Search Results (41)

Readily degradable low-dose hydrate inhibitors are of great significance for flow assurance in the petroleum industry. Recently, α-lipoic acid (LA) was shown to undergo ring-opening reaction via reversible addition–fragmentation chain-transfer copolymerization with acrylamides to introduce labile disulfide bonds into the stable vinyl polymer backbone. Here, LA was copolymerized with acryloyl morpholine (AM) to evaluate their performance as kinetic hydrate inhibitors. Degradability was confirmed for the copolymers with 20 mol.% LA (AM/LA20, M_n = 19 → 9 kDa) after disulfide reduction. Thermogravimetric analysis also indicated faster thermal degradation of AM/LA due to the incorporation of weaker S-S and S-C linkages. Increasing LA content reduced hydrophilicity, and the copolymers were treated with NaOH to ensure water solubility. However, at 700 ppm, poly(AM) homopolymer reduced methane consumption during hydrate growth to 54% with respect to the uninhibited system, while gas consumption for the carboxylate AM/LA20 reached 78%. An advantageous feature of LA is its carboxylic acid, allowing desired functionalities to be grafted onto the degradable copolymer. Isopropyl amine (IPAm) was coupled with LA to form an amide known to be effective during hydrate inhibition (LA(IPAm)). The copolymer AM/LA(IPAm)20 demonstrated better water solubility compared to the original AM/LA20. Furthermore, the desirable IPAm functionality allowed the hydrate inhibition to be re-established at 54%, nearly recovering the performance of the poly(AM) homopolymer. This article assesses the application of LA and LA derivatives as building blocks for degradable amide-based kinetic hydrate inhibitors by validating their degradability with material characterizations and their inhibition performance during structure I hydrate growth. Full article

Atom transfer radical polymerization (ATRP) is a leading reversible deactivation radical polymerization method. It has become an emerging technology to synthesize well-defined, tailor-made polymers, promoting the development of advanced materials (e.g., bioconjugates and nanocomposites) with precisely designed and controlled macromolecular architectures. ATRP-produced polymers or polymeric materials have been successfully applied in the fields of drug delivery, tissue engineering, sample separation, environmental monitoring, bioimaging, clinical diagnostics, etc. In this review, we systematically summarize the progress of ATRP-based chemical and biological sensors in different application fields, including ion sensing, small-molecule detection, bioimaging, and signal amplification for biosensors. Finally, we briefly outline the prospects and future directions of ATRP. This review is expected to provide a fundamental and timely understanding of ATRP-based sensors and guide the design of novel materials and methods for sensing applications. Full article

This review aims to highlight the most recent advances in the field of the synthesis of branched copolymers and nanogels using reversible addition-fragmentation chain transfer (RAFT) polymerization. RAFT polymerization is a reversible deactivation radical polymerization technique (RDRP) that has gained tremendous attention due to its versatility, compatibility with a plethora of functional monomers, and mild polymerization conditions. These parameters lead to final polymers with good control over the molar mass and narrow molar mass distributions. Branched polymers can be defined as the incorporation of secondary polymer chains to a primary backbone, resulting in a wide range of complex macromolecular architectures, like star-shaped, graft, and hyperbranched polymers and nanogels. These subcategories will be discussed in detail in this review in terms of synthesis routes and properties, mainly in solutions. Full article

Atom Transfer Radical Polymerization (ATRP) is an effective catalytic process leading to well-defined polymers with desired properties. This process based on reversible deactivation of propagating chains has a lower rate in comparison with conventional radical polymerization, especially in the case of obtaining polymers with high molecular weights. Thus, the increase of the rate of this process with preserving control over molecular weight distribution is a challenging task. In this work, novel catalytic systems for Activators Generated by Electron Transfer (AGET) ATRP of acrylonitrile based on copper (II) bromide complexes were proposed. It was found that Rochelle salt (potassium sodium tartrate tetrahydrate) may be used as a reducing agent for regeneration of copper-based catalysts to increase the rate of the process. The provided UV-vis spectroscopy experiments have confirmed the reducing ability of tartaric anion. It was found that the use tandem catalytic system based on two copper complexes with different ligands also increases the polymerization rate. The performed experiments allowed us to develop a catalytic system for rapidly obtaining polyacrylonitrile polymers with desired molecular weights exceeding 100 kDa. Full article

