation factor of 18.1 and 95.4 % rejection against BSA, 10.1 and 2.3 times, respectively, higher these of pristine PSF membrane (1.8 and 42.1 %), without obviously sacrificing water flux. Simultaneously, hydration layer enables the ZN-e-CoP_1a membrane with enhanced anti-fouling performance and durability during the long-term operations. The proposed approach opens new pathways to fabricate excellent anti-fouling membranes for precise protein-protein separation.

Switch It Inside-Out: "Schizophrenic" Behavior of All Thermoresponsive UCST-LCST Diblock Copolymers

This feature article reviews our recent advancements on the synthesis, phase behavior, and micellar structures of diblock copolymers consisting of oppositely thermoresponsive blocks in aqueous environments. These copolymers combine a nonionic block, which shows lower critical solution temperature (LCST) behavior, with a zwitterionic block that exhibits an upper critical solution temperature (UCST). The transition temperature of the latter class of polymers is strongly controlled by its molar mass and by the salt concentration, in contrast to the rather invariant transition of nonionic polymers with type II LCST behavior such as poly(N-isopropylacrylamide) or poly(N-isopropyl methacrylamide). This allows for implementing the sequence of the UCST and LCST transitions of the polymers at will by adjusting either molecular or, alternatively, physical parameters. Depending on the location of the transition temperatures of both blocks, different switching scenarios are realized from micelles to inverse micelles, namely via the molecularly dissolved state, the aggregated state, or directly. In addition to studies of (semi)dilute aqueous solutions, highly concentrated systems have also been explored, namely water-swollen thin films. Concerning applications, we discuss the possible use of the diblock copolymers as "smart" nanocarriers.

Exploring Poly(ethylene glycol)-Polyzwitterion Diblock Copolymers as Biocompatible Smart Macrosurfactants Featuring UCST-Phase Behavior in Normal Saline Solution

Nonionic-zwitterionic diblock copolymers are designed to feature a coil-to-globule collapse transition with an upper critical solution temperature (UCST) in aqueous media, including physiological saline solution. The block copolymers that combine presumably highly biocompatible blocks are synthesized by chain extension of a poly(ethylene glycol) (PEG) macroinitiator via atom transfer radical polymerization (ATRP) of sulfobetaine and sulfabetaine methacrylates. Their thermoresponsive behavior is studied by variable temperature turbidimetry and ¹H NMR spectroscopy. While the polymers with polysulfobetaine blocks exhibit phase transitions in the physiologically interesting window of 30⁻50 °C only in pure aqueous solution, the polymers bearing polysulfabetaine blocks enabled phase transitions only in physiological saline solution. By copolymerizing a pair of structurally closely related sulfo- and sulfabetaine monomers, thermoresponsive behavior can be implemented in aqueous solutions of both low and high salinity. Surprisingly, the presence of the PEG blocks can affect the UCST-transitions of the polyzwitterions notably. In specific cases, this results in "schizophrenic" thermoresponsive behavior displaying simultaneously an UCST and an LCST (lower critical solution temperature) transition. Exploratory experiments on the UCST-transition triggered the encapsulation and release of various solvatochromic fluorescent dyes as model "cargos" failed, apparently due to the poor affinity even of charged organic compounds to the collapsed state of the polyzwitterions.

Temperature-/CO2-dual-responsiveness of a zwitterionic “schizophrenic” copolymer

A zwitterionic “schizophrenic” copolymer with dual-responsiveness to temperature and carbon dioxide self-assembles to undergo a reversible phase transition in a weakly alkaline borate buffer solution.

A facile, simple, and inexpensive ionic liquid, 1-alkyl-3-methylimidazole chloride, as ligand for the iron(iii)-mediated reverse atom transfer radical polymerization of methyl methacrylate

The facile, simple, and inexpensive ILs, 1-alkyl-3-methylimidazole chloride ([Rmim][Cl]), are explored for the first time as ligands for the reverse ATRP of methacrylates.

Effect of the zwitterion structure on the thermo-responsive behaviour of poly(sulfobetaine methacrylates)

Modulating the thermo-responsive behaviour of poly(sulfobetaine methacrylates) whereby small structural changes cause big effects but show little logic.

A versatile approach towards multi-functional surfaces via covalently attaching hydrogel thin layers

In this study, a robust and straightforward method to covalently attach multi-functional hydrogel thin layers onto substrates was provided. In our strategy, double bonds were firstly introduced onto substrates to provide anchoring points for hydrogel layers, and then hydrogel thin layers were prepared via surface cross-linking copolymerization of the immobilized double bonds with functional monomers. Sulfobetaine methacrylate (SBMA), sodium allysulfonate (SAS), and methyl acryloyloxygen ethyl trimethyl ammonium chloride (METAC) were selected as functional monomers to form hydrogel layers onto polyether sulfone (PES) membrane surfaces, respectively. The thickness of the formed hydrogel layers could be controlled, and the layers showed excellent long-term stability. The PSBMA hydrogel layer exhibited superior antifouling property demonstrated by undetectable protein adsorption and excellent bacteria resistant property; after attaching PSAS hydrogel layer, the membrane showed incoagulable surface property when contacting with blood confirmed by the activated partial thromboplastin time (APTT) value exceeding 600s; while, the PMETAC hydrogel thin layer could effectively kill attached bacteria. The proposed method provides a new platform to directly modify material surfaces with desired properties, and thus has great potential to be widely used in designing materials for blood purification, drug delivery, wound dressing, and intelligent biosensors.

A thermoresponsive poly(N-vinylcaprolactam-co-sulfobetaine methacrylate) zwitterionic hydrogel exhibiting switchable anti-biofouling and cytocompatibility

A new class of hydrogels were prepared from the combination of the non-ionic VCL with zwitterionic SBMA monomers, exhibiting anti-biofouling and cytocompatibility.

Preparation and thermoresponsive properties of helical polypeptides bearing pyridinium salts

Polypeptides bearing 3-methylpyridinium groups and BF₄⁻ prepared by nuleophilic substitution and ion-exchange reaction showed upper critical solution temperature (UCST)-type transitions in aqueous solutions.