Free Radical Emulsion Polymerization Research Articles

Fabrication of cationic microgels doped MnO2/Fe3O4 nanocomposites, and study of their photocatalytic performance and reusability in organic transformations

AbstractThis article reports, the fabrication of cationic microgel doped MnO2/Fe3O4 nanocomposites (CM@MnO2/Fe3O4) via free radical emulsion polymerization technique, and an economical and environmental friendly approach to some organic transformations, such as heterogeneous photocatalytic reduction of methylene blue (MB, toxic dye), para‐nitro phenol (PNP, harmful pollutant) and dimethyl amino benzaldehyde (DMAB, skin allergic reagent) in presence of UV light (38 W). First of all, three different crosslinked grades of cationic microgels (CMs) have been synthesized by using styrene, dimethyl acrylamide, cyclohexyl methacrylate, [2‐(acryloyloxy)ethyl] trimethylammonium chloride and N‐hydroxymethyl acrylamide monomers by taking different amounts of N‐hydroxymethyl acrylamide, and keeping the other monomers in fixed quantities. Further, all the grades of CMs have been doped by bimetallic MnO2/Fe3O4 nanoparticles, through hydrothermal method. Fabrication of CMs and CM@MnO2/Fe3O4 nanocomposites has been confirmed by the characteristic peaks observed in FT‐IR spectral analysis and their thermal stability has been evidenced by thermogravimetric analysis. TEM and DLS analyses have revealed their particular size. The surface morphology of CMs and CM@MnO2/Fe3O4 nanocomposites has been visualized by scanning electrode microscope analysis. The nanocomposites have effectively and efficiently catalyzed the reduction reactions of MB, PNP, and DMAB, in presence of UV light, by 98%, 98%, and 86%, respectively. The photocatalysts have been reused up to eight cycles without any loss of their catalytic activity. The photocatalytic reductions have also been studied for their kinetics, and exhibited pseudo first order kinetics (kapp, 10−2 min−1).

Preparation of Fluorine Certified Reference Material for Fluoroether Rubber

High-pressure free radical emulsion polymerization was used to prepare the fluorine certified reference material candidates for fluoroether rubber. Ion chromatography method and high performance liquid chromatography were adopted for the determination of the certified reference material, and various sources of uncertainty in the determination process were analyzed and calculated to gain the expanded uncertainty by synthesis. The homogeneity of the certified reference material was checked by F test and the stability was investigated by t test. The results show that the prepared fluorine certified reference material for fluoroether rubber has accurate value and good homogeneity and stability.

High Water Resistance and Enhanced Mechanical Properties of Bio-Based Waterborne Polyurethane Enabled by in-situ Construction of Interpenetrating Polymer Network

In this study, acrylic acid was used as a neutralizer to prepare bio-based WPU with an interpenetrating polymer network structure by thermally induced free radical emulsion polymerization. The effects of the content of acrylic acid on the properties of the resulting waterborne polyurethane-poly (acrylic acid) (WPU-PAA) dispersion and the films were systematically investigated. The results showed that the cross-linking density of the interpenetrating network polymers was increased and the interlocking structure of the soft and hard phase dislocations in the molecular segments of the double networks was tailored with increasing the content of acrylic acid, leading to enhancement of the mechanical properties and water resistance of WPU-PAA films. Notably, with the increase in content of acrylic acid, the tensile strength, Young’s modulus, and toughness of the WPU-PAA-110 film increased by 3 times, and 8 times, and 2.4 times compared with WPU-PAA-80, respectively. The WPU-PAA-100 film showed the best water resistance, and the water absorption rate at 96 h was only 3.27%. This work provided a new design scheme for constructing bio-based WPU materials with excellent properties.

Synthesis of poly(methyl methacrylate)-b-polyethylene (PMMA-b-PE) block copolymers via conventional emulsion polymerization

Block copolymers can be obtained by combining catalytic chain transfer polymerization (CCTP) and conventional free radical emulsion polymerization of ethylene.

