Radical Solution Polymerization Research Articles

30 Years of Macromolecular Theory and Simulations

30 Years of <i>Macromolecular Theory and Simulations</i>

Preparation and polymerization analysis of poly-(alkenyl-based di-ionic ionic liquid)

In this study, bis-imidazole-containing ionic liquids (VDILs) featuring halide counteranions and substituted with different numbers of alkenyl groups were designed and synthesized. The VDILs were further subjected to a one-pot free radical polymerization in aqueous solution, forming hydrophobic PVDILs. GPC, FT-IR, XPS, and XRD were performed to determine the influence of the number and position of the alkenyl groups in the VDIL monomers on the molecular weight, molecular weight distribution, and polymeric structure of the PVDILs. The GPC results showed that the position of the alkenyl groups had a significant influence on the molecular weight of the PVDILs. The linker alkenyl group in the VDIL monomer was easier to polymerize than the alkenyl group connected to the N(1) atom of the imidazole ring of the VDIL due to the steric bulk of the counteranions, which mitigated cross-polymerization of the vinyl groups. As the interconnected polymeric network was being formed, the steric bulk of the anions hindered chain growth, resulting in a lower-than-expected molecular weight of PVDIL-3. XPS and FT-IR results indicated that there were still a certain number of alkenyl groups that remained in the PVDIL-1 and PVDIL-3 structures after polymerization, with the PVDIL-3 sample containing 3% more alkenyl groups than PVDIL-2. This study demonstrates a new method for the polymerization of alkenyl-based DILs and provides a foundation for the application of PDILs.

Two-Dimensional Polymers: Synthesis and Applications.

Two-dimensional (2D) polymers represent an emerging class of nanomaterials possessing covalent sheet-like morphology. They display a set of intriguing properties, including large specific surface area, low density, versatile control over sizes and compositions, and high adaptability. As such, they find application in energy conversion and storage, nanotechnology, and biotechnology. However, it remains challenging to synthesize thin-layer 2D polymers with conventional methods. Herein, in this perspective, recent advances in synthesis and applications of thin-layer 2D polymers via capitalizing on various "top-down" and "bottom-up" strategies are summarized. Particularly, some new methods (e.g., free radical polymerization in solution and surfactant-monolayer-assisted interfacial synthesis) in combination with electrostatic repulsion or steric hindrance effect to engineer single-layer 2D polymers at large scale are highlighted.

PH-Sensitive Hydrogels Based on Copolymers of Chitosan with Acrylamide and Sodium Acrylate

pH-sensitive hydrogels based on chitosan-graft-poly(acrylamide-co-sodium acrylate) were synthesized via radical polymerization in solution. Ammonium persulfate was used as initiator, and various amounts of hexamine were used as a cross-linking agent. The structure of obtained hydrogels was characterized by Fourier transform infrared spectroscopy. Moisture-absorbing power of hydrogels in buffer solution with various pH value (pH = 1.65; 4.01; 12.43) was investigated. It is turned out that such a copolymers have a high moisture retention capacity (swelling index attains the value 1100%) and are capable for reusing, that makes it possible to apply the hydrogels in different areas.

A novel hydrophobically associating polymer based on Twin-tailed amphiphilic Monomer: Experimental study and molecular dynamics simulation

A novel twin-tailed amphiphilic monomer named CGS-12 was synthesized. The copolymer GHPAM was prepared by copolymerization of CGS-12 with acrylamide (AM) and acrylic acid (AA) by photoinitiated free radical polymerization in aqueous solution. The critical micelle concentration of CGS-12 is 1.02 × 10-4 M. The rheological behaviour of the above copolymer was studied. It was found that GHPAM provides better performance at high temperature, exhibits unusual salinity sensitivity and tolerates greater higher shear forces. The viscoelasticity and micro morphologies have been investigated revealing that CGS-12 considerably enhances the crosslinking density and promotes to form a more compact network than the corresponding single-tailed hydrophobic monomer DM-12. Finally, we prove via molecular dynamics simulations that CGS-12 can enhance the hydrophobic association compared to DM-12 while maintaining the same hydrophobic chains content, resulting in improved rheological properties.

