Living Radical Polymerization Research Articles

Controlled Magnetite Grafted Poly(glycidyl methacrylates) for Heavy Metal Absorption and Recovery via SET-LRP

A versatile magnetite based stringent polymer for effective metal capture was prepared by reacting iron oxide based initiator with glycidyl methacrylate monomer via single-electron transfer living radical polymerization (SET-LRP) technique. The versatile grafted polymer was successfully synthesized by metal catalyzed living radical polymerization using the catalyst system Cu/N,N,N',N'',N'''-pentamethyldiethylenetriamine as the ligand. The structural confirmation of the initiator and the grafted polymer was analyzed by using instrumentation methods such as proton nuclear magnetic resonance spectroscopy, UV-visible, TGA, SEM and gel permeation chromatography for molecular weight measurements. As the polymerization time increased, both the conversion and the molecular weight were observed to increase linearly with time. Narrow dispersed lower polydispersity index (PDI) and dispensable magnetite-g-PGMA was utilized for the extract of toxic lead from the wastewater. Sustained binding was observed due to the presence of epoxide ring in the repeating units of the polymer and recovered by magnetic effect. The material shows good stability as evident by TGA curves and better affinity to toxic lead as observed by UV-visible and SEM techniques.

Confinement of Sustainable Carbon Dots Results in Long Afterglow Emitters and Photocatalyst for Radical Photopolymerization.

Sustainable carbon dots based on cellulose, particularly carboxymethyl cellulose carbon dots (CMCCDs), were confined in an inorganic network resulting in CMCCDs@SiO2. This resulted in a material exhibiting long afterglow covering a time frame of several seconds also under air. Temperature-dependent emission spectra gave information on thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) while photocurrent experiments provided a deeper understanding of charge availability in the dark period, and therefore, its availability on the photocatalyst surface. The photo-ATRP initiator, ethyl α-bromophenylacetate (EBPA), quenched the emission from the millisecond to the nanosecond time frame indicating participation of the triplet state in photoinduced electron transfer (PET). Both free radical and controlled radical polymerization based on photo-ATRP protocol worked successfully. Metal-free photo-ATRP resulted in chain extendable macroinitiators based on a reductive mechanism with either MMA or in combination with styrene. Addition of 9 ppm Cu2+ resulted in Mw/Mn of 1.4 while an increase to 72 ppm improved uniformity of the polymers; that is Mw/Mn=1.03. Complementary experiments with kerria laca carbon dots confined materials, namely KCDs@SiO2, provided similar results. Deposition of Cu2+ (9 ppm) on the photocatalyst surface explains better uniformity of the polymers formed in the ATRP protocol.

SET-LRP - A Convenient Polymerization Method to Produce Rapid and Controlled Polymers

In this review study, the principles and evolution of Single Electron Transfer - Living Radical Polymerization (SET-LRP) together with the methodologies currently applied by researchers are discussed. It is considered that the techniques developed by Percec et al will be able to help the researchers and other industrial experts to practice, develop and invent new concepts and methodologies for SET-LRP. This renew deals with general mechanistic feature explained by Percec that undergoes a metal catalysed living radical polymerization by rapid activation and deactivation steps. In addition, the advantage of metal catalysed LRP, in mediating rapid polymerization and retain chain-end functionality necessary for reinitiating in block copolymerization can also be well explained.

