Inverse Suspension Polymerization Research Articles

Study on Preparation and Humidity-Control Capabilities of Vermiculite/Poly(sodium Acrylate-acrylamide) Humidity Controlling Composite.

This paper focuses on the preparation and evaluation of a novel humidity-control material, vermiculite/(sodium polyacrylate(AA)-acrylamide(AM)), using inverse suspension polymerization. Acrylic acid and acrylamide were introduced into the interlayer of modified vermiculite during the polymerization process, leading to the formation of a strong association with the modified vermiculite. The addition of vermiculite increased the specific surface area and pore volume of the composites. To investigate the moisture absorption and desorption properties of the composites, an orthogonal experiment and single-factor experiment were conducted to analyze the impacts of vermiculite content, neutralization degree, and the mass ratio of AA to AM. According to the control experiment, the addition of vermiculite was found to enhance the pore structure and surface morphology of the composite material, surpassing both vermiculite and PAA-AM copolymer in terms of humidity control capacity and rate. The optimal preparation conditions were identified as follows: vermiculite mass fraction of 4 wt%, a neutralization degree of 90%, and mAA:mAM = 4:1. The moisture absorption rate and moisture release rate of the composite material prepared under these conditions are 1.285 g/g and 1.172 g/g. The humidity control process of the composite material is governed by pseudo second-order kinetics, which encompasses the complete adsorption process. These results indicate that the vermiculite/PAA-AM composite humidity control material has excellent humidity control performance and is a simple and efficient humidity control method.

Preparation of a cationic hydrogel microsphere adsorbent for efficient removal of hexavalent chromium from aqueous solution

AbstractHerein, a cationic hydrogel microsphere (CHMS) was prepared by inverse suspension polymerization and freeze‐drying and was applied to the adsorptive removal of hexavalent chromium (Cr(VI)) from aqueous solution. Morphological characterization shows that there are lots of folds and pores on the surface of CHMS with a unique petal‐like appearance. According to the chemical structure analysis, CHMS contains plenty of functional groups such as amine and hydroxyl groups. These features give CHMS a larger specific surface area, faster adsorption rate, and higher adsorption capacity than the conventional cationic hydrogel microparticle (CHMP) adsorbent. The adsorption of Cr(VI) in water by CHMS is mainly based on the combination of electrostatic adsorption and redox reaction, with the electrostatic interaction between the protonated amine and Cr(VI) serving as the predominant adsorption mechanism. Experimental results reveal that CHMS can efficiently remove Cr(VI) from simulated wastewater in both batch and continuous adsorption modes, which is primarily due to its distinctive surface morphology and rich functional groups. Furthermore, the common coexisting metal ions in Cr(VI)‐containing wastewater have no substantial negative influence on the adsorption. Therefore, it can be concluded that CHMS has a promising application prospect in the treatment of Cr(VI)‐containing wastewater.

Micron-Sized Thiol-Functional Polysilsesquioxane Microspheres with Open and Interconnected Macropores: Preparation, Characterization and Formation Mechanism.

Polysilsesquioxane (PSQ) microspheres have shown promise in many fields, but previous studies about porous PSQ microspheres are scarce. Herein, we fabricated novel micron-sized thiol-functional polysilsesquioxane (TMPSQ) microspheres with open and interconnected macropores by combining inverse suspension polymerization with two-step sol-gel and polymerization-induced phase separation processes, without using phase-separation-promoting additives or sacrificial templates. The chemical composition of the TMPSQ microspheres was confirmed using FTIR and Raman spectroscopy. The morphology of the TMPSQ microspheres was characterized using SEM and TEM. TGA was employed to test the thermal stability of the TMPSQ microspheres. Mercury intrusion porosimetry and nitrogen adsorption-desorption tests were performed to investigate the pore structure of the TMPSQ microspheres. The results showed that the TMPSQ microspheres had open and interconnected macropores with a pore size of 839 nm, and the total porosity and intraparticle porosity reached 70.54% and 43.21%, respectively. The mechanism of porous generation was proposed based on the morphological evolution observed using optical microscopy. The macropores were formed through the following four steps: phase separation (spinodal decomposition), coarsening, gelation, and evaporation of the solvent. The macropores can facilitate the rapid mass transfer between the outer and inner spaces of the TMPSQ microspheres. The TMPSQ microspheres are promising in various fields, such as catalyst supports and adsorbents.

