Alternating current (AC) and pulsed electrolysis are gaining traction in electro(organic) synthesis due to their advantageous characteristics. We employed AC electrolysis in electrochemically ...mediated Atom Transfer Radical Polymerization (eATRP) to facilitate the regeneration of the activator CuI complex on Cu0 electrodes. Additionally, Cu0 served as a slow supplemental activator and reducing agent (SARA ATRP), enabling the activation of alkyl halides and the regeneration of the CuI activator through a comproportionation reaction. We harnessed the distinct properties of Cu0 dual regeneration, both chemical and electrochemical, by employing sinusoidal, triangular, and square‐wave AC electrolysis alongside some of the most active ATRP catalysts available. Compared to linear waveform (DC electrolysis) or SARA ATRP (without electrolysis), pulsed and AC electrolysis facilitated slightly faster and more controlled polymerizations of acrylates. The same AC electrolysis conditions could successfully polymerize eleven different monomers across different mediums, from water to bulk. Moreover, it proved effective across a spectrum of catalyst activity, from low‐activity Cu/2,2‐bipyridine to highly active Cu complexes with substituted tripodal amine ligands. Chain extension experiments confirmed the high chain‐end fidelity of the produced polymers, yielding functional and high molecular‐weight block copolymers. SEM analysis indicated the robustness of the Cu0 electrodes, sustaining at least 15 consecutive polymerizations.
The study introduces alternating current (AC) electrolysis in ATRP using a symmetrical Cu/Cu electrode pair to generate the CuI activator complex and drive the polymerization. Square and sinusoidal waves at 0.1 Hz from an AC generator were used to polymerize many monomers (including functionals) in organic solvent, water, and bulk. The same electrode pair and the same AC current value were used for all polymerizations and block copolymerizations.
Abstract
In this paper, a novel strategy for the preparation of solid polycarboxylate superplasticizers (PC-3) with hyperbranched structures was proposed. PC-3 was synthesized by bulk polymerization ...method under a redox initiation system. Dimethylaminoethyl methacrylate (DMAEMA) with an initiating group, as a soluble vinyl monomer was introduced to copolymerize with acrylic acid (AA) and isobutyl alcohol polyoxyethylene ether (HPEG). The reaction mechanism of the system initiated by ammonium persulfate (APS) and DMAEMA was explored, and the formation process of the hyperbranched structure was investigated. The experimental results show that the hyperbranched solid polycarboxylate superplasticizer has a high water-reducing rate and good slump retention. It can be applied in cement-based grouting materials well.
Molecular scaffolds that enable the combinatorial synthesis of new supramolecular building blocks are promising targets for the construction of functional molecular systems. Here, we report a ...supramolecular scaffold based on boroxine that enables the formation of chiral and ordered 1D supramolecular polymers, which can be easily functionalized for circularly polarized luminescence. The boroxine monomers are quantitatively synthesized in situ, both in bulk and in solution, from boronic acid precursors and cooperatively polymerize into 1D helical aggregates stabilized by threefold hydrogen‐bonding and π–π stacking. We then demonstrate amplification of asymmetry in the co‐assembly of chiral/achiral monomers and the co‐condensation of chiral/achiral precursors in classical and in situ sergeant‐and‐soldiers experiments, respectively, showing fast boronic acid exchange reactions occurring in the system. Remarkably, co‐condensation of pyrene boronic acid with a hydrogen‐bonding chiral boronic acid results in chiral pyrene aggregation with circularly polarized excimer emission and g‐values in the order of 10−3. Yet, the electron deficiency of boron in boroxine makes them chemically addressable by nucleophiles, but also sensitive to hydrolysis. With this sensitivity in mind, we provide first insights into the prospects offered by boroxine‐based supramolecular polymers to make chemically addressable, functional, and adaptive systems.
Boronic acid self‐condensation provides ready access to boroxine‐based, C3‐symmetrical monomer architectures that can cooperatively assemble into helical supramolecular polymers. The dynamic boroxine scaffold enables fast intermolecular exchange of boronic acid between different monomers and facilitates the introduction of functionality into assembled structures by co‐condensation with functional boronic acids.