Adsorption mechanism and interactions of coal particles modified with a novel hyperbranched dispersant

This account, a hyperbranched dispersant (Es-SAF-DBM-PSS) was assembled with the skeleton of Es-SAF-DBM (the functional modification of hydroquinone-based sulfonated acetone formaldehyde (SAF)) and numbers of linear polystyrene sodium sulfonate (PSS) chains by single electron transfer living radical polymerization (SET-LRP) in the system of PhBr2m4/Cu wire/PMDETA. The structure of the synthesized Es-SAF-DBM-PSS was detected by FTIR, 1H NMR, XPS, UV and GPC. Series of tests about the polymerization kinetics of Es-SAF-DBM-PSS were executed. Effects of temperatures and initiator concentration on the apparent polymerization rate were investigated, the results showed the low activation energy and higher initiation rate fitted the characteristic of SET-LRP. The rheological behaviors of Es-SAF-DBM-PSS as dispersant applied to coal water slurry (CWS) were tested. The following results were found as expected: the best usage of Es-SAF-DBM-PSS was only 0.3%, maximum coal content reached 63.7%, the viscosity dropped as low as 1000mPa·s. And the penetration ratio of slurry mixed with Es-SAF-DBM-PSS was still 100% even after 35days. Adsorption mechanism and interparticle interactions of coal particles modified with Es-SAF-DBM-PSS were investigated by Langmuir equation, dynamic equations and extended Derjaguin-Landau-Verwey-Overbeek (eDLVO) theory, the results showed the excellent dispersion and stability performance of Es-SAF-DBM-PSS were mainly related to the specific hyperbranched structure.

Synthesis of thermo-responsive polymer gels composed of star-shaped block copolymers by copper-catalyzed living radical polymerization and click reaction

ABSTRACT In recent times, there has been a significant surge in research interest surrounding thermo-responsive water-soluble polyacrylamides, primarily due to their intriguing capability to undergo significant solubility changes in water. These polymers exhibit the remarkable ability to shift from a soluble to an insoluble state in response to temperature variations. The capacity of these polymers to dynamically respond to temperature changes opens up exciting avenues for designing smart materials with tunable properties, amplifying their utility across a spectrum of scientific and technological applications. Researchers have been particularly captivated by the potential applications of thermo-responsive water-soluble polyacrylamides in diverse fields such as drug delivery, gene carriers, tissue engineering, sensors, catalysis, and chromatography separation. This study reports the construction and functionalization of polymer gels consisting of a polymer network of polyacrylamide derivatives with nano-sized structural units. Specifically, thermo-responsive polymer gels were synthesized by combining well-defined star-shaped polymers composed of polyacrylamide derivatives with a multifunctional initiator and linking method through a self-accelerating click reaction. The polymerization system employed a highly living approach, resulting in polymer chains characterized by narrow molecular weight distributions. The method’s high functionality facilitated the synthesis of a temperature-responsive block copolymer gel composed of N-isopropyl acrylamide (NIPA) and N-ethyl acrylamide (NEAA). The resulting polymer gel, comprising star-shaped block copolymers of NIPA and NEAA, showcases smooth volume changes with temperature jumps.

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.

Solving fundamental concepts in supramolecular science with functionality-tolerant living polymerizations of self-assembling monomers and dendronized monomers

The evolution and development of several examples of functionality-tolerant living polymerizations to the level of perfection that they could be employed to solve fundamental concepts in supramolecular science by living polymerization of self-assembling monomers and self-organizable dendronized monomers is briefly reviewed. The review focuses on the development of the living polymerization methodology with brief examples on how they impacted the field of self-assembly and self-organization. The first polymerization reaction discussed is the stereoselective polymerization of phenylacetylene and of other arylacetylenes to generate helical poly(arylacetylene) stereoisomers. The transition from functionality non-tolerant to functionality-tolerant stereoselective polymerizations and the evolution to functionality-tolerant living stereoselective polymerization of phenylacetylene is used as the main example of this brief review. This living polymerization methodology is followed by living polymerization of vinyl ethers, oxazolines, of group transfer polymerization, of cationic ring-opening polymerization of cyclic siloxanes combined with hydrosilylation, of ROMP of cylooxanorbornene. This brief review is concluded by a brief discussion of the capabilities of the above-mentioned living methodologies with living radical polymerizations. The numerous applications in the field of supramolecular science of these living methodologies are not reviewed. However, the reader is directed to numerous comprehensive review articles discussing these applications. The challenges that remain to be solved in all these functionality-tolerant living polymerizations are presented.