Synthesis of green thermo-responsive amphoteric terpolymer functionalized silica nanocomposite derived from waste vegetable oil triglycerides for enhanced oil recovery (EOR)

Despite the high efficiency of polymer flooding as a chemical enhanced oil recovery (CEOR) technique, the low thermal stability and poor salt resistance of widely applied partially hydrolyzed polyacrylamide (HPAM) limited the application of this technique in oil reservoirs at harsh reservoir conditions of high–temperature and high–salinity (HTHS). These inadequacies of HPAM, result in the urge for an environmentally friendly polymer with good viscosifying properties and a substantial effect on mobility ratio at HTHS reservoir conditions. In this research, a high oleic acid waste vegetable oil (WVO) is utilized to synthesize a novel environmentally benign, thermo-responsive amphoteric nanocomposite for EOR applications at HTHS reservoir conditions. A green route transesterification reaction has been utilized to synthesize a novel thermo-sensitive monomer from WVO. The existence of unsaturated fatty acids isolated double bonds and acryloyl functional groups in the synthesized monomer has been confirmed using different characterization methods. The reactive acryloyl double bond in the synthesized monomer has been copolymerized with acrylamide, acrylacyloxyethyltrimethyl ammonium chloride, and 2-acrylamide-2-methylpropane sulfonic acid in presence of dimethylphenylvinylsilane via free radical emulsion polymerization. The synthesized nanocomposite has been characterized by FTIR, 1H NMR, SEM, EDX, TEM, and DLS. The thermal stability of the nanocomposite has been evaluated by TGA and DTA analysis. The results indicated that nanocomposite solution exhibited a pouncing thermo-thickening behaviour and superior viscosifying properties even at an ultra-low polymer concentration of 0.04 wt% as the temperature increased from 25 to 100 °C, with increasing salinity from 10,000 to 230,000 ppm as well as salt-free solutions. Flooding experiments demonstrated that the oil recovery factor reached 15.4 ± 0.1 % using low nanocomposite concentrations of 0.04 wt%, 22.6 ± 0.3 % using nanocomposite concentrations of 0.06 wt% and 25 ± 0.2 % using 0.1 wt% nanocomposite concentrations evaluated under hostile conditions of 100 °C and salinity of about 230,000 ppm. This research offers a new direction for the synthesis of a novel green, high molecular weight thermoresponsive nanocomposite for EOR application at extremely harsh reservoir conditions via WVO valorization.

Synthesis and characterization of dual-responsive poly(N-vinylcaprolactam-co-N-methylolacrylamide) nanogels

ABSTRACT This article reports the synthesis of poly(N-vinylcaprolactam-co-N-methylolacrylamide) (P(NVCL-co-NMA)) nanogels and investigates their thermo-/pH-responsive behavior. The formation of nanogels was synthesized using free radical emulsion polymerization by varying the monomer composition of NVCL:NMA, and their molecular structure was characterized by 1H-NMR and FTIR. It was found that the nanogels were successfully prepared, and the nanogels exhibited LCST-type phase transition behavior. Cloud point transition temperature (Tc) was studied as a function of copolymer composition, MBA concentration, and pH of the solution by exploring their changes in turbidity using UV–vis spectrophotometer. Our studies reveal that Tc nanogels increased with increasing concentration of NMA, which is due to the hydrophilicity of NMA. Our research also demonstrated that the increase in MBA percentage could decrease the Tc of the synthesized nanogels. Interestingly, P(NVCL-co-NMA) nanogels showed not only a thermoresponsive behavior but also a pH response with increasing Tc in a strong acidic environment owing to the H-bonds within the polymer chains. The results show that nanogels with initial monomer composition of NVCL and NMA of 75% and 25%, respectively, and using 4% of MBA showed Tc around 35°C at pH 7.4. In addition, DLS studies also confirmed this result since the particle sizes became much larger after surpassing the temperature of 35°C. Due to this founding, such nanogels might have potential application in controlled release. Nevertheless, further studies regarding the adjustment of Tc are still needed.

