Free Radical Copolymerization Research Articles

Allyl sorbitol crosslinker-based novel hydrogel for the removal of toxic metal ions from water

ABSTRACT The rising concentration of toxic metal ions in waterbodies threatens human and ecological health. Adsorption, especially using hydrogels, is an effective method for removing these pollutants. The newly designed allyl sorbitol crosslinker-based hydrogel (ASCLHs-hydrogel) has been prepared via free radical copolymerisation technique. The synthesised ASCLHs-hydrogels have been characterised by several analytical techniques, viz. Fourier transform infra-red (FTIR) spectroscopy, thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), point of zero charge (ΔpHPZC) analysis, gel permeation chromatography (GPC) analysis, scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDS) analysis and X-ray photoelectron spectroscopy (XPS). Three grades of ASCLHs-hydrogel have been prepared and utilised for the elimination of Ni2+ and Co2+ ions from wastewater. The properties of ASCLHs-hydrogel, i.e. swelling and water retention ratio (WRR), have been studied in distilled water. The maximum swelling of the best grade ASCLHs-1 hydrogel was found to be 367.52 g/g, and WRR of ASCLHs-1 hydrogel was found to be 74.37% in distilled water. Under optimised conditions, the removal efficiencies of the best grade of ASCLHs-1 hydrogel were found to be 96.2% for Co2+ and 94.5% for Ni2+ ions. The Langmuir and Freundlich isotherm models give excellent fitting with experimental data. The maximum adsorption capacities for ASCLHs-1 hydrogel have been found to be 209.20 mg/g for Co2+ and 182.14 mg/g for Ni2+ ions, respectively. The kinetic behaviour of the adsorption between hydrogels and heavy metal ions (HMIs) was found to be controlled by pseudo-second-order (PSO) kinetic model with a rate constant 1.0 × 10−3 g/(mg.min) for Co2+ and 1.2 × 10−3 g/(mg.min) for Ni2+ ions, respectively. The reusability of the ASCLHs-1 hydrogel has been studied for five cycles and the hydrogel showed remarkable desorption efficiency even after the fourth cycle. Overall, these findings suggest that the ASCLHs-1 hydrogel works as an economical, and efficient adsorbent for the removal of Ni2+ and Co2+ ions from aqueous solutions.

Xanthan gum/ZrMOF biodegradable gel fertilizer: Sustainable water retention and crop growth.

To address the problems of ecological pollution and food safety caused by the excessive use of chemical fertilizers in modern agriculture, it has become a hot topic of current research to develop novel low-cost, biodegradable, and efficient gel slow-release fertilizers. Herein, using xanthan gum and ZrMOF as raw materials, urea as a nutrient, acrylic acid and itaconic acid as co-monomers, a novel ZrMOF gel slow-release fertilizer (ZrMOF@CpM) was prepared by free radical copolymerization. After being characterized, its swelling and water retention properties and slow-release behavior were investigated. It was demonstrated that ZrMOF@CpM with a high surface area and mesoporous structure provided rich water and fertilizer channels for slow-release fertilizer. Therefore, beside good water absorption (260.7g/g) and water retention, its nutrient (N) slow-release performance (45 d, 49.1%) was in accordance with the Committee for European Normalization (CEN) standards. The slow-release gel fertilizer also showed good degradation performance (35 d, 56.9%). Additionally, maize pot trials showed that the synthesized slow-release fertilizer materials significantly promoted plant root and leaf growth. Overall, we provide a new strategy for the construction of high-efficiency, high-water retention and biodegradable agricultural gel slow-release fertilizers.

Insight into the rheological performance of plasticized-cement paste containing a tailored comb-shaped polycarboxylate superplasticizers: molecular architecture and functionalizing