New bio-based sustainable polymers and polymer composites based on methacrylate derivatives of furfural, solketal and lactic acid

Monomers derived from renewable sources are of great interest to drive sustainable polymer chemistry. Herein, bio-based furfural, glycerol and lactic acid were used as building blocks to prepare methacrylate monomers via simple transesterification reactions in high yield and purity. The monomers were polymerized and co-polymerized by employing a free radical solution polymerization technique using 1,1-azobis cyclohexanecarbonitrile (ABCN) initiator. The resultant new co-polymers (P(FAMA-co-SoMA), P(FAMA-co-LAMA) and P(SoMA-co-LAMA)) were obtained in high yields and proved to have sizeable molecular weights (Mw from 2540 to 29395 g mol-1 and Mn from 2194 to 7463 gmol-1). Thermogravimetric analysis and differential scanning calorimetry (DSC) measurements on these polymers revealed good thermal properties (thermal stability ranging between 125 °C and 155 °C) with some crystalline regions identified by DCS and PXRD. The polymers were reinforced using cellulose triacetate and polysulfone to give new polymer composites (Psf/PFAMA, Psf/PFAMA-co-SoMA, Psf/PSoMA, CTA/PFAMA, CTA/PFAMA-co-SoMA, CTA/PSoMA), which were amorphous and degraded hydrolytically (in acidic and basic aqueous solutions) by up to 10% in just 24 h. The polymer composites were fashioned into thin films and membranes and applied preliminarily as coatings and water filtration membranes.

Phosphorous-Nitrogen Modification of Epoxy Grafted Poly-Acrylic Resin: Synergistic Flame Retardment Effect.

A novel high-efficient flame retardant epoxy grafted poly-acrylic resin modified by phosphorus and nitrogen was successfully synthesized by radical grafting polymerization and solution polymerization simultaneously. The flame retardancy of copolymer resin was investigated using thermogravimetric analysis (TGA), cone calorimetric test (CONE), limiting oxygen index (LOI) and so on. The micro-morphology and chemical composition of char formed after a CONE calorimetric test was analyzed using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The Kissinger method was used to evaluate the kinetics of thermal decomposition on copolymer resin. The results showed that the flame retardant property of copolymer resin increased with the increase in phosphorus content. With the increase in nitrogen content, however, the flame retardant property first increased and then decreased. The flame retardant property of the resin was the best and the limiting oxygen index could reach 34.3% when the phosphorus content and nitrogen content of the copolymer resin were 6.45 wt% and 2.33 wt%, respectively. Meanwhile, nitrogen-containing compounds will interact with phosphorus-containing compounds to form P-N intermediates during combustion, which have stronger dehydration and carbonization and could further enhance the flame retardant performance of the resin and generate phosphorus-nitrogen synergistic interactions.

Pullulan based hydrogels for the removal of various metal ions from aqueous solutions

Pullulan-graft-poly(acrylic acid) (pullulan-g-poly(AA)) and pullulan-graft-poly(acrylic acid-co-acrylamide) (pullulan-g-poly(AA-co-AAm)) hydrogels were synthesized by free radical solution polymerization. Fourier Transform Infrared Spectroscopy, Thermal Gravimetric Analysis and Scanning Electron Microscopy were used to further understand the formation and the characteristics of the hydrogels. Additionally, the hydrogels’ swelling capacities and swelling kinetics were investigated. Pullulan-g-poly(AA-co-AAm) was found to have the highest swelling capacity with 461% after optimization. Metal ion adsorption and desorption abilities and the reusability properties of the hydrogels were examined, and both of the prepared hydrogels were found to be efficient adsorbents of cadmium(II), copper(II), mercury(II), nickel(II) and zinc(II) ions. The most adequate hydrogel was found to be pullulan-g-poly(AA-co-AAm) for the adsorption of cadmium(II) ions with 169.79 mg/g followed by pullulan-g-poly(AA) hydrogel for the adsorption of cadmium(II) ions with 137.76 mg/g. The desorption tests were conducted by using hydrochloric acid and the hydrogel with the best desorption ability was found to be pullulan-g-poly(AA) hydrogel with 76% for the desorption of Cd(II) ions. The adsorption-desorption cycles were repeated 3 times and the hydrogel that has the best reusability was found to be pullulan-g-poly(AA-co-AAm) with 169.79 mg/g, 124.78 mg/g and 115.34 mg/g for the adsorption of Cd(II) ions in the first, second and third cycles, respectively. All of the synthesized hydrogels were found to be good candidates for the adsorption and desorption of Cd(II), and Cu(II) ions; and pullulan-g-poly(AA-co-AAm) was able to adsorb and desorb Hg(II) ions for at least three times.

