Polymerization Of Vinyl Monomers Research Articles

Toughening of alicyclic epoxy resin by in situ polymerization of modifier vinyl monomers using alkylborane as a radical initiator

AbstractIn this study, we attempted to improve the toughness of alicyclic epoxy cured resin using a vinyl polymer as a modifier which was generated with alkylborane as a radical initiator in parallel with the curing of the resin. Alkylborane has the ability to initiate radical polymerization around room temperature in the presence of oxygen, and the use of diethylmethoxyborane (DEMB) instead of a conventional peroxide radical initiator (DBPC) was found to allow copolymerization of styrene (St) and N‐phenylmaleimide (NPMI) in an alicyclic epoxy resin in the early stage of the multistep curing. As a result, only when DEMB was used as an initiator, a cured product with a phase‐separated structure at which ca. 50–100 nm St/NPMI copolymer phases were dispersed was obtained. The fracture toughness (KIC) of the modified cured resin with DEMB was 0.77 MN/m3/2, which was 30% higher than that of the modified resin with DBPC. Furthermore, the glass transition temperature of the modified cured resin with DEMB reached 247°C, which was 87 and 63°C higher than the unmodified rein and the modified resin with DBPC, respectively, since DEMB acted as a Lewis acid to promote cationic polymerization of the alicyclic epoxy resin.

New Approaches to the Synthesis and Stabilization of Polymer Microspheres with a Narrow Size Distribution.

This article presents the results of investigations on heterophase polymerization of vinyl monomers in the presence of organosilicon compounds of different structures. On the basis of the detailed study of the kinetic and topochemical regularities of the heterophase polymerization of vinyl monomers, the conditions for the synthesis of polymer suspensions with a narrow particle-size distribution using a one-step method have been determined.

Benzylsilane-metal alkoxide initiator systems for anionic polymerization of vinyl monomers

Benzylsilane-metal alkoxide initiator systems for anionic polymerization of vinyl monomers

From Glow to Growth: Chemiluminescence Induced Cationic Polymerization Using Ferrocenium Salt

AbstractChemiluminescence (CL) has recently emerged as a novel light source for triggering various photoreactions with appealing features such as the elimination of continuous power supply and complex instrumentation. Here, CL‐induced cationic photopolymerization using ferrocenium salts as unimolecular photoinitiators is reported. The ferrocenium salts, facilely synthesized via ligand exchange reactions, absorb the visible light emitted from CL reactions and generate Lewis acids capable of initiating the cationic polymerization of oxirane and vinyl monomers. The presented method can be applied to create linear polymer chains and cross‐linked luminescent polymer networks, which have significant potential in the fabrication of new polymeric materials and various bioapplications.

Macro peroxide initiators based on autoxidized unsaturated plant oils: Block/graft copolymer conjugates for nanotechnology and biomedical applications

AbstractThe autoxidation of unsaturated fatty acids and their esters is one of the most important reactions in food and biological systems. Autoxidation is a type of reaction between air oxygen and unsaturated plant oils. This reaction starts with a hydrogen abstraction on the methylene group adjacent double bond, leaving a radical onto the carbon atom. Molecular oxygen attacks this radical leading to produce peroxide and hydroperoxide derivatives of the oligomerized unsaturated plant oils. Because peroxide groups thermally cleave to produce free radicals, hydroperoxide derivatives of unsaturated plant oil oligomers can be used in the free radical polymerization of vinyl monomers leading to the related block/graft copolymers. The obtained copolymers combined with the biodegradable natural plant oil gain superior properties such as biodegradability and softness. In this review article, the in vitro autoxidation of well‐known unsaturated plant oils‐soybean oil, linseed oil, and castor oil and some related unsaturated fatty acids‐oleic acid, linoleic acid, and ricinoleic acid was carried out under atmospheric conditions with or without exposing white light. Because the autoxidized unsaturated oil/fatty acids contain peroxide/hydroperoxide groups (they are referred to as macro peroxide initiators) that they are used in the free radical polymerization of vinyl monomers to obtain block/graft copolymers. The improved polymerization conditions, characterization, and applications of the obtained products will be discussed.

