Transfer Radical Polymerization Research Articles

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.

Thermoresponsive Property of Poly(N,N-bis(2-methoxyethyl)acrylamide) and Its Copolymers with Water-Soluble Poly(N,N-disubstituted acrylamide) Prepared Using Hydrosilylation-Promoted Group Transfer Polymerization.

The group-transfer polymerization (GTP) of N,N-bis(2-methoxyethyl)acrylamide (MOEAm) initiated by Me2EtSiH in the hydrosilylation-promoted method and by silylketene acetal (SKA) in the conventional method proceeded in a controlled/living manner to provide poly(N,N-bis(2-methoxyethyl)acrylamide) (PMOEAm) and PMOEAm with the SKA residue at the α-chain end (MCIP-PMOEAm), respectively. PMOEAm-b-poly(N,N-dimethylacrylamide) (PDMAm) and PMOEAm-s-PDMAm and PMOEAm-b-poly(N,N-bis(2-ethoxyethyl)acrylamide) (PEOEAm) and PMOEAm-s-PEOEAm were synthesized by the block and random group-transfer copolymerization of MOEAm and N,N-dimethylacrylamide or N,N-bis(2-ethoxyethyl)acrylamide. The homo- and copolymer structures affected the thermoresponsive properties; the cloud point temperature (Tcp) increasing by decreasing the degree of polymerization (x). The chain-end group in PMOEAm affected the Tcp with PMOEAmx > MCIP-PMOEAmx. The Tcp of statistical copolymers was higher than that of block copolymers, with PMOEAmx-s-PDMAmy > PMOEAmx-b-PDMAmy and PMOEAmx-s-PEOEAmy > PMOEAmx-b-PEOEAmy.

Group transfer polymerization in bulk methacrylates

AbstractGroup transfer polymerization (GTP) is a polymerization method developed to obtain targeted (meth)acrylic polymers in solution at ambient temperatures. In this work, it is employed with methacrylic monomers to obtain low Ð polymers in bulk. In this regard, different initiator systems that exhibit different mechanisms are compared concerning the molecular weight, the polydispersity and double bond conversion of the resulting bulk polymers. The respective systems were chosen carefully to give a broad overview of earlier developed initiator‐catalyst combinations 1‐methoxy‐1‐(trimethylsiloxy)‐2‐methylprop‐1‐ene (MTS) & tetrabutylammonium cyanide (TBACN) and more recently investigated initiating systems MTS & trityl tetrakis(pentafluorophenyl)borate (TTPB) or dimethyl phenyl silane (DMPS) & tris(pentafluorophenyl)borate (BCF). The described initiating systems are applied as a two‐component (2K) system to ensure a homogeneous distribution of the respective initiator and catalyst in the bulk monomer. In addition to the 2K experiments, photochemical initiation is also applied to bulk formulations. Therefore, a photoacid generator (PAG) and MTS is used to trigger the polymerization reaction by irradiation with UV light. A highly controlled photopolymerization method in bulk was developed that way achieving a low polydispersity polymer with high double bond conversion.

Thermogels based on biocompatible OEGMA-MEGMA diblock copolymers

A series of biocompatible thermoresponsive copolymers were successfully synthesised via group transfer polymerisation (GTP) from methoxy ethylene glycol methacrylate (MEGMA) and methoxy oligo (ethylene glycol) methacrylate (OEGMA, Mn = 300 g mol -1). Statistical and diblock copolymers with molar mass around 8100 g mol−1 and various compositions were investigated. Specifically, the content in OEGMA and MEGMA was varied from 80 to 20, 70–30, 60–40, to 50–50 w/w%. The thermoresponsive and self-assembly behaviour of the copolymers was investigated throughvisual tests, rheology, dynamic light scattering (DLS) and transmission electron microscopy (TEM). Interestingly, the diblock copolymers with higher MEGMA content were able to form gels at relatively low concentrations (as low as 5% w/w) when increasing the temperature, something that is reported for the first time for linear ethylene glycol based copolymers. A transition of spherical micelle to worm-like micelle was observed in these diblock copolymers that promotes gelation. Furthermore, these in-house synthesised polymers were mixed with Pluronic® F127. It was found that the gelation area of Pluronic® F127 was broadened by the addition of the synthesised copolymers with one formulation, specifically a combination of 12.5% w/w Pluronic® F127 and 12.5% w/w of a statistical OEGMA-co-MEGMA, forming a stable gel from 34 °C to 48 °C that is a desirable temperature range for biological applications. Finally, cell viability experiments were performed for the three most promising diblock copolymers and they were confirmed to be non-toxic.