A series of new Me2Si-bridged cyclopentadiene/indene proligands {Me2Si(R2′,5′2-R3′,4′2-Cp)(R2,R4,R5,R6-Ind)H2} (1a–j) with various substitutions both on the indene and cyclopentadiene moieties was ...prepared. The corresponding C1-symmetric group 4 ansa-metallocene complexes (M = Zr, Hf), namely, {Me2Si(Me4Cp)(Ind)}ZrCl2 (2a-Zr), {Me2Si(Me4Cp)(2-Me,4-Ph-Ind)}MCl2 (2b-M), {Me2Si(Me4Cp)(2-Me,4-Ph,6-tBu-Ind)}ZrCl2 (2c-Zr), {Me2Si(Me4Cp)(2-Me,4-Ph,5-OMe,6-tBu-Ind)}MCl2 (2d-M), {Me2Si(Me4Cp)(2-R′,4-(3′,5′-tBu2,4′-OMe-C6H2),5-OMe,6-tBu-Ind)}ZrCl2, R′ = Me (2e-Zr), R′ = Et (2f-Zr), {Me2Si(2,5-Ph2-3,4-Me2-Cp)(2-Me,4-(3′,5′-tBu2,4′-OMe-C6H2),5-OMe,6-tBu-Ind)}ZrCl2 (2g-Zr), {Me2Si(Me4Cp)(2-Me,4-(3′,6′-tBu2-carbazol-4′-yl)-Ind)}ZrCl2 (2h-Zr), {Me2Si(2,5-Me2,3,4-iPr2-Cp)(2-Me,4-Ph-Ind)}ZrCl2 (2i-Zr), {Me2Si(2,5-Me2,3,4-iPr2-Cp)(2-Me,4-Ph,6-tBu-Ind)}ZrCl2 (2j-Zr) and {Me2Si(Me4Cp)(2-Me-4,5-aanthracene-Ind)}MCl2 (2k-Zr) were synthesized and characterized by NMR spectroscopy and mass spectrometry. The solid-state molecular structures of 2b-Zr, 2d-Zr, 2e-Zr, 2f-Zr, 2j-Zr and 2k-Zr were determined by X-ray crystallography. The zirconocene complexes, once activated with MAO in toluene solution, exhibited propylene polymerization activities at 60 °C up to 161 000 kg(PP) mol(Zr)−1 h−1, affording highly isotactic polypropylenes (iPP) with m4 up to 96.5% and Tm up to 157 °C. Also, metallocene complexes 2b–e-Zr were supported on SiO2-MAO and evaluated in slurry bulk propylene polymerization at 70 °C, producing iPPs with m4 = 91.7–96.6 mol% and low regiodefects (0.2–0.3 mol%) content, with productivities up to 636 000 kg(PP) mol(Zr)−1 h−1. DFT calculations allowed rationalizing a polymerization reaction mechanism occurring through “chain-stationary” enchainment with preference for 1,2-insertions.
Poly(lactic acid), PLA, which holds great promise as a biodegradable substitute of fossil resource-derived polyolefins, is industrially produced by the ring-opening polymerization of lactide using a ...potentially harmful tin catalyst. Based on mechanistic insights into the reaction of N-heterocyclic carbene (NHC) iron complexes with carbonyl substrates, we surmised and demonstrate here that such complexes are excellent catalysts for the bulk polymerization of lactide. We show that an iron complex with a triazolylidene NHC ligand is active at lactide/catalyst ratios of up to 10 000 : 1, produces polylactide with relatively high number-average molecular weights (up to 50 kg mol
−1
) and relatively narrow dispersity (
∼ 1.6), and features an apparent polymerization rate constant
k
app
of up to 8.5 × 10
−3
s
−1
, which is more than an order of magnitude higher than that of the industrially used tin catalyst. Kinetic studies and end-group analyses support that the catalytically active species is well defined and that the polymerization proceeds
via
a coordination-insertion mechanism. The robustness of the catalyst allows technical grade lactide to be polymerized, thus offering ample potential for application on larger scale in an industrially relevant setting.
Iron(
ii
) complexes containing a mesoionic triazolylidene ligand are highly efficient catalyst precursors for the ring opening polymerization of lactide to poly(lactic acid), surpassing other iron complexes and also industrially utilized Sn(oct)
2
.
Plastics are indispensable materials in modern society; however, their extensive use has contributed to the depletion of finite natural resources and caused severe environmental issues. One ...end‐of‐use solution for plastics involves the chemical recycling of polymers back to monomers for repolymerization to virgin polymers without changing the material properties, allowing the establishment of a circular material economy. This concept focuses on the critical advantages of chemically recyclable polymers in terms of monomer design, material properties, and the feasibility of bulk depolymerization. The recyclability via bulk thermolysis of various polyesters, CO2‐based polycarbonates, and polyacetals produced via ring‐opening polymerization is highlighted through discussions regarding rational monomer design and efficient catalyst development. An outlook and perspective are provided to delineate the future challenges in the rational design of monomer and polymer structures that deliver the desired materials performance while being suitable for bulk thermolysis with high (de)polymerization activity and selectivity.
The chemical recycling of polymers back to monomers for repolymerization to virgin polymers offers a solution for the end‐of‐use problems of plastics and the potential to establish a circular material economy. This concept focuses on the critical advantages of chemically recyclable polymers in terms of monomer design, material properties, and the feasibility of bulk depolymerization.
