Radical Polymerization Of Acrylate Research Articles

Photo‐induced organo‐manganese‐mediated radical polymerization of acrylates under LED irradiation

The role of manganese in photo‐induced organometallic‐mediated radical polymerization (photo‐OMRP) under LED (light‐emitting diode) irradiation has not been previously explored. In this study, four manganese (II) complexes, namely [Mn(6‐tert‐butyl‐N,N′‐propanebis [salicylimine])] (Mn‐Bu), [Mn(6,3‐di‐tert‐butyl‐N,N′‐propanebis [salicylimine])] (Mn‐Bu2), [Mn(6‐ethoxy‐N,N′‐propanebis [salicylimine])] (Mn‐Ethoxy), and [Mn(6,3‐di‐ethoxy‐N,N′‐propanebis [salicylimine])] (Mn‐Ethoxy2), were synthesized using both symmetrical and non‐symmetrical tetradentate N2O2 Schiff base ligands. The Schiff base ligands were characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–Vis), and nuclear magnetic resonance spectroscopy (NMR). The Mn (II) complexes were characterized by FTIR, UV–Vis, elemental analysis, molar conductivity, cyclic voltammetry, MALDI‐TOF mass spectrometry, electron paramagnetic resonance, and rationalized with density functional theory (DFT) studies. All complexes were evaluated as photo‐OMRP mediators under LED irradiation at 390 nm and in the 400–800 nm range. The photopolymerization utilized methyl acrylate (MA) and diphenyl(2,4,6‐trimethylbenzoyl)phosphine oxide (TPO) in varying molar ratios of [MA]/[MnII]/[TPO] (900/1/1, 600/1/1, and 600/1/0.5). The photo‐OMRP of MA mediated by Mn‐Bu2 showed the best control over molecular weight (Mn matching Mn,th) and dispersity (Ð < 1.30) at a [MA]/[MnII]/[TPO] = 600/1/0.5 M ratio. The polymerization system demonstrated a living character, as evidenced by reversible “on/off” light source switching. Furthermore, a block copolymer of poly (methyl acrylate)‐b‐poly (butyl acrylate) was successfully synthesized employing a sequential visible‐light‐induced process, with the Mn‐Bu2 system showing the best results.

Improved Approach for ab Initio Calculations of Rate Coefficients for Secondary Reactions in Acrylate Free-Radical Polymerization.

Secondary reactions in radical polymerization pose a challenge when creating kinetic models for predicting polymer structures. Despite the high impact of these reactions in the polymer structure, their effects are difficult to isolate and measure to produce kinetic data. To this end, we used solvation-corrected M06-2X/6-311+G(d,p) ab initio calculations to predict a complete and consistent data set of intrinsic rate coefficients of the secondary reactions in acrylate radical polymerization, including backbiting, β-scission, radical migration, macromonomer propagation, mid-chain radical propagation, chain transfer to monomer and chain transfer to polymer. Two new approaches towards computationally predicting rate coefficients for secondary reactions are proposed: (i) explicit accounting for all possible enantiomers for reactions involving optically active centers; (ii) imposing reduced flexibility if the reaction center is in the middle of the polymer chain. The accuracy and reliability of the ab initio predictions were benchmarked against experimental data via kinetic Monte Carlo simulations under three sufficiently different experimental conditions: a high-frequency modulated polymerization process in the transient regime, a low-frequency modulated process in the sliding regime at both low and high temperatures and a degradation process in the absence of free monomers. The complete and consistent ab initio data set compiled in this work predicts a good agreement when benchmarked via kMC simulations against experimental data, which is a technique never used before for computational chemistry. The simulation results show that these two newly proposed approaches are promising for bridging the gap between experimental and computational chemistry methods in polymer reaction engineering.

