Cationic Ring Opening Research Articles

Photomediated Cationic Ring-Opening Polymerization of Cyclosiloxanes with Temporal Control

Photomediated Cationic Ring-Opening Polymerization of Cyclosiloxanes with Temporal Control

Cationic Ring-Opening Photopolymerization of Long-Chain Epoxides in the Rotator Phase: Confirmation, Mechanism, and Combination

Cationic Ring-Opening Photopolymerization of Long-Chain Epoxides in the Rotator Phase: Confirmation, Mechanism, and Combination

Dual‐Wavelength Vat Photopolymerization 3D Printing with Hybrid Acrylate‐Epoxy Resins: Influence of Resin Composition on Microstructure and Mechanical Properties

Dual‐wavelength vat photopolymerization 3D printing represents a convenient technology for the fabrication of objects with heterogeneous and locally controlled mechanical properties. By using two λ‐orthogonal cross‐linking reactions, it is possible to produce soft and stiff photopolymers with a single resin vat by switching the light source. Herein, hybrid acrylate‐epoxy resins are selectively cured by using either visible or UV light. At 405 nm, a free radical curing of the acrylate monomers is induced while irradiation with 365 nm triggers an additional cationic ring opening reaction of the epoxy monomer yielding interpenetrating photopolymer networks. In a comprehensive approach, the influence of the resin composition and the applied wavelength on cure kinetics, film morphology, (thermo)mechanical properties, and printability are studied. Fully separated as well as homogenous network morphologies are obtained depending on the ratio between acrylate and epoxy monomers, cure rate and applied light source (405 vs 365 nm). In general, glass transition temperature, stiffness, and tensile strength of the photopolymers increase with rising epoxy content. In contrast, a higher epoxy concentration in combination with a higher amount of the cationic photoinitiator compromises on the system's orthogonality, giving rise to the important role of the resin composition in dual‐wavelength vat photopolymerization 3D printing.

Protecting group free synthesis of nitroxide-functionalized poly(2-oxazoline)s: direct access to electroactive polynitroxides.

Herein, we report the simple and direct cationic ring opening polymerization (CROP) of a nitroxide bearing 2-oxazoline monomer to yield redox-active poly[1-oxyl-2,2,6,6-tetramethylpiperidin-4-(2-oxazoline)] (PTOx) with no requirement for protecting group chemistries. The spin and redox activity of the polymer are quantitatively retained as confirmed by cyclic voltammetry and electron paramagnetic resonance spectroscopy, while yielding a comparable oxidation potential to that of PTMA in preliminary electrochemical characterization.

Amino-modified 2-oxazoline copolymers for complexation with DNA

Novel amino-functionalized 2-oxazoline-based copolymers able to form complexes with DNA were obtained. Their efficiency of DNA condensation into polyplexes of scales appropriate for effective cellular internalization was studied.

Organo-Catalyzed Cationic Ring-Opening Copolymerization of Cyclic Anhydrides with Oxolanes: Access to Structurally Diverse Polyesters

Organo-Catalyzed Cationic Ring-Opening Copolymerization of Cyclic Anhydrides with Oxolanes: Access to Structurally Diverse Polyesters

Microstructural Analysis of Benzoxazine Cationic Ring-Opening Polymerization Pathways.

Herein, an evaluation of the initial step of benzoxazine polymerization is presented by mass spectrometry, with a focus on differentiating the phenoxy and phenolic products formed by distinct pathways of the cationic ring opening polymerization (ROP) mechanism of polybenzoxazine formation. The use of infrared multiple photon dissociation (IRMPD) and ion mobility spectrometry (IMS) techniques allows for differentiation of the two pathways and provides valuable insights into the ROP mechanism. The results suggest that type I pathway is favored in the initial stages of the reaction yielding the phenoxy product, while type II product should be observed at later stages when the phenoxy product would interconvert to the most stable type II phenolic product. Overall, the findings presented here provide important information on the initial step of the benzoxazine polymerization, allowing the development of optimal polymerization conditions and represents a way to evaluate other multifunctional polymerization processes.

