Cationic Polymerization Research Articles

Statistical Kinetic Modeling Procedure to Predict Exo-Olefin Content in Cationic Polymerization and Its Application to Polyisobutylene

Statistical Kinetic Modeling Procedure to Predict Exo-Olefin Content in Cationic Polymerization and Its Application to Polyisobutylene

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.

Study of the interaction of the H<sub>2</sub>O-BF<sub>3</sub> complex catalyst with <i>p</i>-methylstyrene in toluene of stoichiometric composition 1:1:2 using the <i>ab initio</i> method

For the first time, a quantum-chemical study of the reaction of protonation of the monomer of cationic polymerization of p-methylstyrene in the presence of a complex catalyst boron fluoride – water in toluene with a stoichiometric composition of 1:1:2 was carried out by the ab initio method with the reaction coordinate RC1-H20. I t is shown that the value of the activation energy is 123 kJ/mol, and the thermal effect of the reaction is 86 kJ/mol. It has been proved that the interaction of the studied catalytic complex with p-methylstyrene in toluene of stoichiometric composition 1:1:2 is a coordinated process.

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.

Thermally initiated cationic frontal polymerization of epoxies and vinyl ethers through a lone onium salt

AbstractFrontal polymerization (FP) of epoxy monomers is typically achieved with a radical‐induced cationic frontal polymerization (RICFP) process that combines a thermal radical initiator with an onium salt superacid generator. In this paper, we show that both thermal and UV‐initiated cationic frontal polymerizations are possible for common epoxy and vinyl ether monomers with only an iodonium superacid generator in the absence of a standalone thermal radical initiator. Increasing superacid generator concentration resulted in an increase in front velocity, as did the addition of vinyl ether to epoxies. The front velocity is reduced by the addition of 4‐methoxyphenol (MeHQ), indicating free‐radicals play a significant role.

Polyselenonium Salt as a Heterogeneous Catalyst for Living/Controlled Cationic Polymerization

Polyselenonium Salt as a Heterogeneous Catalyst for Living/Controlled Cationic Polymerization

Solvation structure reorganization and interface regulation of poly (glycidyl POSS)-based electrolyte for quasi-solid-state lithium-ion batteries

The interfacial stability and some unexpected side reactions in quasi-solid-state lithium-ion batteries (LIBs) impede the practical application of the in-situ crosslinked polymer electrolytes. Herein, a novel in-situ crosslinked polymer electrolyte with eight-armed crosslinked supramolecular structure is constructed via cationic ring-opening polymerization of glycidyl polyhedral oligomeric silsesquioxane (POSS). The strong electrostatic and hydrogen bonding interactions of the POSS blocks with anions reorganize the solvation structure, and the overall oxidation resistance of anions can be also effectively enhanced benefiting from the relatively electron-withdrawing effect of the POSS blocks. Simultaneously, a hierarchical cathode-electrolyte interphase with flexibility and oxidation resistance is constructed involving the boron difluoride radical-catalyzed cleavage of Si-O-Si linkages in POSS frameworks. The poly (glycidyl POSS)-based electrolyte enables the Li||NCM83 cell to possess a high capacity retention of 79.1 % after 500 cycles. Moreover, the SiOx||NCM83 battery shows a capacity retention of 87.6 % after 200 cycles. These insights gained form this work opens up an avenue for the development and practical application of quasi-solid-state LIBs.

Ceramic bodies without warping using epoxide–acrylate hybrid ceramic slurry for photopolymerization‐based 3D printing

AbstractTo be able to produce ceramic bodies with complex shapes without interlayer delamination and warping through vat photopolymerization‐based 3D printing techniques, photosensitive ceramic slurries should be studied to prepare 3D printed green and sintered bodies. In this study, we developed dual curable acrylate–epoxide ceramic slurries for digital light processing (DLP) 3D ceramic printing. The dual curing process of the slurries is a combination of photo‐radical polymerization of acrylate and thermal cationic polymerization of cyclo‐aliphatic epoxide. The green bodies prepared by dual curing of the slurries showed higher fracture strength and better adhesion between layers and between starting particles and binder polymer in comparison to acrylate‐based green body. These advantages were due to higher crosslinking density of the binder matrix and hydrogen bonding by hydroxyl groups from epoxide ring opening. The green and sintered bodies printed with improved slurry and DLP 3D printer had flat shape without warping unlike those from acrylate‐based bodies. Moreover, the distribution of inter‐particle necking in the sintered body was uniform and the interface boundary between layers was not observed. This is because of excellent uniformity of the dual cured acrylate–epoxide polymer matrix (uniform crosslinking density in layers) in the green body and hydroxyl groups generated by epoxy ring opening.