Synthesis and characterization of poly(vinyl carbazole-co-ethoxy ethyl methacrylate) and its nanocomposites

Poly(vinyl carbazole-co-ethoxy ethyl methacrylate) Poly(VK-co-EOEMA) was prepared through free radical solution polymerization. The non-functionalized silica (SiO2) and alumina (Al2O3) nanoparticles were added into the polymeric matrix to yield polymer nanocomposite by blending technique. The compatibility of the polymer with nanoparticles were examined by Fourier Transform Infra-Red Spectroscopy (FTIR) and X-ray Diffraction (XRD) studies. The morphological changes due to the addition of nanoparticles was observed using Scanning Electron Microsphere (SEM). Thermal analysis of the polymer and its nanocomposites was performed by Thermo Gravimetric Analysis (TGA). An optical property of the polymer and its nanocomposites was carried out using UV–Vis spectroscopy.

Optimization of a 3D-printed tubular reactor for free radical polymerization by CFD

A flow reactor for the complex reaction network of the free radical solution polymerization of n-butyl acrylate was optimized by a combination of kinetic modeling, computational fluid dynamics (CFD) and additive manufacturing. CFD was used to model a flow reactor with SMX mixing elements. An optimized geometry was 3D-printed from polypropylene. The modeled residence time behavior was compared to relevant experiments, giving a validation for the flow behavior of the reactor. A kinetic model for the free radical solution polymerization of n-butyl acrylate (BA) was in addition implemented into the CFD model. It was used to predict the polymerization behavior in the flow reactor and the resulting product properties. The experimental and computational results were in acceptable agreement.Graphical abstract

Preparation and dispersion properties of polycarbonate superplasticizers based on RAFT polymerization

Comb-like polycarbonate superplasticizers (PCEs) are widely used as a cement additive, and obtaining high-performance PCEs has become a hot topic. PCEs are usually kind of random polymers obtained by free radical solution polymerization, and thus it is hard to clarify the relationship between the properties of PCE and its structure. In this work, the block copolymers PCEs with the clear structure were synthesized by the reversible addition-fragmentation chain transfer (RAFT) polymerization. The relationship between the structure of PCE and its dispersion properties in cement was systematically discussed based on the flowability data of the cement paste with PCEs and the adsorption data of PCEs on the cement particles. Effects of the monomer ratio and the molecular weight on the adsorption and dispersion ability of PCEs in cement paste were studied. The results showed that the adsorption capacity and dispersion properties of PCEs in cement paste are related to the structural parameters of the polymer molecules. PCEs exhibited the optimal dispersion properties when the ratio of the monomers was 6:1 and the molecular weight was no greater than PCE-8 (Mn = 53,450, Mw = 62,358).

Optimization and modeling of reactive conditions for free radical solution polymerization of SA-co-BA copolymer based on the yield using response surface methodology

In the recent years, response surface methodology (RSM) is one of the most common optimization methods employed in the chemical process. The satisfactory model for predicting the maximum yield in solution polymerization has been a challenge due to various conditions during the synthesis process. In this study, interactive impacts of three parameters which are reaction time, concentration of initiator, and reaction temperature on the yield in free radical polymerization of SABA copolymer using toluene as solvent was investigated using experimental design central composite design (CCD) model under response surface methodology (RSM). The result showed the optimization conditions were reaction time of 7 h, initiator concentration of 1 wt %, and reaction temperature of 90 oC with the corresponding yield of 97.31%. The analysis of the regression model (ANOVA) detected an R2 value of 0.9844, that the model is able to clarify 98.44% of the data variation, and just 1.23% of the whole differences is not clarified by the model. Three experimental validation runs were carried out using the optimal replicate conditions and the highest average yield value obtained is 97.15%. There is an error of about 0.97% as compared to the expected value.Therefore, the results indicate that this model is reliable and is able to predict the yield response accurately. it established that the regression model is extremely significant, indicating a strong agreement between the expected and the experimental values of SABA yield.

The study of a highly efficient and environment-friendly scale inhibitor for calcium carbonate scale in oil fields

A highly efficient and environment-friendly scale inhibitor (MA-VA-VS) was synthesized via free radical solution polymerization method, where maleic anhydride (MA), vinyl acetate (VA) and vinyl sulfonate (VS) acted as monomers, while ammonium persulfate was used as initiator. The inhibition performance and the structure as well as properties was characterized using static jar measurement and dynamic test, Fourier transform infrared spectroscopy and thermogravimetric analysis. The surface morphology and composition of scale formed in the solution were examined using scanning electron microscopy and X-ray diffraction, respectively. The binding energies of inhibitor with calcite (104) face were calculated using Materials Studio 2017 (MS) at 323 K. The results show that the inhibition efficiency gradually increases with increasing inhibitor concentration. While as the Ca2+ concentration increases, the efficiency first increases and then decreases. With the increase in temperature or pH, the efficiency generally decreases. It is confirmed that the inhibition efficiency can reach 91.4% when 150 mg/L MA-VA-VS is used in a flow condition. Both the calculated binding energy and inhibition performance evaluation results demonstrate that the scale inhibition performance of MA-VA-VS is better than a commercial scale inhibitor (HPMA). The excellent inhibition performance of this inhibitor is due to its chelation and dispersion properties.

