Free Radical Solution Research Articles

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.

Methylene blue uptake by gum arabic/acrylic amide/3-allyloxy-2-hydroxy-1-propanesulfonic acid sodium salt semi-IPN hydrogel

In this study, the capacity of methylene blue (MB) uptake from aqueous solution was investigated using acrylic amide-co-3-Allyloxy-2-hydroxy-1-propanesulfonic acid sodium salt/Gum Arabic semi-IPN hydrogel. The semi-IPN hydrogels were prepared by the classical free radical solution technique. The swelling experiments were carried out gravimetrically and the swelling kinetics parameters were calculated. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) confirmed the semi-IPN hydrogel formation. The MB uptake was studied by the batch technique and the impact of different conditions was investigated. It was found that the obtained semi-IPN hydrogels gave adsorption capacity for the dye within a range of 101–187 mg g−1 at the initial dye concentration of 100 mg/L. The adsorption kinetics (pseudo-first-order and pseudo-second-order) and the adsorption isotherms (Langmuir, Freundlich, and Temkin equations) were tested and the adsorption data was well described by the pseudo-second-order and Freundlich models, respectively. The maximum adsorption capacity calculated by the Langmuir model (R2 = 0.8718) was 655.2 mg g−1. The thermodynamic study indicated the spontaneity and the endothermic nature of MB adsorption. Furthermore, the usability study showed that the prepared adsorbents could be employed repeatedly for successive 5 cycles of adsorption and desorption.

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

Efficient electrospun terpolymer nanofibers for the removal of cationic dyes from polluted waters: A non-linear isotherm and kinetic study

Most of the nanomaterials used as adsorbents are in powdered form, which in turn demands highly sophisticated techniques for separating them following the adsorption process. In this study, a series of novel terpolymers were prepared based on poly(sodium styrene sulfonate–co–acrylonitrile–co–styrene) P(SSAS) via solution-free radical polymerization. The synthesized terplymers were blended with polyacrylonitrile (PAN) and converted to nanofiber sheets by electrospinning technique and used as easily-handleable and effective nanoadsorbent. The terpolymers and terpolymer/polyacrylonitrile nanofibers (SSAS/PAN NFs) were characterized using Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC) and Scanning electron microscope (SEM). The TGA results indicated that the terpolymers feature a single glass transition (Tg) and that their values (82.32–111.34 ℃) are a function of the monomer ratio. Additionally, SEM images of the as-prepared SSAS/PAN NFs revealed a homogeneous and smooth morphology with diameters ranging from 529 to 947 nm, depending on the monomer ratio. Importantly, the prepared SSAS/PAN NFs exhibited powerful action as a nanoadsorbent for the removal of crystal violet (CV) dye from aqueous solutions across a wide pH domain and without further filtration/centrifugation processes being required. The measured adsorption capacity of different SSAS/PAN NFs for the removal of CV dye adhered to the following order: SSAS/PAN NFs-1 (439.85 mg/g) >SSAS/PAN NFs-2 (255.60 mg/g) and >SSAS/PAN NFs-3 (185.96 mg/g) >PAN NFs (85.43 mg/g), with SSAS/PAN NFs-1 having an adsorption capacity eight times higher than that of PAN NFs alone. The estimated thermodynamic parameters indicate that the adsorption of CV dye on the surface of SSAS/PAN NFs was a spontaneous and endothermic process. Ultimately, the obtained kinetic and thermodynamic results clearly attest to the fact that the investigated SSAS/PAN NFs offer a facile approach to the design of an efficient nanoadsorbent for the removal of cationic impurities from wastewater.

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.

Mathematical Modeling of Free Radical Solution Terpolymerization Reactions in a Batch and Continuous Flow Stirred Tank Reactors

AbstractA mathematical model that describes a free radical solution terpolymerization is applied to styrene (St), methyl methacrylate (MMA), and maleic anhydride (MAh) polymerization system. This terpolymerization model allows for the use of either monofunctional or bifunctional peroxide initiators, and it is applied to batch and continuous reactions. The key model outputs are global monomer conversion, terpolymer composition, terpolymer average molecular weights, and terpolymer monomer sequence distributions. A few kinetic parameters are estimated such that global conversion is properly predicted by the model including initiator efficiency and two termination rate constants. Molecular weights are shown to be dominated by chain transfer reactions. Experimental trends of conversion, terpolymer molar masses (molecular weights), and composition are reasonably well predicted by the model.