The Use of High‐Temperature Semi‐Batch Radical Polymerization to Synthesize Acrylate Based Macromonomers and Structured Copolymers

AbstractA high‐temperature starved‐feed semi‐batch operating policy is developed to produce p(acrylates) with high macromonomer content, taking advantage of side reactions inherent to acrylate radical polymerization. This operating strategy results in significantly higher macromonomer content for the polymerization of isobornyl acrylate (iBoA) versus n‐butyl acrylate (BA) under identical operating conditions. This is because steric hindrance favors fragmentation (i.e., terminal double bond (TDB) formation) over addition (i.e., short‐chain or long‐chain branch (LCB) formation), thus increasing the p(iBoA) TDB content and decreasing polymer dispersity. The p(iBoA) macromonomer solution serves as an excellent addition‐fragmentation agent to polymerize a second monomer in a single pot process controlled by sequential feeding, as demonstrates by the production of iBoA‐BA block and comb copolymer structures at different temperatures and macromonomer concentrations. The incorporation of the p(iBoA) macromonomer into a copolymer product is verified by various techniques, including polymer fractionation followed by TDB, composition, and molar mass analyses. Reaction temperature plays a key role in determining whether a blocky versus comb copolymer structure is produced. The ability to synthesize block and comb copolymers by radical polymerization without a mediating agent offers the potential to efficiently produce structured copolymers for industrial applications.

Controlled Radical Polymerization of Acrylates and Isocyanides Installs Degradable Functionality into Novel Copolymers.

Installing ketones into a polymer backbone is a known method for introducing photodegradability into polymers; however, most current methods are limited to ethylene-carbon monoxide copolymerization. Here we use isocyanides in place of carbon monoxide in a copolymerization strategy to access degradable nonalternating poly(ketones) that either maintain or enhance the thermal properties. A cobalt-mediated radical polymerization of acrylates and isocyanides synthesizes nonalternating poly(acrylate-co-isocyanide) copolymers with tunable incorporation using monomer feed ratios. The kinetic product of the polymerization is a dynamic β-imine ester that tautomerizes to the β-enamine ester. Hydrolysis of this copolymer affords a third copolymer microstructure─the elusive nonalternating poly(ketone)─from a single copolymerization strategy. Analysis of the copolymer properties demonstrates tunable thermal properties with the degree of incorporation. Finally, we show that poly(acrylate-co-isocyanide) and poly(acrylate-co-ketone) are photodegradable with 390 nm light, enabling chain cleavage.

Copper(II)bromide/2,4,6‐tri‐(2‐pyridyl)‐1,3,5‐triazine Complex for the Photo Atom Transfer Radical Polymerization of Acrylate and Methacrylate Monomers

Abstract2,4,6‐tri‐(2‐pyridyl)‐1,3,5‐triazine (TPT) has been successfully utilized as an effective ligand for the photo atom transfer radical polymerization (photoATRP) of acrylate and methacrylate monomers in the absence of photoinitiators or photosensitizers. The UV light (λmax=365 nm, I=10 mW/cm2) assisted photoATRP of methyl methacrylate (MMA) yields poly(methyl methacrylate) (PMMA) with high monomer conversion (88.5 %), low PDI (1.21), and high end‐group fidelity using 100 ppm concentration of copper(II) bromide. The efficacy of the TPT ligand was further scrutinized by polymerizing different acrylate and methacrylate monomers, including methyl acrylate (MA), MMA, n‐butyl acrylate (n‐BA), n‐butyl methacrylate (n‐BMA), n‐benzyl methacrylate (n‐bMA), and ethylene glycol dimethacrylate. The kinetic study revealed the first‐order polymerization behavior of PMMA with an induction period of 2 h, suggesting the livingness of polymerization. The temporal control experiments were also performed, indicating the efficient activation and deactivation mechanism of the polymerization.