Preparation of porous superabsorbent particles based on starch by supercritical CO2 drying and its water absorption mechanism

The slow water-absorption speed of starch-based superabsorbent resin (St-SAP) limits its application. In this study, porous St-SAP (P-St-SAP) was prepared by inverse suspension polymerization and supercritical CO2 drying, the aim is to provide a preparation method of fast absorbent resin. The P-St-SAP at 33 % starch content had an interpenetrating porous structure with macropores, mesopores and micropores, and the surface area, pore volume and average pore diameter were 32.06 m2·g−1, 0.116 cm3·g−1 and 21.6 nm, respectively. The water-absorption process included rapid-section, medium-section and slow-section, according with internal diffusion, double-constant and quasi second-order kinetic models, respectively. In the initial 30 s, a water-absorption speed of 262.6 g·g−1·min−1 in distilled water was much higher than some previous research results, and the equilibrium absorption value of 517.9 g·g−1 in distilled water and 72.9 g·g−1 in 0.9 % saline was better than that of non-porous St-SAP at similar starch content. Moreover, at the same stage the percentage of saline absorption ratio to equilibrium absorption value was 1.0– 2.0 times higher than that of distilled water. These research results indicate that the P-St-SAP has fast water-absorption speed and good salt resistance, which will have greater application prospects in sanitary materials, building concrete pouring, and flood control blocking piping.

Insights into the synthesis of hydrogels containing glycerol-based macromonomers for wastewater treatment: Focus on the efficient extraction of caffeine and mercury

The present study explores the production of microparticulate hydrogels for the selective adsorption of caffeine and mercury in wastewater treatment. Modified glycerol macromonomers, obtained through esterification reactions of glycerol with acrylic acid (n-ACG AA) and methacrylic acid (n-ACG MA), were successfully employed for the synthesis of these versatile materials using inverse suspension polymerization. The impact of different parameters, such as initiator, suspension agents, and monomers concentrations, and reaction time, on the final hydrogel characteristics – including morphology, swelling degree, and reaction yield – was assessed. Ultimately, microparticulate hydrogels (∼110 µm) with distinct absorption capacities were synthesized. Among the hydrogels produced, the n-ACG AA hydrogel exhibited an absorption capacity of 542% (w/w). This hydrogel was synthesized under optimized conditions using n-ACG AA (20 wt%), acrylic acid (50 wt%), bis-acrylamide (30 wt%), and 5% Span-60. The n-ACG MA hydrogel displayed an absorption capacity of 445% (w/w) and was synthesized with n-ACG MA (20 wt%), acrylic acid (50 wt%), bis-acrylamide (30 wt%), and 5% Span-80. Lastly, the hydrogel resulting from the combination of n-ACG AA and sodium acrylate (n-ACG AA/SA) demonstrated the highest absorption of 760% (w/w). It was synthesized with n-ACG AA (20 wt%), sodium acrylate (50 wt%), bis-acrylamide (30 wt%), and 5% Span-60. To evaluate the adsorption capacity of the materials, equilibrium adsorption isotherm assays were performed. The maximum adsorption capacity observed in caffeine assays was 91.55 mg g−1 for the n-ACG AA hydrogel. In mercury assays, the best capacity was found to be 369.75 mg g−1 with the hydrogel synthesized using n-ACG AA macromonomer combined with sodium acrylate. For both adsorbates, the Freündlich model was proven to be the most suitable for describing the adsorption isotherms. These results reveal the potential application of modified glycerol-based hydrogels in wastewater treatment processes.