Modelling of polymerization kinetics and molar mass development in the nitroxide‐mediated polymerization (NMP) of styrene in supercritical carbon dioxide using the PC‐SAFT equation of state

AbstractA mathematical model for polymerization kinetics and molar mass development in the nitroxide‐mediated polymerization (NMP) of vinyl monomers in supercritical carbon dioxide (scCO2) has been developed. The method of moments is used for molar mass development. The perturbed‐chain statistical associating fluid theory (PC‐SAFT) equation of state is used to estimate the number of stable phases present at equilibrium in the reaction mixture, critical number average chain length at which polymer particles are formed, and monomer concentration in each phase. Pure and binary PC‐SAFT interaction parameters are estimated from liquid–liquid equilibrium (LLE) and liquid–vapour equilibrium (LVE) experimental data at 60 to 129°C. The effect of pressure on monomer conversion and molar mass development in the polymerization of styrene (Sty) using benzoyl peroxide (BPO) and 2,2,6,6‐Tetramethylpiperidinyl‐1‐oxyl (TEMPO) at 120°C and 300–500 bar is studied. It was observed that increasing pressure increases polymerization rate without significantly affecting molar mass development.

SYNTHESIS AND PROPERTIES OF POLYMER SUSPENSIONS OBTAINED BY HETEROPHASE POLYMERIZATION IN THE PRESENCE OF α,ω BIS[3 GLYCIDOXYPROPYL]POLYDIMETHYLSILOXANE

Polymeric microspheres with glycidoxy groups on the surface can be used as bioligand carriers in diagnostic test systems. However, the possibility of synthesizing aggregatively stable functional polymeric microspheres in a wide range of diameters is an urgent problem of modern polymer chemistry. This article is devoted to a systematic study of the kinetics of styrene and methyl methacrylate polymerization in the presence of an organosiloxane surfactant with terminal glycidoxy groups – α,ω-bis[3-glycidoxyproopyl]-polydimethylsiloxane, PDMS(CHOCH2). The article shows the influence of phases volume ratio, initiator and surfactant concentration, synthesis temperature and pH of initial medium on the properties of polymer suspensions (their aggregative stability, monodispersity, particle diameter). The formation of polymer-monomer particles during polymerization has been studied and it has been shown that polymer suspensions retain high aggregation stability from early period of monomer conversion, and the particle diameter changes untill 30% of the monomer conversion. Due to the high surface activity of the organosiloxane surfactant used and its incompatibility with the resulting polymer, aggregatively stable functional polymer suspensions with diameters from 0.09 to 1.1 μm were obtained by a single-stage synthesis. Studies of the hydration degree of polymer microspheres have shown that the presence of functional glycidoxy groups on their surface ensures the formation of a hydration shell, which increases the stability of polymer particles, and also makes it possible to use the resulting microspheres as carriers of bioligands. Thus, the use of water-insoluble organosiloxane surfactants as stabilizers for the heterophase polymerization of vinyl monomers makes it possible to synthesize aggregatively stable functional polymer suspensions in a wide range of diameters. The use of organosiloxane surfactants with various functional groups expands the range of functional polymer microspheres used in various fields of application.

Asymmetric Ion-Pairing in Stereoselective Vinyl Polymerization

Controlling polymer tacticity is a key consideration in macromolecular synthesis due to the impact of stereochemistry on a material’s thermomechanical and optical properties. Recently, inspired by work in small molecule catalysis, asymmetric ion-pairing has emerged as a valuable approach to control the stereochemistry of polymers made through chain growth polymerization of vinyl monomers. This Perspective outlines some of the challenges inherent to polymer stereocontrol as well as highlights recent catalyst development in the area of asymmetric ion-pairing that has enabled control of both the configuration and conformation of vinyl polymers. Several synthetic opportunities and mechanistic questions have been identified that will expand the impact of asymmetric ion-pairing in polymer synthesis.