Tailored Fluorosurfactants through Controlled/Living Radical Polymerization for Highly Stable Microfluidic Droplet Generation.

Droplet-based microfluidics represents a disruptive technology in the field of chemistry and biology through the generation and manipulation of sub-microlitre droplets. To avoid droplet coalescence, fluoropolymer-based surfactants are commonly used to reduce the interfacial tension between two immiscible phases to stabilize droplet interfaces. However, the conventional preparation of fluorosurfactants involves multiple steps of conjugation reactions between fluorinated and hydrophilic segments to form multiple-block copolymers. In addition, synthesis of customized surfactants with tailored properties is challenging due to the complex synthesis process. Here, we report a highly efficient synthetic method that utilizes living radical polymerization (LRP) to produce fluorosurfactants with tailored functionalities. Compared to the commercialized surfactant, our surfactants outperform in thermal cycling for polymerase chain reaction (PCR) testing, and exhibit exceptional biocompatibility for cell and yeast culturing in a double-emulsion system. This breakthrough synthetic approach has the potential to revolutionize the field of droplet-based microfluidics by enabling the development of novel designs that generate droplets with superior stability and functionality for a wide range of applications.

Tailored Fluorosurfactants through Controlled/Living Radical Polymerization for Highly Stable Microfluidic Droplet Generation

AbstractDroplet‐based microfluidics represents a disruptive technology in the field of chemistry and biology through the generation and manipulation of sub‐microlitre droplets. To avoid droplet coalescence, fluoropolymer‐based surfactants are commonly used to reduce the interfacial tension between two immiscible phases to stabilize droplet interfaces. However, the conventional preparation of fluorosurfactants involves multiple steps of conjugation reactions between fluorinated and hydrophilic segments to form multiple‐block copolymers. In addition, synthesis of customized surfactants with tailored properties is challenging due to the complex synthesis process. Here, we report a highly efficient synthetic method that utilizes living radical polymerization (LRP) to produce fluorosurfactants with tailored functionalities. Compared to the commercialized surfactant, our surfactants outperform in thermal cycling for polymerase chain reaction (PCR) testing, and exhibit exceptional biocompatibility for cell and yeast culturing in a double‐emulsion system. This breakthrough synthetic approach has the potential to revolutionize the field of droplet‐based microfluidics by enabling the development of novel designs that generate droplets with superior stability and functionality for a wide range of applications.

Synthesis of magneto-thermal biresponsive temperature-sensitive copolymer/inorganic hybrid green nanoemulsifier with tunable LCST behavior and simulation and calculation of LCST transition behavior of its copolymer

In recent years, intelligent nano-emulsifiers have received a lot of attention in oil fields. Here, a temperature-sensitive copolymer layer, P(NIPAM-co-DMAA), has been grafted in situ on the surface of Fe3O4@SiO2 nanoparticles using two monomers, N-isopropylacrylamide and N,N-dimethylacrylamide, by a single-electron-transfer living radical polymerization method. In this way, magneto-thermal dual-responsive temperature-sensitive copolymer/inorganic hybrid nanoparticles, Fe3O4@SiO2@P(NIPAM-co-DMAA), whave been successfully prepared. The lowest critical solution temperature (LCST) of P(NIPAM-co-DMAA) could be regulated between 39 and 58 °C by modulating the ratio of monomers, endowing Fe3O4@SiO2@P(NIPAM-co-DMAA) nanoparticles with a broader response temperature range for use in more applications. We have used density functional theory and molecular dynamics simulation to thoroughly study the LCST transition behavior of the temperature-sensitive copolymer P(NIPAM-co-DMAA) in water. The intelligent Pickering emulsion obtained by using Fe3O4@SiO2@P(NIPAM-co-DMAA) as a solid particle emulsifier can be regulated between “on” (emulsification) and “off” (breakage) states using temperature and magnetic field as trigger switches. A magnetic field allows the samples to be recycled and reused, which is in line with the energy saving concept. Therefore, the present research may find promising applications in enhanced oil recovery, and other industrial fields, and provides useful insight into the LCST transition behavior of temperature-sensitive polymers.