Janus particles by simplified RAFT-based emulsion polymerization process for polymer coating

We describe a simplified method to synthesize film forming polymer Janus particles by phase separation during RAFT-based free radical emulsion polymerization. Fully crosslinked snowman- or football-shaped polystyrene Janus particles (PSJPs) were first produced in a one-step batch process using amphiphilic triblock macro-RAFT copolymers as stabilizers. Such particles were in turn employed as seeds in a continuous emulsion polymerization in which a monomer mixture of methyl methacrylate (MMA) and butyl acrylate (BA) (1/1 by weight) was constantly injected into the reaction in the presence of a water soluble initiator. The added monomers wetted seed particle surface and their polymerization led to formations of 93-nm film forming single- or two-headed Janus particles. The resulted latex was successfully used to disperse and encapsulate solid calcite extender.Graphical abstract

Recoverable Thermo-Responsive Polymeric Surfactants for the Synthesis of Bulk Plastics from Latexes

Free-radical emulsion polymerization (eFRP) is widely adopted in industries due to the great advantages that this technique offers in terms of a high polymerization rate, good heat management, and conduction in a non-toxic solvent like water. On the other hand, eFRP requires surfactants to stabilize the produced polymer nanoparticles (NPs). At the same time, the recovery of a bulk material from a NP suspension needs the addition of salts or alkali for the destabilization of the emulsion and the precipitation of the polymer. These can contaminate the final product and affect its properties. For this reason, alternative strategies able to coagulate the NP latex avoiding the addition of exogenous compounds are needed. In this work, we synthesized thermo-responsive polymeric surfactants that are able to promote the NP formation during the eFRP and to allow the recovery of the bulk polymer by simply increasing the environment temperature. Surfactants with a tunable hydrophilic–lipophilic balance were produced through reversible-addition fragmentation chain transfer (RAFT) emulsion polymerization by chain-extending a polyethylene glycol-based macromolecular chain transfer agent with butyl methacrylate, in order to obtain a series of block copolymers with high blocking efficiency, controlled molecular weight distribution, and well-defined thermo-responsive behavior. Then, the RAFT agent was removed to avoid the further extension of the block copolymers, and the surfactants were tested in the eFRP of different monomers (i.e., butyl methacrylate, methyl methacrylate, and styrene) to produce stable NP latexes. Finally, the possibility of triggering the NP aggregation and of guaranteeing the recovery of both surfactants and bulk material by simply changing the temperature of the system was assessed.

“Chemical modification of guar by different synthetic vinyl monomers for enhancing oil recovery under severe sandstone reservoir conditions”

Nowadays more emphasis is given to biodegradable polymers owing to their distinct properties. Biopolymers are natural, inexpensive, available, and environmentally friendly substitutes that are planned to substitute HPAM for enhanced oil recovery (EOR). In this research, grafted guar with different vinyl monomers prepared through a free radical emulsion polymerization reaction to enhance the drawbacks of native guar gum. Structure characterization was conducted by various spectroscopic techniques including (FTIR) spectroscopy, atomic force microscope (AFM), nuclear magnetic resonance (1H NMR), and thermal analysis established by TGA analysis. Rheological characteristics were tested at severe reservoir conditions. Laboratory flooding experiments performed by sandstone packed model. It is indicated from the rheological analysis that the modified composites have more temperature resistance, salt tolerance, and improved viscosity properties than native gum. The flooding data assumed that the prepared GG-g-AM& MMA and GG-g-AM, MMA&TEVS are suitable for EOR techniques where they can withstand the severe reservoir condition and achieve a recovery factor up to (47.7%) from residual oil by using GG-g-AM& MMA and (55.5%) of residual oil by using GG-g-AM, MMA&TEVS while native guar achieves only (27.7%).

