Initiation Of Polymerization Research Articles

Polymerisation of cyanoacrylates: The effect of sclero-embolic and contrast agents.

The objective is to investigate the interaction of sclero-embolic and contrast agents with the polymerisation of medical grade n-butyl-cyanoacrylates. An in vitro spectrophotometric absorbance method was developed to detect changes in light transmission to measure n-BCA polymerisation. The initiation and the rate-of-polymerisation of mixtures of n-BCA with sclero-embolic and contrast agents were investigated. Initiation of polymerisation: VENABLOCK™ and HISTOACRYL® were the fastest agents to polymerise, while VENASEAL™ was the slowest. Rate of polymerisation: Hypertonic saline inhibited the polymerisation of all n-BCAs, while hypertonic glucose prolonged the polymerisation rate. ETHANOL and detergent sclerosants had no effect. Contrast agents OMNIPAQUE™ and ULTRAVIST® initiated and prolonged the polymerisation of n-BCA, but in contrast, LIPIODOL® failed to initiate the process. The commercially available medical cyanoacrylates differ in their polymerisation rates. These polymerisation rates are further affected when these products are used in conjunction with other compounds, such as sclero-embolic and contrast agents.

Zinc Complexes Containing Substituted 1,10-Phenanthrolines as Ligands: Synthesis, Structure and Application as Initiators of ε-Caprolactone, Rac- and L-Lactides Polymerization

Zinc Complexes Containing Substituted 1,10-Phenanthrolines as Ligands: Synthesis, Structure and Application as Initiators of ε-Caprolactone, Rac- and L-Lactides Polymerization

Heterotelechelic Silicones: Facile Synthesis and Functionalization Using Silane-Based Initiators.

The synthetic utility of heterotelechelic polydimethylsiloxane (PDMS) derivatives is limited due to challenges in preparing materials with high chain-end fidelity. In this study, anionic ring-opening polymerization (AROP) of hexamethylcyclotrisiloxane (D3) monomers using a specifically designed silyl hydride (Si-H)-based initiator provides a versatile approach toward a library of heterotelechelic PDMS polymers. A novel initiator, where the Si-H terminal group is connected to a C atom (H-Si-C) and not an O atom (H-Si-O) as in traditional systems, suppresses intermolecular transfer of the Si-H group, leading to heterotelechelic PDMS derivatives with a high degree of control over chain ends. In situ termination of the D3 propagating chain end with commercially available chlorosilanes (alkyl chlorides, methacrylates, and norbornenes) yields an array of chain-end-functionalized PDMS derivatives. This diversity can be further increased by hydrosilylation with functionalized alkenes (alcohols, esters, and epoxides) to generate a library of heterotelechelic PDMS polymers. Due to the living nature of ring-opening polymerization and efficient initiation, narrow-dispersity (Đ < 1.2) polymers spanning a wide range of molar masses (2-11 kg mol-1) were synthesized. With facile access to α-Si-H and ω-norbornene functionalized PDMS macromonomers (H-PDMS-Nb), the synthesis of well-defined supersoft (G' = 30 kPa) PDMS bottlebrush networks, which are difficult to prepare using established strategies, was demonstrated.

Advances in cyclic ester ring‐opening polymerization using heterogeneous catalysts

Aliphatic polyesters' propensity to be biocompatible and biodegradable, as well as their prospective applications in the medical and agricultural industries, has prompted much research into their synthesis. As ring‐opening polymerization (ROP) technology has advanced rapidly, the invention of discrete, thoroughly characterized heterogeneous catalysts, which are potent polymerization initiators for ROP, has received much attention during the last decade. Numerous polyester microstructures have been produced because of recent developments in the catalyst design of new heterogeneous catalysts and applied in initiating the ROP of cyclic esters. This study reviewed the ROP of cyclic ester catalysts composed of a heterogenous catalyst such as metal–organic frameworks (MOFs) and supported catalyst. MOFs are crystalline porous materials with tunable frameworks that make them potential mediums for polymerization. The MOF structure's precise design is important to control polymerizations because it provides control over both primary and higher‐order structures. Additionally, the stability of the heterogeneous catalyst is also discussed. Finally, the conclusion to the previous study and a stance for future prospects is given. This article intends to provide valuable information for building a heterogeneous catalyst for the ROP of cyclic esters with enhanced activity.