Photoinitiation Mechanisms of Novel Phenothiazine‐Based Oxime and Oxime Esters Acting as Visible Light Sensitive Type I and Multicomponent Photoinitiators

AbstractIn this work, three new photoinitiators, based on the phenothiazine scaffold as a chromophore and potentially bearing the oxime ester functionality as an initiating group are designed and synthesized for the free radical polymerization of acrylates, the cationic polymerization of epoxides, and the formation of interpenetrated polymer networks upon irradiation with a light emitting diode emitting at 405 nm. These phenothiazine‐based oxime and oxime esters revealed impressive photoinitiation ability manifested by excellent polymerization rates and high final reactive function conversions. Significantly, they can be used as both; one‐component (Type I) and two‐component photoinitiating systems. Photoinitiation mechanisms through which reactive species are produced are investigated by means of different complementary techniques including real‐time Fourier transform infrared spectroscopy, UV–visible absorption spectroscopy, electron spin resonance spectroscopy, fluorescence (steady state and time resolved), cyclic voltammetry, and molecular modeling calculations. Thermal initiation behavior of the different oxime esters is also studied by using differential scanning calorimetry, highlighting their dual thermal/photochemical initiation ability. Finally, 3D printed objects are successfully fabricated by conducting both direct laser writing and 3D printing experiments.

Latest Advances in Highly Efficient Dye-Based Photoinitiating Systems for Radical Polymerization.

Light-activated polymerization is one of the most important and powerful strategies for fabrication of various types of advanced polymer materials. Because of many advantages, such as economy, efficiency, energy saving and being environmentally friendly, etc., photopolymerization is commonly used in different fields of science and technology. Generally, the initiation of polymerization reactions requires not only light energy but also the presence of a suitable photoinitiator (PI) in the photocurable composition. In recent years, dye-based photoinitiating systems have revolutionized and conquered the global market of innovative PIs. Since then, numerous photoinitiators for radical polymerization containing different organic dyes as light absorbers have been proposed. However, despite the large number of initiators designed, this topic is still relevant today. The interest towards dye-based photoinitiating systems continues to gain in importance, which is related to the need for new initiators capable of effectively initiating chain reactions under mild conditions. In this paper we present the most important information about photoinitiated radical polymerization. We describe the main directions for the application of this technique in various areas. Attention is mainly focused on the review of high-performance radical photoinitiators containing different sensitizers. Moreover, we present our latest achievements in the field of modern dye-based photoinitiating systems for the radical polymerization of acrylates.

Novel Peroxide-Free redox initiator based on Saccharin/Electron Donor/Copper salt for radical polymerization

In this work, a peroxide-free redox initiating system for radical polymerization of acrylate is suggested, based on the combination of saccharin, aromatic amine and copper salt. Free radical redox polymerization was investigated through differential scanning calorimetry (DSC), highlighting the efficiency of the redox initiating system. The role of the different components was studied mainly through liquid chromatography-coupled mass spectrometry (LC-MS), evidencing the involvement of aminoalkyl radical as initiating species. When p-toluenesulfonate is added as accelerator, the corresponding radical, as well as the oxygenated derived one, were found to act also as initiating radical. The oxidation state of the copper catalyst during the reaction is studied by UV–visible spectroscopy experiments, using bathophenanthroline as a probe for the involvement of Cu(I). From these experiments, a mechanism is proposed to account for the initiation reaction.

Preparation of cationic polyacrylate W/O crude oil emulsion demulsifier by free‐radical solution polymerization

AbstractThe block polyether demulsifier prepared by ring‐opening polymerization of ethylene oxide and propylene oxide under high temperature and high pressure is the most widely used demulsifier for water in crude oil emulsion. It has the high synthesis risk and cost. Therefore, the development of non‐block polyether demulsifier has attracted more and more attention. In this article, a new type of demulsifier was sythesized by radical polymerization of acrylate and cationic monomer. It was found that the copolymer PMA‐co‐PDBC of methyl acrylate (MA) and benzyldimethyl [2‐[(1‐oxoallyl)oxy] ethyl] ammonium chloride (DBC) synthesized in the mixed solvent of dipropylene glycol methyl ether and water had a good performance. When dosage of PMA‐co‐PDBC was 200 mg/L, the dehydration rate of water in crude oil emulsion with 50% water content can reach 80% at 80°C within 4 h. Structural and interface properties analysis presented that PMA‐co‐PDBC had a microblock structure similar with block polyether and it can effectively reduce the strength of W/O interfacial film to realize the demulsification. Although the demulsification performance of PMA‐co‐PDBC was not better than block polyether, its preparation safety and cost are much better. The results of this article can provide a new option for the development of crude oil demulsifier.