Evaluation of Hydrophobic Attraction between Polystyrene Layer and Silanated Silica Surface by Atomic Force Microscopy

Abstract In this study, hydrophobic surfaces were prepared by depositing polystyrene (PS) on a glass substrate using three different methods to measure the interaction forces against a hydrophobized particle by atomic force microscopy. We found that smooth surfaces prepared by spin coating and living radical polymerization generated hydrophobic attraction, whereas uneven surfaces obtained by free radical polymerization produced only steric repulsion, even though they had sufficient hydrophobicity. Based on these results, the origin of the hydrophobic attraction was suggested.

The Effect of mPEGA/EHA Ratio and Copolymer Composition on the Solution Behavior of Amphiphilic, Comb‐Shape Copolymers Synthesized via Cu(0)‐Mediated SET‐LRP for Potential Drug Delivery Applications

AbstractComb‐shape, block copolymers from hydrophilic poly(ethylenglycol) monomethyl ether acrylate (mPEGA, A) and hydrophobic 2‐ethylhexyl acrylate (EHA, B) are synthesized by copper(0)‐mediated single‐electron transfer living radical polymerization (SET‐LRP) via sequential addition of the two monomers, resulting in different compositions (AB, ABA, BAB, BA), molar masses, and mPEGA/EHA ratios. All polymers show narrow molar mass distributions and molecular weights of 7.7–25.50 kg mol−1, demonstrating precise control over the polymerization and molecular weights through the utilization of SET‐LRP. Kinetic experiments are conducted to investigate the polymerization behavior of mPEGA and EHA in N,N‐dimethylformamide as a rather uncommon solvent for SET‐LRP further underlining a living‐type polymerization. Amphiphilic properties are investigated by critical micelle concentration (CMC) measurements and formation of micelles in water. A reverse relation between mPEGA/EHA ratio and CMC values reveals that an increased hydrophobicity leads to decreased CMC values. The self‐assembly behavior of polymers in water confirms the formation of uniform and stable micelles in water with a size between 12 and 184 nm depending on the composition of the polymers. With increased hydrophilicity, micelle sizes increase as well. In vitro tests of the obtained polymers show excellent biocompatibility even at high concentrations further affirming their suitability for drug delivery applications.

Exfoliated Poly (styrene-co-urethane) Grafted - Polymethylmethacrylate /Layered Double Hydroxide Nanocomposite Synthesized by Metal Catalyzed Living Radical Polymerization and Solvent Blending Method

Exfoliated Poly (styrene-co-urethane) Grafted - Polymethylmethacrylate /Layered Double Hydroxide Nanocomposite Synthesized by Metal Catalyzed Living Radical Polymerization and Solvent Blending Method

PVA free-radical diblock copolymer for nanoencapsulation with enhanced biodegradability in the environment