Versatile synthesis of siloxane‐based graft copolymers with tunable grafting density

AbstractA versatile synthetic platform is reported that affords high molecular weight graft copolymers containing polydimethylsiloxane (PDMS) backbones and vinyl‐based polymer side chains with excellent control over molecular weight and grafting density. The synthetic approach leverages thiol‐ene click chemistry to attach an atom‐transfer radical polymerization (ATRP) initiator to a variety of commercially available poly(dimethylsiloxane‐co‐methylvinylsiloxane) backbones (PDMS‐co‐PVMS), followed by controlled radical polymerization with a wide scope of vinyl monomers. Selective degradation of the siloxane backbone with tetrabutylammonium fluoride confirmed the controlled nature of side‐chain growth via ATRP, yielding targeted side‐chain lengths for copolymers containing up to 50% grafting density and overall molecular weights in excess of 1 MDa. In addition, by using a mixture of thiols, grafting density and functionality can be further controlled by tuning initiator loading along the backbone. For example, solid‐state fluorescence of the graft copolymers was achieved by incorporating a thiol‐containing fluorophore along the siloxane backbone during the thiol‐ene click reaction. This simple synthetic platform provides facile control over the properties of a wide variety of grafted copolymers containing flexible PDMS backbones and vinyl polymer side chains.

Synthesis and applications of a Y‐inimer with two orthogonal controlled free radical polymerization initiators

AbstractWe report the synthesis of a Y‐shaped inimer that contains two orthogonal initiators for ATRP and NMP. The inimer is synthesized through a one‐pot multi‐component reaction that vastly simplifies the typically cumbersome synthesis of similar compounds. The Y‐inimer has the versatility to be homopolymerized into a backbone for A/B Janus bottlebrush synthesis or copolymerized with glycidyl methacrylate (GMA) and cross‐linked into an ultra‐thin coating for mixed A/B brush growth from planar surfaces. Importantly, the Y‐shaped nature of the inimer ensures growth of A and B brushes are consistently in a 1:1 ratio. We demonstrate the application of the Y‐inimer in the synthesis of a PMMA/PS Janus bottlebrush as well as two different mixed A/B polymer brushes, one with the ability to microphase separate, and a second mixed polyelectrolyte brush with opposite charges. The inimer is compatible with various A/B monomer systems and offers a universal approach to the “grafting‐from” polymerization of dual vinyl polymer side chains. This study provides a unique way of utilizing multi‐component reactions in polymer chemistry to access complex functional architectures.

Rapidly Synthesized Single‐Ion Conductive Hydrogel Electrolyte for High‐Performance Quasi‐Solid‐State Zinc‐ion Batteries

AbstractSingle‐ion conductive electrolytes can largely eliminate electrode polarization, reduce the proportion of anion migration and inhibit side reactions in batteries. However, they usually suffer from insufficient ion conductivity due to the strong interaction between cations and cationic receptors. Here we report an ultrafast light‐responsive covalent organic frameworks (COF) with sulfonic acid groups modification as the acrylamide polymerization initiator. Benefiting from the reduced electrostatic interaction between Zn2+ and sulfonic acid groups through solvation effects, the as‐prepared COF‐based hydrogel electrolyte (TCOF‐S‐Gel) receives an ion conductivity of up to 27.2 mS/cm and Zn2+ transference number of up to 0.89. In addition, sufficient hydrogen bonds endow the single‐ion conductive TCOF‐S‐Gel electrolyte to have good water retention and superb mechanical properties. The assembled Zn||TCOF‐S‐Gel||MnO2 full zinc‐ion battery exhibits high discharge capacity (248 mAh/g at 1C), excellent rate capability (90 mAh/g at 10C) and superior cycling performance. These enviable results enlist the instantaneously photocured TCOF‐S‐Gel electrolyte to be qualified to large‐scaled flexible high‐performance quasi‐solid‐state zinc‐ion batteries.

