Polymerization Of Various Monomers Research Articles

Multi-Functional Integration of Phosphor, Initiator, and Crosslinker for the Photo-Polymerization of Flexible Phosphorescent Polymer Gels.

A general approach to constructing room temperature phosphorescence (RTP) materials involves the incorporation of a phosphorescent emitter into a rigid host or polymers with high glass transition temperature. However, these materials often suffer from poor processability and suboptimal mechanical properties, limiting their practical applications. In this work, we developed benzothiadiazole-based dialkene (BTD-HEA), a multifunctional phosphorescent emitter with a remarkable yield of intersystem crossing (ΦISC, 99.83 %). Its high triplet exciton generation ability and dialkene structure enable BTD-HEA to act as a photoinitiator and crosslinker, efficiently initiating the polymerization of various monomers within 120 seconds. A range of flexible phosphorescence gels, including hydrogels, organogels, ionogels, and aerogels were fabricated, which exhibit outstanding stretchability and recoverability. Furthermore, the unique fluorescent-phosphorescent colorimetric properties of the gels provide a more sensitive method for the visual determination of the polymerization process. Notably, the phosphorescent emission intensity of the hydrogel can be increased by the formation of ice, allowing for the precise detection of hydrogel freezing. The versatility of this emitter paves the way for fabricating various flexible phosphorescence gels with diverse morphologies using microfluidics, film-shearing, roll coating process, and two/three-dimensional printing, showcasing its potential applications in the fields of bioimaging and bioengineering.

Multi‐Functional Integration of Phosphor, Initiator, and Crosslinker for the Photo‐Polymerization of Flexible Phosphorescent Polymer Gels

AbstractA general approach to constructing room temperature phosphorescence (RTP) materials involves the incorporation of a phosphorescent emitter into a rigid host or polymers with high glass transition temperature. However, these materials often suffer from poor processability and suboptimal mechanical properties, limiting their practical applications. In this work, we developed benzothiadiazole‐based dialkene (BTD‐HEA), a multifunctional phosphorescent emitter with a remarkable yield of intersystem crossing (ΦISC, 99.83 %). Its high triplet exciton generation ability and dialkene structure enable BTD‐HEA to act as a photoinitiator and crosslinker, efficiently initiating the polymerization of various monomers within 120 seconds. A range of flexible phosphorescence gels, including hydrogels, organogels, ionogels, and aerogels were fabricated, which exhibit outstanding stretchability and recoverability. Furthermore, the unique fluorescent‐phosphorescent colorimetric properties of the gels provide a more sensitive method for the visual determination of the polymerization process. Notably, the phosphorescent emission intensity of the hydrogel can be increased by the formation of ice, allowing for the precise detection of hydrogel freezing. The versatility of this emitter paves the way for fabricating various flexible phosphorescence gels with diverse morphologies using microfluidics, film‐shearing, roll coating process, and two/three‐dimensional printing, showcasing its potential applications in the fields of bioimaging and bioengineering.

Casein-based conjugates and graft copolymers. Synthesis, properties, and applications.

Biobased natural polymers, including polymers of natural origin such as casein, are growing rapidly in the light of the environmental pollution caused by many mass-produced commercial synthetic polymers. Although casein has interesting intrinsic properties, especially for the food industry, numerous chemical reactions have been carried out to broaden the range of its properties, most of them preserving casein's nontoxicity and biodegradability. New conjugates and graft copolymers have been developed especially by Maillard reaction of the amine functions of the casein backbone with the aldehyde functions of sugars, polysaccharides, or other molecules. Carried out with dialdehydes, these reactions lead to the cross-linking of casein giving three-dimensional polymers. Acylation and polymerization of various monomers initiated by amine functions are also described. Other reactions, far less numerous, involve alcohol and carboxylic acid functions in casein. This review provides an overview of casein-based conjugates and graft copolymers, their properties, and potential applications.

Photochemically generated ionic species for cationic and step-growth polymerizations

Developing innovative photochemical methods for the purpose of attaining green chemistry and mitigating global warming has recently become a very important concept. While we have to move towards a more sustainable world, daily life is becoming increasingly dependent on the use of polymeric materials. Conventional thermal polymerization systems fail to fulfill the requirements of sustainable chemistry, resulting in an increase in energy demand. This article outlines cationic and step-growth polymerizations of various monomers initiated by different photochemically generated ionic species and their advantages over conventional polymerization systems. Typical examples of photoinduced cationic and step-growth polymerizations performed under UV, visible and near-infrared (NIR) light are summarized under two main categories; direct and indirect initiating systems. In direct initiating systems the use of commercially available and structurally modified onium salts as one-component photoinitiators for both polymerizations are summarized. Indirect initiating systems, proceeding through i) photoinduced electron/energy transfer (PET), ii) charge-transfer complexation and iii) free-radical promoted cationic polymerization (FRPCP), are summarized with a focus on the recent step-growth methods developed in our laboratory.

