Suspension Polymerization Research Articles

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.

Synthesis of Amphiphilic Triblock Copolymers by ATRP and Coalescence Suppression Effect in Suspension Polymerization

Synthesis of Amphiphilic Triblock Copolymers by ATRP and Coalescence Suppression Effect in Suspension Polymerization

Simultaneous removal of nitrogen and phosphorus nutrients from secondary effluent by magnetic resin containing two types of quaternary ammonium adsorption sites: Preparation, characterization, and application

The direct discharge of secondary effluent (SE) from wastewater treatment plants without proper nitrogen and phosphorus treatments can result in the eutrophication of landscape water bodies. The primary objective of advanced treatment should focus on the removal of NO3− and PO43− as the optimal approach. In this study, magnetic resin microspheres known as MGE (derived from the initials of the three organic monomers used, namely methyl methacrylate, glycidyl methacrylate, and 3,4-epoxy-1-butene) were successfully prepared through suspension polymerization. MGE incorporated two types of sites specifically designed for the removal of anionic nitrogen and phosphorus nutrients. The removal of NO3−, PO43−, and humic acid (HA) by MGE fit well with the pseudo-second-order kinetic and Freundlich adsorption isotherm models (R2 = 0.884–0.993 and 0.918–0.969, respectively). The removal efficiencies of ultraviolet absorbance at 254 nm, total nitrogen, total phosphorus, NO3−, PO43−, and total fluorescence in SE by MGE were 50.4 %, 20.9 %, 27.1 %, 21.5 %, 30.2 %, and 42.0 %, respectively, which were significantly higher than those achieved by commercially available MIEX® and D201. The molecular dynamic simulation results indicated that the increased removal of NH4+ by resin after adsorption of HA can be attributed to the aggregation effect of HA and NH4+ caused by H-bonds. The nitrogen and phosphorus indicators of the MGE effluent met the GB/T 18921-2019 water quality standard for scenic environmental use in China. MGE exhibited exceptional adsorption capacity and rapid achievement of adsorption equilibrium, making it a potential adsorbent for the removal of anionic nitrogen and phosphorus nutrients in engineering applications.

Experimental investigation into effects of the natural polymer and nanoclay particles on the EOR performance of chemical flooding in carbonate reservoirs

This paper aims to investigate the tragacanth gum potential as a natural polymer combined with natural clay mineral (montmorillonite, kaolinite, and illite) nanoparticles (NPs) to form NP–polymer suspension for enhanced oil recovery (EOR) in carbonate reservoirs. Thermal gravimetric analysis (TGA) tests were conducted initially in order to evaluate the properties of tragacanth gum. Subsequently, scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) tests were used to detect the structure of clay particles. In various scenarios, the effects of natural NPs and polymer on the wettability alteration, interfacial tension (IFT) reduction, viscosity improvement, and oil recovery were investigated through contact angle system, ring method, AntonPaar viscometer, and core flooding tests, respectively. The entire experiment was conducted at 25, 50, and 75 °C, respectively. According to the experimental results, the clay minerals alone did not have a significant effect on viscosity, but the addition of minerals to the polymer solution leads to the viscosity enhancement remarkably, resulting mobility ratio improvement. Among clay NPs, the combination of natural polymer and kaolinite results in increased viscosity at all temperatures. Considerable wettability alteration was also observed in the case of natural polymer and illite NPs. Illite in combination with natural polymer showed an ability in reducing IFT. Finally, the results of displacement experiments revealed that the combination of natural polymer and kaolinite could be the best option for EOR due to its substantial ability to improve the recovery factor.