Rapidly Synthesized Single-Ion Conductive Hydrogel Electrolyte for High-Performance Quasi-Solid-State Zinc-ion Batteries.

Single-ion conductive electrolytes can largely eliminate electrode polarization, reduce the proportion of anion migration and inhibit side reactions in batteries. However, they usually suffer from insufficient ion conductivity due to the strong interaction between cations and cationic receptors. Here we report an ultrafast light-responsive covalent organic frameworks (COF) with sulfonic acid groups modification as the acrylamide polymerization initiator. Benefiting from the reduced electrostatic interaction between Zn2+ and sulfonic acid groups through solvation effects, the as-prepared COF-based hydrogel electrolyte (TCOF-S-Gel) receives an ion conductivity of up to 27.2 mS/cm and Zn2+ transference number of up to 0.89. In addition, sufficient hydrogen bonds endow the single-ion conductive TCOF-S-Gel electrolyte to have good water retention and superb mechanical properties. The assembled Zn||TCOF-S-Gel||MnO2 full zinc-ion battery exhibits high discharge capacity (248 mAh/g at 1C), excellent rate capability (90 mAh/g at 10C) and superior cycling performance. These enviable results enlist the instantaneously photocured TCOF-S-Gel electrolyte to be qualified to large-scaled flexible high-performance quasi-solid-state zinc-ion batteries.

First-Row d6 Metal Complex Enables Photon Upconversion and Initiates Blue Light-Dependent Polymerization with Red Light.

Photosensitizers for sensitized triplet-triplet annihilation upconversion (sTTA-UC) often rely on precious heavy metals, whereas coordination complexes based on abundant first-row transition metals are less common. This is mainly because long-lived triplet excited states are more difficult to obtain for 3d metals, particularly when the d-subshell is only partially filled. Here, we report the first example of sTTA-UC based on a 3d6 metal photosensitizer yielding an upconversion performance competitive with precious metal-based analogues. Using a newly developed Cr0 photosensitizer featuring equally good photophysical properties as an OsII benchmark complex in combination with an acetylene-decorated anthracene annihilator, red-to-blue upconversion is achievable. The upconversion efficiency under optimized conditions is 1.8 %, and the excitation power density threshold to reach the strong annihilation limit is 5.9 W/cm2 . These performance factors, along with high photostability, permit the initiation of acrylamide polymerization by red light, based on radiative energy transfer between delayed annihilator fluorescence and a blue light absorbing photo-initiator. Our study provides the proof-of-concept for photon upconversion with elusive first-row analogues of widely employed precious d6 metal photosensitizers, and for their application in photochemical reactions triggered by excitation wavelengths close to near-infrared.

Transitioning from Photoinitiation to Thermal Initiation in RAFT Dispersion Polymerization via a Small Modification of the Macro-RAFT Agent: A Scalable Approach for Monodisperse Surface-Functional Polymeric Microspheres

Transitioning from Photoinitiation to Thermal Initiation in RAFT Dispersion Polymerization via a Small Modification of the Macro-RAFT Agent: A Scalable Approach for Monodisperse Surface-Functional Polymeric Microspheres

Bifunctional Carbanionic Synthesis of Fully Bio-Based Triblock Structures Derived from β-Farnesene and ll-Dilactide: Thermoplastic Elastomers.