Oxygen-Enhanced Atom Transfer Radical Polymerization through the Formation of a Copper Superoxido Complex.

In controlled radical polymerization, oxygen is typically regarded as an undesirable component resulting in terminated polymer chains, deactivated catalysts, and subsequent cessation of the polymerization. Here, we report an unusual atom transfer radical polymerization whereby oxygen favors the polymerization by triggering the in situ transformation of CuBr/L to reactive superoxido species at room temperature. Through a superoxido ARGET-ATRP mechanism, an order of magnitude faster polymerization rate and a rapid and complete initiator consumption can be achieved as opposed to when unoxidized CuBr/L was instead employed. Very high end-group fidelity has been demonstrated by mass-spectrometry and one-pot synthesis of block and multiblock copolymers while pushing the reactions to reach near-quantitative conversions in all steps. A high molecular weight polymer could also be targeted (DPn = 6400) without compromising the control over the molar mass distributions (Đ < 1.20), even at an extremely low copper concentration (4.5 ppm). The versatility of the technique was demonstrated by the polymerization of various monomers in a controlled fashion. Notably, the efficiency of our methodology is unaffected by the purity of the starting CuBr, and even a brown highly-oxidized 15-year-old CuBr reagent enabled a rapid and controlled polymerization with a final dispersity of 1.07, thus not only reducing associated costs but also omitting the need for rigorous catalyst purification prior to polymerization.

Poly(acrylic acid) block copolymers as stabilizers for dispersion polymerization

Dispersion polymerization stabilized with poly(acrylic acid) has been performed for decades to produce polymer particles whose surfaces are modified with pH-responsive poly(acrylic acid) moieties. To improve stabilizer efficiency, poly(acrylic acid) block copolymers, in which a poly(acrylic acid) chain is attached to the terminus of a polystyrene or PMMA chain, were used as stabilizers for the dispersion polymerization of styrene or MMA. Compared with the poly(acrylic acid) homopolymer, polystyrene-block-poly(acrylic acid) was found to improve the controllable ranges of particle size and the carboxylic-acid-group surface density of the resulting polystyrene particles. Furthermore, we also investigated the effect of heterogeneity between the polymer species of the particle core and the attached polystyrene or PMMA chains in the poly(acrylic acid) block copolymers. Finally, we also examined the applicability of polystyrene-block-poly(acrylic acid) as a stabilizer and surface modifier for the dispersion polymerization of various monomers.

Ultrafast gelation of silk fibroin-assisted conductive hydrogel with long-term environmental stability using self-catalytic dopamine/metal/H2O2 system

Anti-freezing organo-hydrogels gain great popularity for their excellent performances at subzero temperatures. However, the traditional fabrication of such gels always requires a complex process with external stimuli like high temperature and additional catalysts, bringing inconvenience and restrictions in large-scale applications. Hence, inspired by the mussel-inspired catechol-based chemistry, a novel, green and ultrafast self-catalysis initiation system is established by the special redox equilibrium among dopamine (DA), iron (Fe3+) and hydrogen peroxide (H2O2) with multi-functional capabilities. The ternary DA-Fe3+–H2O2 complex generated plentiful hydroxyl radicals to initiate the rapid polymerization of acrylic acid (AA) with oxygen tolerance. Simultaneously, silk fibroin (SF) as a natural bio-material was employed to enhance the structural integrity of the PAA network, via dopamine-initiated co-coupling of tyramine residues from silk fibroin (SF) chains with the vinyl radicals within 40 s at a low temperature. Moreover, the introduction of DA-Fe3+ pair provides the obtained organo-hydrogel fascinating UV-blocking, good adhesion property to a variety of materials, companying with encouraging conductivity, while the glycerol-water dual phase endows the organo-hydrogel with intriguing environmental stability, like anti-freezing and anti-drying properties. The present work expands the potential of dopamine-based self-catalysis in polymerization of various monomers and its application in construction of diverse gel-like multi-functional materials as well.