Synthesis and molecular structure of highly compact star-like poly(methyl methacrylate) and poly(butyl methacrylate)

Poly(methyl methacrylate) and poly(n-butyl methacrylate) highly dense star-like polymers with a varied number and length of arms were prepared by the arm-first group transfer polymerization. The work is focused on the detailed characterization of the molecular structure and dilute solution properties of star-like polymers. The refractive index increment of the star-like polymers was compared with that of corresponding linear homopolymers. The prepared polymers were characterized by size exclusion chromatography coupled with a multi-angle light scattering detector and an online viscometer. Except for the commonly used molar mass, root mean square radius, and intrinsic viscosity, the obtained data also allowed the determination of the distribution of the arms per molecule, the calculation of the average number of arms per molecule, and the determination of the molar mass dependency of the draining factor. The relation between the number of arms per molecule and molar mass was estimated using various theoretical equations and compared with the true values obtained by the division of the slice molar mass by the molar mass of arms.

Polymer brush grafted immobilized metal ion affinity adsorbent based on polydopamine/polyethyleneimine-coated magnetic graphene oxide for selective enrichment of cytokinins in plants

Animmobilized metal affinity (IMAC) adsorbent was prepared for selective enrichment of adenine type CKs, via grafting polymer chain pendant with iminodiacetic acid (IDA) from polydopamine (PDA)/polyethyleneimine (PEI)-coated magnetic graphene oxide (magGO) via surface-initiated-atom transfer radical polymerization (SI-ATRP). The prepared IMAC sorbent exhibited remarkable adsorption performances and good selectivity for adenine-type CKs and was utilized as a sorbent of magnetic solid-phase extraction (MSPE) for effectiveenrichment of four adenine-type CKs in bean sprouts. Under the optimized extraction conditions, an analytical method for four adenine type CKs in bean sprouts was established by combining the MSPE combined with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The recoveries of the analytes were between 80.4 ± 1.9% and 114.6 ± 1.5% (n = 3). The limits of detection (LODs) range from 0.63 to 2.30 pg⋅mL-1. The relative standard deviations of intra-day and inter-day were less than 12.6%. Theestablished method was successfully applied to the selective extraction and sensitive detection of trace adenine-type CKs in plant samples.

Hydrosilylation-Promoted Group Transfer Polymerization of Ethyl Sorbate: A Controlled/Living System Applied to the Synthesis of an α-End Functionalized Polymer and a Triblock Copolymer with a (Meth)acrylate Polymer

The polymerization method, preparation of well-defined (co)polymers, and controlled/living property of ethyl sorbate (ES) have been investigated using hydrosilylation-promoted group transfer polymerization (GTP). The GTP of ES with hydrosilane (R3SiH) was performed in a living manner to produce well-defined poly(ethyl sorbate) (PES) via two methods: single catalyst and catalyst switch. For the single catalyst method, B(C6F5)3 served as the catalyst for the hydrosilylation of ES and R3SiH, yielding silyl ketene acetal (SKA), as well as the polymerization of ES and PES with the trans structure. SKA was prepared using the catalyst switch method via equimolar hydrosilylation with B(C6F5)3, and the phosphazene base of t-Bu-P4 catalyzed the polymerization of ES, yielding PES with cis and trans structures. The kinetic experiments demonstrated that the propagation rate kp for t-Bu-P4-catalyzed GTP is significantly higher than that for B(C6F5)3. The α-end-functionalized PES was synthesized via the hydrosilylation-promoted GTP of ES using a sorbate ester with a functional group as the moisture-stable latent initiator via the catalyst switch method. Furthermore, the controlled/living property has enabled the hydrosilylation-promoted GTP of ES with MMA and n-butyl acrylate (nBA) to produce the AB-diblock copolymer and ABA- and ABC-triblock copolymers composed of PES, PMMA, and PnBA.