The synthesis of readily biodegradable amphiphilic polyvinyl alcohol diblock copolymers (poly(VA-b-MDO)) was achieved through the combination of radical ring-opening polymerization (rROP) and reversible addition-fragmentation chain-transfer (RAFT)-living radical polymerization using 2-methylene-1,3-dioxepane (MDO) and vinyl acetate (VAc) monomers in three steps. The chemistry features solvent-free conditions (bulk polymerization) and subsequent deprotection of the acetyl group under mild conditions. With this optimized method, various lengths of poly(VA) and poly(MDO) in poly(VA-b-MDO) were synthesized by controlling the molecular weight distribution of both blocks. The self-assembly of diblock copolymers to nanoparticles with narrow size distribution and subsequent encapsulation of personal care and pharma active ingredients (e.g., curcumin and fenofibrate) and their controlled release were investigated. In vitro release experiments demonstrated that encapsulated nanoparticles release the actives at a slow and consistent rate compared to free actives. Stability experiments showed that the particle size distribution and purity of curcumin and fenofibrate remained unchanged after being exposed to light for ten months. More importantly, our environmental biodegradability studies revealed that the degradable poly(VA-b-MDO) (6b), consisting of 35 mol% poly(VA) and 65 mol% poly (MDO) blocks, achieves a biodegradability of 78% in 28 days. This is owing to the higher mole ratio of degradable polyester units in the polymer backbone as compared to poly(VA-b-MDO) (6c), which contains 64 mol% poly(VA) and 36 mol% poly(MDO) blocks (33% in 28 days). Our results provide insights into the potential applicability of these polymers in personal care and pharmaceutical products where biodegradability is a crucial factor. By developing a sustainable methodology from synthesis to application, our work helps to harness the potential of biodegradable diblock copolymers in the consumer care and medical fields.

Separable and recyclable SBA-15 based catalyst for metal-free ATRP

The aminoated SBA-15 (SBA-15-NH2) was obtained by the condensation reaction between the hydroxyl group on the surface of SBA-15 and the ethoxy group of 3-aminopropyl triethoxysilane (KH550) coupling agent. And then the fluorescein acyl chloride (Flu-Cl) or rhodamine B acyl chloride (RB-Cl) was loaded onto SBA-15 surface to gain two kinds of SBA-15 based catalysts (SBA-15-Flu and SBA-15-RB) via the reaction between the amino group of SBA-15-NH2 and the acyl chloride group of Flu-Cl or RB-Cl. The metal-free ATRP of methyl methacrylate (MMA) was carried out under 365 nm UV light using SBA-15 based catalyst as photocatalyst, and ethyl 2-bromoisobutyrate (EBIB) as initiator. The structure of the two SBA-15 based catalysts was confirmed by fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and thermogravimetry analysis (TGA). The morphology and surface area of SBA-15 before and after modification were observed by scanning electron microscopy (SEM) and brunauer emmett teller (BET) respectively. The results showed that Flu-Cl and RB-Cl have been successfully loaded onto SBA-15 surface. Gel permeation chromatograph (GPC) and kinetic experiments illustrated the polymerization process was controllable and the molecular weight distribution was relatively narrow, which conforms to the characteristics of living radical polymerizations. After polymerization, the SBA-15 based photocatalyst was separated by simple centrifugation and recycled three or four times for metal-free ATRP. In these cyclic catalytic processes, the separated SBA-15 based photocatalyst exhibited excellent catalytic effect, the polymerization product is pure and has no residual catalyst.

Cellular Internalization and Exiting Behavior of Zwitterionic 4-Armed Star-Shaped Polymers.

The zwitterionic phospholipid polymer poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (PMB) is amphiphilic copolymer, and it has been reported to directly penetrate cell membranes and have good cytocompatibility. Conventional PMBs are linear-type random copolymers that are polymerized by a free radical polymerization technique. In contrast, star-shaped polymers, or simple branched-type polymers, have unique properties compared to the linear types, for example, a viscosity based on the effect of the excluded volume. In this study, a branched architecture was introduced into a PMB molecular structure, and a 4-armed star-shaped PMB (4armPMB) was synthesized by an atom transfer radical polymerization (ATRP) technique known as living radical polymerization. Linear-type PMB was also synthesized using ATRP. The effects of the polymer architecture on cytotoxicity and cellular uptake were investigated. Both 4armPMB and LinearPMB were successfully synthesized, and these polymers were verified to be water soluble. Pyrene fluorescence in the polymer solution indicated that the architecture had no effect on the behavior of the polymer aggregates. In addition, these polymers caused no cytotoxicity or cell membrane damage. The 4armPMB and LinearPMB penetrated into the cells after a short incubation period, with similar rates. In contrast, the 4armPMB showed a quicker back-diffusion from the cells than that of LinearPMB. The 4armPMB showed fast cellular internalization and exiting behaviors.