Diethylaluminum chloride-co-initiated cationic polymerization of isoprene: dramatic effect of the nature of alkyl halide on the properties of synthesized polymers

The cationic polymerization of isoprene using alkyl halide/Et2AlCl initiating system (alkyl halide: tert-butyl chloride, tert-butyl bromide, 2-chloro-2-methylbutane and isopropyl chloride) at different temperatures has been studied. It was shown for the first time that using of tertiary alkyl halide in conjunction with Et2AlCl allowed to synthesize fully soluble solid thermoplastic polymers with reduced unsaturation (41–48 mol%) as well as relatively high glass transition temperature (52–60°С) and softening point (102–128°С). The substitution of tertiary alkyl halides on the secondary one (isopropyl chloride) results in the obtaining of cross-linked polymers due to the low activity of isopropyl chloride in chain transfer to alkyl halide. It was found that alkyl halide nature, the ratio of alkyl halide to Et2AlCl, duration and temperature of the polymerization of isoprene have dramatic effect on the unsaturation of synthesized polymers as well as their molecular weight, polydispersity, physical and chemical properties.

Mechanism of Action of Oxazoline-Based Antimicrobial Polymers Against Staphylococcus aureus: In Vivo Antimicrobial Activity Evaluation.

Antimicrobial-resistant pathogens have reached alarming levels, becoming one of the most pressing global health issues. Hence, new treatments are necessary for the fight against antimicrobial resistance. Synthetic nanoengineered antimicrobial polymers (SNAPs) have emerged as a promising alternative to antimicrobial peptides, overcoming some of their limitations while keeping their key features. Herein, a library of amphiphilic oxazoline-based SNAPs using cationic ring-opening polymerization (CROP) is designed. Amphipathic compounds with 70% cationic content exhibit the highest activity against clinically relevant Staphylococcus aureus isolates, maintaining good biocompatibility in vitro and in vivo. The mechanism of action of the lead compounds against S. aureus is assessed using various microscopy techniques, indicating cell membrane disruption, while the cell wall remains unaffected. Furthermore, a potential interaction of the compounds with bacterial DNA is shown, with possible implications on bacterial division. Finally, one of the compounds exhibits high efficacy in vivo in an insect infection model.

Mechanistic Insights into the Stereoselective Cationic Polymerization of N-Vinylcarbazole.

The synthesis of stereoregular polymers through ionic mechanisms using asymmetric ion-pairing (AIP) catalysis is emerging as an effective strategy to achieve differentiated material properties from readily available building blocks. Stereoselective cationic polymerization in particular is primed for advancement using AIP by leveraging the breadth of Brønsted and Lewis acid small-molecule catalysis literature; however, mechanistic studies that address polymer-specific phenomena are scarce and, as a result, the lack of mechanistic understanding has limited catalyst design. In a recent study, we demonstrated the only example of a stereoselective and helix-sense-selective cationic vinyl polymerization of N-vinylcarbazole using chiral scandium-bis(oxazoline) Lewis acids. To better understand the mechanism of this highly stereoselective polymerization and elicit design principles for future advances, we present a combined experimental and computational study into the relevant factors that determine tacticity and helicity control. Key mechanistic experiments suggest two competing elementary steps-chain-end conformation equilibration and propagation-whose relative rates can be influenced by monomer concentration, isotope effects, and catalyst design to tune tacticity. In contrast, helicity is influenced by complex relationships between the stereoselectivity of the first monomer propagation and a time-dependent initiator-catalyst mixing time. The more complete understanding of stereoselective cationic polymerization through AIP developed herein provides insights into polymer-specific mechanisms for stereocontrol, which we believe will motivate continued catalyst discovery and development for stereoselective vinyl polymerization.