Microencapsulation of Bacillus thuringiensis strains for the control of Aedes aegypti

In this study, we investigated the microencapsulation of two strains of the entomopathogenic bacteria Bacillus thuringiensis (B. thuringiensis) (BtMA-750 and BtMA-1114), which are biopesticides of high toxicity for the mosquito vector Aedes aegypti. The encapsulation of different concentrations of microorganisms in starch microparticles was evaluated, and the inverse suspension polymerization technique was explored. It was possible to observe that the higher amounts of the biopesticide caused a slight decrease in the diameter of the particles; however, even when encapsulated, the biopesticide still presents an average diameter that is able to be consumed by the larvae of Aedes aegypti. Furthermore, it was noticed that the presence of both of the B. thuringiensis strains did not affect the thermal stability of the particles. The microencapsulated bacterial strains presented a high number of viable spores and preserved the expression of proteins with molecular masses corresponding to the insecticidal toxins Cry and Cyt, indicating that the encapsulation process was conducted satisfactorily. Finally, the encapsulated strains were tested against Ae. aegypti larvae and maintained 100% larval mortality even after 35 days. Therefore, microencapsulation of B. thuringiensis not only guarantees the bacterial activity, but also prolongs the action of the biopesticide. Collectively, such findings highlight the great potential of the new biopesticides, which may help to reduce the population indices of the mosquito vector Ae. aegypti via a sustainable and environment-friendly route.

Degradation Kinetics of Disulfide Cross-Linked Microgels: Real-Time Monitoring by Confocal Microscopy.

Although biodegradable microgels represent a useful drug delivery system, questions remain regarding the kinetics of gel degradation and subsequent drug release. Spherical microgels (~Ø10-300 µm) were synthesized using an inverse suspension polymerization method. Specifically, acrylamide and acrylonitrile monomers were thermally co-polymerized with N,N'-bis(acryloyl)cystamine as a cross-linker with disulfide bridges. The kinetics and mechanism of degradation of these cross-linked, degradable, fluorescently labeled microgels (PAAm-AN-BAC-FA) were quantitatively studied under confocal microscopy at various concentrations of glutathione (reducing agent) ranging from 0.06 to 91.8 mM. It was found that polymer network degradation via the cleavage of disulfide bonds was accompanied by two overlapping processes: diffusion-driven swelling and dissolution-driven erosion. A slow increase in microgel size (swelling) resulted from partial de-cross-linking in the bulk of the microgel, whereas a faster decrease in fluorescence intensity (erosion) resulted from the complete cleavage of disulfide bonds and the release of uncleaved polymeric chains from the microgel immediate surface into the solution. Swelling and erosion exhibited distinct kinetics and characteristic times. Importantly, the dependence of kinetics on glutathione concentration for both swelling and erosion suggests that degradation would occur faster in cancer cells (higher concentration of reductants) than in normal cells (lower concentration of reductants), such that drug release profiles would be correspondingly different. A greater comprehension of microgel degradation kinetics would help in (i) predicting the drug release profiles for novel multifunctional drug delivery systems and (ii) using redox-sensitive degradable hydrogel particles to determine the concentrations of reducing agents either in vitro or in vivo.

Preparation, characterization, and adsorption performance of porous polyamine lignin microsphere

In this study, a porous polyamine lignin microsphere (PPALM) was prepared through the inverse suspension polymerization combined with freeze-drying, during which sodium lignosulfonate and polyetheramine (PEA) were crosslinked with epichlorohydrin (ECH) as the cross-linker. By adjusting the amount of ECH and PEA, the optimized PPALM exhibited suitable crosslinking degree, ensuring a balance of framework flexibility and rigidity, thereby facilitating the formation of abundant and fine pores. PPALM demonstrated good mechanical properties comparable to commercial sulfonated polystyrene cationic resin, with a porosity of 61.12 % and an average pore size of 283.51 nm. The saturation adsorption capacity of PPALM for Pb2+ was measured to be 156.82 mg/g, and it remained above 120 mg/g after five cycles of regeneration. Particularly, the concentration of 50 mg/L Pb2+ solution could be reduced to 0.98 mg/L after flowing through the PPALM packed bed, indicating the great potential of PPALM for application in wastewater treatment.

