Cationic Polymerization Research Articles

Thioxanthone-Based Siloxane Photosensitizer for Cationic/Radical Photopolymerization and Photoinduced Sol-Gel Reactions.

In this investigation, a multifunctional visible-light TX-based photosensitizer containing a siloxane moiety (TXS) was designed with a good overall yield of 54%. The addition of a siloxane moiety enabled the incorporation of a TX photosensitizer into a siloxane network by photoinduced sol-gel chemistry, thus avoiding its release. Both liquid 1H and solid-state 29Si NMR measurements undeniably confirmed the formation of photoacids resulting from the photolysis of the TXS/electron acceptor molecule (Iodonium salt), which promoted the photoinduced hydrolysis/condensation of the trimethoxysilane groups of TXS, with a high degree of condensation of its inorganic network. Notably, the laser flash photolysis, fluorescence, and electron paramagnetic resonance spin-trapping (EPR ST) experiments demonstrated that TXS could react with Iod through an electron transfer reaction through its excited states, leading to the formation of radical initiating species. Interestingly, the TXS/Iod was demonstrated to be an efficient photoinitiating system for free-radical (FRP) and cationic (CP) polymerization under LEDs@385, 405, and 455 nm. In particular, whatever the epoxy monomer mixtures used, remarkable final epoxy conversions were achieved up to 100% under air. In this latter case, we demonstrated that both the photoinduced sol-gel process (hydrolysis of trimethoxysilane groups) and the cationic photopolymerization occurred simultaneously.

Crosslinked Gel Polymer Electrolyte from Trimethylolpropane Triglycidyl Ether by In Situ Polymerization for Lithium-Ion Batteries.

Electrolytes play a critical role in battery performance. They are associated with an increased risk of safety issues. The main challenge faced by many researchers is how to balance the physical and electrical properties of electrolytes. Gel polymer electrolytes (GPEs) have received increasing attention due to their satisfactory properties of ionic conductivity, mechanical stability, and safety. Herein, we develop a gel network polymer electrolyte (GNPE) to address the challenge mentioned earlier. This GNPE was formed by tri-epoxide monomer and bis(fluorosulfonyl)imide lithium salt (LiFSI) via an in situ cationic polymerization under mild thermal conditions. The obtained GNPE exhibited a relatively high ionic conductivity (σ) of 2.63 × 10-4 S cm-1, lithium transference number (tLi+, 0.58) at room temperature (RT), and intimate electrode compatibility with LiFePO4 and graphite. The LiFePO4/GNPE/graphite battery also showed a promising cyclic performance at RT, e.g., a suitable discharge specific capacity of 127 mAh g-1 and a high Coulombic efficiency (>97%) after 100 cycles at 0.2 C. Moreover, electrolyte films showed good mechanical stability and formed the SEI layer on the graphite anode. This study provides a facile method for preparing epoxy-based electrolytes for high-performance lithium-ion batteries (LIBs).

Reply to the ‘Comment on “Lewis acid-surfactant complex catalyzed polymerization in aqueous dispersed media: cationic or radical polymerization?”’ by I. V. Vasilenko, F. Ganachaud and S. V. Kostjuk, Polym. Chem., 2024, 15, DOI: 10.1039/D3PY00661A

We respond to the comment of Vasilenko et al. on our work entitled “Lewis acid-surfactant complex catalyzed polymerization in aqueous dispersed media: cationic or radical polymerization?” (Polym. Chem., 2020, 11, 5757).

Mechanism of cationic ring-opening polymerisation of ε-caprolactone using metallocene/borate catalytic systems: a DFT and NCI study on chain initiation, propagation and termination.