Polystyrene carbon composite foam with enhanced insulation and fire retardancy for a sustainable future: Critical review

Polystyrene (PS) composite foams are an intriguing class of materials that are well established for thermal insulation in construction and lightweight recyclable components in automotives. Research has shown the remarkable properties of these foams in terms of thermal and sound insulation and fire retardancy that can be enhanced by incorporating carbon fillers such as graphite, graphene, and biochar. Several methods have been examined by researchers to mix carbon with the polystyrene matrix and prepare PS carbon composite foams, which can broadly be categorized into suspension polymerization, solution mixing and melt blending. These methodologies along with foaming techniques for the expansion of PS using various blowing agents are reviewed. We also review the most relevant research studies in the field of PS carbon composite foams for insulation (thermal and sound) and fire retardancy. Due to its high infrared radiation absorption capacity and hetero nucleating action, expandable graphite and graphene can lead to excellent thermal and sound insulation along with fire retardancy in a PS foam, thus resulting in significant energy savings in a building. Biochar, due to its inherent low thermal conductivity and nucleating action, modifies the foam morphology, leading to enhanced heat and sound absorption and thus is a low-cost renewable carbon alternative that promotes the circular economy.

Preparation of a novel polymer suspensions with high stabilization, and their superior performances in high salinity

Amphoteric polymerhave attracted immense research interest in hydraulic fracturing.However, current fracturing fluids prepared using conventional suspensions have poor stability and cannot be adapted to field applications in highly mineralized oilfield blocks, and they cannot reuse highly mineralized oilfield wastewater. To solve the above problems, a new concentrated suspension was prepared as a fracturing fluid thickener. The crystal layer spacing of SMB-2 exhibited an improved value of d = 13.564 nm. Experimental findings indicate that SRS-2 exhibited rapid thickening in saline water within a 5-minute timeframe. The viscosity of SRS-2 in high-salinity solutions demonstrated an impressive viscosity retention rate of 96.8 %, highlighting its excellent salt resistance properties. The zeta potential was measured at -62.13 mV. Notably, there was no significant settlement observed even after 30 days, with a settling velocity of 9.2592 × 10−3 mm/s, underscoring its superior stability performance. Therefore, this new suspension thickener has good potential for applications as an alternative material in multiple fields, such as oil extraction and sewage treatment.

Preparation of a novel polymer microspheres and application in solid phase extraction combined with hollow fiber membrane system for capturing lactic acid from simulated fermentation broth

To separate the fermentation products in real time and improve the fermentation yield, a novel poly-4-vinylpyridine-vinylbenzeneboronic acid polymer microspheres (p4VP-VPBA) with bifunctional groups was prepared by suspension polymerization. The spherical p4VP-VPBA was 5–20 μm and thermally stable below 355.4 °C. The elemental contents of N and O were 1.36% and 5.72%, respectively, and the content of boronic acid was 0.1357 mmol/g. Its adsorption performance to lactic acid was satisfactory. Under pH 4 and 20 °C, the maximum static adsorption of p4VP-VPBA was up to 185.31 mg/g in 3 h. Its selectivity on lactic acid to glucose was 70.05 at pH 2, 7.71 at pH 4, and only 0.81 at pH 10, which indicated a good selectivity to lactic acid at low pH fitting to fermentation process. Furthermore, a p4VP-VPBA-combined with hollow fiber membrane (HFM) separation system was proposed and the removal rate of 5 mg/mL lactic acid was maintained at about 90% after 5 consecutive cycles. These data showed a huge potential for future real-time capturing lactic acid from fermentation, which also was a reference for other fermentation inhibited by product concentration.

Polymeric Nanocapsules Containing Ozonated Oil and Terbinafine Hydrochloride as a Potential Treatment Against Dermatophytes.