Synthesis of a Cation-Exchange Resin by Inverse Suspension Polymerization for Lactoferrin Extraction from Whey.

Lactoferrin (LF), the main iron-binding protein of milk, has important nutritional, biological, and pharmaceutical properties. It is an essential nutritional component of newborn diets and also for adult health. Small amounts of lactoferrin can be found in whey, a nutritionally and biologically useful byproduct of the dairy industry. Although the amount of lactoferrin in whey is less than that in other sources like milk and bovine colostrum, the extraction of LF from this underused source has many economic and environmental benefits. The most common technique for the isolation of LF from dairy products is the use of cation-exchange resins. Here, we present the synthesis of a strong cation-exchange resin for the extraction of high-purity lactoferrin from whey. This resin was synthesized by inverse suspension copolymerization of aqueous solutions of sodium 2-acrylamido-2-methyl-1-propanesulfonate and N,N-methylenebisacrylamide in corn oil. The adsorption efficiency of this resin showed selective extraction of lactoferrin from four different whey sources. The adsorption efficiency of lactoferrin from these whey samples ranged from 93.8 to 97.4%.

Highly selective recovery of Ni(II) in neutral and acidic media using a novel Ni(II)-ion imprinted polymer.

In this work, an original ion-imprinted polymer (IIP) was synthetized for the highly selective removal of Ni(II) ions in neutral and acidic media. First a novel functional monomer (AMP-MMA) was synthetized through the amidation of 2-(aminomethyl)pyridine (AMP) with methacryloylchloride. Following Ni(II)/AMP-MMA complex formation study, the Ni(II)-IIP was produced via inverse suspension polymerization (DMSO in mineral oil) and characterized with solid state 13C CPMAS NMR, FT-IR, SEM and nitrogen adsorption/desorption experiments. The Ni(II)-IIP was then used in solid-phase extraction of Ni(II) exploring a wide range of pH (from neutral to strongly acidic solution), several initial concentrations of Ni(II) (from 0.02 to 1g/L), and the presence of competitive ions (Co(II), Cu(II), Cd(II), Mn(II), and Mg(II)). The maximum Ni(II) adsorption capacity at pH 2 and pH 7 reached values of 138.9mg/g and 169.5mg/g, that are among the best reported in literature. The selectivity coefficients toward Cd(II), Mn(II), Co(II), Mg(II) and Cu(II) are also very high, with values up to 38.6, 32.9, 25.2, 23.1 and 15.0, respectively. The Ni(II)-IIP showed good reusability of up to 5 cycles both with acidic and basic Ni(II) eluents.

Micron sized anionic poly (methacrylic acid) microgel particles for the adsorptive elimination of cationic water pollutants

Abstract In this article, we reported the micron sized particles of poly (methacrylic acid) (p [MAA]) microgel and explored their applications as anionic adsorbents. The micron sized particles of poly (methacrylic acid) microgel were prepared by a simple inverse suspension polymerization method. The adsorptive elimination of adsorbates of cationic nature including malachite green (MG) and methylene blue (MB) from the aqueous medium was studied systematically. The adsorption tests were carried out using various initial concentrations of dyes and with different amounts of adsorbents. The adsorption equilibrium was established in 60 min. The adsorption capacity of the p (MAA) microgel was found as high as 351 mg/g for MG and 65 mg/g for MB. The maximum removal percentage for MG and MB was recorded as 88 and 68%, respectively. The adsorption data was computed with adsorption isotherm models including Langmuir, Freundlich, and Temkin. The Langmuir model was observed to be more applicable for the adsorption of MG while the adsorption of MB was best matched with Temkin model. The adsorption data was also treated with pseudo first order and pseudo second order kinetic models along with intraparticle diffusion and Elovich models. The pseudo second order kinetic model was most suitable with adsorption of both the MG and MB.