Current environmental challenges and the shrinking fossil-fuel feedstock are important criteria for the next generation of polymer materials. In this context, we present a fully bio-based material, which shows promise as a thermoplastic elastomer (TPE). Due to the use of β-farnesene and L-lactide as monomers, bio-based feedstocks, namely sugar cane and corn, can be used. A bifunctional initiator for the carbanionic polymerization was employed, to permit an efficient synthesis of ABA-type block structures. In addition, the "green" solvent MTBE (methyl tert-butyl ether) was used for the anionic polymerisation, enabling excellent solubility of the bifunctional anionic initiator. This afforded low dispersity (Đ=1.07 to 1.10) and telechelic polyfarnesene macroinitiators. These were employed for lactide polymerization to obtain H-shaped triblock copolymers. TEM and SAXS revealed clearly phase-separated morphologies, and tensile tests demonstrated elastic mechanical properties. The materials featured two glass transition temperatures, at - 66 °C and 51 °C as well as gyroid or cylindrical morphologies, resulting in soft elastic materials at room temperature.

Coordination of ε-Caprolactone to a Cationic Niobium(V) Alkoxide Complex: Fundamental Insight into Ring-Opening Polymerization via Coordination-Insertion.

We report three niobium-based initiators for the catalytic ring-opening polymerization (ROP) of ε-caprolactone, exhibiting good activity and molecular weight control. In particular, we have prepared on the gram-scale and fully characterized a monometallic cationic alkoxo-Nb(V) ε-caprolactone adduct representing, to the best of our knowledge, an unprecedented example of a metal complex with an intact lactone monomer and a functional ROP-initiating group simultaneously coordinated at the metal center. At 80 °C, all three systems initiate the immortal solution-state ROP of ε-caprolactone via a coordination-insertion mechanism, which has been confirmed through experimental studies, and is supported by computational data. Natural bond orbital calculations further indicate that polymerization may necessitate isomerization about the metal center between the alkoxide chain and the coordinated monomer. The observations made in this work are expected to inform mechanistic understanding both of amine tris(phenolate)-supported metal alkoxide ROP initiators, including various highly stereoselective systems for the polymerization of lactides and of coordination-insertion-type ROP protocols more broadly.

New substituted pentazadienes as initiators of free-radical polymerization: synthesis, photochemical properties and perspectives for holographic media

The series of 4,4′-substituted 3-hydroxyethyl-pentaza-1,4-dienes were synthesized in the reaction of aromatic diazonium salts with an ethanol amine. Photolysis of pentaza-1,4-dienes was investigated by means of UV/Vis spectroscopy. Electron donating methyl and methoxy substituents were found to increase photosensitivity whereas electron withdrawing chloro-substituents cause higher photolytic stability. 3-hydroxyethyl-pentaza-1,4-dienes as a radical polymerization initiator has been successfully investigated in 10% methyl methacrylate solution in DMF. Gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) were used for obtained polymers characteristics evaluation. The highest values of PMMA Mn and Đ can be obtained in the case of chloro-substituted derivative. The holograms of a plane wavefront were recorded in media based on obtained PMMA doped by azo-dye by a 532 nm laser in a ∼1-μm-thick sample. The diffraction efficiency values for parallel polarized acting light increased in Cl→Me→OMe series.

First‐Row d6 Metal Complex Enables Photon Upconversion and Initiates Blue Light‐Dependent Polymerization with Red Light

Photosensitizers for sensitized triplet‐triplet annihilation upconversion (sTTA‐UC) often rely on precious heavy metals, whereas coordination complexes based on abundant first‐row transition metals are less common. This is mainly because long‐lived triplet excited states are more difficult to obtain for 3d metals, particularly when the d‐subshell is only partially filled. Here, we report the first example of sTTA‐UC based on a 3d6 metal photosensitizer yielding an upconversion performance competitive with precious metal‐based analogues. Using a newly developed Cr(0) photosensitizer featuring equally good photophysical properties as an Os(II) benchmark complex in combination with an acetylene‐decorated anthracene annihilator, red‐to‐blue upconversion is achievable. The upconversion efficiency under optimized conditions is 1.8%, and the excitation power density threshold to reach the strong annihilation limit is 5.9 W/cm2. These performance factors, along with high photostability, permit the initiation of acrylamide polymerization by red light, based on radiative energy transfer between delayed annihilator fluorescence and a blue light absorbing photo‐initiator. Our study provides the proof‐of‐concept for photon upconversion with elusive first‐row analogues of widely employed precious d6 metal photosensitizers, and for their application in photochemical reactions triggered by excitation wavelengths close to near‐infrared.