Terbinafine hydrochloride is a synthetic allylamine whose mechanism of action consists of inhibiting the enzyme squalene epoxidase that participates in the first stage of ergosterol synthesis, interfering with fungal membrane function. Ozonated oils are used for topical application of ozone, producing reactive oxygen species that cause cellular damage in microorganisms, therefore being an alternative treatment for acute and chronic skin infections. This study aimed to develop and characterize Eudragit® RS100 nanocapsules, obtained by interfacial deposition of preformed polymer method, containing 0.5% terbinafine hydrochloride and 5% ozonated sunflower seed oil as a potential treatment against dermatophytes. The polymeric nanocapsules were characterized regarding particle size, zeta potential, pH, drug content, encapsulation efficiency, and stability. The in vitro drug release, in vitro skin permeation, and in vitro antifungal activity were also evaluated. The particle size was around 150nm with a narrow size distribution, the zeta potential was around + 6mV, and the pH was 2.2. The drug content was close to 95% with an encapsulation efficiency of 53%. The nanocapsules were capable to control the drug release and the skin permeation. The in vitro susceptibility test showed greater antifungal activity for the developed nanocapsules, against all dermatophyte strains tested, compared to the drug solution. Therefore, the polymeric nanocapsules suspension containing terbinafine hydrochloride and ozonated oil can be considered a potential high-efficacy candidate for the treatment of dermatophytosis, with a possible reduction in the drug dose and frequency of applications. Studies to evaluate safety and efficacy in vivo still need to be performed.

Encapsulating carbon dots in polymethyl methacrylate nanoparticles toward improved solid-state fluorescence quantum yield

In this paper, we prepare carbon dots (CDs) through hydrothermal method, and then the CDs are encapsulated in polymethyl methacrylate (PMMA) nanoparticles through the suspension polymerization of MMA nanodroplets, obtaining a CD/PMMA nanocomposite with a CD concentration of 0.3 wt%. The CDs of the nanocomposite are confined in the PMMA nanoparticles, so there is no excessive resonance energy transfer or direct π-π interaction among the CDs in different nanoparticles, weakening the aggregation caused quenching compared with conventional CD/PMMA composite fabricated by directly blending the CDs with bulk PMMA. Consequently, the quantum yield (QY) of this CD/PMMA nanocomposite is higher than that of the conventional CD/PMMA composite, and even very close to that of the dilute CD solution. This study may provide a universal method to prepare CD/polymer solid-state fluorescent materials with higher QYs compared with conventional CD/polymer composites prepared through direct blending CDs with bulk polymers.

Preparation of a composite of polyacrylate and nano‐SiO2 particles and evaluation of its performance of oil–water mixture treatment

AbstractTo acquire a material with simultaneous oil–water emulsion demulsification and oil‐absorbing performance, SiO2 nanoparticles were introduced into the acrylate polymerization system to prepare oil absorbent SiO2/P (SMA‐co‐MMA‐co‐BA) (PSA‐SiO2). PSA‐SiO2 was synthesized from monomers and functional materials, including methyl methacrylate (MMA), butyl acrylate (BA), octadecyl methacrylate (SMA) and SiO2 hydrophobically modified by vinyltrimethoxysilane. The molecular structure of PSA‐SiO2 was characterized by FT‐IR, and its morphology was observed using scanning electron microscopy. In addition, the optimal synthesis conditions for the polymerization system, such as the monomer ratio, the amount of crosslinker and stabilizer and then the particle size and dose of SiO2, were discussed in detail. PSA‐SiO2 had a decent oil absorbency for pure halogenated and aromatic hydrocarbons (49.10, 56.41, 47.32, 43.45, 36.22, and 30.14 g/g for CH2Cl2, CHCl3, CCl4, C2Cl4, toluene and styrene, respectively). Furthermore, SiO2, as a functional material, makes composites that possess excellent demulsification properties for oil‐in‐water emulsions. The oil removal efficiency of CHCl3 in Tween 80‐stabilized and CTAB‐stabilized emulsions were 94.88% and 98.11%, respectively. All results indicated that PSA‐SiO2 had valuable potential for oil removal and emulsion treatment.Highlights An organic–inorganic composite was synthesized by suspension polymerization. The composite was applied for absorbing pure oil or removing oil form water. By modification, the composite acquired the demulsification ability. The composite accomplished one‐step demulsification and emulsion treatment. The oil absorption and emulsion treatment could achieve at room temperature.