Hydrophilic polyelectrolyte microspheres as a template for poly(3,4-ethylenedioxythiophene) synthesis.

Conducting polymer polyelectrolyte microspheres are typically composed of a cationic conducting polymer and an anionic polymer. The polymer chains inside these microspheres are physically or chemically cross-linked, creating a network that enables high water retention. Poly(3,4-ethylenedioxythiophene) (PEDOT) being an electrically conductive polymer exhibits a high conductivity and has great biotechnological applications. The unique combination of properties of PEDOT containing polyelectrolyte microspheres makes them widely investigated materials for electroresponsive cells, tissue engineering, and bio-sensors. The demand to produce PEDOT with varied properties depending the specific application requires the understanding of the basic principles of template formation. In the present work, we studied the inverse suspension polymerization of p-styrenesulfonic acid in the presence of a cross-linking agent as a synthetic way for the formation of porous polyelectrolyte microspheres. We traced how the nature of the emulsifier affected both the structure of the surface layer of the microspheres and the degree of their cross-linking. The porous structure of polyelectrolyte microspheres obtained is found to promote the polymerization of EDOT in their presence throughout the entire microsphere volume. The structural characteristics of the polyelectrolyte/PEDOT complexes in relation to their electrochemical properties have been studied.

Poly (hydroxyethyl methacrylate - acrylic acid) microspheres loaded with magnetically responsive Fe3O4 nanoparticles for arterial embolization, drug loading and MRI detection

In recent decades, transcatheter arterial embolization (TAE) has been attached great importance in the noninvasive vascular interventional therapy for treating various diseases. In this study, a novel magnetic embolic agent of Fe3O4-loaded hydrophilic poly (hydroxyethyl methacrylate - acrylic acid) microspheres (FPHA-Ms) was constructed using inverse suspension polymerization and sequential in situ co-precipitation method. The loading of Fe3O4 nanoparticles in FPHA-Ms was verified by infrared spectrum, vibrating sample magnetometer, X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The weight percentage of iron content in lyophilized FPHA-Ms was measured by inductive coupled plasma emission spectrometer. The morphology, particle size distribution, equilibrium water content, elasticity, drug loading & eluting capacity, biosafety, magnetic resonance imaging (MRI) detectability and embolic efficacy of FPHA-Ms were systematically evaluated, respectively. FPHA-Ms possessed many merits including spherical shape, uniform and wide size range, considerable water content, high drug loading, sustained drug release and good elasticity and biocompatibility. The in vivo experiments showed FPHA-Ms could effectively block the blood supply and could be detected by MRI device. All the results proved that FPHA-Ms could serve as a novel MRI-visible multi-functional embolic agent for clinical vessel embolization, drug loading and MRI tracing in the near future.

Synthesis and characterization of a new super absorbent polymer (SAP) via the use of low-grade kaolin through inverse suspension polymerization

The water absorption of ionic SAP in cement-based materials is small. Therefore, this study synthesized a low-grade kaolin-enhanced SAP through inverse suspension polymerization, and its performances in deionized water, the saturated Ca(OH)2 solution and the supernatant of the cement slurry were investigated. The results indicate that the synthesized SAP revealed a spherical shape with a uniform particle size, showing well dispersion after water saturation. In addition, the use of low-grade kaolin could be beneficial concerning the absorbency of SAP especially using 7.5% low-grade kaolin, as reflected by the consistency results, but its absorbency is sensitive to water temperatures and environmental relative humidity. Besides, compounding inorganic materials into SAP can reduce the cost of SAP synthesis and provide cost efficiency. Finally, the growth of the acrylamide content could deteriorate the absorbency of SAP, but their final equilibrium absorbency could increase, and the absorbency of the synthesized SAP were similar in the media of the saturated Ca(OH)2 solution and the supernatant of cement slurry.