Improvement of osmosis performance by n-hexane rinse: A missing parameter when developing thin film composite membrane

The development of thin film composite (TFC) membrane is restricted by the inherent permeability/selectivity trade-off. Comprehensive attempts have been made to break the restriction. The n-hexane rinse, conducted following the initial interfacial polymerization (IP) process of the active layer, represents an overlooked parameter in conventional membrane preparation methodologies. This study investigated the influences of the n-hexane rinse on the formation, morphology and surface chemistry of the active layer. The transport property and osmosis performance of the TFC membrane were evaluated. The water flux of the membrane rinsed by n-hexane increased by 25.5 % without scarifying the selectivity in the forward osmosis (FO) mode. The simple method effectively improved the perm-selectivity of the TFC membrane.

Bifunktionelle carbanionische Synthese vollständig biobasierter Triblock‐Copolymere aus β‐Farnesen und LL‐Dilactid: Thermoplastische Elastomere

AbstractAktuelle ökologische Herausforderungen und die Endlichkeit fossiler Rohstoffe sind wichtige Kriterien, welche für die nächste Generation von Polymermaterialien eine zentrale Rolle spielen. In diesem Zusammenhang wird ein vollständig biobasiertes Material mit potenzieller Anwendung als thermoplastisches Elastomer (TPE) vorgestellt. Durch die Verwendung der Monomere β‐Farnesen und l‐Lactid können biobasierte Rohstoffe wie Zuckerrohr und Mais verwendet werden. Für die carbanionische Polymerisation wurde ein bifunktioneller Initiator eingesetzt, um eine effiziente Synthese von ABA‐artigen Blockstrukturen zu ermöglichen. Zusätzlich kam das potenziell nachhaltige Lösungsmittel MTBE (Methyl‐tert‐butylether) zum Einsatz, da es eine hervorragende Löslichkeit des bifunktionellen Initiators gewährleistet. Dies ermöglichte die Herstellung von telechelen Polyfarnesen‐Makroinitiatoren mit niedrigen Dispersitäten (Đ=1.07 bis 1.10). Diese wurden anschließend für die Lactidpolymerisation verwendet, um H‐förmige Triblockcopolymere zu erhalten. TEM und SAXS‐Messungen zeigten deutlich phasengetrennte Morphologien, und mittels Zugversuche konnten elastische Eigenschaften nachgewiesen werden. Die Triblockstrukturen weisen jeweils zwei Glasübergangstemperaturen bei −66 °C und 51 °C sowie gyroide oder zylindrische Morphologien auf, was bei Raumtemperatur zu weichelastischen Materialien führt.

Overview of Butadiene Chemical Reaction Fouling in Steam Crackers and Its Control by Carbon Steel Surface Modification

The main objective of the Steam Cracker is to produce monomers prone to polymerization. The drawback is that polymerization can occur in the Steam Cracker itself. The main monomers fouling precursor is Butadiene. All along the separation process, Butadiene concentration and process temperature change. This implies step changes in polymer structure and fouling level. Several techniques are used to control this fouling, including oxygen ingress control, the use of additives such as antioxidants and free radical scavengers. By a catalytic effect, the metal surfaces can also be a polymerization initiator. The objective of passivation is to modify the Carbon Steel surface into stable magnetite and maghemite. Using electrochemistry to characterize different Carbon Steel samples, we were able to improve our passivation procedure. And when applying metal passivation, we were able to increase run length of Depropanizer reboilers limiting the fouling rate and its impact on operation.