Metalloporphyrin-anchored 2D MOF nanosheets as highly accessible heterogeneous photocatalysts towards cytocompatible living radical polymerization

Two-dimensional (2D) metal–organic framework (MOF) nanosheets have emerged as a promising hybrid material due to the highly exposed active sites and high aspect ratio originating from their large lateral dimension and ultrathin thickness. Herein, PCN-134(Zn)-2D (PCN = porous coordination network) nanosheets were investigated as a versatile and effective platform supporting metalloporphyrins to boost their photocatalytic performance for single oxygen generation and living radical polymerization. This method enabled the radical polymerizations of various monomers using low catalyst dosages under a wide range of wavelengths, affording well-defined polymers with high monomer conversions, low polydispersities and tunable functionalities. Compared to three-dimensional (3D) bulk MOF crystals, PCN-134(Zn)-2D exhibited fast polymerization kinetics due to the larger surface area and more accessible catalytic sites within the 2D planar architecture. Most significantly, the polymerization kinetics could be orthogonally regulated by solution pH and light stimuli. Exploiting the oxygen tolerance and fast kinetics, we demonstrated PET-RAFT polymerization at high monomer dilutions and in a human cell culture medium. Illustrations of chain extension and catalyst-recycling test further substantiated the photocatalytic performance of these 2D MOF catalysts outperforming most reported metalloporphyrin-based heterogeneous catalysts towards living radical polymerization.

On‐Surface RAFT Polymerization using Oxygen to form Triblock Copolymer Brushes

AbstractSurface‐initiated polymerization of various monomers (methacrylic acid, methacrylate, acrylate, acrylamide, and zwitterionic monomer) is conducted to form triblock copolymer brushes using oxygen‐initiated reversible addition−fragmentation chain‐transfer polymerization in the presence of air. An ellipsometry analysis, water contact angle analysis, X‐ray photoelectron spectroscopy, and atomic force microscopy confirm the successful formation of polymer brushes with complex architectures on a silicon substrate.

Expanding the Scope of 2D Black Phosphorus Catalysis to the Near-Infrared Light Initiated Free Radical Photopolymerization.

In the drive toward the development of efficient and stable inorganic semiconductor materials with broadband solar absorption ability to induce various photochemical processes is a highly attractive research field. In this study, two-dimensional (2D) few-layer black phosphorus (BP) exfoliated in a solvent is utilized as photocatalyst to initiate the polymerization of various monomers under visible and near-IR (NIR) light irradiation. Upon the light exposure, few-layer BP generates excited electrons and holes, which undergo electron transfer reactions with the onium salts to form free radicals capable of initiating free radical polymerization. Among the onium salts tested, aryldiazonium salt was found to be the most efficient in the photopolymerization process owing to its favorable reduction potential with the conduction edge potential of BP. The presented strategy also provides the possibility for the in situ preparation of BP-polymer composite materials.

Porphyrinic Zirconium Metal–Organic Frameworks (MOFs) as Heterogeneous Photocatalysts for PET‐RAFT Polymerization and Stereolithography

AbstractIn this study, porphyrinic zirconium (Zr) MOFs were investigated as heterogeneous photocatalysts for photoinduced electron transfer‐reversible addition‐fragmentation chain transfer (PET‐RAFT) polymerization of various monomers under a broad range of wavelengths, producing polymers with high monomer conversions, narrow molecular weight distributions, low dispersity and good chain‐end fidelity. Screening of various porphyrinic Zr‐MOFs (Zn) containing Zn‐metalled porphyrinic ligands demonstrated that MOF‐525 (Zn) with the smallest size had the best photocatalytic activity in PET‐RAFT polymerization, due to enhanced dispersion and light penetration. Oxygen tolerance and temporal control were also demonstrated during MOF catalysed PET‐RAFT. Results suggested that the polymerization rates were significantly affected by changing the size and surface area of MOFs, and the heterogeneous MOF photocatalysts could be easily separated and recycled for up to five independent PET‐RAFT polymerizations without an obvious decrease in efficiency. Finally, the MOF photocatalysts were utilized to create three‐dimensional polymeric objects with high resolution via visible light mediated stereolithography in an open‐air environment.

Porphyrinic Zirconium Metal-Organic Frameworks (MOFs) as Heterogeneous Photocatalysts for PET-RAFT Polymerization and Stereolithography.