This study deals with developing efficient comb-shaped polycarboxylate superplasticizers (PCs) with different molecular architectures as sustainable additives for mortar and concrete processing. The PC synthesis involved polycondensation of methacrylic acid (MAA) and methoxy polyethylene glycol (MPEG) with different molecular weights (750, 1000, and 2000 Da), followed by free-radical copolymerization of MAA, 2-acrylamide-2-methylpropane sulfonic acid (AMPS), hydroxyethyl methacrylate, acrylamide, and the attained MPEG-grafted macromonomer. Successful copolymerization and grafting were approved by employing H NMR, FTIR, and GPC. The performance of PCs was evaluated for their dispersing ability in cement paste (water/cement: 0.30, PC content: 0.25 wt.%) through the slump retention, fluidity, apparent viscosity monitoring, and rheological behavior of cement pastes via the Herschel–Bulkley model using shear stress versus shear rate diagrams to calculate the yield stress. It was found that the grafted and ungrafted copolymers based on MAA-AMPS (with mass ratio of MAA:AMPS of 50:50 wt%) display greater workability due to the higher negative charge density and better adsorption on cement particles owing to sulfonate (−SO3 −) and CONH2 groups. So, slump values of 300 mm and 400 mm were attained by ungrafted and MPEG750-grafted MAA-AMPS copolymers, respectively. Furthermore, the findings demonstrated that longer MPEG side chains higher than 750 Da greatly weaken the dispersing ability due to the lower steric hindrance repulsive forces, lower electrostatic interactions, and more chain-folding. Moreover, the incorporation of 0.25 wt.% by weight of cement of MPEG750-grafted MAA-AMPS copolymer in cement pastes reduced the yield stress over than 90%. Consequently, the know-how for tailoring effective MPEG-grafted superplasticizers with great slump retention (400 mm), low viscosity (lower than 0.1 Pa·s at a shear rate: 10 s−1), and low yield stress (2.22 e−14 Pa), compared to industrial ones, was achieved. Accordingly, this attempt provides a beneficial insight into developing high-performance water-reducing superplasticizers, as a promising candidate for advanced greener cement-based materials.

Solar-Active Carbon Nitride Film Integrated by Free Radical Copolymerization for Photocatalytic Indoor Air Purification.

The current lack of stable, scalable, and efficient coating technology dramatically limits the exploitation of solar-driven graphitic carbon nitride (CN) photocatalysts. Herein, a unique, efficient, and scalable method is reported to immobilize CN powder on various substrates ranging from Fluorine tin oxide (FTO), glass, Plexiglas, Al foil, Ti foil, and Granite stone, to even wood. The film shows an outstanding thickness of 212µm, which is the highest value ever reported. The formation process is ascribed to free radical copolymerization between the tri-s-triazine backbone and polyacrylamide, followed by cross-linking. The smooth, non-oxidizable, and well-defined continuous coating exhibits excellent adherence and durability. The distinctive sequence segments preserve the light transition within the film while enhancing the optical absorption in the solar spectrum. Under visible light illumination, the film shows outstanding photodegradation performance toward air pollutants, whether for gaseous acetaldehyde (Act) or toluene (Tol). This method is a great step forward that can open new opportunities for the commercial applications of CN powder.

Radiation-assisted tailoring of swelling behavior and water retention of Na-CMC/PAAm hydrogels for enhancing Beta Vulgaris under drought stress

This study investigates the negative impact of climate change on water resources, specifically water for agricultural irrigation. It describes how to optimize swelling, gel properties and long-term water retention capacities of Na-CMC/PAAm hydrogels for managing drought stress of Sugar beet plants through techniques such as changing the composition, synthetic conditions and chemical modification. Gamma radiation-induced free radical copolymerization was used to synthesize superabsorbent hydrogels using sodium carboxymethyl cellulose (Na-CMC) and acrylamide (AAm). The study also explored how varying Na-CMC/AAm ratio and radiation dose influence their swelling behaviour, gel fraction, and water retention. FTIR showed that CMC and PAAm components are part of the hydrogel structure. The equilibrium swelling reached a maximum value of ~ 500 g/g at a Na-CMC/AAm ratio of 60/40. High content of AAm reduced swelling because it caused increased hydrophobicity while high radiation doses up to 50 kGy increased crosslinking resulting in improved but limited swelling from 65 to 85 (g/g). After the second cycle, KOH modification reached maximum swelling capacity by introducing anionic carboxylate groups up to 415 (g/g). SEM images revealed uniform pores in an unmodified scaffold while larger cavities were formed upon modification facilitating Water absorption. Surprisingly, the improved hydrogels retained more water: about 75% even after 16 days as opposed to a 50% drop within five days in the case of unmodified ones. This hydrogel significantly enhanced shoot length by 18%, root length by 32%, fresh weight shoot by 15%, and dry weight shoot by 15% under severe drought conditions. As a result, yield increased by 22%, proteins went up by 19%, and carbohydrates rose by 13%. Leaf chlorophyll content increased with a corresponding decline in stress enzymes indicating decreased oxidative damage. This eco-friendly Na-CMC/PAAm-based hydrogel seems to have potential use for addressing water scarcity and agricultural challenges.