One-pot catalyst-switching synthesis of thermoresponsive amphiphilic diblock copolymers consisting of poly(N,N-diethylacrylamide) and biodegradable polyesters

A method for the syntheses of thermoresponsive amphiphilic diblock copolymers through sequential organocatalyzed polymerizations using group transfer polymerization (GTP) and ring-opening polymerization (ROP), respectively, is described.

Thermoresponsive property of poly(N,N-bis(2-ethoxyethyl)acrylamide) and its multiblock copolymers with poly(N,N-dimethylacrylamide) prepared by hydrosilylation-promoted group transfer polymerization

Poly(N,N-bis(2-ethoxyethyl)acrylamide) (PEOEAm), a new thermoresponsive polyacrylamide, has been studied from the perspectives of synthesis and thermal phase transition.

Post-polymerization modification of poly(ethyl sorbate) leading to various alternating copolymers

Eight novel alternating copolymers that are not accessible with general methodologies have been synthesized by the post-polymerization modification of poly(propylene-alt-allyl alcohol)100 (PPAA100). PPAA100 is obtained from a group transfer polymerization (GTP) made poly(ethyl sorbate)100 (PES100) by first hydrogenating its backbone double bonds followed by reducing its pendent esters to hydroxyl groups using lithium aluminum hydride. The post-polymerization modification of PPAA100 includes its condensation reactions with three reactive electrophiles, and its Mitsunobu reactions with five nucleophiles. The chemical transformations of the hydroxyl group to other functionalities have resulted in the eight unique head-to-head alternating copolymers which possess a fixed propylene structural unit and an allyl alcohol derived monomeric unit, such as allyl ester, sulfonate, phosphate, ether, halide, and imide. The chemical structures of the obtained polymers are verified by 1H and 13C NMR and FT-IR spectroscopies. Finally, the thermal properties of the resulting polymers with different side groups are studied.

Asymmetric Diels‐Alder Reaction Catalyzed by Facile Recoverable Ionically Core‐Corona Polymer Microsphere‐Immobilized MacMillan Catalyst

AbstractCore‐corona polymer microsphere having sulfonic acid moiety was successfully synthesized by the surface initiated‐atom transfer radical polymerization (SI‐ATRP) of an achiral monomer with phenyl p‐styrenesulfonate using benzyl halide‐functionalized polymer microsphere, followed by the regeneration of sulfonic acid. Ionically core‐corona polymer microsphere‐immobilized MacMillan catalyst was successfully synthesized by the neutralization reaction between core‐corona polymer microsphere having sulfonic acid moiety and chiral imidazolidinone precursor. The catalyst containing hydrophobic core and corona exhibited high catalytic activity with excellent enantioselectivity (99% ee for the exo isomer and >99% for the endo isomer) in the asymmetric Diels‐Alder reaction of trans‐cinnamaldehyde and 1,3‐cyclopentadiene. The catalyst with more than 1μm diameter could be recovered quantitatively by centrifugation and reused at least four cycles without loss of the enantioselectivity.