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.

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.

SYNTHESIS, CHARACTERIZATION AND IN VIVO EVALUATION OF PH SENSITIVE HYDROXYPROPYL METHYL CELLULOSE-GRAFT-ACRYLIC ACID HYDROGELS FOR SUSTAINED DRUG RELEASE OF MODEL DRUG NICORANDIL

Background: Anti hypertensive drugs like “Nicorandil” require frequent dosing due to their shorter half-life. Such drugs are also pH sensitive, due to which greater portions of these drugs are degraded in acidic pH of stomach resulting in lesser bioavailability. The objective of this study was to formulate graft polymeric carrier system for sustained delivery of nicorandil to minimize dosing frequency and enhance patient compliance. Materials Methods: This animal model study was conducted in Department of Pharmacy, Islamia University of Bahawalpur, Pakistan. Hydroxypropyl methyl cellulose-graft-acrylic acid hydrogels were synthesized by free radical solution polymerization with diverse weight ratios of polymer, monomer and cross linker. Total duration of study was 1.5 years from March 2013 to August 2015. The N, N-methylene bis acrylamide and potassium persulfate were used as crosslinker and initiator respectively. Hydrogels were characterized for swelling ratio, equilibrium swelling, gel content, porosity and in vitro drug release. The surface morphology of synthesized hydrogels was evaluated by using Scanning Electron Microscopy. Thermal properties of hydrogels were evaluated by Thermogravimetric Analysis and Differential Scanning Calorimetry whereas FTIR was done to examine chemical compatibility. Finally, in vivo evaluation of prepared hydrogels was carried out in rabbits using simple parallel study design to estimate various pharmacokinetic parameters.Results: HPMC-co-AA hydrogels had good pH sensitivity whereas; they demonstrated maximum and minimum swelling at pH 7.4 and 1.2 respectively. Swelling ratio, gel fraction and cumulative percent drug release were decreased with increasing crosslinker concentration while these parameters were increased with increasing AA and HPMC concentrations. A porous network was observed in the SEM images. All formulation ingredients of prepared hydrogels showed good compatibility as determined by FTIR. Results of in vivo study proved the pH sensitivity and sustained drug release of prepared hydrogels.Conclusion: The HPMC-graft-AA hydrogels showed good pH-sensitivity and sustained-release profile for model drug nicorandil.

4-(6-Aminohexyl) amino-4-oxo-2-butenoic acid as a novel hydrophilic monomer for synthesis of cellulose-based superabsorbents with high water absorption capacity

An efficient cellulosic superabsorbent based on a novel functional monomer 4-(6-aminohexyl) amino-4-oxo-2-butenoic acid (AHOB) and acrylic acid was successfully synthesized by free-radical solution polymerization and the effect of the AHOB monomer on the structure, morphology, thermal behavior and viscoelastic features of this superabsorbent was investigated by FTIR, SEM, TGA and rheology methods. Also, the influence of this monomer on the water absorption capacity in various pH and different saline solutions, kinetic behavior, water retention capacity and reusability of the superabsorbent was perused. The results of these experiments confirmed the significant role of the AHOB monomer in improving the properties of the superabsorbent. The excellent absorbency (800.37 g/g in distilled water and 78.02 g/g in 1 wt.% NaCl solution) and high water retention capacity of the prepared superabsorbent showed that it can be used as an efficient water-saving material for agricultural applications.