SOLID-PHASE EXTRACTION OF S-TRIAZINE HERBICIDES BASED ON NEW ORGANIC-INORGANIC HYBRID COPOLYMER

In this study, a new organic-inorganic hybrid copolymer (P(MAA-MPTS)/Sil) was synthesized, characterized, and applied as a sorbent for s-triazines. The P(MAA-MPTS)/Sil was prepared by coupling free radical copolymerization of methacrylic acid and methacryloxypropyltrimethoxysilane and sol-gel processing, using tetramethoxysilane as a cross-linker. Scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption-desorption measurements were used for the characterization of the copolymer particles. The extraction efficiency of hybrid copolymer toward s-triazines was studied by batch procedure. High recoveries for all studied compounds (ametryne, atrazine, propazine, simazine, simetryn, and terbuthylazine) were achieved in the pH range 7 - 8 within 30 min. Quick quantitative desorption was achieved using a mixture of methanol and acetic acid. An analytical procedure based on solid-phase extraction of s-triazines on newly synthesized hybrid copolymer and HPLC measurements was developed for their quantification in surface waters. Experiments performed with different types of waters (tap, lake, river) and determination limits achieved demonstrated the successful applicability of P(MAA-MPTS)/Sil in monitoring programs for quality control of tap and surface waters.

Efficient removal of anionic dye congo red by Chitosan/Poly (dimethyl diallyl ammonium chloride-co-acrylamide) composite hydrogel.

Chitosan, as a natural and environmentally friendly material, has attracted significant attention in the field of water treatment. In this study, a Chitosan/poly (dimethyl diallyl ammonium chloride-co-acrylamide) composite hydrogel (CPDA hydrogel) featuring a semi-interpenetrating network structure was synthesized via free radical copolymerization for the removal of the anionic dye Congo Red (CR) from wastewater. SEM-EDS, FTIR, XPS, TG, Zeta potential, and mercury intrusion porosimetry (MIP) were employed to analyze the physical and chemical changes in the hydrogel before and after adsorption. The results revealed that the CPDA hydrogel can selectively adsorb anionic dyes through electrostatic interactions. The study on the adsorption performance of the CPDA hydrogel demonstrated its excellent swelling capacity and stable adsorption of Congo Red over a broad pH range of 4 to 10. Subsequently, the adsorption process of Congo Red followed the Pseudo-Second-Order kinetic model and the Hill isotherm model, suggesting that Congo Red may self-assemble into ribbon-like micelles for cooperative adsorption and achieving a maximum adsorption capacity of 1803.507mg/g. Furthermore, the CPDA hydrogel exhibited outstanding reusability over six adsorption-desorption cycles. Thus, the prepared CPDA hydrogel shows great potential as a material for the selective removal of Congo Red from mixed dye solutions.

Kinetic modeling of the concurrent tandem free-radical copolymerization / transesterification: Copolymers via in-situ MMA transformation from the DEAEMA alcoholysis

Kinetic modeling of the concurrent tandem free-radical copolymerization / transesterification: Copolymers via in-situ MMA transformation from the DEAEMA alcoholysis

Circular Cross-Linked Polyethylene Enabled by In-Chain Ketones.

Cross-linked polyethylenes (PEs) are widely employed, but the permanent links between the chains impede recycling. We show that via imine formation with diamines keto-functionalized polyethylenes from both free-radical (keto-low-density PE, keto-LDPE) and catalytic (keto-high-density PE, keto-HDPE) nonalternating ethylene-CO copolymerization can be cross-linked efficiently in the melt, resulting in gel fractions of the formed cross-linked PEs of up to 85% and improved tensile properties. The imine-based cross-links in the material can be hydrolyzed at 140 °C to recycle up to 97% of the initial thermoplastic keto-polyethylene. Low keto contents of ≤1.5 mol % are found ideal to retain PE-like thermal properties, achieve sufficient cross-link density, and maintain circular recyclability.