Measurement and Modeling of Methyl Acrylate Radical Polymerization in Polar and Nonpolar Solvents

Measurement and Modeling of Methyl Acrylate Radical Polymerization in Polar and Nonpolar Solvents

Chemical engineering around the 5,12-dihydroindolo[3,2-a]carbazole scaffold: Fine tuning of the optical properties of visible light photoinitiators of polymerization

5,12-Dihydroindolo[3,2-a]carbazole is a promising scaffold for the design of visible light photoinitiators of polymerization due to the simultaneous presence of two carbazole moieties that can be differently functionalized. Notably, redshift of the absorption spectra can be facilely obtained by nitration of one of the two carbazoles, the second carbazole group being functionalized with various groups. Dinitration of 5,12-dihydroindolo[3,2-a]carbazole is another efficient approach for designing dyes with strong absorptions extending over the visible range. In this work, a series of 36 compounds never reported in the literature and differing by the substitution pattern have been designed and synthesized. Notably, the possibility to design push–pull dyes by Knoevenagel and Claisen Schmidt reactions, to introduce electroactive groups such as thiophene by Suzuki cross-coupling reactions or to design water soluble chromophore has been explored. To evidence the interest of these structures, photopolymerization experiments have been carried out at 405 nm and the polymerization of acrylates has been examined in thick and thin films. To support the polymerization efficiency, mechanisms involved in the free radical polymerization of acrylates have been established by the combination of various techniques including UV–visible absorption and fluorescence spectroscopy, cyclic voltammetry and photolysis experiments.

Novel chalcone-based phenothiazine derivative photoinitiators for visible light induced photopolymerization with photobleaching and good biocompatibility

Two novel visible light photoinitiators 4-(10-methyl-10H-phenothiazin-3-yl) but-3-en-2-one (PBO) and (1E,4E)-1,5-bis(10-methyl-10H-phenothiazin-3-yl)-1,4-pentadien-3-one (BMPPO) were successfully designed and synthesized. PBO and BMPPO have broad absorption range from 350 to 500 nm with the maximum absorption wavelength at 400 nm and 440 nm respectively. Three-component photoinitiating system of BMPPO/iodonium/amine was developed for free radical polymerization of acrylates. The results demonstrated that the photoinitiating system displayed rapid polymerization and high final vinyl group conversions under the irradiation of UV-LED (365 nm), blue LED (440) nm and solar light resource. Moreover, photopolymerization kinetics was studied by real-time FT-IR spectrum, the double band conversion was achieved up to 90% for BMPPO. The photocuring mechanism was identified via steady state photolysis and electron spin resonance spin-trapping experiments. The possible photoinduced mechanism of PBO and BMPPO in the presence of a co-initiator occurred through electron transfer. In addition, BMPPO possesses rapid photobleaching and good biocompatibility performance tested by photoinduced degradation and cytotoxicity experiments respectively, which exhibited that BMPPO has potential for light-color coatings and food packaging field.

Liquid Crystalline Elastomers Based on Click Chemistry.

Liquid crystalline elastomers (LCEs) have emerged as an important class of functional materials that are suitable for a wide range of applications, such as sensors, actuators, and soft robotics. The unique properties of LCEs originate from the combination between liquid crystal and elastomeric network. The control of macroscopic liquid crystalline orientation and network structure is crucial to realizing the useful functionalities of LCEs. A variety of chemistries have been developed to fabricate LCEs, including hydrosilylation, free radical polymerization of acrylate, and polyaddition of epoxy and carboxylic acid. Over the past few years, the use of click chemistry has become a more robust and energy-efficient way to construct LCEs with desired structures. This article provides an overview of emerging LCEs based on click chemistries, including aza-Michael addition between amine and acrylate, radical-mediated thiol-ene and thiol-yne reactions, base-catalyzed thiol-acrylate and thiol-epoxy reactions, copper-catalyzed azide-alkyne cycloaddition, and Diels-Alder cycloaddition. The similarities and differences of these reactions are discussed, with particular attention focused on the strengths and limitations of each reaction for the preparation of LCEs with controlled structures and orientations. The compatibility of these reactions with the traditional and emerging processing techniques, such as surface alignment and additive manufacturing, are surveyed. Finally, the challenges and opportunities of using click chemistry for the design of LCEs with advanced functionalities and applications are discussed.