Synthesis and properties of PAM/PLA composite degradable particle temporary plugging agent

AbstractUsing acrylamide (AM) and polylactic acid (PLA) as raw materials, polyacrylamide (PAM)/PLA composite temporary plugging agent TZDJ (TZDJ is a synthetic self‐degrading stopper) was synthesized by inverse suspension polymerization. The chemical structure, chemical composition, microscopic morphology, and thermal stability of TZDJ were characterized by Fourier infrared spectral analysis (FT‐IR), carbon nuclear magnetic resonance spectroscopy (13C NMR), scanning electron microscope (SEM), and thermogravimetric analysis (TGA). The degradation and plugging properties of TZDJ were studied by laboratory experiments, and the self‐degradation mechanism of TZDJ was proposed. The results show that TZDJ has good temperature and salt resistance, and it is completely degraded by hydrolysis at 180°C for 120 h. The fracture core displacement experiment shows that TZDJ has good plugging and core permeability recovery performance, and its temporary plugging rate and core permeability recovery rate are all above 90%. The FT‐IR and SEM analysis showed that the degradation process of TZDJ was divided into three stages: degradation of shell PAM, core PLA, and degradation product small molecules.

Fabrication of hydrophilic titanium (IV)-immobilized polydispersed microspheres via inverse suspension polymerization for enrichment of phosphopeptides in milk

It is prerequisite to efficient extraction of phosphopeptides in bottom-up strategy for protein phosphorylation research. A kind of Ti4+-immobilized polydispersed phosphate-rich microsphere was fabricated via inverse suspension polymerization by employing vinylphosphonic acid (VPA) and N,N-methylenebisacrylamide (MBA) as functional monomer and crosslinker, respectively. The resulting microsphere demonstrated excellent sensitivity (as low as 10 fmol), selectivity (the mass ratio of β-casein to BSA digests is 1/500), and adsorption capacity (up to 200 mg g−1). What's more, 113 unique phosphopeptides assigned to 25 unique phosphoproteins were indiscriminately identified from 5 μL of pasteurized milk digest, exhibiting great performance in capturing phosphopeptides. In this approach, only two steps were required to synthesize Ti4+-IMAC (Ti4+-Immobilized metal affinity chromatography). Compared with other methods required multistep modifying process, this strategy is simple and time-saving, offering a prospect of pilot production and commercialization. It is expected that the application of IMAC in milk and other food samples will still make it possible to unravel the huge complexity of the Foodome in the near future.

A Multifunctional Microspheric Soil Conditioner Based on Chitosan-Grafted Poly(acrylamide-co-acrylic acid)/Biochar.

A multifunctional microspheric soil conditioner based on chitosan-grafted poly(acrylamide-co-acrylic acid)/biochar [CS-g-P(AM-co-AA)/BC] was prepared. First, the P(AM-co-AA) was synthesized and successfully grafted onto CS, and the three-dimensional network structure of microspheres was formed with N,N-methylenebis(acrylamide) as the cross-linking agent according to the inverse suspension polymerization method. Meanwhile, BC and urea were encapsulated into the body of microspheres during the polymerization. The structure of the microspheres was analyzed by Fourier transform infrared spectroscopy, polarized optical microscopy, and scanning electron microscopy, and the mechanism of adsorption of Cu2+ on the microspheres was investigated by X-ray photoelectron spectroscopy. Furthermore, the experimental results demonstrated the excellent water absorption and retention capabilities of microspheres, and the release rate of urea was dramatically reduced. Importantly, the introduction of BC significantly enhanced the adsorption performance of the microspheres with respect to heavy metal ions. Consequently, the multifunctional soil conditioner held promise for use in soil improvement and agricultural production.