Synthesis of Antimicrobial and Antioxidant Zinc Oxide Hydrogel for Drug Delivery Applications

A novel and simple method was used to synthesize antimicrobial and antioxidant porous (N-tert-butylacrylamide-co-N-vinylpyrrolidone) zinc oxide hydrogel via free radical copolymerization. The hydrogel was characterized by NMR, XRD, and SEM. Thermodynamic properties of the hydrogel were described quantitatively by the Flory-Rehner method. The results indicate that the synthesized hydrogel exhibits strong antioxidant activity, making it a potential candidate for use in preventing degenerative diseases. The antimicrobial tests showed that the hydrogel could inhibit the growth of Gram-positive and Gram-negative bacteria, as well as some pathogenic bacteria and fungi. The inhibition zones ranged from 10 to 15 mm for bacteria and from 5.2 to 9.1 mm for fungi. The reactivity ratio r1 × r2 equal to 1 confirmed ideal copolymerization showed the composition of the copolymer and the comonomer feed are same. The hydrogel's structure and reactivity are significant for constructing effective delivery systems for specific applications. Optimizing the monomer proportion could enhance hydrogel efficiency and release behavior. The hydrogel's water solubility, non-toxicity, and antioxidant properties suggest it could be safe and effective throughout the drug delivery process, contributing both passive and reactive targeting functions.

Multiple hydrogen bonding induced by semi-interpenetrating polymer network binder to enhance the electrochemical performance of sodium-ion batteries electrodes

Multiple hydrogen bonding induced by semi-interpenetrating polymer network binder to enhance the electrochemical performance of sodium-ion batteries electrodes

Synthesis and application of an amphiphilic polymer bearing benzimidazole and long alkyl benzene sulfonamide groups for enhancing heavy oil recovery

Synthesis and application of an amphiphilic polymer bearing benzimidazole and long alkyl benzene sulfonamide groups for enhancing heavy oil recovery

Reversible Solubility Switching of a Polymer Triggered by Visible-Light Responsive Azobenzene Photochromism with Negligible Thermal Relaxation.

This study reports the reversible solubility switching of a polymer triggered by non-phototoxic visible light. A photochromic polymerizable azobenzene monomer with four methoxy groups at the ortho-position (mAzoA) was synthesized, exhibiting reversible photoisomerization between trans- and cis-states using green (546 nm) and blue light (436 nm). Free radical copolymerization of hydrophilic dimethylacrylamide (DMAAm) with mAzoA produced a light-responsive random copolymer (P(mAzoA-r-DMAAm)) that shows a reversible photochromic reaction to visible light. Optimizing mAzoA content resulted in P(mAzoA10.7-r-DMAAm)3.0kDa exhibiting LCST-type phase separation in PBS (pH 7.4) with trans- and cis-states at 39.2°C and 32.9°C, respectively. The bistable temperature range of 6.3°C covers 37°C, suitable for mammalian cell culture. Reversible solubility changes were demonstrated under alternating green and blue light at 37°C. 1H NMR indicated significant retardation of thermal relaxation from cis- to trans-states, preventing undesired thermal mechanical degradation. Madin Darby Canine Kidney (MDCK) cells adhered to the P(mAzoA-r-DMAAm) hydrogel, confirming its non-cytotoxicity and potential for biocompatible interfaces. This principle is useful for developing hydrogels that can reversibly stimulate cells mechanically or chemically in response to visible light.

Poly(carboxylated ether)s as Cement Additives: The Effect of the Addition Method on Hydration Kinetics.

Polycarboxylate ether (PCE) superplasticisers have been widely used in cement formulations. However, it is not until recently that several studies have analysed the relationship between the properties and the molecular structure. In the present work, PCEs with different side chain lengths and charge densities synthesised through free radical copolymerisation are used to analyse the effect they have on the hydration of ordinary Portland cement (OPC). It was found that the addition method of these PCEs to the OPC significantly affects the hydration kinetics of the cement paste. When PCEs are added through the direct addition method, a linear dependency between the retardation of hydration and the microstructure of the used PCEs is observed. On the contrary, when PCEs are added through the delayed addition method (PCEs are added to the cement paste 5 min after water), no retardation in hydration is observed, but the rate of hydration is reduced.