Enhancement of elongation at break and UV-protective properties of poly(lactic acid) film with cationic ring opening polymerized (CROP)-lignin

In this study, the intrinsic brittleness of poly(lactic acid) (PLA) was overcome by chemical modification using ethyl acetate-extracted lignin (EL) via cationic ring-opening polymerization (CROP). The CROP was conducted to promote homopolymerization under starvation of the initiator (oxyrane). This method resulted in the formation of lignin-based polyether (LPE). LPE exhibited enhanced interfacial compatibility with nonpolar and hydrophobic PLA owing to the fewer hydrophilic hydroxyl groups and a long polyether chain. In addition, because of the UV-protecting and radical-scavenging abilities of lignin, LPE/PLA exhibited multifunctional properties, resulting in improved chemical properties compared with the neat PLA film. Notably, one of the LPE/PLA films (EL_MCF) exhibited excellent elongation at break of 297.7% and toughness of 39.92MJ/m3. Furthermore, the EL_MCF film showed superior UV-protective properties of 99.52% in UVA and 88.95% in UVB ranges, both significantly higher than those of the PLA film, without sacrificing significant transparency in 515nm. In addition, the radical scavenging activity improved after adding LPE to the PLA film. These results suggest that LPEs can be used as plasticizing additives in LPE/PLA composite films, offering improved physicochemical properties.

Design, synthesis and curing mechanism of two novel photothermal dual-curing adhesives for propellants and explosives

Photothermal dual-curing adhesive is not only required to realize the basic curing function, but also has the characteristics of rapid setting and strong curing, which possesses a vital role in the molding speed, stability and structure integrity for 3D-printed propellants and explosives. Herein, the acrylate hydroxyl terminated polybutadiene, as novel photothermal dual-curing binders, were designed and synthesized utilizing cationic ring opening polymerization and active monomer mechanism as the strategy of photothermal dual-curing reaction. The mechanical properties and thermal stability of the photothermal dual-curing elastomers were systematically investigated. The results suggested that the target MAHTPB(Acrylate hydroxy‑terminated polybutadiene)-based adhesives could be cured rapidly within 5 s under UV light irradiation and completely cured in 1.5 h under heating conditions. Specifically, the elastomer film formed by MAHTPB-based photothermal dual-curing has a tensile strength of 4.63 MPa and an elongation of 386%, which exhibits stronger mechanical properties than the elastomer film formed by single photo- or thermal-curing. As a result, the synthesized photothermally cured adhesives have performed 3D printing experiments and achieved relatively satisfactory printing effects. Our study aims to solve the problems of short photocuring time, slow curing rate and incomplete curing for traditional photocuring, which lays a solid foundation to achieve rapid prototyping and precise performance control in 3D printing of propellants and explosives.

Biobased Copolymers via Cationic Ring-Opening Copolymerization of Levoglucosan Derivatives and ε-Caprolactone.

Simultaneous ring-opening copolymerization is a powerful strategy for the synthesis of highly functional copolymers from different types of cyclic monomers. Although copolymers are essential to the plastics industry, environmental concerns associated with current fossil-fuel-based synthetic polymers have led to an increasing interest in the use of renewable feedstock for polymer synthesis. Herein, we report a scalable synthetic platform to afford unique polysaccharides with different pendant functional groups from biomass-derived levoglucosan and ε-caprolactone via cationic ring-opening copolymerization (cROCOP). Biocompatible and recyclable bismuth triflate was identified as the optimal catalyst for cROCOP of levoglucosan. Copolymers from tribenzyl levoglucosan and ε-caprolactone, as well as from tribenzyl and triallyl levoglucosan, were successfully synthesized. The tribenzyl levoglucosan monomer composition ranged from 16% to 64% in the copolymers with ε-caprolactone and 22% to 79% in the copolymers with triallyl levoglucosan. The allylic levoglucosan copolymer can be utilized as a renewably derived scaffold to modify copolymer properties and create other polymer architectures via postpolymerization modification. Monomer reactivity ratios were determined to investigate the copolymer microstructure, indicating that levoglucosan-based copolymers have a gradient architecture. Additionally, we demonstrated that the copolymer glass transition temperature (Tg, ranging from -44.3 to 33.8 °C), thermal stability, and crystallization behavior could be tuned based on the copolymer composition. Overall, this work underscores the utility of levoglucosan as a bioderived feedstock for the development of functional sugar-based copolymers with applications ranging from sustainable materials to biomaterials.

Living Cationic Ring-Opening Polymerization of Hetero Diels-Alder Adducts to Give Multifactor-Controlled and Fast-Photodegradable Vinyl Polymers.