Cross-Linking Strategies for Fluorine-Containing Polymer Coatings for Durable Resistant Water- and Oil-Repellency.

Functional coatings for application on surfaces are of growing interest. Especially in the textile industry, durable water and oil repellent finishes are of special demand for implementation in the outdoor sector, but also as safety-protection clothes against oil or chemicals. Such oil and chemical repellent textiles can be achieved by coating surfaces with fluoropolymers. As many concerns exist regarding (per)fluorinated polymers due to their high persistence and accumulation capacity in the environment, a durable and resistant coating is essential also during the washing processes of textiles. Within the present study, different strategies are examined for a durable resistant cross-linking of a novel fluoropolymer on the surface of fibers. The monomer 2-((1,1,2-trifluoro-2-(perfluoropropoxy)ethyl)thio)ethyl acrylate, whose fluorinated side-chain is degradable by treatment with ozone, was used for this purpose. The polymers were synthesized via free radical polymerization in emulsion, and different amounts of cross-linking reagents were copolymerized. The final polymer dispersions were applied to cellulose fibers and the cross-linking was induced thermally or by irradiation with UV-light. In order to investigate the cross-linking efficiency, tensile elongation studies were carried out. In addition, multiple washing processes of the fibers were performed and the polymer loss during washing, as well as the effects on oil and water repellency were investigated. The cross-linking strategy paves the way to a durable fluoropolymer-based functional coating and the polymers are expected to provide a promising and sustainable alternative to functional coatings.

Stabilization of silver nanoparticles in crosslinked polymer colloids through chelation for catalytic degradation of p-nitroaniline in aqueous medium

Poly (N-isopropylacrylamide-2-hydroxy ethyl methacrylate-acrylic acid) [P(NHA)] colloidal particles of core-shell morphology were obtained by free radical emulsion polymerization. Loading of Silver nanoparticles within P(NHA) colloidal particles was attained by in-situ reduction. P(NHA) and Ag-P(NHA) particles were characterized by UV–Vis and TEM. For probing catalytic ability of Ag-P(NHA) hybrid particles, catalytic reduction of 4-Nitroaniline (4-NA) was carried out as an exemplary reaction. Ag-P(NHA) hybrid particles served as an exceptional nano-catalyst for reduction of 4-NA. Comparison of current study with academic literature proves that our system provides rapid and simple approach for efficient and cost-effective reduction of 4-NA in aqueous condition.

Preparation and anti-leakage properties of hydroxyethyl cellulose-g-poly (butyl acrylate-co-vinyl acetate) emulsion

A hydroxyethyl cellulose-g-poly (butyl acrylate-co-vinyl acetate)(HEC-g-P (BA-co-VAc)) emulsion was synthesized by free radical emulsion polymerization method from hydroxyethyl cellulose (HEC), butyl acrylate (BA) and vinyl acetate (VAc) in the presence of emulsifier sodium dodecyl benzene sulfonate (SDBS). The structure, thermal stability and morphology of the emulsion were characterized by Fourier-transform infrared (FTIR), thermogravimetric analysis (TGA), transmission electron microscope (TEM) and other analytical techniques. The results proved that BA and VAc monomers had grafted with HEC. Its thermal stability was also significantly improved compared to HEC. Moreover, the prepared emulsion was evaluated to study the performance of preventing water leakage in soil. Compared with the published anti-leakage materials prepared by directly doping hydroxyethyl cellulose, the emulsion interacted with attapulgite to form a dense consolidation layer, which had better anti-leakage performance and water retention. Therefore, the material was more favorable for popularization and application in arid and semi-arid areas.