Poly (acrylic acid-co-2-hydroxyethyl methacrylate)-grafted gum ghatti hydrogel for capturing heavy metal ions

Poly (acrylic acid-co-2-hydroxyethyl methacrylate)-grafted gum ghatti hydrogel for capturing heavy metal ions

Smudge-resistant antimicrobial ladder-like polysilsesquioxane coatings

Smudge-resistant antimicrobial ladder-like polysilsesquioxane coatings

Self-healing and degradable functionalization of EVA hot-melt adhesives based on disulfide bonds and polymer free radical copolymerization

Self-healing and degradable functionalization of EVA hot-melt adhesives based on disulfide bonds and polymer free radical copolymerization

Synthesis and characterization of allyl mannitol cross-linker based novel hydrogel for capturing of toxic metal ions from aqueous solution

ABSTRACT Three grades of allyl-mannitol cross-linker-based hydrogel (AMCLHs hydrogel) have been synthesized with the help of acrylic acid and acrylamide monomers using a free radical co-polymerization technique. The three prepared grades of AMCLHs hydrogel have been referred to as AMCLHs-1, AMCLHs-2, and AMCLHs-3, respectively. The prepared AMCLHs hydrogels have been characterized by several analytical techniques viz. Fourier transform infrared (FTIR) spectroscopy, thermogravimetric (TG) analysis, point of zero charge (ΔpHPZC), analysis, and scanning electron microscope (SEM) analysis, respectively. The synthesized hydrogels have been utilized for the elimination of Cu2+ and Co2+ ions from wastewater. The properties of prepared AMCLHs hydrogels, i.e. swelling and water retention ratio have been studied in distilled water under optimized conditions. The maximum swelling ratio of the best grade of hydrogel (AMCLHs-1) has been found to be 400.5 g/g with the water retention ratio of 75.09% during 24 h. These findings indicate the AMCLHs-1 hydrogel has remarkable swelling and water retention capacity. The maximum metal ion removal efficiency of AMCLHs-1 hydrogel from aqueous solutions has been found to be 96.6% for Cu2+ and 94.2% for Co2+ ions under optimum conditions. The experimental data fitted well with the Langmuir and Freundlich adsorption models, revealing maximum adsorption capacities of 431.03 mg/g for Cu2+ ions and 414.93 mg/g for Co2+ ions, respectively. In addition, the rate for the adsorption of Cu2+ and Co2+ ions onto AMCLHs-1 hydrogel follows both Pseudo first and second-order kinetic models. The negative ΔG values indicate that the adsorption process occurs spontaneously, while positive ΔH values suggest that the adsorption process is exothermic in nature. The prepared AMCLHs hydrogel is reusable and exhibits high desorption efficiency with 87.63% for Cu2+ and 85.21% for Co2+ metal ions even after the fourth cycle. Overall, AMCLHs hydrogel is a cost-effective and reusable adsorbent that possesses a significant potential for heavy metal ion removal from aqueous solutions.

Synthesis and structural characterization of acrylonitrile/vinyl imidazole copolymers and their amidoximated derivatives

Recently, environmental applications of copolymers such as CO2 capture and separation have become of significant interest. The development of copolymers with basic functional groups, such as amidoxime (AO) groups, represents a successful approach for enhancing absorption and separation of acidic molecules, such as CO2. In this research, acrylonitrile/N-vinyl imidazole (AN/VIM) copolymers were first synthesized through a free radical copolymerization method using 2,2′-azobisisobutyronitrile (AIBN) as the initiator and dimethylformamide as the solvent. The synthesized copolymers were then functionalized using hydroxylamine hydrochloride (NH2OH · HCl), the result being amidoximated (AO) copolymers. The synthesized copolymers were characterized by nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis and Fourier transform infrared spectroscopy. The analytical results simply confirmed that the copolymers and their amidoximated derivatives had successfully been synthesized. A microstructural study of amidoximated polymers using NMR spectroscopy clearly showed the tautomerization of AO groups.

Preparation and performance study of thermo-responsive P(NIPAM-AM-ABP)/keratin composite nanofiber membrane for bio-application

Preparation and performance study of thermo-responsive P(NIPAM-AM-ABP)/keratin composite nanofiber membrane for bio-application