Precise control of multiple structural parameters associated with vinyl polymers is important for producing materials with the desired properties and functions. While the development of living polymerization methods has provided a way to control the various structural parameters of vinyl polymers, the concomitant control of their sequence and regioregularity remains a challenging task. To overcome this challenge, herein, we report the living cationic ring-opening polymerization of hetero Diels-Alder adducts. The scalable and modular synthesis of the cyclic monomers was achieved by a one-step protocol using readily available vinyl precursors. Subsequently, living polymerization of the cyclic monomers was examined, allowing the synthesis of vinyl polymers while controlling multiple factors, including molecular weight, dispersity, alternating sequence, head-to-head regioregularity, and end-group functionality. The living characteristics of the developed method were further demonstrated by block copolymerization. The synthesized vinyl polymers exhibited unique thermal properties and underwent fast photodegradation even under sunlight.

Straightforward Access To Block And Gradient Light-Responsive Poly(2-Oxazoline)S Via Cationic Ring Opening Polymerization Of 2-Azobenzenyl-2-Oxazoline.

Light-responsive polymers are a prospective area of smart materials. The increasing number of potential applications of these materials requires the development of new polymers sensitive to external irradiation. However, most of the polymers reported so far are represented by poly(meth)acrylates. In this work, we propose the straightforward approach to the synthesis of light-responsive poly(2-oxazoline)s via cationic ring-opening polymerization of 2-azobenzenyl-2-oxazoline (2-(4-(phenyldiazenyl)phenyl)-2-oxazoline). Polymerization kinetics studies revealed significant activity of the new monomer in both homopolymerization and copolymerization with 2-ethyl-2-oxazoline. The difference in monomer reactivity allows obtaining both gradient and block copolymers via simultaneous or subsequent one-pot polymerization, respectively, leading to a set of well-defined gradient and block copoly(2-oxazoline)s with 10-40% of azobenzene units. Due to their amphiphilic nature, the materials self-assemble in water, which was proven by dynamic light scattering and transmission electron microscopy. The change in polarity caused by the isomerization of azobenzene fragments in response to UV light irradiation results in a change of nanoparticle size. The obtained results provide a new impulse for the development of light-responsive materials based on poly(2-oxazoline)s. This article is protected by copyright. All rights reserved.

Synthesis of poly(2-isopropyl-2-oxazoline)-b-poly(2-phenyl-2-oxazoline)-b-poly(2-isopropyl-2-oxazoline) and its self-assembly into polymersomes: Temperature-dependent aqueous solution behavior

This study reports on synthesis of poly(2-isopropyl-2-oxazoline)-b-poly(2-phenyl-2-oxazoline)-b-poly(2-isopropyl-2-oxazoline) (PiPOX-b-PPhOX-b-PiPOX) by a three-step sequential monomer addition through cationic ring opening polymerization (CROP). Self-assembly of PiPOX-b-PPhOX-b-PiPOX was triggered through solvent shifting or double emulsion methods, resulting in formation of polymersomes with hydrophilic and temperature-responsive PiPOX inner/outer coronae and hydrophobic PPhOX membrane. Double emulsion method provided smaller polymersomes with greater colloidal stability. Increasing the temperature of the polymersome solution led to formation of polymersome clusters and this transition was found to be irreversible. Glucose oxidase (GOx) encapsulated polymersomes were used as nanoreactors for GOx/horseradish peroxidase (HRP) cascade reactions. The increase in the rate of the enzymatic reaction with increasing temperature was found to be smaller for the encapsulated enzymes compared to free enzymes.

Optimal combination of UV‐induced cationic ring opening polymerization monomers for light‐weight automotive plastic coating

AbstractCROP reactivity of organic coatings composed of three structurally different monomers with epoxy or oxetane derivatives was investigated, focusing on rheological and surface mechanical properties. Real‐time crosslinking behavior of CROP monomers was monitored using a rotational rheometer. Results of differential scanning calorimetry with in situ UV irradiation revealed that the ring opening reactivity of CROP monomers protonated by a photoacid generator (PAG) was correlated with the heat released during the exothermic polymerization reaction. In addition, reaction conversions of monomers with epoxy and oxetane groups were compared using Fourier transform infrared spectroscopy (FT‐IR) under dark curing conditions. Surface and internal mechanical properties of coating films, including adhesion with polycarbonate substrate, were comprehensively evaluated by nano‐indentation, nano‐scratch, and surface and interfacial cutting analysis system (SAICAS) tests. By understanding the unique crosslinking characteristics of each CROP monomer, the ternary CROP monomer system, optimally containing with ECC of 53.6 wt%, DOX of 22.9 wt%, and DEO of 15.3 wt%, exhibited improved crosslinking density (G′ from 104 to 107 Pa) and exceptional mechanical (with scratch resistance increasing from 7.11 to 16.17 mN for Lc1), adhesion (with crosscut resistance increasing from 0 to 5B), and transparency properties, surpassing the performance of unitary ECC coating system.