The Impact of AN Contribution on the Thermal Characteristics and Molecular Dynamics of Novel Acrylonitrile-Styrene-Styrene Sodium Sulfonate Terpolymers.

We performed a free radical solution polymerization of new acrylonitrile (AN), styrene (St) and styrene sodium sulfonate (SSS) acceptor–donor acceptor monomer systems. The compositions and structures of the produced terpolymers were elucidated using CHNS elemental analysis, and Fourier transform infrared (FTIR) spectroscopies. Three terpolymers candidates were chosen for detailed thermal investigations, where the AN molar ratio varied almost threefold (from ~6.9% to ~17.4%) while the molar ratios of St and SSS varied slightly, at average values around 76.0% and 12.9%, respectively. The glass transition (Tg) values of the terpolymers were measured calorimetrically. In addition, thermal gravimetric analyses (TGA) of the samples were conducted in the temperature range from room temperature to 800 °C. All terpolymers exhibited a single Tg value, indicating random copolymerization of the monomeric species. TGA results revealed that variation of the AN molar ratio had a significant influence on the thermal stabilities of the terpolymers. The impact of AN contribution on the molecular dynamics of the glass transition in the terpolymers was explained quantitatively in a framework of a molecular model.

Stochastic Modeling of Poly(acrylate) Distributions Obtained by Radical Polymerization under High‐Temperature Semi‐Batch Starved‐Feed Conditions: Investigation of Model Predictions versus Experimental Data

AbstractSecondary reactions significantly affect acrylate polymerization rates as well as the architecture of polymer produced by high‐temperature solution radical polymerization. This impact is amplified under the semi‐batch starved‐feed policy used to keep monomer concentration low. Thus, the importance of intramolecular chain transfer (backbiting) is significantly increased, generating a tertiary radical center capable of termination, propagation, and scission. In this investigation, a comprehensive stochastic model is formulated to represent results from an experimental study designed to increase the fraction of reactive terminal double bonds (TDB) in the poly(butyl acrylate) product. Model predictions generated using three sets of literature kinetic parameters for backbiting and scission are compared. While each provides reasonable predictions of some reaction characteristics (e.g., free monomer levels, polymer molecular weights, polymer TDB content), none provide an adequate representation of all aspects of the polymerization. It is concluded that other reaction pathways might be needed to represent the system under semi‐batch conditions, thus explaining the discrepancies seen among the current parameter estimates.

Absorption and adsorption studies of polyacrylamide/sodium alginate hydrogels

The aim of this study is to investigate the use of hydrogels as adsorbent in the removal of methylene blue (MB), a cationic dyestuff commonly used in industry, by adsorption from waste water. Therefore, sodium alginate-modified polyacrylamide-sodium alginate (PAAm/SA) hydrogels with the different concentration of sodium alginate were synthesized by free radical solution polymerization under normal atmospheric conditions. The absorbents were characterized using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The absorption and adsorption experiments were performed and the effects of several experimental parameters including pH and contact time upon the adsorption process were evaluated. As a result of swelling tests, PAAm/SA hydrogels swelled in the range of 12.72–25.52 gwater gdry gel−1 in water, while PAAm hydrogel swelled to 8.5 gwater gdry gel−1. Methylene blue adsorption, which showed a rapid increase with increasing pH in the range of pH 2.0–6.0, reached the highest value at pH 7.0. Adsorption equilibrium was investigated by using Langmuir, Freundlich, and Temkin isotherm models. Two kinetic models, (i) pseudo-first-order and (ii) pseudo-second-order kinetic models, were applied to test the experimental data. Pseudo-second-order kinetic model well fitted the kinetic results, suggesting chemisorption as the most probable adsorption mechanism. Adsorption of methylene blue with hydrogels was well fitted with the Freundlich isotherm model, indicating the multilayer adsorption process on heterogeneous surfaces. The prepared hydrogels can be potential candidates for use as absorbents to treat wastewater.