Coumarinacyl Anilinium Salt: A Versatile Visible and NIR Photoinitiator for Cationic and Step-Growth Polymerizations

A coumarinacyl anilinium (CAA) salt, facilely synthesized via a one-pot reaction, is shown to be a versatile visible and NIR photoinitiator for cationic and step-growth polymerizations. CAA salt exhibits superior photoinitiation performance as compared to commercial iodonium salt in cationic polymerization. Upon visible-light irradiation, this salt undergoes hemolytic and heterolytic cleavage and subsequent electron transfer and hydrogen abstraction reactions, forming reactive species capable of initiating cationic polymerization of epoxides and vinyl monomers. After a short irradiation period, polymerization also proceeds in the dark due to the non-nucleophilic nature of the counteranion. NIR-induced polymerizations were successfully conducted based on upconversion photochemistry. CAA salt can also initiate step-growth polymerization of N-ethyl carbazole (NEC) by oxidation of the monomer by the photochemically formed anilium radical cations. Subsequent proton release and radical coupling reactions essentially yield polycarbazole. CAA salt, featuring straightforward synthesis and long-wavelength sensitivity as well as versatile photoinitiating performance, has great potential in various applications.

Stereoselective Polymerization of Aromatic Vinyl Polar Monomers

AbstractPolar vinyl polymers, a class of polymers with polar groups as side chains, have significant advantages over conventional nonpolar polyolefin materials in terms of viscosity, toughness, interfacial properties (dyeability and printability), and compatibility with solvents or other polymers. Among them, aromatic polar vinyl polymers are of interest because of their good heat resistance properties. In addition, stereoselective polymerization of aromatic polar vinyl monomers has been rapidly developed because the steric structure of the polymer has a significant impact on its physical properties. In this paper, we review the research progress of stereoselective polymerization catalysts for aromatic polar vinyl monomers in recent years, discuss in detail the influence of ligand structure, electronic effect of substituents, spatial site resistance effect, central rare earth metal species and polymerization solvents on the activity and stereoselectivity of polymerization reactions, and explore the possible mechanism of polymerization reaction.

Preparation and Characterization of Cellulose Nanoparticles from Agricultural Wastes and Their Application in Polymer Composites

, Page no - | ABSTRACT | PDF | FULL TEXT | e-PUB Background: The development of innovative eco-sustainable bio-nano-composites materials based on cellulose nanomaterials obtained from agricultural waste such as rapeseed plant straw and polymeric materials with improved properties. At first, cellulose was extracted from rapeseed plant straw and cellulosic and no cellulosic materials were estimated. It was found that the rapeseed plant straw contained about 43.48 wt.% cellulosic materials and 56.52 wt.% no cellulosic materials. It was also found that the rapeseed plant straw content about 34.84 wt.% α- cellulose. Then, nano-cellulose was prepared by acid hydrolysis of α -cellulose obtained from rapeseed plant straw. Poly vinyl acetate (PVAc) was prepared by soap free emulsion polymerization of vinyl monomer. Natural rubber (NR) collected as latex was oxidized by KMnO4. Blends of NR and oxidized NR with PVAc of different compositions such as NR60/PVAc40, NR40/PVAc60, ONR60/PVAc40, ONR40/PVAc60 were prepared by mixing NR latex and PVAc emulsion and followed by drying in an oven at 60°C. Composites of NR60/PVAc40 and ONR60/PVAc40 reinforced nano-cellulose (NC) were also prepared in similar way. The blends and composites were then characterized by FTIR, SEM, and Tensile test (TS). FTIR analysis confirmed the oxidation of NR and shown the variation of the functional groups in the blends and composites compared with the FTIR spectrum of NR, ONR and PVAc. SEM study exhibited that the nano-cellulose were dispersed within NR/PVAc and ONR/PVAc blends matrices with a little agglomeration. The tensile test results showed that the strength in composites was increased due to the reinforcing effect of nano-cellulose (NC). Objectives: The aim of this study is to assess the Preparation and characterization of binary blends of NR and oxidized NR with PVAc. Methods: This is an observational study. The study used to be carried out in the admitted patient’s Department of Applied Chemistry and Chemical Engineering, Islamic University, Kushtia-7003, Bangladesh. The duration of the period from Data was entered in MS Excel and Statistical analysis was done using SPSS trial version. Results: This study shows that the according to Constituent, Cellulose was 43.4822%, Alpha-Cellulose were 34.8427% and Cellulose were 8.6395%. And according to Source, Rice Straw were 32.15% %, Sugarcane were 41-43%, Rye Straw were 31.8-42.64%, Corn Stalks were 29.80% and Wheat Straw were 34-40%. Conclusion: Novel eco-friendly bio-nano-composites substances primarily based on renewable and sustainable assets namely natural rubber (NR) and nano-cellulose received from rapeseed plant straw as properly as poly vinyl acetate (PVAc) have been developed. In order to enhance the interfacial interactions amongst the composite factors such as NR, PVAc and NC, oxidation of the NR latex was once carried out by way of KMnO4 before blending mixing with PVAc emulsion and NC suspension.