We describe a method of partial moments devised for accurate simulation of the time/conversion evolution of polymer composition and molar mass. Expressions were derived that enable rigorous evaluation of the complete molar mass and composition distribution for shorter chain lengths (e.g., degree of polymerization, X_n = N < 200 units) while longer chains (X_n ≥ 200 units) are not neglected, rather they are explicitly considered in terms of partial moments of the molar mass distribution, ${\mu }_x^N(\mathrm{P})={\displaystyle \sum _{n=N+1}^{\infty }{n}^x[{\mathrm{P}}_n]}$ (where P is a polymeric species and n is its’ chain length). The methodology provides the exact molar mass distribution for chains X_n < N, allows accurate calculation of the overall molar mass averages, the molar mass dispersity and standard deviations of the distributions, provides closure to what would otherwise be an infinite series of differential equations, and reduces the stiffness of the system. The method also allows for the inclusion of the chain length dependence of the rate coefficients associated with the various reaction steps (in particular, termination and propagation) and the various side reactions that may complicate initiation or initialization. The method is particularly suited for the detailed analysis of the low molar mass portion of molar mass distributions of polymers formed by radical polymerization with reversible addition-fragmentation chain transfer (RAFT) and is relevant to designing the RAFT-synthesis of sequence-defined polymers. In this paper, we successfully apply the method to compare the behavior of thermally initiated (with an added dialkyldiazene initiator) and photo-initiated (with a RAFT agent as a direct photo-iniferter) RAFT-single-unit monomer insertion (RAFT-SUMI) and oligomerization of N,N-dimethylacrylamide (DMAm). Full article

The kinetics of nitroxide-mediated dispersion copolymerization with crosslinking of styrene (STY) and divinylbenzene (DVB) in supercritical carbon dioxide (scCO₂) is addressed experimentally. 2,2,6,6-Tetramethylpiperidinyl-1-oxy (TEMPO) and dibenzoyl peroxide (BPO) were used as nitroxide controller and initiator, respectively. A high-pressure cell with lateral sapphire windows at 120 °C and 207 bar was used to carry out the polymerizations. The nitroxide-mediated homopolymerization (NMP) of STY, as well as the conventional radical copolymerization (FRC) of STY/DVB, at the same conditions were also carried out as reference and for comparison purposes. The effect of nitroxide content on polymerization rate, evolution of molecular weight averages, gel fraction, and swelling index was studied. Full article

Copolymers with two distinguished reactive repeating units are of great interest, as such copolymers might open the possibility of obtaining selective and/or consequent copolymers with different chemical structures and properties. In the present work, copolymers based on two active esters (pentafluorophenyl methacrylate and p-nitrophenyl methacrylate) with varied compositions were synthesized by Cu(0)-mediated reversible deactivation radical polymerization. This polymerization technique allows the preparation of copolymers with high to quantitative conversion of both comonomers, with moderate control over dispersity (Đ = 1.3–1.7). Additionally, by in-depth study on the composition of each copolymer by various techniques including elemental analysis, NMR, FT-IR, and XPS, it was possible to confirm the coherence between expected and obtained composition. Thermal analyses by DSC and TGA were implemented to investigate the relation between copolymers’ composition and their thermal properties. Finally, an evaluation of the difference in reactivity of the two monomer moieties was confirmed by post-modification of copolymers with a primary amine and a primary alcohol as the model. Full article

In this study, a brush-like polymer with aggregation-induced emission (AIE) features was synthesized for drug delivery and intracellular drug tracking. The polymer consisting of tetraphenylethene (TPE) chain-end as well as oligo-poly (ethylene glycol) (PEG) and hydrazine functionalities was successfully synthesized through copper (0)-mediated reversible-deactivation radical polymerization (Cu⁰-mediated RDRP). Anticancer drug doxorubicin (DOX) was conjugated to the polymer and formed a prodrug named TPE-PEGA-Hyd-DOX, which contains 11% DOX. The hydrazone between DOX and polymer backbone is a pH-sensitive linkage that can control the release of DOX in slightly acidic conditions, which can precisely control the DOX release rate. The drug release of 10% after 96 h in normal cell environments compared with about 40% after 24 h in cancer cell environments confirmed the influence of the hydrazone bond. The ratiometric design of fluorescent intensities with peaks at 410 nm (emission due to AIE feature of TPE) and 600 nm (emission due to ACQ feature of DOX) provides an excellent opportunity for this product as a precise intracellular drug tracker. Cancer cells confocal microscopy showed negligible DOX solution uptake, but an intense green emission originated from prodrug uptake. Moreover, a severe red emission in the DOX channel confirmed a promising level of drug release from the prodrug in the cytoplasm. The merged images of cancer cells confirmed the high performance of the TPE-PEGA-Hyd-DOX compound in the viewpoints of cellular uptake and drug release. This polymer prodrug successfully demonstrates low cytotoxicity in healthy cells and high performance in killing cancer cells. Full article