Lignin‐Based Microgels by Inverse Suspension Polymerization: Syntheses and Dye Removal

AbstractLignin, as a sustainable building block, has become popular in developing the hydrogel absorbents since the last two decades. Herein, lignosulfonate‐graft‐poly[acrylamide‐co‐(acrylic acid)], LS‐g‐P(AAm‐co‐AA) microgels are synthesized by inverse suspension, a well‐known and practical industrial process. Taking advantage of a chain transfer reaction with lignosulfonate (LS), no modification of lignin is therefore required. LS is confirmed to incorporate in the microgels as evidenced by elemental analysis, FTIR, DOSY 1H NMR, and XPS spectroscopies. Microgel particles with a high percent LS grafting are obtained by decreasing the monomer concentration in the disperse phase. Additionally, the LS‐g‐P(AAm‐co‐AA) microgels containing LS promote thermal stability and render the faster and stronger methylene blue (MB) adsorption. The adsorption kinetics and isotherms understudy indicate that the adsorption behavior of MB on the microgels follows the pseudo‐second order and Langmuir model. It is found that the LS‐g‐P(AAm‐co‐AA) microgels can take up MB with 154 mg g−1 of adsorption capacity. More importantly, the LS‐g‐P(AAm‐co‐AA) microgels can be degraded by laccase enzyme derived by fungi in nature.

A survey on surface morphology control of cross-linked poly(N-vinylpyrrolidone) polymer particle via inverse suspension polymerization

This study mainly centers on the preparation and characterization of the cross-linked poly(NVP) microspheres by means of inverse suspension polymerization technique. The effect of the cross-linker content, the volumetric ratio of dispersed phase to suspension phase (DP/CP), agitation rate, and the reaction temperature on the characteristics of the microparticles were investigated meticulously using SEM, and the optimum preparation conditions were determined. The findings revealed that the morphological and surface properties of the obtained particles could be controlled easily by changing these parameters. Accordingly, the microparticles having the perfect spherical with smooth surface and good roundness, dumbbell-shaped, snowman besides dented, sunked and macelike appearance were obtained. At low cross-linker content, bulky, distorted and accumulated particles were detected, while more stable, well-defined, and desired microspheres were observed at high content. Furthermore, as DP/CP decreased, the microspheres tended to have collapsed, distorted and little wrinkled (buckled) and indented morphologies due to the heterogeneous shrinkages in droplets. Additionally, it was apparent that the increment in stirring rates caused systematically decrement in the size of the microspheres. At relatively higher reaction temperature, the mace-like microparticles having needle-like occurrences extending outwardly perpendicular on the surface started to appear due to the stiff character of the cross-linker.

Optimization of N,N’-methylenebis(acrylamide), and ammonium persulfate content in carbonaceous/acrylic acid-co-acrylamide superabsorbent polymer

Carbon filler addition in the superabsorbent polymers (SAP) network shows excellent water absorption capability. However, other than filler, the water absorbency was also influenced by crosslinker, initiator, and monomer contents during the SAP synthesis. This work aimed to optimize the amount of N,N’-methylenebisacrylamide (NNMBA) as a crosslinker, and ammonium persulfate (APS) as initiator using Response Surface Methodology (RSM) for carbonaceous/acrylic acid-co-acrylamide based SAP (C-SAP) synthesis. Inverse suspension polymerization was used for the C-SAP synthesis with a fixed amount of acrylic acid, acrylamide, and carbonaceous filler at 70 °C for 3 h. The characteristics of the C-SAP were further analyzed using the tea bag method, FTIR, and FESEM. The highest water absorbency recorded is 453.11 g/g at 0.006 wt% APS and 0.0009 wt% NNMBA with R2 of 0.9077, which is low content of crosslinker and initiator. Overall, optimum crosslinker and initiator are important parameters that increase the prospect of C- SAP, particularly in agricultural applications.