Mechanochemical solid-state vinyl polymerization with anionic initiator.

Mechanochemistry has been extended to various polymer syntheses to achieve efficiency, greenness, and new products. However, many fundamental polymerization reactions have not been explored, although anionic polymerization of vinyl compounds has been pursued under mechanochemical conditions. Two solid monomers, 4-biphenyl methacrylate and 4-vinyl biphenyl, representing methacrylate and styrenic classes, respectively, were reacted with secondary butyl lithium under high-speed ball-milling. The alkyl-anion-promoted polymerization process was established by excluding radical initiation and producing the expected polymers with good efficiency. However, the generally expected features of anionic polymerization, such as molecular weight control and narrow dispersity, were not observed. Analysis of the milling parameters, reaction monitoring, and microstructural analysis revealed that the mechanism of the mechanochemical process differs from that of conventional anionic polymerizations. The mechanical force fractured the newly formed polymer chains via anionic initiation and generated macroradicals, which participated in the polymerization process. The anionic process governs the initiation step and the radical process becomes dominant during the propagation step.

Quo Vadis Carbanionic Polymerization?

Living anionic polymerization will soon celebrate 70 years of existence. This living polymerization is considered the mother of all living and controlled/living polymerizations since it paved the way for their discovery. It provides methodologies for synthesizing polymers with absolute control of the essential parameters that affect polymer properties, including molecular weight, molecular weight distribution, composition and microstructure, chain-end/in-chain functionality, and architecture. This precise control of living anionic polymerization generated tremendous fundamental and industrial research activities, developing numerous important commodity and specialty polymers. In this Perspective, we present the high importance of living anionic polymerization of vinyl monomers by providing some examples of its significant achievements, presenting its current status, giving several insights into where it is going (Quo Vadis) and what the future holds for this powerful synthetic method. Furthermore, we attempt to explore its advantages and disadvantages compared to controlled/living radical polymerizations, the main competitors of living carbanionic polymerization.

Highly stretchable and self-healable polymer gels from physical entanglements of ultrahigh-molecular weight polymers.

Highly stretchable and self-healing polymer gels formed solely by physical entanglements of ultrahigh–molecular weight (UHMW) polymers were fabricated through a facile one-step process. Radical polymerization of vinyl monomers in ionic liquids under very low initiator concentration conditions produced UHMW polymers of more than 106 g/mol with nearly 100% yield, resulting in the formation of physically entangled transparent polymer gels. The UHMW gels showed excellent properties, such as high stretchability, high ionic conductivity, and recyclability. Furthermore, the UHMW gel exhibited room temperature self-healing ability without any external stimuli. The tensile experiments and molecular dynamics simulations indicate that the nonequilibrium state of the fractured surfaces and microscopic interactions between the polymer chains and solvents play a vital role in the self-healing ability. This study provides a physical approach for fabricating stretchable and self-healing polymer gels based on UHMW polymers.