Tailoring Polymerization Controllability and Dispersity through a Photoswitchable Catalyst Strategy.

Modulating on-demand polymerization is a challenge in synthetic macromolecules. Herein, tailoring polymerization controllability and dispersity during single-electron transfer mediated living radical polymerization (SET-LRP) of MMA was achieved. Hexaarylbiimidazole (HABI) was employed as a photoswitchable catalyst, allowing reversible control of catalytic activity between an active and inactive state. In the presence of HABI and with light on (active state), controlled SET-LRP of MMA followed first-order kinetics, resulting in polymers with narrow molecular weight distribution. In contrast, polymerization responded to light and reverted to their original uncontrolled state with light off (inactive state). Therefore, repeatable resetting polymerization could be easily performed. The key to photomodulating dispersity is to use an efficient molecular switch to tailor the breadths of dispersity. Besides, the mechanism of HABI-mediated SET-LRP with switchable ability is proposed. This article is protected by copyright. All rights reserved.

Where is the induction from? Effect of disproportionation and comproportionation in Cu(0)-mediated reversible deactivation radical polymerization

There is a controversial debate about the mechanism of reversible deactivation radical polymerization (RDRP) in the presence of Cu(0). Two mechanism models have been proposed - supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) and single-electron transfer living radical polymerization (SET-LRP), however, they are contradictory to each other, and neither of them are able to fully explain experimental phenomenon in the Cu(0)-mediated RDRP process, especially a period of slow addition i.e., induction period occurs under certain reaction conditions. In this work, the induction phenomenon and its underlying mechanism was explored and clarified by using different catalyst systems (CuI, Cu(0), Cu(0)&CuII) and different initiator systems i.e., EBriB (ethyl α-bromoisobutyrate), EBrP (ethyl 2-bromopropionate), MBrP (methyl 2-bromopropionate) and MClP (methyl 2-chloropropionate). New insights on the roles of different copper species and their mutual conversion kinetics were provided. It is proved that the appearance/absence of the induction period is due to the difference in the relative concentrations of CuI and CuII accumulated at the early stage of the reaction. Moreover, the disproportionation and comproportionation co-exist in the Cu(0)-mediated RDRP system and play an essential role in establishing the equilibrium among different copper species (Cu0, CuI and CuII) at the early reaction stage.

Correlation between Self-Folding Behavior of Amphiphilic Polymers and Their Molecular Flexibility.

Self-folding behavior of amphiphilic polymers in aqueous environments mimics the structures of biomacromolecules (e.g., proteins). Since both the three-dimensional structure (static) and the molecular flexibility (dynamic) of a protein are essential for its biological functions, the latter should be considered when designing synthetic polymers that are intended to mimic proteins. Herein, we investigated the correlation between the self-folding behavior of amphiphilic polymers and their molecular flexibility. We synthesized amphiphilic polymers by subjecting N,N-dimethylacrylamide (hydrophilic) and N-benzylacrylamide (hydrophobic) to living radical polymerization. Polymers containing 10, 15, and 20 mol % of N-benzylacrylamide demonstrated self-folding behavior in an aqueous phase. The spin-spin relaxation time (T2) of the hydrophobic segments decreased with the percent collapse of the polymer molecules, indicating that mobility was restricted by the self-folding behavior. Furthermore, comparison of the polymers with random and block sequences revealed that the mobility of hydrophobic segments was not affected by the component of the local segments.

Rare earth–cobalt bimetallic catalysis mediates stereocontrolled living radical polymerization of acrylamides

Rare earth–cobalt bimetallic catalysis mediates stereocontrolled living radical polymerization of acrylamides