Effects of the charge density of anionic copolymers on the properties of fresh cement pastes

In this work, the effects of the charge density of the anionic copolymers on the properties of fresh cement pastes were fully discussed. A series of random copolymers based on anionic acrylic acid (AA) and nonionic N, N-dimethyl acrylamide (DMAA) were prepared by free radical solution polymerization. By varying the initiator concentration, the obtained polymers have different charge densities but similar molecular weights. The adsorption, fluidity, bleeding and rheology of the cement pastes mixed with different polymers were tested, respectively. The results indicate that the anionic and nonionic monomer of the polymers effect on the properties of fresh cement paste cooperatively, and the polymer with medium charge density can effect on the cement paste strongest. Our study is quite beneficial to understand the structure–property relationships and action mechanism of anionic polymers in cement pastes.

Copolymerization of N-Tert-Butylacrylamide (NTB) and 7-Methacryloyloxy-4-Methyl coumarin (MAMC): Synthesis and characterization

Copolymers of various feed ratio of N-tert-butylacrylamide (NTB) and 7-methacryloyloxy-4-methyl coumarin (MAMC) were prepared by free radical solution polymerization in DMF at 70 °C using AIBN as an initiator. Synthesised copolymers were characterized and copolymer compositions were obtained by 1H NMR analysis data. By using Fineman-Ross, Kelen-Tudos and extended Kelen-Tudos methods, monomer reactivity ratios (r1 and r2) were calculated. Mean sequence lengths of the copolymers were estimated from monomer reactivity ratio (r1 and r2) values. Thermal characterizations of the copolymers were carried out using thermogravimetric analysis. The antimicrobial effects of obtained copolymers were also tested on various bacteria, and fungi.

Swelling equilibria of novel propenamide/2-acrylamido-2-methyl-1-propanesulfonic acid/guar gum/clinoptilolite biohybrid hydrogels and application as a sorbent for BV1 removal

A series of novel propenamide/2-acrylamido-2-methyl-1-propanesulfonic acid/guar gum/clinoptilolite biohybrid hydrogels were prepared by free radical solution polymerization using ammonium persulfate/N,N,N’,N’-tetramethylethylenediamine as redox initiating pair in the presence of poly(ethylene glycol) diacrylate as cross-linker. Swelling experiments were performed in water at 25 °C, gravimetrically. The hydrogels had high water absorbency. Equilibrium water uptake ratio ranges are 7.26–146.07 for the hydrogels. Diffusion behavior was investigated, and diffusion into hydrogels was found to be non-Fickian in character. FT-IR analysis was applied for characterization. Sorption of water-soluble cationic dye, basic violet 1, into the hydrogels was studied with the batch sorption technique at 25 °C. For equilibrium sorption studies, removal percentage, dye uptake performance, and partition coefficient of the hydrogels were investigated. The dye uptake performance values of the hydrogels varied between 1.15 × 10–5—2.03 × 10–5 mol g−1. The values for removal percentage of the hydrogels varied from 92.10–96.25%, and the values for partition coefficient of the hydrogels were between 11.67 and 25.69.

Design and synthesis of triazole conjugated novel 2,5-diaryl substituted 1,3,4-oxadiazoles as potential antimicrobial and anti-fungal agents

A series of triazole conjugated novel 2,5-diaryl 1,3,4-oxadiazole derivatives 8a-q are efficiently synthesized starting from methyl salicylate. All the synthesized compounds were characterized based on their 1H NMR, 13C NMR, Mass and IR data. All the compounds have been investigated for antibacterial activity against Staphylococcus aureus, Escherichia coli and Bacillus subtilis and antifungal activity against Aspergillus niger and Saccharomyces cerevisiae. It is interesting to note that all compounds 8a-q were found to be effective, potent and active against microbial growth when compared with standard antibacterial agents. Our findings suggest that compounds 8d-f, 8l and 8o are the major ones shown anti-fungal activity among all the synthesized compounds. From our results, it is found that all the compounds 8a-q have exhibited no appreciable potency towards clearing the free radicals in solution. Molecular docking studies of the synthesized compounds with penicillin-binding proteins (PDB ID: 3HUN and 3ITA) are in good agreement with their inhibition activity. The compounds 8p and 8q were found to be effective against microbial growth in gram-positive bacteria, whereas in gram-negative bacteria compound 8d shown good synergy with biological assays and docking studies. These novel series of compounds have shown promising features in inhibiting the microorganisms by interacting with enzymes involved in peptidoglycan synthesis and bacterial cell wall biosynthesis.