Cationic polymerization of butadiene with isomerization of the initiator structure

Cationic polymerization of butadiene with isomerization of the initiator structure

Photoinduced Superacceleration of Metal-Free Living Cationic Polymerization Using Diaryliodonium Salts as Organic Lewis Acid Catalysts

Photoinduced Superacceleration of Metal-Free Living Cationic Polymerization Using Diaryliodonium Salts as Organic Lewis Acid Catalysts

Photoactivable alizarin and eugenol-based materials for antibacterial applications

We report herein the design of a new visible-light epoxy-based alizarin photosensitizer (AE) of iodonium salt (Iod) for the cationic polymerization (CP) of epoxidized eugenol monomers under visible-light irradiation. The combination of AE and Iod demonstrates highly efficient photoinitiating properties under air. As highlighted by fluorescence, laser flash photolysis (LFP) and electron paramagnetic resonance spin-trapping (ESR ST) experiments, AE acts as an electron donating molecule, and reacts with Iod under light exposure through its excited singlet and triplet states via a photoinduced electron transfer reaction, producing thus protonic acids, H+, able to initiate CP. Also, we demonstrate by EPR ST that the addition of diepoxy eugenol monomer may lead to the formation of reactive radical species which may be oxidized by Iod to form cationic species. Thus, new bio-based and photoactivable materials were designed by cationic photopolymerization with the use of alizarin-based photosensitizer and eugenol derived monomers. By tuning the weight proportion of eugenol derived epoxy monomers (mono- (EE) and di-epoxidized (EdE) eugenol), we can modulate the thermal and mechanical properties of the resulting materials. The new AE-based materials have demonstrated two interesting properties: first, the presence of EE in the polymer network has considerably decreased the number of colony forming units (CFUs) at the surface of materials whatever the bacterial strains used, and these samples demonstrate photoactivable properties as they produce, under visible-light irradiation, singlet oxygen, a biocide agent against bacteria. Interestingly, the irradiation of the AE/Iod/EE(50)/EdE(50) materials lead to a tremendous decrease of the number of E. coli and S. aureus CFUs at their surface. A reduction by 100% of the bacterial adhesion is observed upon visible-light exposure.

3D-VAT printing of nanocomposites by photopolymerisation processes using amino-meta-terphenyls as visible light-absorbing photoinitiators

ABSTRACT In this article, the application of 10 new amino-m-terphenyls in 3D-VAT printing was described. New compounds have specially designed D-π-A structure, where the central phenyl ring with nitrile and amino groups is the acceptor and the modifiable amino group is donor. Such design eliminates problem with acid scavenging and guaranteed desire properties and photoactivity as well as it allows further development of such system for 3D-VAT printing. Efficient excitation with intramolecular charge transfer provides excellent absorption and electrochemical properties, which can be tuned by modification of the amino group. The design allows photoinitiation of free radical, hybrid and especially cationic polymerisation even at 455 nm with more than 70% of monomer conversion. Such properties allow to use the developed compounds as efficient visible light photoinitiators for 3D printing of nanocomposite materials. The terphenyls can efficiently cure resins containing CuO and Al2O3 nano additives leading to high-resolution 3D prints.

Polylactide-based networks containing dynamic tetraphenylethane groups for 3D printed repairable and reprocessable constructs

This study aims to synthesize sustainable polylactide (PLA) materials, specifically polyester-urethanes based on PLAs with various molecular weights, to enhance thermal shape stability through crosslinking and enable reprocessing due to the presence of a new type of dynamic/reversible covalent bonds in the polymer structure. PLA-based networks containing dynamic bonds were prepared by coupling (using hexamethylene diisocyanate) PLA star polymers bearing four terminal -OH groups with a low molecular weight diol containing groups that undergo reversible dissociation upon heating. The PLAs prepolymers of two molecular weights (Mn = 3700 and 7800 g/mol) were synthesized via cationic polymerization of D,L-lactide to obtain the networks of different crosslinking densities. The low molecular weight diol, containing a tetraphenylethane moiety (TPE) with an easy dissociating bond, was synthesized from 4-hydroxybenzophenone. Networks without reversible bonds, containing 1,1′-bi-2-naphthol (binol) instead of TPE units, were also prepared as a reference. All networks were analyzed by Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis and were subjected to tensile tests. The tensile strength of all networks was in the range of 22–45 MPa. The elongations at break of networks differed based on the type of used low molecular weight diol, with values in the range of 28–67% for TPE-containing networks, in comparison with 10% for reference samples. Rheological studies of these materials were performed at a higher temperature (150 °C) to clearly demonstrate the behavioral differences between networks with and without “reversible” bonds. Only the networks with TPE groups were able to recover their previous strength after strain deformation at 150 °C in four subsequent cycles. Moreover, it was shown that networks with reversible groups were repairable and 3D printable at temperatures as low as 150 °C, while those containing non-reversible bonds did not exhibit such capability.

