Organocatalyzed Photo-Controlled Synthesis of Ultrahigh-Molecular-Weight Fluorinated Alternating Copolymers

Design of an Ultrafast and Controlled Visible Light-Mediated Photoiniferter RAFT Polymerization for Polymerization-Induced Self-Assembly (PISA)

In this contribution, we designed a new xanthate RAFT agent by introducing (5,6,7,8-tetrahydro-2-naphthalenyl)oxy (TNO) as the Z group, namely 2-[(((5,6,7,8-Tetrahydro-2-naphthalenyl)oxycarbonothioyl)thio)ethyl propanoate] (TNXEP). Due to the presence of the TNO group, TNXEP enabled highly controlled and ultrafast photoiniferter RAFT polymerization under violet (λ=405 nm) and blue (λ=450 nm) light. This approach was effectively extended to aqueous media for polymerization-induced self-assembly (PISA), facilitating the synthesis of polymeric nanoparticles. Leveraging the rapid photolysis and extended absorption of TNXEP, we demonstrated the first photoiniferter PISA system realizing ultrafast polymerization (>90 % monomer conversion in minutes) under visible light irradiation. Enhanced visible light penetration improved photopolymerization uniformity, enabling rapid and scalable production of polymeric nanoparticles at a 30 g scale in just 10 minutes, with tunable morphologies, including spheres, worms, and vesicles.

Diverse reactivity of maleimides in polymer science and beyond

Maleimides are remarkably versatile functional groups, capable of participating in homo- and copolymerizations, Diels-Alder and (photo)cycloadditions, Michael additions, and other reactions. Their reactivity has afforded materials ranging from polyimides with high upper service temperatures to hydrogels for regenerative medicine applications. Moreover, maleimides have proven to be an enabling chemistry for pharmaceutical development and bioconjugation via straightforward modification of cysteine residues. To exert spatiotemporal control over reactions with maleimides, multiple approaches have been developed to photocage nucleophiles, dienes, and dipoles. Additionally, further substitution of the maleimide alkene (e.g., mono- and di-halo-, thio-, amino-, and methyl-maleimides, among other substituents) confers tunable reactivity and dynamicity, as well as responsive mechanical and optical properties. In this mini-review, we highlight the diverse functionality of maleimides, underscoring their notable impact in polymer science. This moiety and related heterocycles will play an important role in future innovations in chemistry, biomedical, and materials research.

Synthesis of Star Polymers with Ultrahigh Molecular Weights and Tunable Dispersities via Photoiniferter Polymerization

Simultaneous control over macromolecular chain topology, molecular weight, and dispersity is an important synthetic goal in polymer chemistry. The synthesis of well-defined poly(methyl acrylate) star polymers with ultrahigh molecular weights (>106 g mol-1) and tunable dispersities is realized for the first time via blue light-controlled photoiniferter polymerization using a tetrafunctional switchable RAFT agent (SRA4). The spectroscopic properties and polymerization activity of SRA4 can be reversibly tuned by addition of acid/base. For example, protonation of SRA4 with 4-toluenesulfonic acid (TsOH) leads to enhanced UV-visible light absorption, a faster polymerization rate, and a lower dispersity for the resulting star polymer. Star polymers were prepared with predicted molecular weights (Mn ≈ 80-1550 kg mol-1) and tunable dispersities (Đ ≈ 1.8-1.2) when targeting degrees of polymerization in the range of 1000-20000 in the presence of varying amounts of TsOH. High end-group fidelity for such star polymers was confirmed by one-pot chain extension experiments, which afforded a series of pseudoblock copolymers with controlled dispersities. Finally, rotational rheology was used to examine the effect of molecular weight, dispersity, and chain topology (whether linear or star-shaped) on solution viscosity.

Highly Alternating Copolymer of [1.1.1]Propellane and Perfluoro Vinyl Ether: Forming a Hydrophobic and Oleophobic Surface with <50% Fluorine Monomer Content

Utilizing the unique properties of fluorine substitution is an effective strategy for constructing highly functional materials. Here, we synthesized a novel copolymer composed of [1.1.1]propellane and perfluoro(propyl vinyl ether) (PPVE), rich in alternating sequences. The spin-coated copolymer film was amorphous, and its surface exhibited an extremely low surface free energy (γ). The γ value was lower than that of polytetrafluoroethylene despite containing only 40 mol % PPVE units. This can be attributed to the cancellation of the C-F dipole moments by the entirely random orientation of the fluorine units.

Constructing an Artificial Interface as a Bifunctional Promoter for the Li Anode and the NCM Cathode in Lithium Metal Batteries

The bottleneck of Li metal batteries toward practical applications lies at inferior cyclability as well as Li dendrite issues. As a promising solution, an interface engineering strategy is proposed herein for the Li anode through constructing a hybrid artificial interface. It is assembled onto the Li anode using photocontrolled free radical polymerization (photo-CRP) of polyethylene glycol diacrylate-hexafluorobutyl methacrylate and hexafluorobutyl methacrylate-trifluoroethyl carbonate (PEGDA-HFMBA@HFMBA-FEMC or PH@HF layer). Among such hybrid interfaces, the interior layer of PEGDA-HFMBA exists as a protective shield with flexibility and fracture resistance, while the exterior layer of HFMBA-FEMC plays a role as a LiF reservoir to promote Li mass transfer and its even electrodeposition. In the meantime, some excess HFMBA and FEMC monomers further dissolve into the electrolyte as molecular additives, followed by in situ generation of a thin and robust LiF-rich cathode electrolyte interface (CEI). With the resulting Li anode, Li/NCM811 full cells showcase multifold cyclability amplification in comparison to cells using Bare-Li, covering durable cyclability with a capacity retention of 81.8% after 400 cycles. When the cutoff voltage is elevated to 4.5 V or the working temperature is elevated to 45 °C, the cells still maintain a stable operation for extending 300 cycles.

Controlled Radical Copolymerization toward Tailored F/N Hybrid Polymers by Using Light-Driven Organocatalysis

Controlled radical copolymerizations present attractive avenues to obtain polymers with complicated compositions and sequences. In this work, we report the development of a visible-light-driven organocatalyzed controlled copolymerization of fluoroalkenes and acyclic N-vinylamides for the first time. The approach enables the on-demand synthesis of a broad scope of amide-functionalized main-chain fluoropolymers via novel fluorinated thiocarbamates, facilitating regulations over chemical compositions and alternating fractions by rationally selecting comonomer pairs and ratios. This method allows temporally controlled chain-growth by external light, and maintains high chain-end fidelity that promotes facile preparation of block sequences. Notably, the obtained F/N hybrid polymers, upon hydrolysis, afford free amino-substituted fluoropolymers versatile for post modifications toward various functionalities (e.g., amide, sulfonamide, carbamide, thiocarbamide). We further demonstrate the in situ formation of polymer networks with desirable properties as protective layers on lithium metal anodes, presenting a promising avenue for advancing lithium metal batteries.

Ag-In-Zn-S alloyed nanocrystals as photocatalysts of controlled light-mediated radical polymerization

We report on the first case of the use of nonstoichiometric ternary (Ag-In-Zn-S) semiconductor nanocrystals as photoinitiators and photocatalysts of methyl methacrylate (MMA) polymerization. Two types of nanocrystals were tested, differing in their composition and characterized by red (λmax = 731 nm) and green (λmax = 528 nm) photoluminescence, respectively. Exploiting their reducing properties and capability of free radical generation we demonstrate that under ultraviolet (UV) radiation they effectively photoinitiate radical polymerization of MMA whereas under visible light (blue or green) they act as photocatalysts of living radical polymerization.