Ionic strength-responsive poly(sulfobetaine methacrylate) microgels for fouling removal during ultrafiltration

Zwitterionic materials have received a lot of interest in the field of membrane science and water treatment due to their excellent fouling resistance, super-hydrophilicity, and ionic strength response. However, they have typically been utilized for surface functionalization. In this study, we report the synthesis of zwitterionic poly(sulfobetaine methacrylate), p(SBMA), microgels, and demonstrate the effect of their ionic-strength responsive behavior on the extent and reversibility of fouling on ultrafiltration membranes using Bovine Serum Albumin (BSA) and Baker's yeast as model foulants. The microgels synthesized using inverse emulsion free radical polymerization showed ionic strength response with increasing hydrodynamic diameter from 208 ± 4 nm to 316 ± 7 nm with increasing NaCl concentration from 0 to 0.5 M. The size change upon changing ionic strength was utilized by two approaches: co-depositing microgels with the foulants, and pre-depositing microgels on the membrane. When the microgels were co-deposited with the foulants, there was a small improvement in fouling reversibility while when the microgels were first deposited on the membrane by filtering them through, there formed a stable, continuous layer of p(SBMA) on the surface which clearly increased the fouling reversibility.

Multiscale modeling of a free-radical emulsion polymerization process: Numerical approximation by the Finite Element Method

A multiscale modeling description of free-radical polymerization processes is presented. The polymerization process is described at the macroscale by coupling the Fokker-Planck Equation (FPE) for the particle size distribution (PSD) prediction at the mesoscale with a kinetic Monte Carlo (kMC) simulation at the microscale. The finite element method is adopted to solve the mesoscopic scale to capture the nonlinear evolution of the PSD, successfully facing challenges related to accuracy and computational cost in the FPE numerical solution. Additionally, the proposed model captures the evolution of the average number of free-radicals and secondary nucleation rate at the microscopic level. The control of the secondary nucleation rate is in fact critical to satisfactorily obtain high quality structured polymer particles. Finally, a closed-form model is developed at the microscopic scale to handle the curse of dimensionality. Simulations to evaluate the capabilities of the proposed numerical scheme and sensitivity analyses with respect to the system inputs and uncertainties in the initial condition of the PSD are performed.

A Methodology Towards Mechanical Properties Optimization of Three-Component Polymers by the Gradual Variation of Feed Composition in Semi-Continuous Emulsion-Free Radical Polymerization.

In this work, a new methodology for the synthesis of three-component polymers (TCPs) was developed using a seeded, semi-continuous free-radical emulsion polymerization towards the optimization of the moduli–ultimate deformation performance and energy dissipation capacity for a styrene (S), n-butyl acrylate (BA), and 4-vinylbenzyl chloride (VBC) system. The three components were sequentially fed in pairs, varying feed composition along the conversion using S as the common monomer. To prepare a reference material, an industrial method was utilized with those monomers, using an equivalent global composition in a two-stage batch process (TS). Nanophase formation in the particles was observed by transmission electron microscopy (TEM), while the separation of the phases in the solid samples was observed by atomic force microscopy (AFM). The changes in glass transition temperature were determined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The latter was primarily used to compare mechanodynamic properties as a function of temperature for the two synthesis methods used. Thus, the higher toughness of the forced composition three-component polymeric materials was evaluated by means of their energy dissipation capacity, toughness, and stress–strain measurements at several temperatures.

Cross-Linked Primer Strategy for Pigment Encapsulation. 1. Encapsulation of Calcium Carbonate by Emulsion Polymerization

We demonstrate a versatile method to encapsulate calcium carbonate particles with a shell of polymer by means of a conventional free radical emulsion polymerization process. Our strategy relies on the encapsulation of the pigment particles with a thin primer layer of cross-linked poly(acrylate). Starved-fed addition and emulsion polymerization of di(ethylene glycol) diacrylate and methacrylic acid allow the uniform decoration of the pigment particles with the polymer primer shell. We demonstrate efficient encapsulation of calcium carbonate, from which we produce hollow particles upon calcium carbonate etching. The thickness of the polymer shell can easily be controlled, which we demonstrate with sequential seeded polymerization of methyl methacrylate under starved-fed conditions.