Synthesis and application of geminal dicationic ionic liquids and poly (ionic liquids) combined imidazolium and pyridinium cations as demulsifiers for petroleum crude oil saline water emulsions

New geminal dicationic ionic liquids, ILs, containing both imidazolium and pyridinium cations were synthesized to apply as effective demulsifiers for stable sea water-in-heavy petroleum crude oil emulsions. In this respect, vinyl imidazolium and 4- amino-4-pyridyl diethoxylate (APE) or 4-pyridyl tetradecanamide were quaternized either with 1,4-dibromobutane or 1,12-dibromododecane to produce ILs monomers. Their vinyl group was polymerized via solution radical polymerization to produce geminal poly (ionic liquids), PILs, and their chemical structures were identified by nuclear magnetic resonance. The thermal stability and thermal characteristics of the prepared geminal dicationic imidazolium and pyridinium cations indicate that all prepared compounds behave as ILs and PILs having lower melting temperature below 100 °C and lower glass transition temperatures below 0 °C. The surface activity, micellization or aggregation, and adsorption at air/seawater or seawater/petroleum crude oil interfaces were investigated from surface and interfacial tension measurements. The interactions of the prepared ILs and PILs with asphaltenes were evaluated from particle sizes and zeta potentials. The demulsification of stable W/O emulsions at temperature of 60 °C using different concentrations of the prepared ILs and PILs confirm that the demulsification was carried out at lower injection dose (from 100 to 250 ppm) and shorter demulsification time (from 40 to 240 min).

Characterization of AAm/4-Styrenesulfonic Acid Sodium Salt/PEG Hydrogels Crosslinked by PEGDA as Highly Swollen Adsorbents for the Effective Removal of Janus Green B from Aqueous Solutions

In this study, it has been investigated that the incorporation of poly(ethylene glycol) and 4-styrenesulfonic acid sodium salt into acrylamide hydrogel during free radical solution polymerization synthesis for novel highly swollen adsorbents and for the effective removal of some potential pollutants from aqueous solutions such as cationic dyes. Poly(ethylene glycol)diacrylate was used as a multifunctional crosslinker. The main purpose of this study was to combine both monomers and a polymer in a new polymeric system. Dye sorption properties of the polymeric hydrogels were investigated by using cationic dye such as Janus Green B. Swelling and sorption studies were carried out at 25°C. For structural characterization, FT-IR analysis and SEM studies were applied. To determine the sorption behaviors of Janus Green B, some sorption parameters such as dye removal capacity, adsorption percentage, and partition coefficient of the polymeric hydrogels were investigated.

Initiator Feeding Policies in Semi-Batch Free Radical Polymerization: A Monte Carlo Study

A Monte Carlo simulation algorithm is developed to visualize the impact of various initiator feeding policies on the kinetics of free radical polymerization. Three cases are studied: (1) general free radical polymerization using typical rate constants; (2) diffusion-controlled styrene free radical polymerization in a relatively small amount of solvent; and (3) methyl methacrylate free radical polymerization in solution. The number- and weight-average chain lengths, molecular weight distribution (MWD), and polymerization time were computed for each initiator feeding policy. The results show that a higher number of initiator shots throughout polymerization at a fixed amount of initiator significantly increases average molecular weight and broadens MWD. Similar results are also observed when most of the initiator is added at higher conversions. It is demonstrated that one can double the molecular weight of polystyrene and increase its dispersity by 50% through a four-shot instead of a single shot feeding policy. Similar behavior occurs in the case of methyl methacrylate, while the total time drops by about 5%. In addition, policies injecting initiator at high monomer conversions result in a higher unreacted initiator content in the final product. Lastly, simulation conversion-time profiles are in agreement with benchmark literature information for methyl methacrylate, which essentially validates the highly effective and flexible Monte Carlo algorithm developed in this work.

Benchmarking Stochastic and Deterministic Kinetic Modeling of Bulk and Solution Radical Polymerization Processes by Including Six Types of Factors Two

AbstractBulk and solution radical polymerization is important in daily live. A challenge is still to maximize polymerization rate and control over molecular characteristics such as the molar mass distribution. The last decades have made clear that kinetic modeling is indispensable with originally most focus on deterministic implementations such as the method of moments (MoM) and only more recently promising results for event‐driven kinetic Monte Carlo (kMC) simulations that belong to stochastic methods. Computationally, a critical reaction is termination for which one has both distinguishable and nondistinguishable distributed species, which requires a delicate treatment of a stoichiometric factor 2. Proper benchmarking of MoM and kMC simulations demands thus a careful translation of this factor in the Monte Carlo (MC) reaction probabilities. However, limited attention has been paid in the kMC field to the detailed description of such translations. Here, a rigorous derivation is presented on the level of individual termination rates. Emphasis is on termination by recombination and disproportionation. It is highlighted that six types of factor 2 exist that all need to be incorporated with care, including an IUPAC‐based one. The consistency is demonstrated by a successful benchmark of essential modeling results for free radical polymerization of methyl methacrylate.