Sunlight Induced Polymerization Photoinitiated by Novel Push–Pull Dyes: Indane‐1,3‐Dione, 1H‐Cyclopenta[b]Naphthalene‐1,3(2H)‐Dione and 4‐Dimethoxyphenyl‐1‐Allylidene Derivatives

AbstractThe free radical polymerization of acrylates photo‐initiated by push–pull dye‐based photoinitiating systems (PISs) is widely investigated in previous works. As a supplementary investigation on push–pull dyes, here in this article, 25 push–pull structures comprising electron acceptors derived from indane‐1,3‐dione and 1H‐cyclopenta[b]naphthalene‐1,3(2H)‐dione (series 1) and 4‐dimethoxyphenyl‐1‐allylidene moieties (series 2) and various electron donors are synthesized and examined as innovative structures for photoinitiation. Among the two series of dyes examined in this work and by monitoring the polymerization processes by RT‐FTIR measurements, four dyes are determined as exhibiting excellent photoinitiation performances and these dyes are selected to perform further studies concerning the chemical mechanisms occurring inside the three‐component PISs, for example, steady state photolysis, fluorescence quenching measurements, and cyclic voltammetry. Markedly, their reactivity is also proved by photoinitiation performance upon sunlight. These results prompt us to develop high performance push–pull dyes as photosensitizers and sunlight can be used as a mild and ecofriendly light source, which can advantageously replace LEDs for the free radical photopolymerization in the future. Finally, the formation of 3D patterns with an excellent gradient of resolution is successfully achieved by the direct laser write (DLW) with/without silica fillers.

Novel photoinitiators based on difluoroborate complexes of squaraine dyes for radical polymerization of acrylates upon visible light

The present article describes the efficiency of novel two-component photoinitiators based on a typical squaraine dye and its difluoroborate analogues for the radical polymerization of acrylate monomers.

Recent progress in the development of highly active dyeing photoinitiators based on 1,3-bis(p-substituted phenylamino)squaraines for radical polymerization of acrylates

Squaraines are an important and very interesting group of organic functional dyes because of their unique physicochemical properties. These compounds have found many applications in different areas of science and technique.

High-Performance UV-Vis Light Induces Radical Photopolymerization Using Novel 2-Aminobenzothiazole-Based Photosensitizers.

The popularity of using the photopolymerization reactions in various areas of science and technique is constantly gaining importance. Light-induced photopolymerization is the basic process for the production of various polymeric materials. The key role in the polymerization reaction is the photoinitiator. The huge demand for radical and cationic initiators results from the dynamic development of the medical sector, and the optoelectronic, paints, coatings, varnishes and adhesives industries. For this reason, we dealt with the subject of designing new, highly-efficient radical photoinitiators. This paper describes novel photoinitiating systems operating in UV-Vis light for radical polymerization of acrylates. The proposed photoinitiators are composed of squaraine (SQ) as a light absorber and various diphenyliodonium (Iod) salts as co-initiators. The kinetic parameters of radical polymerization of trimethylolpropane triacrylate (TMPTA), such as the degree of double bonds conversion (C%), the rate of photopolymerization (Rp), as well as the photoinitiation index (Ip) were calculated. It was found that 2-aminobenzothiazole derivatives in the presence of iodonium salts effectively initiated the polymerization of TMPTA. The rates of polymerization were at about 2 × 10−2 s−1 and the degree of conversion of acrylate groups from 10% to 36% were observed. The values of the photoinitiating indexes for the most optimal initiator concentration, i.e., 5 × 10−3 M were in the range from 1 × 10−3 s−2 even to above 9 × 10−3 s−2. The photoinitiating efficiency of new radical initiators depends on the concentration and chemical structure of used photoinitiator. The role of squaraine-based photoinitiating systems as effective dyeing photoinitiators for radical polymerization is highlighted in this article.