Cationic β‐Scission of C−H and C−C Bonds for Selective Dimerization and Subsequent Sulfur‐Free RAFT Polymerization of α‐Methylstyrene and Isobutylene

AbstractA series of exo‐olefin compounds ((CH3)2C(PhY)−CH2C(=CH2)PhY) were prepared by selective cationic dimerization of α‐methylstyrene (αMS) derivatives (CH2=C(CH3)PhY) with p‐toluenesulfonic acid (TsOH) via β‐C−H scission. They were subsequently used as reversible chain transfer agents for sulfur‐free cationic RAFT polymerization of αMS via β‐C−C scission in the presence of Lewis acid catalysts such as SnCl4. In particular, exo‐olefin compounds with electron‐donating substituents, such as a 4‐MeO group (Y) on the aromatic ring, worked as efficient cationic RAFT agents for αMS to produce poly(αMS) with controlled molecular weights and exo‐olefin terminals. Other exo‐olefin compounds (R−CH2C(=CH2)(4‐MeOPh)) with various R groups were prepared by different methods to examine the effects of R groups on the cationic RAFT polymerization. A sulfur‐free cationic RAFT polymerization also proceeded for isobutylene (IB) with the exo‐olefin αMS dimer ((CH3)2C(Ph)−CH2C(=CH2)Ph). Furthermore, telechelic poly(IB) with exo‐olefins at both terminals was obtained with a bifunctional RAFT agent containing two exo‐olefins. Finally, block copolymers of αMS and methyl methacrylate (MMA) were prepared via mechanistic transformation from cationic to radical RAFT polymerization using exo‐olefin terminals containing 4‐MeOPh groups as common sulfur‐free RAFT groups for both cationic and radical polymerizations.

Cationic β-Scission of C-H and C--C Bonds for Selective Dimerization and Subsequent Sulfur-Free RAFT Polymerization of α-Methylstyrene and Isobutylene.

A series of exo-olefin compounds ((CH3)2C(PhY)-CH2C(=CH2)PhY) were prepared by selective cationic dimerization of α-methylstyrene (αMS) derivatives (CH2=C(CH3)PhY) with p-toluenesulfonic acid (TsOH) via β-C-H scision. They were subsequently used as reversible chain transfer agents for sulfur-free cationic RAFT polymerization of αMS via β-C-C scission in the presence of Lewis acid catalysts such as SnCl4. In particular, exo-olefin compounds with electron-donating substituents, such as a 4-MeO group (Y) on the aromatic ring, worked as efficient cationic RAFT agents for αMS to produce poly(αMS) with controlled molecular weights and exo-olefin terminals. Other exo-olefin compounds (R-CH2C(=CH2)(4-MeOPh)) with various R groups were prepared by different methods to examine the effects of R groups on the cationic RAFT polymerization. A sulfur-free cationic RAFT polymerization also proceeded for isobutylene (IB) with the exo-olefin αMS dimer ((CH3)2C(Ph)-CH2C(=CH2)Ph). Furthermore, telechelic poly(IB) with exo-olefins at both terminals was obtained with a bifunctional RAFT agent containing two exo-olefins. Finally, block copolymers of αMS and MMA were prepared via mechanistic transformation from cationic to radical RAFT polymerization using exo-olefin terminals containing 4-MeOPh groups as common sulfur-free RAFT groups for both cationic and radical polymerizations.

Polyampholyte Polymers‐Based Sensors: A Review on Stimuli and Applications

AbstractPolyampholytes are a specific type of zwitterionic materials composed of monomers with both positive and negative charges. These materials can be synthesized through various methods, such as free radical, anionic, or cationic polymerization, or by modifying existing polymers through postpolymerization processes. Polyampholytes possess unique properties that make them attractive for a wide range of applications, particularly in sensor technology. They can undergo conformational changes in response to external stimuli like pH variations, temperature fluctuations, or changes in salt concentration. These properties have led to their application in biosensors, salt and ion sensors, pH sensors, fluorescence‐based sensors, strain sensors, and thermosensitive sensors. It is worth noting that in some cases polyampholytes can respond to multiple stimuli simultaneously. Overall, polyampholytes are drawing great attention for their excellent mechanical properties including self‐healing, high toughness, and fatigue resistance. Thus, this review is focused on advances that are made to develop polyampholyte polymer‐based sensors in different applications.