Synthesis and characterization of a pH and photoresponsive copolymer of acrylamide and spiropyran

In this research, the solution properties of acrylamide and spiropyran acrylate copolymers were investigated. Spiropyran acrylate was synthesized by the reaction of 1′,3′,3′‐trimethyl‐6‐hydroxyspiro(2H‐1‐benzopyran‐2,2′‐indoline) and acryloyl chloride. The free radical solution polymerization was used to attain a specialty responsive polymer. Characterization was carried out using nuclear magnetic resonance (NMR), Fourier‐transform spectroscopy (FTIR), and ultraviolet‐visible spectroscopy (UV‐vis). The FTIR and NMR results showed that the copolymer synthesis was successful, and the copolymer contained spiropyran monomer. UV analyses indicated that the photoresponsive behavior of the copolymer in the protic and aprotic solvents was quite the opposite, and the polymer absorption spectrum in the basic aqueous solutions was red‐shifted.

Microwave irradiation versus conventional heating assisted free-radical copolymerization in solution

Microwave (MW) irradiation has arisen as a more sustainable alternative to conventional heating (CH) for chemical reactions because it provides non-contact, volumetric equal and fast heating. However, in free-radical polymerization, the MW effect is still quite controversial, probably due to the lack of reliable, comparable experimental data of both CH and MW assisted polymerization processes. In this work, taking advantage of technically superior MW reactor design, similar temperature profiles and conditions of CH and MW assisted polymerization reactions were enabled. Copolymerization of various monomer couples with different polarity and dielectric properties was studied in solution of different organic solvents in the presence of different initiators. As a result, it was concluded that the interaction of the reaction components with the MW irradiation is essential and will determine if any effect of MW irradiation on the reaction and products occurs. On the contrary to some reported studies, for the typical monomers used in free radical polymerization studied here (acrylates, methacrylates, styrene) no difference in reaction rates, copolymer composition and properties were observed between the MWH and CH processes, independently of the solvent and initiator used. However, in the case of the presence of an organometallic monomer within the monomer couple, an observable reaction rate enhancement was obtained under MW irradiation, along with changes in the reactivity ratios and differences in the copolymer composition. This effect is considered a specific microwave effect, for the first time demonstrated in free-radical solution polymerization process and was explained by the principles of selective heating of the organometallic reaction components in solution.

Controlled synthesis of Ag-doped CuO nanoparticles as a core with poly(acrylic acid) microgel shell for efficient removal of methylene blue under visible light

Nowadays, constructing a narrow bandgap nanocomposite photocatalyst that can degrade contamination under visible light is critical but challenging. In this report, poly (acrylic acid) microgel (PAA) based nanocomposites (Ag@CuO/PAA NC) were constructed via free radical solution polymerization by varying the concentration of silver-doped copper oxide nanoparticles (Ag@CuO NPs) from 0 to 12%. As prepared Ag@CuO and Ag@CuO/PAA were characterized by X‐ray diffraction spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopy. The size of Ag@CuO NPs was found to be 30–50 nm. The photocatalytic activity of CuO is increased by Ag doping and C3 NPs show the best photodegradation of methylene blue (MB). Then, 4% of Ag@CuO nanoparticles were incorporated into PAA microgel, the resultant nanocomposite showed a drastic increase in photodegradation of MB. Ag@CuO/PAA NC completely degraded dye in only 30 min which was degraded up to 65% in 60 min. by Ag@CuO NPs. The successful combination of PAA with Ag@CuO boosts the photocatalytic activity because microgel provides a large surface to adsorb pollutants. Ag@CuO/PAA NC reused successfully for photodegradation of dye due to the recycling ability of microgels. This study gives a good insight into planning a significant visible‐light‐driven photocatalyst for environmental remediation.