Detailed Understanding of Solvent Effects for the Cationic Ring-Opening Polymerization of 2-Ethyl-2-oxazoline

Polymerization of 2-ethyl-2-oxazoline (EtOx) has often been in the spotlight for fundamental studies of poly(2-alkyl/aryl-2-oxazoline)s (PAOx) polymerization, especially initiator screening, solvent screening, and copolymerization trends. In this work, we build on previous observations of solvent effects on the cationic ring-opening polymerization (CROP) of EtOx, with additional experimental observations of previously unreported solvents to expand the explored parameter space. Our objective is to find solvents with the lowest activation energy (Ea) and higher Arrhenius preexponential factor (A), which will allow us to produce narrow molar mass distributions at higher molecular weights, in the least time. To achieve this, we examined the various single factors like Dimroth ET(30) values, the Kamlet–Abraham–Taft (KAT) linear free-energy relationship (LFER) equation(s), and the Catalan LFER equations. Only one of Catalan’s equations sufficiently disentangled dipolarity and polarizability to give a good fit due to contradictory effects. It was found that solvent nucleophilicity, electrophilicity, and polarizability affected the Ea, but not dipolarity. All four factors affected the A. This indicates that the Ea is minimized in solvents that do not solvate ions well (i.e. force ion-pairing), and A was minimized in more dipolar solvents that solvate the polymer chains well. A strongly negative activation entropy (ΔS‡) shows that the propagation reaction is associative. The Catalan LFER allows for the prediction of Ea, A, ΔH‡, and ΔS‡, and the derived kp, across a broad range of solvents.

Poly(2-oxazoline) - Ferrostatin-1 drug conjugates inhibit ferroptotic cell death.

Ferroptosis is a form of non-apoptotic iron induced cell death mechanism implicated in neurodegeneration, yet can be ameliorated with potent radical scavengers such as ferrostatin-1 (Fer-1). Currently, Fer-1 suffers from low water solubility, poor biodistribution profile and is unsuitable for clinical application. Fer-1 polymer-drug conjugates (PDCs) for testing as an anti-ferroptosis therapeutic candidate have yet to be described. Here, we report the synthesis and characterization of a library of water-soluble Fer-1 based poly(2-oxazoline)-drug conjugates. The cationic ring opening polymerization (CROP) of water-soluble 2-oxazoline monomers, and a novel protected aromatic aldehyde 2-oxazoline (DPhOx), produced defined copolymers, which after deprotection were available for modification with Fer-1 via reductive amination and Schiff base chemistry. The conjugates were tested for their activity against RSL3-induced ferroptosis in vitro, and first structure-activity relationships were established. Irreversibly conjugated Fer-1 PDCs possessing an arylamine structural motif showed a greatly increased anti-ferroptosis activity compared to reversibly (Schiff base) linked Fer-1. Overall, this work introduces the first active ferrostatin-PDCs and a new highly tuneable poly(2-oxazoline)-based PDC platform, which provides access to next generation polymeric nanomaterials for anti-ferroptosis applications.

Development of in situ polymerized amines into mesoporous silica for direct air CO2 capture

Direct air CO2 capture (DAC) is inevitable to achieve negative emissions and lower CO2 concentration in the atmosphere. The use of class III supported amine materials has shown great potential as effective materials for CO2 capture from both flue gas and low concentrations of CO2. In this work, a linear polyethylene amine tethered to mesoporous silica foam was synthesized by controlled in situ cationic ring opening polymerization of 2-methyl-2-oxazoline. The sorbent was characterized based on porosity, FTIR, elemental analysis, and surface morphology. The CO2 capture performance at different temperatures was measured using a volumetric method, whereas the dynamic breakthrough analysis (DBA) technique was evaluated using simulated air of 400 ppm CO2 at different temperatures and relative humidities. The CO2 adsorption isotherms were studied in the temperature range from 5 to 80 °C and were fitted using different isotherm models. To evaluate the effects of moisture on the CO2 capture performance, breakthrough experiments were performed using 400 ppm CO2 at various relative humidities (0–65%). It was found that the CO2 uptake calculated from the breakthrough experiment is enhanced at higher moisture contents and decreases at higher temperatures. The maximum CO2 uptake was 1.50 mmol/g at 25 °C and 65% RH. The CO2 adsorption kinetics of the sorbent was found to follow the Avrami model, whereas the dual site Langmuir model was found to be the best fit for the adsorption isotherms. The developed sorbent exhibited a stable cyclic performance and retained its initial CO2 uptake during 10 consecutive cycles. This study demonstrates that in situ polymerization of amines into porous supports is a viable route for designing sorbents with high CO2 adsorption performance for DAC applications.