In this study, porphyrinic zirconium (Zr) MOFs were investigated as heterogeneous photocatalysts for photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization of various monomers under a broad range of wavelengths, producing polymers with high monomer conversions, narrow molecular weight distributions, low dispersity and good chain-end fidelity. Screening of various porphyrinic Zr-MOFs (Zn) containing Zn-metalled porphyrinic ligands demonstrated that MOF-525 (Zn) with the smallest size had the best photocatalytic activity in PET-RAFT polymerization, due to enhanced dispersion and light penetration. Oxygen tolerance and temporal control were also demonstrated during MOF catalysed PET-RAFT. Results suggested that the polymerization rates were significantly affected by changing the size and surface area of MOFs, and the heterogeneous MOF photocatalysts could be easily separated and recycled for up to five independent PET-RAFT polymerizations without an obvious decrease in efficiency. Finally, the MOF photocatalysts were utilized to create three-dimensional polymeric objects with high resolution via visible light mediated stereolithography in an open-air environment.

Ru-Catalyzed, cis-Selective Living Ring-Opening Metathesis Polymerization of Various Monomers, Including a Dendronized Macromonomer, and Implications to Enhanced Shear Stability.

An unsaturated polymer's cis/trans-olefin content has a significant influence on its properties. For polymers obtained by ring-opening metathesis polymerization (ROMP), the cis/trans-olefin content can be tuned by using specific catalysts. However, cis-selective ROMP has suffered from narrow monomer scope and lack of control over the polymerization (giving polymers with broad molecular weight distributions and prohibiting the synthesis of block copolymers). Herein, we report the versatile cis-selective controlled living ROMP of various endo-tricyclo[4.2.2.02,5]deca-3,9-diene and various norbornene derivatives using a fast-initiating dithiolate-chelated Ru catalyst. Polymers with cis-olefin content as high as 99% could be obtained with high molecular weight (up to Mn of 105.1 kDa) and narrow dispersity (<1.4). The living nature of the polymerization was also exploited to prepare block copolymers with high cis-olefin content for the first time. Furthermore, owing to the successful control over the stereochemistry and narrow dispersity, we could compare cis- and trans-rich polynorbornene and found the former to have enhanced resistance to shear degradation.

Iron Catalysts in Atom Transfer Radical Polymerization.

Catalysts are essential for mediating a controlled polymerization in atom transfer radical polymerization (ATRP). Copper-based catalysts are widely explored in ATRP and are highly efficient, leading to well-controlled polymerization of a variety of functional monomers. In addition to copper, iron-based complexes offer new opportunities in ATRP catalysis to develop environmentally friendly, less toxic, inexpensive, and abundant catalytic systems. Despite the high efficiency of iron catalysts in controlling polymerization of various monomers including methacrylates and styrene, ATRP of acrylate-based monomers by iron catalysts still remains a challenge. In this paper, we review the fundamentals and recent advances of iron-catalyzed ATRP focusing on development of ligands, catalyst design, and techniques used for iron catalysis in ATRP.

Localized Surface Plasmon Resonance Meets Controlled/Living Radical Polymerization: An Adaptable Strategy for Broadband Light-Regulated Macromolecular Synthesis.

The photophysical process of localized surface plasmon resonance (LSPR) is, for the first time, exploited for broadband photon harvesting in photo-regulated controlled/living radical polymerization. Efficient macromolecular synthesis was achieved under illumination with light wavelengths extending from the visible to the near-infrared regions. Plasmonic Ag nanostructures were in situ generated on Ag3 PO4 photocatalysts in a reversible addition-fragmentation chain transfer (RAFT) system, thereby promoting polymerization of various monomers following a LSPR-mediated electron transfer mechanism. Owing to the LSPR-enhanced broadband photon harvesting, high monomer conversion (>99 %) was achieved under natural sunlight within 0.8 h. The deep penetration of NIR light enabled successful polymerization with reaction vessels screened by opaque barriers. Moreover, by trapping active oxygen species generated in the photocatalytic process, polymerization could be implemented without pre-deoxygenation.

Localized Surface Plasmon Resonance Meets Controlled/Living Radical Polymerization: An Adaptable Strategy for Broadband Light‐Regulated Macromolecular Synthesis

AbstractThe photophysical process of localized surface plasmon resonance (LSPR) is, for the first time, exploited for broadband photon harvesting in photo‐regulated controlled/living radical polymerization. Efficient macromolecular synthesis was achieved under illumination with light wavelengths extending from the visible to the near‐infrared regions. Plasmonic Ag nanostructures were in situ generated on Ag3PO4 photocatalysts in a reversible addition‐fragmentation chain transfer (RAFT) system, thereby promoting polymerization of various monomers following a LSPR‐mediated electron transfer mechanism. Owing to the LSPR‐enhanced broadband photon harvesting, high monomer conversion (&gt;99 %) was achieved under natural sunlight within 0.8 h. The deep penetration of NIR light enabled successful polymerization with reaction vessels screened by opaque barriers. Moreover, by trapping active oxygen species generated in the photocatalytic process, polymerization could be implemented without pre‐deoxygenation.