We present a comprehensive DFT investigation on the cationic ring-opening polymerisation (CROP) of ε-caprolactone (CL) using zirconocene/borate catalyst systems. All possible pathways of the interaction between cationic species [Cp2ZrMe+] and counteranions, [A-] = [MeB(C6F5)3]- and [B(C6F5)4]-, were examined during chain initiation, propagation, and termination steps. The calculations reveal an active chain-end mechanism with O-alkyl bond cleavage of the polymerisation. The catalytic performance of the two counteranions is found to be identical, and they influence the initial process through stabilisation of the cationic species via non-covalent interactions (NCI), with the [MeB(C6F5)3]- anion stabilising the catalyst-monomer complex more effectively than the [B(C6F5)4]- anion by 24.3 kJ mol-1. The first two propagations are likely the rate-determining step, with calculated free-energy barriers of 61.4-71.2 and 73.9-80.6 kJ mol-1 with and without the anions (A-), respectively. The presence of the counteranion significantly affects the third propagation rate, lowering the barriers up to 20 kJ mol-1. Comparison of the first termination and the third propagation shows that they are not competitive, with the termination being less facile. We also studied the initiation and propagation steps for the hafnocene catalyst and found that the Hf catalyst slightly favours the CL CROP in comparison to the Zr catalyst. Analysis of solvent and dispersion interaction demonstrates that both factors play an important role in the process. NCI analysis reveals weak (van der Waals) interactions at the contacts between the cationic species and the counteranions during the reaction course. Overall, our results offer insights into the structures and interactions involved in the polymerisation.

Metal-free living cationic ring-opening polymerization of cyclic esters using selenonium salts as Lewis acids

Selenonium salts were employed as a new class of metal-free Lewis acid catalysts for the cationic ring-opening polymerization (ROP) of various cyclic esters.

Bidentate selenium-based chalcogen bond catalyzed cationic polymerization of p-methoxystyrene.

The application of selenium-based non-covalent bond catalysis in living cationic polymerization has rarely been reported. In this work, the cationic polymerization of p-methoxystyrene (pMOS) was performed using a bidentate selenium bond catalyst - a new water-tolerant Lewis acid catalyst. A polymer with controllable molecular weight and narrow molecular weight distribution can be obtained at room temperature, with a maximum molecular weight of 23.3 kDa. This selenium bond compound can also catalyze the controllable cationic polymerization of p-methoxy styrene under environmental conditions. By changing the monomer feeding ratio, a secondary feeding experiment and DFT analysis, it is shown that the selenium bond catalyst can induce polymer chain growth by reversibly activating dormant covalent bonds (C-OH).

Combining photocontrolled-cationic and anionic-group-transfer polymerizations using a universal mediator: enabling access to two- and three-mechanism block copolymers.

An ongoing challenge in polymer chemistry is accessing diverse block copolymers from multiple polymerization mechanisms and monomer classes. One strategy to accomplish this goal without intermediate compatibilization steps is the use of universal mediators. Thiocarbonyl thio (TCT) functional groups are well-known mediators to combine radical with either cationic or anionic polymerization, but a sequential cationic-anionic universal mediator system has never been reported. Herein, we report a TCT universal mediator that can sequentially perform photocontrolled cationic polymerization and thioacyl anionic group transfer polymerization to access poly(ethyl vinyl ether)-block-poly(thiirane) polymers for the first time. Thermal analyses of these block copolymers provide evidence of microphase separation. The success of this system, along with the established compatibility of radical polymerization, enabled us to further chain extend the cationic-anionic diblock using radical polymerization of N-isopropylacrylamide. The resulting terpolymer represents the first example of a triblock made from three different monomer classes incorporated via three different mechanisms without any end-group modification steps. The development of this simple, sequential synthesis using a universal mediator approach opens up new possibilities by providing facile access to diverse block copolymers of vinyl ethers, thiiranes, and acrylamides.

Stereoregular poly(2-phenylthiirane) via cationic ring-opening polymerization.

Herein, we describe an effective strategy for synthesizing polythioethers with a well-defined structure through the cationic polymerization of thiirane with electron-withdrawing substituents. This strategy allows for precisely controlling the regio- and stereochemistry of the ring-opening polymerization of 2-phenylthiirane, thus allowing for producing poly(2-phenylthiirane) with high stereoregularity using enantiomeric pure thiirane.

Revealing the photoredox potential of azulene derivatives as panchromatic photoinitiators in various light-initiated polymerization processes

Herein, the application of previously unknown azulene derivatives as effective panchromatic photosensitizers in the visible light range in the initiation of light-induced cationic and free-radical polymerization processes was investigated.

Novel thermal initiator systems for radical induced cationic frontal polymerization

Frontal polymerization is an extremely efficient and rapid method for producing bulk polymers, characterized by a self-sustaining curing front that propagates throughout the resin.