A reduced-order multiscale model of a free-radical semibatch emulsion polymerization process

Free-radical emulsion polymerization is a heterogeneous process where simultaneous and competitive physicochemical events occur over a wide range of time/length scales. Although a highly accurate representation of the process is possible by multiscale modeling, common approaches face several issues, including the stochastic nature of finer scales, the timely exchange of information between scales, and the high computational load for the model solution. In this work, a reduced-order computationally-tractable multiscale model is proposed while preserving a good predictive capability. The model integrates microscopic-scale calculations based on kinetic Monte Carlo simulations (stochastic), a mesoscopic-scale representation of the particle size distribution through a novel statistical approach and a deterministic description of the macroscopic-scale. The proposed model resulted in faster satisfactory predictions (compared to the model based on the Fokker Planck Equation) of traditional macro and mesoscopic variables, along with the average number of free radicals and secondary nucleation on a microscopic scale.

Polyaniline coated core-shell polyacrylates: Control of film formation and coating application for corrosion protection

Aqueous polymer colloidal nanoparticles, composed by poly(methyl metacrylate), butyl acrylate, and acrylic acid, as “core” (P(MMA/BA/AA)); and polyaniline (PAni) doped with dodecylbenzenesulfonic acid (DBSA), as “shell”, were prepared. The complete synthesis consisted of two-steps. In the first step P(MMA/BA/AA) particles were obtained in a semi-continuous process by free radical emulsion polymerization, followed by a second step where the chemical oxidative polymerization of aniline monomers upper the “core” surfaces occurred. Transmission electron microscopy images (TEM) and dinamic light scattering (DLS) confirmed the obtaining of spherical nanoparticles, which are stable for further free solid film preparation and coatings for metal protection. The free films were characterized by FTIR, Raman, UV–vis, X-Ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), thermogravimetry (TGA), optical and scanning electron microscopy (SEM), static contact angle, mechanical properties and water absorption. The metal protection was evaluated after check the adhesion properties and the impedance parameters. The presence of a low concentration of PAni-DBSA (3 wt. %) on the acrylic polymer altered the hydrophilicity and the water uptake properties of the coatings without affecting the capability of obtaining passive layers for the protection of phosphatized carbon steel surface against corrosion, even after almost 20 days of immersion in NaCl aggressive solutions.

Modeling and process optimization of a full-scale emulsion polymerization reactor

One of the most common but promising processes for the production of paints and coatings is the free radical emulsion polymerization reaction involving different types of monomers. As it is also demonstrated by statistics concerning accidents in chemical industries, polymerizations are one of the most frequent causes of thermal runaway; therefore such syntheses require a very high level of control of all the operating variables, especially at full plant scale where safety problems are of paramount importance.The main aims of this work were the modeling and the industrial scale optimization of a complex polymerization process. Since four different monomers are involved in different proportions in such a process, the pseudo-homopolymer approach together with available literature correlations for the estimation of the main constitutive parameters of the system were used to solve the mathematical model and simulate the dynamics of the synthesis at the full plant scale.The proposed model and all the constitutive parameters estimates were validated through the comparison with both laboratory and full-scale experimental data, demonstrating a good agreement. Finally, the results of the optimization procedure were validated at laboratory scale.

SPION-Decorated Nanofibers by RAFT-Mediated Free Radical Emulsion Polymerization-Induced Self Assembly.

RAFT-mediated free-radical emulsion polymerization is successfully used to synthesize polystyrene nanofibers using triblock amphiphilic macro-RAFT copolymers as stabilizers. The polymerization is under RAFT control, producing various morphologies from spherical particles, nanofibers, nanoplatelets, and polymer vesicles. Optimum conditions are established for the synthesis of predominantly negatively charged polymer nanofibers. Superparamagnetic iron oxide nanoparticles (SPION)-decorated nanofibers are formed by simple mixing of the SPIONs with the fibers at an appropriate pH. The composite material has been found to be superparamagnetic and could be aligned under a magnetic field.