Ring‐opening polymerizations (ROP) of l‐lactide (LA) are conducted in bulk at 130, 160, or 180 °C and are initiated with two different alcohols at 160 °C. The lactide/initiator ratio (LA/In) is ...varied from 50/1 (20/1 at 180 °C) to 900/1 and the lactide/catalyst ratio (LA/Cat) between 2000/1 and 8000/1. At all temperatures a nearly perfect control of number average molecular weight (Mn) via the LA/In ratio is feasible up to LA/In = 200/1, but at higher ratios the Mn value lags behind the theoretical values and the discrepancy increases with higher LA/Cat ratios. Variation of the LA/Cat ratio influences the formation of cycles but does not significantly influence Mn, when the LA/In ratio is kept constant. The formation of cycles is favored by lower In/Cat ratios and is the main reason for the unsatisfactory control of Mn at high LA/In ratios. The results also suggest that the cycles are mainly or exclusively formed by end‐to‐end cyclization and not, as believed previously, by back‐biting.
Alcohol‐initiated ROPs of l‐lactide in bulk at 130–180 °C allow for perfect control of the molecular weight up to lactide/initiator ratios around 200/1, whereas at higher ratios the real molecular weights are lower due to increasing cyclization.
The high demand for light‐emitting and display devices made luminescent organic materials as attractive candidates. Solvent‐free organic liquids are one of the promising emitters among them due to ...the salient features. However, the inherent limitations of forming sticky and noncurable surfaces must be addressed to become an alternate emitter for large‐area device applications. Herein, we functionalized solvent‐free organic liquids having monomeric emission in bulk with polymerizable groups to improve the processability. The polymerizable group on carbazole, naphthalene monoimide, and diketopyrrolopyrrole‐based solvent‐free liquid emitters enabled on‐surface polymerization. These emitters alone and in combinations can be directly coated on a glass substrate without the help of solvents. Subsequent photo or thermal polymerization leads to stable, non‐sticky, flexible, foldable, and free‐standing large‐area films with reasonably high quantum yield. Our demonstration of the tunable and white light‐emitting films using polymerizable solvent‐free liquids might be a potential candidate in flexible/foldable/stretchable electronics. The new concept of polymerizable liquid can be extended to other functional features suitable for futuristic applications.
A new polymerizable solvent‐free organic liquid approach has been introduced to overcome the inherent limitations of organic liquid emitters. On‐surface thermochemical polymerization of the hybrid liquids results in flexible and foldable large‐area luminescent films. Our strategy is well suited for developing tunable and white light‐emitting free‐standing large‐area flexible and transparent films suitable for futuristic applications.
Water is an environmentally friendly medium for conducting reversible deactivation radical polymerizations. In this paper, we report the investigation of iodine-mediated photocontrolled atom transfer ...radical polymerization (photoATRP) in aqueous media. The iodine-based initiator was generated by an
in situ
halogen exchange from a commercially available bromine-based initiator, ethyl α-bromophenylacetate, using different iodide salts. Fast and well-controlled polymerization of a water-soluble methacrylate monomer was achieved in water under visible light irradiation, including blue, green and yellow lights. The nature of the reaction medium greatly affected the kinetics and control over the growth of polymers. Polymerizations in water resulted in a well-controlled reaction that provided high monomer conversion and polymers with low dispersities, whereas control over the polymerization was poor in bulk or in an organic solvent,
N
,
N
-dimethylformamide. Polymerizations were performed over a wide range of visible light in the absence of any photocatalyst. The selection of water as a reaction medium enabled use of iodide salts without the need for solubilizing agents. Moreover, iodine-mediated photoATRP was successfully performed in the presence of residual oxygen, signifying the potential of this polymerization system to tolerate oxygen without performing deoxygenation processes.
Iodine-mediated photoATRP was conducted in aqueous media enabling fast and well-controlled polymerizations under visible light without deoxygenation.
Soft nanoconfinement can increase chemical reactivity in nature and has therefore led to considerable interest in transferring this universal feature to artificial biological systems. However, little ...is known about the underlying principles of soft nanoconfinement responsible for the enhancement of biochemical reactions. Herein we demonstrate how enzymatic polymerization can be expanded, optimized, and engineered when carried out under soft nanoconfinement mediated by lipidic mesophases. By systematically varying the water content in the mesophase and thus the diameter of the confined water nanochannels, we show higher efficiency, turnover rate, and degrees of polymerization as compared to the bulk aqueous solution, all controlled by soft nanoconfinement effects. Furthermore, we exploit the unique properties of unfreezing soft nanoconfined water to perform the first enzymatic polymerization at −20 °C in pure aqueous media. These results underpin lipidic mesophases as a versatile host system for chemical reactions and promote them as an original and unexplored platform for enzymatic polymerization.
The enzymatic synthesis of dextran in lipidic mesophase catalyzed by the enzyme dextransucrase DSR‐M not only yields polymers at 30 °C that are six times longer than in bulk solution at identical concentrations of reactants, but also allows the reaction to be carried out in subzero liquid water at temperatures as low as −20 °C.
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