Radical promoted cationic RAFT polymerization by photo electron transfer reaction

A radical promoted cationic reversible addition–fragmentation chain transfer (RAFT) polymerization of various vinyl ethers via photo electron transfer reaction was developed and applied in photocuring.

Organoboron-mediated polymerizations.

The scientific community has witnessed extensive developments and applications of organoboron compounds as synthetic elements and metal-free catalysts for the construction of small molecules, macromolecules, and functional materials over the last two decades. This review highlights the achievements of organoboron-mediated polymerizations in the past several decades alongside the mechanisms underlying these transformations from the standpoint of the polymerization mode. Emphasis is placed on free radical polymerization, Lewis pair polymerization, ionic (cationic and anionic) polymerization, and polyhomologation. Herein, alkylborane/O2 initiating systems mediate the radical polymerization under ambient conditions in a controlled/living manner by careful optimization of the alkylborane structure or additives; when combined with Lewis bases, the selected organoboron compounds can mediate the Lewis pair polymerization of polar monomers; the bicomponent organoboron-based Lewis pairs and bifunctional organoboron-onium catalysts catalyze ring opening (co)polymerization of cyclic monomers (with heteroallenes, such as epoxides, CO2, CO, COS, CS2, episulfides, anhydrides, and isocyanates) with well-defined structures and high reactivities; and organoboranes initiate the polyhomologation of sulfur ylides and arsonium ylides providing functional polyethylene with different topologies. The topological structures of the produced polymers via these organoboron-mediated polymerizations are also presented in this review mainly including linear polymers, block copolymers, cyclic polymers, and graft polymers. We hope the summary and understanding of how organoboron compounds mediate polymerizations can inspire chemists to apply these principles in the design of more advanced organoboron compounds, which may be beneficial for the polymer chemistry community and organometallics/organocatalysis community.

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.

Comment on “Lewis acid-surfactant complex catalysed polymerisation in aqueous dispersed media: cationic or radical polymerisation?” by A. Destephen, L. Lezama and N. Ballard, Polym. Chem., 2020, 11, 5757

Cationic polymerization catalysed by LASC occurs when radical production is inhibited and at low temperature. Large molar mass distributions obtained in this process call for a mechanism involving preferential coordination of dienic or styrenic monomers by the catalyst.

Dual control of stereoregularity and molecular weight in cationic polymerization of vinyl ether by tunable TADDOLs/TiCl4 initiating systems

The stereoregularity and molecular weight of poly(isobutyl vinyl ether) was simultaneously controlled by TADDOL/TiCl4 initiating systems with various aryl substituents on TADDOL.

A theoretical study of the mechanism of cationic polymerization of isobutylene catalysed by EtAlCl2/t-BuCl with bis(2-chloroethyl)ether in hexanes.

The mechanism of cationic polymerization of isobutylene catalyzed by t-BuCl/ethylaluminum dichloride (EADC) combined with bis(2-chloroethyl)ether (CEE) in n-hexane solvent has been investigated using ab initio molecular dynamics (AIMD) and metadynamics (MTD) simulations. The results indicated that the polyisobutylene (PIB) initiation stage involves a clear two-step mechanism. Calculation of the free energy landscapes of the other two ether reactions reveals that the energy barriers of diisopropyl ether (i-Pr2O) and 2-chloroethyl ethyl ether (CEEE) are much higher than those of CEE, which is consistent with the experimental results. During the chain propagation phase, the required free energy barrier gradually decreases and tends to reach equilibrium as the chain length increases. Finally, the oxonium mechanism during the chain initiation stage was investigated by calculating the 1H NMR spectra and MTD simulation. Our calculations can confirm that the existence of tert-butyloxonium ions during the reaction is possible. Their contribution to the whole reaction is further discussed.

Lewis acid ionic liquid catalysed synthesis of bioderived surfactants from β-pinene

Cationic polymerisation of β-pinene (βP) via earth abundant catalysis has been investigated as a route to low molar mass poly(β-pinene) (PBP) for surfactant applications. As a ‘greener’ alternative to the...