Self-Catalyzed Living Radical Polymerization Using Quaternary-Ammonium-Iodide-Containing Monomers

Self-catalyzed living radical polymerization using quaternary ammonium iodide (QAI)-containing monomers is reported. The monomer contains a polymerizable methacrylate or acrylate moiety and QAI as a catalytic moiety at the side chain. Several (functional) methacrylates and acrylates were successfully copolymerized with QAI-containing monomers without additional catalysts, generating QAI-containing copolymers. The obtained QAI-containing polymers were further used as catalytic macroinitiators, enabling self-catalyzed block polymerizations of various monomers without additional catalysts. This self-catalyzed living radical polymerization was also used to prepare a QAI-containing polymer brush on a solid surface. This technique is attractive for its wide range of amenable monomers and metal-free nature. The obtained QAI-containing polymers may find biomedical and antibacterial applications.

Integration of Polymerization and Biomineralization as a Strategy to Facilely Synthesize Nanotheranostic Agents.

Integration of biological macromolecules with inorganic materials via biomineralization has demonstrated great potential for development of nanotheranostic agents. To produce multifunctionality, integration of multiple components in the biomineralized theranostic agents is required; however, how to efficiently and reproducibly implement this is challenging. In this report, a universal biomineralization strategy is developed by incorporation of oxidization polymerization into albumin-templated biomineralization for facile synthesis of nanotheranostic agents. A series of biomineralized polymers and manganese dioxide hybrid nanoparticles (PMHNs) can be synthesized via the polymerization of various monomers, including dopamine (DA), epigallocatechin (EGC), pyrrole (PY), and diaminopyridine (DP), along with the reduction of KMnO4 and formation of manganese dioxide nanoparticles in albumin templates. These biomineralized PMHNs demonstrate ultrahigh MRI (longitudinal relaxivity up to 38 mM-1 s-1) and ultrasonic (US) imaging contrasting capabilities and have excellent photothermal therapy efficacy with complete ablation of orthotopic tumors. Moreover, these biomineralized hybrid nanoparticles can be effectively excreted through the kidneys, avoiding potential systemic toxicity. Thus, integration of polymerization into biomineralization presents a strategy for the fabrication of hybrid nanomaterials, allowing the production of multifunctional and biocompatible nanotheranostic agents via a facile one-pot method.

Heteroatom‐Doped Carbon Dots (CDs) as a Class of Metal‐Free Photocatalysts for PET‐RAFT Polymerization under Visible Light and Sunlight

AbstractA key challenge of photoregulated living radical polymerization is developing efficient and robust photocatalysts. Now carbon dots (CDs) have been exploited for the first time as metal‐free photocatalysts for visible‐light‐regulated reversible addition–fragmentation chain‐transfer (RAFT) polymerization. Screening of diverse heteroatom‐doped CDs suggested that the P‐ and S‐doped CDs were effective photocatalysts for RAFT polymerization under mild visible light following a photoinduced electron transfer (PET) involved oxidative quenching mechanism. PET‐RAFT polymerization of various monomers with temporal control, narrow dispersity (Đ≈1.04), and chain‐end fidelity was achieved. Besides, it was demonstrated that the CD‐catalyzed PET‐RAFT polymerization was effectively performed under natural solar irradiation.

Heteroatom-Doped Carbon Dots (CDs) as a Class of Metal-Free Photocatalysts for PET-RAFT Polymerization under Visible Light and Sunlight.

A key challenge of photoregulated living radical polymerization is developing efficient and robust photocatalysts. Now carbon dots (CDs) have been exploited for the first time as metal-free photocatalysts for visible-light-regulated reversible addition-fragmentation chain-transfer (RAFT) polymerization. Screening of diverse heteroatom-doped CDs suggested that the P- and S-doped CDs were effective photocatalysts for RAFT polymerization under mild visible light following a photoinduced electron transfer (PET) involved oxidative quenching mechanism. PET-RAFT polymerization of various monomers with temporal control, narrow dispersity (Đ≈1.04), and chain-end fidelity was achieved. Besides, it was demonstrated that the CD-catalyzed PET-RAFT polymerization was effectively performed under natural solar irradiation.