The parallel development of reversible deactivation radical polymerization and click reaction concepts significantly enriches the toolbox of synthetic polymer chemistry. The synergistic effect of combining these approaches manifests itself in a growth of interest to the design of well-defined functional polymers and their controlled conjugation with biomolecules, drugs, and inorganic surfaces. In this review, we discuss the results obtained with reversible addition–fragmentation chain transfer (RAFT) polymerization and different types of click reactions on low- and high-molar-mass reactants. Our classification of literature sources is based on the typical structure of macromolecules produced by the RAFT technique. The review addresses click reactions, immediate or preceded by a modification of another type, on the leaving and stabilizing groups inherited by a growing macromolecule from the chain transfer agent, as well as on the side groups coming from monomers entering the polymerization process. Architecture and self-assembling properties of the resulting polymers are briefly discussed with regard to their potential functional applications, which include drug delivery, protein recognition, anti-fouling and anti-corrosion coatings, the compatibilization of polymer blends, the modification of fillers to increase their dispersibility in polymer matrices, etc. Full article

The aqueous Cu(0)-mediated reversible deactivation radical polymerization (RDRP) of triblock copolymers with two block sequences at 0.0 °C is reported herein. Well-defined triblock copolymers initiated from PHEAA or PDMA, containing (A) 2-hydroxyethyl acrylamide (HEAA), (B) N-isopropylacrylamide (NIPAM) and (C) N, N-dimethylacrylamide (DMA), were synthesized. The ultrafast one-pot synthesis of sequence-controlled triblock copolymers via iterative sequential monomer addition after full conversion, without any purification steps throughout the monomer additions, was performed. The narrow dispersities of the triblock copolymers proved the high degree of end-group fidelity of the starting macroinitiator and the absence of any significant undesirable side reactions. Controlled chain length and extremely narrow molecular weight distributions (dispersity ~1.10) were achieved, and quantitative conversion was attained in as little as 52 min. The full disproportionation of CuBr in the presence of Me₆TREN in water prior to both monomer and initiator addition was crucially exploited to produce a well-defined ABC-type triblock copolymer. In addition, the undesirable side reaction that could influence the living nature of the system was investigated. The ability to incorporate several functional monomers without affecting the living nature of the polymerization proves the versatility of this approach. Full article

The synthesis of surface-grafted polymers with variable functionality requires the careful selection of polymerization methods that also enable spatially controlled grafting, which is crucial for the fabrication of, e.g., nano (micro) sensor or nanoelectronic devices. The development of versatile, simple, economical, and eco-friendly synthetic strategies is important for scaling up the production of such polymer brushes. We have recently shown that poly (3-methylthienyl methacrylate) (PMTM) and poly (3-trimethylsilyl-2-propynyl methacrylate) (PTPM) brushes with pendant thiophene and acetylene groups, respectively, could be used for the production of ladder-like conjugated brushes that are potentially useful in the mentioned applications. However, the previously developed syntheses of such brushes required the use of high volumes of reagents, elevated temperature, or high energy UV-B light. Therefore, we present here visible light-promoted metal-free surface-initiated ATRP (metal-free SI-ATRP) that allows the economical synthesis of PMTM and PTPM brushes utilizing only microliter volumes of reaction mixtures. The versatility of this approach was shown by the formation of homopolymers but also the block copolymer conjugated brushes (PMTM and PTPM blocks in both sequences) and patterned films using TEM grids serving as photomasks. A simple reaction setup with only a monomer, solvent, commercially available organic photocatalyst, and initiator decorated substrate makes the synthesis of these complex polymer structures achievable for non-experts and ready for scaling up. Full article