Ferrocene/ferrocenium redox shuttling: Peroxide decomposition catalysis applied to vinyl monomers polymerization under suspension conditions

Ascorbic acid derivatives in combination with ferrocenyl-based activators in catalytic amounts, referred to as kickers, are described as powerful redox systems to promote the decomposition of organic peroxides into radicals for the polymerization of vinyl monomers under suspension conditions. According to the nature of both the vinylic monomer and the peroxide, the initial polymerization rates can be improved by a factor up to 8. In the presence of ferrocene/ascorbyl palmitate kicker, the overall polymerization time of VCM was reduced from 3 to 2 h under industrial conditions. However, crusting during polymerization as well as yellowing of PVC upon thermal tests were observed. The first problem was solved by changing the surfactant, while optimizing the injection mode of the kicker improved the efficiency of the process without affecting the quality of the resulting PVC. This study demonstrates the effectiveness of ferrocene-based kickers in improving the polymerization of vinyl monomers under suspension conditions.

Effects of ionic liquids and dual curing on vat photopolymerization process and properties of 3d-printed ionogels

Ionic liquids (ILs) can facilitate photopolymerization reactions involved in the fabrication of ionogels (IGs). In this study, ILs were immobilized by 3D printing through polymerization of vinyl-monomers in their medium. The effect of ILs on the vat photopolymerization (VP) process was studied. Multiple IL-compatible photopolymer formulations were developed by using EmimBF4, BmimBF4, OmimBF4, and EmimTFSI ionic liquids and photocurable N-vinylpyrrolidone (NVP) and triethylene glycol dimethacrylate (TEGDMA) monomers. The photoinduced radical copolymerization of NVP with TEGDMA was studied using a combination of photo-DSC, Jacobs working curves and FTIR methods. The analysis revealed a dichotomy of IL-based VP as the addition of ILs led to a significant acceleration of polymerization and an increase in the critical exposure energy due to a higher conversion degree necessary for the gelation. Moreover, the Jacobs working curves showed that penetration depth dramatically changed with IL type. Based on these results, overcuring time was calculated and applied in the VP process to ensure that enough monomers were converted in each 3d-printed layer to prevent interlayer cracking. Furthermore, the dual curing approach was applied to achieve the highest possible conversion by adding a thermal initiator (AIBN). Dual curing increased the mechanical properties of ionogels but led to a reduced ionic conductivity due to an inhibition of IL’s mobility. In addition, this study found IL compositions for ionogels demonstrating no shrinkage after photopolymerization and post-curing. We suggest that the outcomes of the present study created a platform for fabricating high-resolution 3d-printed nonvolatile and nonflammable ionogels.

A Hydrometalation Initiation Mechanism via a Discrete Cobalt-Hydride for a Rapid and Controlled Radical Polymerization.

Cobalt-mediated radical polymerization (CMRP) is a versatile technique for controlling the polymerization of vinyl monomers via reversible termination using CoII complexes as persistent radical deactivators. Here, we report a facile approach for the in situ generation of Co-H as a discrete initiator and mediator for CMRP of acrylate and acrylamide monomers, overcoming the limitations of existing initiation strategies. In situ oxidation of a CoII complex followed by transmetalation with silane generates a Co-H species, which initiates polymerization via hydrometalation of the monomer. This method precludes an induction period with excellent control over targeted molecular weight and dispersity. Strikingly, our approach allows complete polymerization when the induction period ends for conventional CMRP. A broad scope of monomers is amenable to this protocol, including acrylates and acrylamides. Tunable catalyst electronics afford tailored dispersity while maintaining agreement in molecular weight in stark contrast to conventional methods. Elimination of this induction period imbues polymerization behavior entirely to the catalyst electronic effects on reversible deactivation/activation rates.