Synthesis and Characterization of Gel Polymer Electrolyte Based on Epoxy Group via Cationic Ring-Open Polymerization for Lithium-Ion Battery.

The polymer electrolytes are considered to be an alternative to liquid electrolytes for lithium-ion batteries because of their high thermal stability, flexibility, and wide applications. However, the polymer electrolytes have low ionic conductivity at room temperature due to the interfacial contact issue and the growing of lithium dendrites between the electrolytes/electrodes. In this study, we prepared gel polymer electrolytes (GPEs) through an in situ thermal-induced cationic ring-opening strategy, using LiFSI as an initiator. As-synthesized GPEs were characterized with a series of technologies. The as-synthesized PNDGE 1.5 presented good thermal stability (up to 150 °C), low glass transition temperature (Tg < −40 °C), high ionic conductivity (>10−4 S/cm), and good interfacial contact with the cell components and comparable anodic oxidation voltage (4.0 V). In addition, PNGDE 1.5 exhibited a discharge capacity of 131 mAh/g after 50 cycles at 0.2 C and had a 92% level of coulombic efficiency. Herein, these results can contribute to developing of new polymer electrolytes and offer the possibility of good compatibility through the in situ technique for Li-ion batteries.

Synthesis and characterization of dendritic compounds containing nitrogen: monomer precursors in the construction of biomimetic membranes

In this article, we synthesized a novel dendritic 2-oxazoline, 2-(3,4,5-tris(4-dodecyloxybenzyloxy)phenyl)-4,5-dihydro-1,3-oxazole), and its amide precursor N-(2-hydroxyethyl)-3,4,5-tris(4-dodecyloxybenzyloxy)benzamide. Of the distinct synthetic routes explored, it was established that the direct amidation of esters with sodium methoxide followed by the dehydrative cyclisation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone as oxidizing agent and triphenylphosphine was the most efficient route to synthesize the dendritic 2-oxazoline. Besides, N-(2-hydroxyethyl)-3,4,5-tris(4-dodecyloxybenzyloxy)benzamide exhibited a monotropic columnar mesophase, whilst the dendritic 2-oxazoline does not exhibited a liquid crystalline mesophase. At the end, the first attempts to polymerize the 2-oxazoline monomer via cationic ring opening polymerization showed promising results. Therefore, the dendritic 2-oxazoline could be used as a mesogenic monomer in the synthesis of side-chain liquid-crystalline polyoxazolines that might self-assembly into columnar structures.

Janus Polymerization: A One‐Shot Approach towards Amphiphilic Multiblock Poly(ester‐acetal)s Directly from 1,3‐Dioxolane with ε‐Caprolactone

Comprehensive SummaryJanus polymerization consists of anionic and cationic ring opening polymerizations (AROP and CROP) at the two ends of a single propagating polymer chain, followed by a self‐triggered chain extension generating multiblock copolymers (MBCPs) in one step. In the contribution, Janus polymerization by Tm(OTf)3 or Er(OTf)3 catalyst with an epoxy initiator is applied to synthesize MBCPs of semi‐crystalline poly(ε‐caprolactone) (PCL) blocks from coordinated AROP and poly(1,3‐dioxolane‐co‐ε‐caprolactone) (P(DO‐co‐CL)) blocks from CROP of DO with CL. Meanwhile, amorphous random copolymers [P(DO‐r‐CL)] are synthesized as control by employing other rare earth triflates [RE(OTf)3, RE = Y, Nd, Gd and Lu] as catalysts or in the absence of an initiator via CROP. On account of the distinguishable chemical structures and thermal properties between Janus MBCPs and cationic random copolymers, Janus features are confirmed including the CROP and AROP at a single propagating chain. The resultant amphiphilic copolymers self‐assemble to nanoparticles in aqueous solution with designable diameters with the corresponding ratios of hydrophilic and hydrophobic segments. MBCPs exhibit good shape memory properties with appropriate deformation temperature close to human body's, providing a prospect on the applications in biomedical devices.