Synthesis, Performance and Mechanism of an Anionic Scale Inhibitor in a Salt System

AbstractA novel non‐phosphorus and non‐nitrogen scale inhibitor IA‐HEMA was synthesized in the presence of only C, H and O using itaconic acid (IA) and 2‐hydroxyethyl methacrylate (HEMA) as the raw materials and hydrogen peroxide‐ascorbic acid (H2O2‐ASA) as the initiating system. The synthesis conditions were optimized with the response surface method (RSM). The results indicated that the material ratio had the largest effect on the scale inhibition rate, followed by initiator dosage, polymerization temperature and polymerization time successively. As demonstrated by the static scale inhibition experiment, the scale inhibition rate was 97.27 % when the IA‐HEMA concentration was 100 mg/L. The mechanism was explored by molecular dynamics (MD). The results indicated that IA‐HEMA was able to overcome its own distortion and adsorb on the crystal surface, and the scale inhibition performance was related to its chelating and lattice‐distortion ability, which effectively inhibited the formation and precipitation of scale. All these findings suggest that IA‐HEMA is a quite promising environmentally friendly scale inhibitor in the salt system.

Compressible, anti-freezing, and ionic conductive cellulose/polyacrylic acid composite hydrogel prepared via AlCl3/ZnCl2 aqueous system as solvent and catalyst

From the perspective of environmental sustainability, introducing cellulose into ionic conductive hydrogel is an inevitable trend for the development of flexible conductive materials. We report a double-network cellulose/polyacrylic acid (Cel/PAA) composite hydrogel based on the dissolving of cellulose by AlCl3/ZnCl2 aqueous system. The Cel/PAA composite hydrogel consists of rigid cellulose chains and flexible polyacrylic acid, which synergistically realize the improvement of the mechanical properties. The AlCl3/ZnCl2 aqueous system not only serves as the green solvent for cellulose, but also the Al3+ and Zn2+ metal ions can be served as a catalyst to activate the initiator for polymerization of acrylic acid. Compared with pure cellulose hydrogel, the compression strain of the Cel/PAA composite hydrogel was significantly improved to 80 %, and its conductivity increased by 28.1 %. In addition, its compression stress was enhanced over 2 times than pure PAA hydrogel. The Cel/PAA composite hydrogel exhibits excellent anti-freezing (−45 °C), weight retention (90 %), and conductivity (2.70 S/m) properties, still maintaining transparency and storage stability in the extreme environment. This work presents a facile strategy to develop an ionic conductive cellulose-based composite hydrogel with good conductivity and mechanical properties, which shows potential for the application fields of flexible sensors and 3D-printing functional materials.

On the benefits of vegetable oil addition for the pore structure and acid resistance of alkali-activated systems

The impact of high additions of vegetable oil (12 vol%) on the mechanical and microstructural properties of metakaolin-slag-based alkali-activated materials (AAMs) was studied. The addition of oil resulted in a slight decrease in initial polymerization kinetics but did not affect the final degree of reaction. AAM-oil-composite-mortars exhibited approximately ∼30% lower compressive strength primarily due to the entrainment of air voids. Newly formed soap phases significantly reduced the volume of small capillary and gel pores (pore radii <15 nm), leading to a decrease in specific inner surface area by a factor of up to 15. The porosity modification induced by the oil addition greatly enhanced the resistance of AAMs against sulfuric acid attack, shifting the dominant processes from diffusion and cracks to framework-dissolution controlled by the inherent phase stabilities. Following the immersion in sulfuric acid (pHstat = 2) for 8 weeks, the depth of corroded layer decreased by 70% and no cracks due to expansive phases were observed. These promising findings suggest that the incorporation of vegetable oil in AAMs has the potential to address durability concerns associated with diffusion-based corrosion processes, thereby expanding the range of future applications.