Terminology for chain polymerization (IUPAC Recommendations 2021)

Abstract Chain polymerizations are defined as chain reactions where the propagation steps occur by reaction between monomer(s) and active site(s) on the polymer chains with regeneration of the active site(s) at each step. Many forms of chain polymerization can be distinguished according to the mechanism of the propagation step (e.g., cyclopolymerization – when rings are formed, condensative chain polymerization – when propagation is a condensation reaction, group-transfer polymerization, polyinsertion, ring-opening polymerization – when rings are opened), whether they involve a termination step or not (e.g., living polymerization – when termination is absent, reversible-deactivation polymerization), whether a transfer step is involved (e.g., degenerative-transfer polymerization), and the type of chain carrier or active site (e.g., radical, ion, electrophile, nucleophile, coordination complex). The objective of this document is to provide a language for describing chain polymerizations that is both readily understandable and self-consistent, and which covers recent developments in this rapidly evolving field.

Современные методы контролируемой радикальной полимеризации для получения разветвлённых полимеров акриламида, акриловой кислоты и (мет)акрилатов

A search and analysis has been carried out of English-language 2005–2020 scientific literature devoted to methods of obtaining branched (co)polymers of acrylamide, acrylic acid and (met)acrylates in order to obtain novel materials with valuable properties. It has been found that modern methods of controlled radical polymerization are mainly used for this purpose, namely, atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT) and group transfer polymerization (GTP). In most cases, original synthesized compounds were the chain transfer agents in RAFT. Depending on the order of synthesis, a distinction is made between the “core–arms” and “arms–core” approaches. The prospects of using branched polymers of acrylamide, acrylic acid and (met)acrylates for bioconjugation, surface immobilization, tissue engineering, oil production enhancement, and flocculation are estimated.

Block Copolymer Synthesis by a Sequential Addition Strategy from the Organocatalytic Group Transfer Polymerization of Methyl Methacrylate to the Ring‐Opening Polymerization of Lactide

Sequential block copolymerization involving comonomers belonging to different classes, e.g., a vinyl-type monomer and a heterocycle, is a challenging task in macromolecular chemistry, as corresponding propagating species do not interconvert easily from one to the other by crossover reactions. Here, it is first evidenced that 1-methoxy 2-methyl 1-trimethylsilyloxypropene (MTS), i.e., a silyl ketene acetal (SKA)-containing initiator, can be used in presence of the P4 -t-Bu phosphazene organic base to control the ring-opening polymerization (ROP) of racemic lactide (rac-LA). The elementary reaction, which rapidly transforms SKA groups into propagating alkoxides, can be leveraged to directly synthesize well-defined poly(methyl methacrylate)-b-polylactide block copolymers. This is achieved using P4 -t-Bu as the single organic catalyst and MTS as the initiator for the group transfer polymerization of methyl methacrylate, followed by the ROP of rac-LA. Both polymerization methods are implemented under selective and controlled/living conditions at room temperature in THF. This sequential addition strategy further expands the scope of organic catalysis of polymerizations for macromolecular engineering of block copolymers involving propagating species of disparate reactivity.

Macromolecular Rhenium–Ruthenium Complexes for Photocatalytic CO2 Conversion: From Catalytic Lewis Pair Polymerization to Well-Defined Poly(vinyl bipyridine)–Metal Complexes

Herein, the first catalytical polymerization of 4-vinyl-4′-methyl-2,2′-bipyridine (VBpy) via Lewis pair-mediated group-transfer polymerization using different combinations of Lewis acidic trialkyl aluminum compounds and Lewis basic phosphines is reported. In this context, a broad screening of different Lewis pairs is conducted, demonstrating the necessity of an adjustment of the steric and electronic properties of the Lewis pair to the demands of the monomer. Further, end-group analysis of short-chain oligomers via electrospray ionization mass spectrometry (ESI-MS) for the experimentally determined optimum combination Al(i-Bu)3/PMe3 (Đ = 1.31–1.36, I.E. = 45–51%) reveals the presence of two initiation pathways via conjugate addition and deprotonation. The well-defined polymers are subsequently loaded in a two-step synthesis protocol with different ratios of Re(CO)5Cl and Ru(dmb)2Cl2, forming a photocatalytically active rhenium–ruthenium polymer complex with poly(vinyl bipyridine) as the macroligand. Catalyst loadings are characterized thoroughly by means of Ultraviolet–visible (UV–vis), photoluminescence (PL), and IR spectroscopy as well as inductively coupled plasma (ICP)-MS. Finally, a comparison of the photocatalytic CO2 reduction performance of the polymeric catalysts in irradiation experiments is presented, revealing particularly high photostabilities and activities for PVBpy5/95 (TON = 5650, TOF = 66 h–1). This is due to an efficient electron transfer of the Ru(II)-one-electron-reduced species (OERS) to the rhenium centers facilitated by the spatial proximity of both metals attached to the macromolecular ligand PVBpy.