Reversible-deactivation radical polymerization (RDRP) serves as a powerful tool nowadays for the preparations of unique linear and non-linear macromolecules. In this study, enhanced spin capturing polymerizations (ESCPs) of styrene (St) and tert-butyl acrylate (tBA) monomers were, respectively, conducted in the presence of difunctional (1Z,1′Z)-1,1′-(1,4-phenylene) bis (N-tert-butylmethanimine oxide) (PBBN) nitrone. Four-arm (PSt)₄ and (PtBA)₄ star macroinitiators (MIs) can be afforded. By correspondingly switching the second monomer (i.e., tBA and St), miktoarm star copolymers (μ-stars) of (PSt)₂-μ-(PtBA-b-PSt)₂ and (PtBA)₂-μ-(PSt-b-PtBA)₂) were thus obtained. We further conducted hydrolysis of the PtBA segments to PAA (i.e., poly(acrylic acid)) in μ-stars to afford amphiphilic μ-stars of (PSt)₂-μ-(PAA-b-PSt)₂ and (PAA)₂-μ-(PSt-b-PAA)₂. We investigated each polymerization step and characterized the obtained two sets of “sequence-isomeric” μ-stars by FT-IR, ¹H NMR, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). Interestingly, we identified their physical property differences in the case of amphiphilic μ-stars by water contact angle (WCA) and atomic force microscopy (AFM) measurements. We thus proposed two microstructures caused by the difference of polymer chain sequences. Through this polymerization transformation (Ŧ) approach (i.e., ESCP-Ŧ-NMP), we demonstrated an interesting and facile strategy for the preparations of μ-stars with adjustable/switchable interior and exterior polymer structures toward the preparations of various nanomaterials. Full article

This review describes the use of nanocrystal-based photocatalysts as quantum photoinitiators, including semiconductor nanocrystals (e.g., metal oxides, metal sulfides, quantum dots), carbon dots, graphene-based nanohybrids, plasmonic nanocomposites with organic photoinitiators, and tunable upconverting nanocomposites. The optoelectronic properties, cross-linking behavior, and mechanism of action of quantum photoinitiators are considered. The challenges and prospects associated with the use of quantum photoinitiators for processes such as radical polymerization, reversible deactivation radical polymerization, and photoinduced atom transfer radical polymerization are reviewed. Due to their unique capabilities, we forsee a growing role for quantum photoinitiators over the coming years. Full article

In this work, copper-mediated reversible deactivation radical polymerization (RDRP) of homo-polyacrylamides was conducted in aqueous solutions at 0.0 °C. Various degrees of polymerization (DP = 20, 40, 60, and 80) of well-defined water-soluble homopolymers were targeted. In the absence of any significant undesirable side reactions, the dispersity of polydiethylacrylamide (PDEA) and polydimethylacrylamide (PDMA) was narrow under controlled polymerization conditions. To accelerate the polymerization rate, disproportionation of copper bromide in the presence of a suitable ligand was performed prior to polymerization. Full conversion of the monomer was confirmed by nuclear magnetic resonance (NMR) analysis. Additionally, the linear evolution of the polymeric chains was established by narrow molecular weight distributions (MWDs). The values of theoretical and experimental number average molecular weights (Mn) were calculated, revealing a good matching and robustness of the system. The effect of decreasing the reaction temperature on the rate of polymerization was also investigated. At temperatures lower than 0.0 °C, the controlled polymerization and the rate of the process were not affected. Full article

The synthesis of polymer-grafted nanoparticles (PGNPs) or hairy nanoparticles (HNPs) by tethering of polymer chains to the surface of nanoparticles is an important technique to obtain nanostructured hybrid materials that have been widely used in the formulation of advanced polymer nanocomposites. Ceramic-based polymer nanocomposites integrate key attributes of polymer and ceramic nanomaterial to improve the dielectric properties such as breakdown strength, energy density and dielectric loss. This review describes the “grafting from” and “grafting to” approaches commonly adopted to graft polymer chains on NPs pertaining to nano-dielectrics. The article also covers various surface initiated controlled radical polymerization techniques, along with templated approaches for grafting of polymer chains onto SiO₂, TiO₂, BaTiO₃, and Al₂O₃ nanomaterials. As a look towards applications, an outlook on high-performance polymer nanocomposite capacitors for the design of high energy density pulsed power thin-film capacitors is also presented. Full article