The new LED-Sensitive photoinitiators of Polymerization: Copper complexes in free radical and cationic photoinitiating systems and application in 3D printing

A ligand (A1) and four copper complexes (Cu1, Cu2, Cu3 and Cu4) were examined as photosensitizers in various photoinitiating systems (PISs). Interestingly, excellent photochemical reactivities were determined with the different compounds. Especially, notable photoinitiation abilities were determined upon exposure to LED@405 nm during the free radical polymerization of acrylates and the cationic polymerization of epoxides when combined with an iodonium salt and an amine. With regards to their remarkable reactivities, the different photoinitiating systems were applied to 3D printing experiments. By combining steady state photolysis and electron spin resonance spin trapping, the chemical mechanism supporting the polymerization processes could be fully detailed and proved. Among all PISs studied, the three-component PISs furnished the best monomer conversions during the free radical polymerization of trimethylolpropane triacrylate (TMPTA) and the cationic polymerization of (3,4-epoxycyclohexane)methyl 3,4-epoxycyclohexylcarboxylate (EPOX) monomers. The conversion process was monitored by real-time Fourier transform infrared spectroscopy (RT-FTIR). Three-component PISs based on A1, Cu1 and Cu2 showed better performances than those based on Cu3, Cu4 and the different two-component PIS (comprising only the iodonium salt or the amine) in FRP experiments. Based on the outstanding photoinitiation abilities of A1 and Cu1 with both TMPTA and EPOX, smooth and regular 3D patterns could be obtained by direct laser write experiments by generating interpenetrating polymer networks (IPN) with the blend of these two monomers.

5,12-Dihydroindolo[3,2-a]carbazole: A promising scaffold for the design of visible light photoinitiators of polymerization

5,12-Dihydroindolo[3,2-a]carbazole is a polycyclic structure combining in its scaffold two carbazole moieties sharing a fused aromatic ring. Since the pioneering works reported in 2019 on this structure concerning the substitution of the two carbazoles by similar functional groups, no recent investigation has been devoted to asymmetrize the substitution of the two carbazoles. In this work, a series of 13 compounds based on the 5,12-dihydroindolo[3,2-a]carbazole scaffold is presented. By carefully controlling the reaction conditions, functional groups such as a formyl, a nitro or an acetyl group could be selectively introduced on one of the two carbazoles. By combining X-ray diffraction and 2D NMR experiments, the higher reactivity of one of the two carbazoles could be clearly evidenced, enabling to generate asymmetrically substituted structures. Thanks to this unprecedented approach on the 5,12-dihydroindolo[3,2-a]carbazole scaffold, the absorption of the resulting dyes could be shifted towards the visible range whereas the parent structure (5,12-dihexyl-6,7-diphenyl-5,12-dihydroindolo[3,2-a]carbazole) exhibits a strongly UV-centered absorption. In light of their visible light absorption properties, several dyes have been examined as photoinitiators of polymerization activable at 405 nm and under low light intensity in two-component photoinitiating systems for the free radical polymerization of acrylates or the cationic polymerization of epoxides. Chemical mechanisms supporting the different polymerization processes have been fully elucidated by combining several techniques including cyclic voltammetry, UV–visible absorption and photoluminescence spectroscopy as well as photolysis experiments.

Synthesis and radical polymerization of acrylate and methacrylate bearing an isocyanurate core with adamantyl bisurethane moieties

AbstractIn this article, we report the synthesis of acrylate and methacrylate bearing an isocyanurate core with two adamantyl urethane moieties and their radical homo‐ and copolymerization with n‐butyl methacrylate (BMA). The synthesized polyacrylate exhibits higher 5% weight loss and glass transition temperatures (Td5 and Tg) than those of the comparative polyacrylate, synthesized from the isocyanurate‐based acrylate with two hexyl urethane moieties, suggesting that the rigid adamantane core incorporated in the side chains of polymer largely contributes to increase in thermal stability of polymer. Similarly, the obtained copolymers show higher Tg values than that of homopolymer derived from BMA, leading to the synthesized monomers are useful as a comonomer to enhance thermal property of polymer.