Thermoresponsive Properties of Poly[oligo(ethylene glycol) sorbate]s Prepared by Organocatalyzed Group Transfer Polymerization

The current contribution presents the synthesis of poly[oligo(ethylene glycol) sorbate]s (PREGmSs) by the t-Bu-P4-catalyzed group transfer polymerization (GTP) method, their postpolymerization modification at the backbone double bond, and thermoresponsive properties in aqueous solution. Four oligo(ethylene glycol) sorbate monomers (REGmSs), including 2-(2-methoxyethoxy)ethyl sorbate (MeEG2S), 2-(2-(2-methoxyethoxy)ethoxy)ethyl sorbate (MeEG3S), 2-(2-(2-ethoxyethoxy)ethoxy)ethyl sorbate (EtEG3S), and 2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl sorbate (MeEG4S), are newly designed to study the thermoresponsive properties of their related polymers. The t-Bu-P4-catalyzed GTP of REGmS only proceeds in a 1,4-regioselective addition manner to quantitatively produce the backbone trans-rich (ca. 80%) PREGmS. The complete hydrogenation and epoxidation of the backbone double bonds result in hydrogenated and epoxidized polymers (PREGmS-H2 and PREGmS-epoxy, respectively), which have different main-chain structures and rigidity from their parent PREGmS. Given the 1,4-substituted structure of a sorbate monomer, the chemical structure determination of PREGmS-H2 by 13C NMR spectra demonstrates that the above polymers have an erythro-rich (ca. 60%) structure in diastereochemistry and a diisotactic/disyndiotactic ratio around 1:1 in stereoregularity. The thermoresponsive properties of PREGmS, PREGmS-H2, and PREGmS-epoxy in aqueous solutions are studied in detail from various aspects in terms of polymer mass concentration, molecular weight, length and end group of the oligo(ethylene glycol) side chain, and main-chain structure by turbidity, 1H NMR spectroscopy, and dynamic light scattering (DLS) methods, which are discussed below.

Eu3+- and Tb3+-Based Coordination Complexes of Poly(N-Isopropyl,N-methylacrylamide-stat-N,N-dimethylacrylamide) Copolymer: Synthesis, Characterization and Property.

This contribution reports the syntheses, structural analyses and properties of europium (Eu3+)- and terbium (Tb3+)-based coordination complexes of poly(N-isopropyl,N-methylacrylamide-stat-N,N-dimethylacrylamide) (poly(iPMAm-stat-DMAm)) copolymer, named as poly-Eu(III) and poly-Tb(III), respectively. In greater detail, poly(iPMAm85-stat-DMAm15) is first prepared by random copolymerization of N-isopropyl,N-methylacrylamide (iPMAm) and N,N-dimethylacrylamide (DMAm) via group transfer polymerization (GTP). Next, poly(iPMAm85-stat-DMAm15) is used as the polymer matrix for chelating with Eu3+ and Tb3+ cations at its side amide groups, to produce poly-Eu(III) and poly-Tb(III). Their structural characterizations by FT-IR spectroscopy and XPS confirm the formation of polymeric complexes. The study on their fluorescence emission characteristics and luminescence lifetime demonstrates that Poly-Eu(III) shows four strong emission peaks at 578, 593, 622, and 651 nm, which are responsible for the electron transitions from the excited 5D0 state to the multiplet 7FJ (J = 0, 1, 2, 3) states, respectively, and poly-Tb(III) also displays four emission peaks at 489, 545, 588, and 654 nm, mainly due to the electron transitions of 5D4 → 7Fi (i = 6, 5, 4, 3). The luminescence lifetimes of poly-Eu(III) (τpoly-Eu(III)) and poly-Tb(III) (τpoly-Tb(III)) are determined to be 4.57 and 7.50 ms, respectively. In addition, in aqueous solutions, poly-Eu(III) and poly-Tb(III) are found to exhibit thermoresponsivity, with their cloud temperatures (Tcs) locating around 36.4 and 36.8 °C, respectively. Finally, the cytotoxicity study on the human colon carcinoma cells LoVo and DLD1 suggests that the luminescent Eu3+ and Tb3+ in the chelated state with poly(iPMAm-stat-DMAm) show much better biocompatibility and lower toxicity than their inorganic salts.