BIOCOMPATIBLE ELASTIC POLYMER NANOCOMPOSITES BASED ON MULTIWALLED CARBON NANOTUBES FOR APPLICATION IN CARDIOVASCULAR SURGERY

HighlightsThe incorporation of multi-walled carbon nanotubes into the structure of the poly(styrene-block-isobutylene-block-styrene) polymer matrix leads to an increase in the tensile strength and Young's modulus of the nanocomposites. The resulting nanocomposites retain high biocompatibility and can be used as elements of implanted cardiovascular products. AbstractAim. To synthesize and modify poly(styrene-block-isobutylene-block-styrene) (SIBS) with two types of multi-walled carbon nanotubes (MWCNTs) in different concentrations to improve its mechanical properties.Methods. SIBS was synthesized by controlled cationic polymerization. Polymer nanocomposites were prepared using ultrasonic dispersion followed by casting films from a polymer solution. The resulting nanocomposite films were subjected to mechanical tests under uniaxial tensile conditions. Tensile strength, elastic-strain properties, and plastic deformation under cyclic loading were assessed. The structure of the nanocomposites was analyzed by scanning electron microscopy. The hydrophilicity of the surface of the materials was studied by measuring the contact angle with water. The cytotoxicity of the resulting polymer films was assessed by the viability and metabolic activity of endothelial cells cultured on the surface of the nanocomposites.Results. Polymer nanocomposites with a uniform distribution of MWCNTs in the polymer matrix were obtained. SIBS films modified with 1% MWCNTs with a diameter of 50–90 nm showed an increase in tensile strength by 16.4% compared to SIBS polymer. Increasing the concentration of MWCNTs to 8% led to a decrease in the strength of polymer materials by 19,6%. The inclusion of nanoparticles into the polymer matrix significantly increased the Young's modulus of the studied polymers with a MWCNT content above 4%. With an increase in the content of MWCNTs in the nanocomposites, an increase in hydrophilicity was also observed, while the cytotoxicity of the samples towards endothelial cells was not noted.Conclusion. Nanocomposites based on SIBS and MWCNTs, due to their high strength and biocompatibility, can become a promising material for the development of various medical products, in particular prosthetic heart valves.

Thienothiophene and biphenyl based conjugated porous polymer as a photocatalyst for visible light induced free radical and cationic polymerization

Over the last few decades, photopolymerization has been the center of great attention owing to a variety of desirable features such as mild reaction conditions, cost efficiency and especially, spatiotemporal controllability. In particular, visible light induced polymerizations have been attracting considerable attention due to the concerns on cost efficiency, light penetration and environment safety. In this work, a crosslinked conjugated polymer, TT-BP, was designed and synthesized by Pd (0) catalyzed Suzuki coupling reaction. It was used as a photocatalyst for visible light induced free radical and cationic polymerizations in the presence of diphenyliodonium salt. The reactions were performed for 8 and 24 h in high yields, for which the photocatalyst TT-PB was used repeatedly for each reaction. The maximum conversion reached to 76 % in free radical polymerization of MMA, while the maximum conversion was obtained in cationic polymerization of IBVE with 82 %. This report on reusable conjugated polymer that have been used as a photocatalyst during free-radical and cationic photopolymerizations may lead to the emergence of a new perspective for photocatalyst and photopolymerization processes.

Thermo-Responsive Shape-Memory Dual-Cured Polymers Based on Vegetable Oils.

The development of thermo-responsive shape-memory polymers has attracted attention due to their ability to undergo reversible deformations based on temperature changes. Vegetable oils are confirmed to be an excellent biorenewable source of starting materials for the synthesis of polymers. Therefore, the objective of this research was to synthesize thermo-responsive shape-memory polymers based on vegetable oils by using the dual-curing technique and obtaining polymers with tailorable properties. Acrylated epoxidized soybean oil and two epoxidized vegetable oils, linseed oil and camelina oil, were chosen for dual curing with m-xylylenediamine. Rheological tests were used to analyze the curing kinetics of systems undergoing radical photopolymerization, thermal cationic polymerization, and dual-curing processes. The rheological, mechanical, and thermal characteristics of the polymers were enhanced by the second curing stage. Dual-cured vegetable oil-based polymers had shape-memory properties with a recovery ratio of 100%, making them suitable for a variety of applications, including electronics, biomedical devices, and robotics.