Porous Polymeric Catalysts Constructed from Vinylated Functionalities

ConspectusPorous organic polymers (POPs) have revolutionized the production of advanced catalytic materials with unique features such as a large surface area, tunable pore structure, ease of functionalization with a wide range of functional groups, and the ability to function as hosts for encapsulation of functional species, making them appealing for task-specific applications. Although numerous POP-based catalysts have been developed, they are rarely used as a common tool for preparatory-scale operations in laboratories. The high costs of these materials, because of the expensive reagents and catalysts often used in coupling reactions during their synthesis, primarily hinder their adoption. Since its discovery, free-radical polymerization of vinyl monomers to yield polymers has continuously attracted scientific and industrial attention and has been extensively adopted as an effective reaction for polymer production. Our group has targeted the synthesis of porous polymers via free-radical solvothermal polymerization of vinylated functionalities owing to the high efficiency, cost-effectiveness, and general applicability. More significantly, because of the flexibility of alkyl chains derived from the polymerized vinyl groups, the resulting frameworks are highly flexible, which is beneficial to facilitating the cooperation of catalytic components therein. Given the high catalytic efficiency of enzymes and amenable synthesis of POPs using vinylated functionalities, we have designed efficient heterogeneous catalysts by targeting the following aspects of enzyme mimicry: control over the second sphere of active sites, design of flexible ligand pockets, and construction of hydrophobic reaction microenvironments in POPs. In terms of control over the second sphere of active sites, we proposed the introduction of auxiliary groups or solvation environments via customized synthesis of POPs to perturb reaction pathways, reduce activation energies, and consequently improve catalytic performance. In terms of the design of flexible ligand pockets, we proposed the design concept of “porous ligand sponges” to fabricate quasi-homogeneous organometallic catalysts. The spatial continuity of the ligands on the flexible polymer chains enables their cooperation during catalysis, addressing the long-term challenges posed by the degradation of the catalytic performance after their heterogeneity, thus providing a possible replacement for homogeneous organometallic catalysts. In terms of adjusting the reaction microenvironments, we proposed the creation of hydrophobic environments to concentrate hydrophobic reagents in the vicinity of active sites and repel hydrophilic products to facilitate catalytic transformation.This Account highlights our ongoing research on the construction of POP-based catalysts. We also discuss the design strategies and principles involved with the aim of underscoring the unique features of POPs fabricated via solvothermal free-radical polymerization of vinylated functionalities in designing catalytic materials. This article summarizes our more than a decade of innovation in this field and is anticipated to advance the development of genuinely competitive artificial enzymes.

Effect of UV-curing conditions on the cationic polymerization kinetics of vinyl ether monomers

In this study, the performance of a new triarylsulfonium photoinitiator in the initiation of cationic polymerization of vinyl monomers was investigated by infrared spectroscopy (IR). The effect of the emission spectrum of light sources on the kinetics of the curing process was examined. The results indicate that the light source characterized by a total overlap of its emission spectrum with the photoinitiator absorption spectrum is the best system for effective cure. In the case of smaller overlap of spectrums, the conversion degree and the rate are lower. Nevertheless, it is easy to regulate by extending the energy of the emitted light. At the UVB light source, the maximal conversion degree is 71.8%, with the polymerization rate of 1.68 s-1, which is faster than the corresponding free-radical photopolymerization of acrylic monomers.

Aggregation-Induced Emissive Silicone Elastomer with Multiple Stimuli Responsiveness

Stable and highly efficient fluorescent silicone elastomers have attracted tremendous attention. In this contribution, a series of fluorescent silicone elastomers are facilely fabricated by combining aggregation-induced emission (AIE)-active polymers with a silicone matrix. The investigated AIE-active macromolecules are synthesized by reversible addition–fragmentation chain-transfer polymerization of vinyl monomers containing a tetraphenylethylene pendant. Detailed experimental characterizations demonstrate that macromolecular fluorescent compounds have good dispersibility and leaching resistance in silicone elastomers. Especially, the fluorescence properties of the silicone elastomers can be modulated by changing the molecular weight or aggregation state of the fluorescent macromolecules. Moreover, the prepared fluorescent silicone films show multiple stimulus responsiveness to strain, temperature, and organic solvents. The present work provides a simple and universal strategy toward fluorescent silicone elastomers for both scientific research and future practical applications.