A Novel Terpolymer Membrane-Based Electrode Sensor for Selective Determination of Cd(II) Ions

A new polymeric membrane sensor for Cd(II) ion based on methyl acrylate-acrylonitrile-methyl methacrylate terpolymer as membrane carrier has been synthesized via atom transfer radical polymerization (ATRP) method at 60 ºC. Preliminary investigation with the membrane exhibited promising selectivity for Cd(II) ion with a slope of 32.02 mV/decade and the same could be estimated in the concentration range of 1 × 10-6 − 1 × 10-1 M in the working pH range of 4-6 for up to 90 days. The potentials generated across the membrane were reproducible and the response time was less than one minute. The electrode works well even in a partially non-aqueous media. The effect of surfactant and detergent on the working of Cd(II) selective electrode was also studied. A decrease in potential was observed in the presence of appreciable amount of surfactant and detergent. Addition of plasticisers was found to greatly improve the performance of membrane, best results being obtained with the membrane ratio (NaTPB:TP:TBP::1:100:06), exhibiting a working concentration range of 1 × 10-6 − 1 × 10-1 mol L-1 with a short response time of 10 s. The proposed sensor shows significantly good selectivity toward Cd(II) ion in comparison with some alkali, alkaline earth, transition and heavy metal ions. It was successfully employed as an indicator electrode in potentiometric titration of cadmium(II) ions against EDTA solution.

Organocatalyzed Group Transfer Polymerization of Alkyl Sorbate: Polymer Synthesis, Postpolymerization Modification, and Thermal Properties

Organocatalyzed Group Transfer Polymerization of Alkyl Sorbate: Polymer Synthesis, Postpolymerization Modification, and Thermal Properties

Responsive Quaternized PDMAEMA Copolymers with Antimicrobial Action.

In this work, the antimicrobial action of partially quaternized poly(2-(dimethylamino)ethyl methacrylate) (PQDMAEMA) copolymers using different alkyl halides is presented. The poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) homopolymer was synthesized by group transfer polymerization, followed by the modification of its tertiary amine groups, using bromoethane, iodoethane, bromohexane and bromoethanol, to introduce permanent cationic, quaternary ammonium salt moieties, randomly distributed along the polymer chains. In all cases, the degree of quaternization was low, at ~10 mol%, as verified by proton nuclear magnetic resonance spectroscopy to preserve the thermo-responsive character of the PDMAEMA precursor polymer. The biocidal activity of the lightly quaternized PQDMAEMA copolymers against Escherichia coli and Staphylococcus aureus was evaluated by calculating the minimum inhibitory concentration (MIC) as well as the minimum bactericidal concentration (MBC) of the polymers and by comparing them to the respective values of the precursor non-quaternized PDMAEMA homopolymer. The antibacterial mechanism of action in the solution was studied by zeta potential measurements, scanning electron microscopy and protein leakage tests signifying the disruption of the outer membrane of the bacterial cells to release their periplasmic proteins.