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 and performance evaluation of a micron-size silica-reinforced polymer microsphere as a fluid loss agents

A silica-reinforced polymer microsphere was prepared by reverse suspension polymerization using acrylamide (AM), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and silica nanoparticles modified with methacryloyloxypropyltrimethoxysilane as a filtrate reductant resistant to high temperature and salt contamination. The filtration volume of American Petroleum Institute (API) sodium-based bentonite fluids was reduced by 63.5% after aging with the addition of 3.0 wt% M-SiO2/ZMD at 150 °C. M-SiO2/ZMD also exhibited significant salt resistance when compared to ZMD. The test results demonstrate that M-SiO2/ZMD exhibits excellent rheological and filtration properties even at elevated temperatures. A significant filtration reduction effect was also shown in the water-based drilling fluid system. The filtrate volumes before and after aging at 150 °C were 5.2 mL and 5 mL, respectively, when the addition amount was 1.0 wt%. Finally, the possible filtration loss reduction mechanisms involved in M-SiO2/ZMD are also discussed. This study provides a new heat- and salt-resistant fluid loss reduction material for water-based drilling fluids in oilfields, and provides theoretical support for its practical application.

Synthesis of Crosslinked Microparticles Based on Glycidyl Methacrylate and N‐Vinylimidazole

AbstractIn this study, suspension polymerization technique is used to obtain 3D porous networks based on two monofunctional monomers (glycidyl methacrylate and N‐vinylimidazole) and one of the following difunctional monomers known as crosslinking agents: mono‐, di‐, and triethylene glycol dimethacrylate or divinylbenzene. The influence of various operational parameters like: monomer molar ratio, amount and type of crosslinkers, composition of stabilization system, stirring speed, amount of porogenic agent on the reaction yield, surface morphologies, particle size distribution, and porous characteristics are investigated in order to find the optimal conditions for the synthesis of microparticles possessing the desired properties for further chemical modification. Crosslinked porous microparticles are structurally characterized by Fourier transform inrared (FTIR) spectroscopy, X‐ray photoelectron spectroscopy, and elemental analysis by determination of nitrogen and epoxy groups. The microparticle morphologies as a function of investigated parameters are revealed by scanning electron microscopy, whereas the porous structure is highlighted by mercury porosimetry and dynamic water vapor sorption methods. All the crosslinked networks exhibit porous structures with different surface morphologies and specific surface area values (1.15–48.32 m2 g−1) depending on the operational parameters. These microparticles can be considered precursors for the preparation of various functional polymeric materials.

Engineering Polymeric Phase-Change Sub-Microcapsules with a High Encapsulation Fraction by Facile, Versatile Suspension Polymerization

Engineering Polymeric Phase-Change Sub-Microcapsules with a High Encapsulation Fraction by Facile, Versatile Suspension Polymerization

Chemical and Process Inherent Safety Analysis of Large-Scale Suspension Poly(Vinyl Chloride) Production

In this work, a safety assessment was carried out for the suspension polymerization method, known for the lack of studies about its sustainable performance and long history of chemical accidents. Therefore, a safety analysis was conducted using the inherent safety methodology to assess and determine the inherent risks of the poly(vinyl chloride) (PVC) suspension production process using computer-aided process engineering (CAPE). The indicators were calculated using data from safety databases and the specialized literature, considering downstream stages like vinyl chloride monomer (VCM) recovery, PVC purification and PVC drying. The obtained indicators revealed that the process has a negative performance regarding inherent safety, with a total inherent safety index of 30. The chemical inherent safety index had a value of 19, with the main chemical risk of the process being presented by the vinyl chloride monomer (with a value of 11), along with the risk of the exothermic reactions. The process safety index had a value of 15, highlighting the inventory as the primary concern of the process (with a value of 5), followed by the presence of unsafe equipment such as furnaces, burners, and dryers. The safety structure index had a score of 3, categorizing the process as probably risky, with the reaction and purification stages being more susceptible to accidents. Lastly, it is recommended to reduce the size of the process inventory and to substitute out unsafe process units.

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%.

Microencapsulated waste cooking oil derivatives for building thermoregulation

The utilization of waste resources and the intelligence of building materials are of great significance to the sustainable development of human society. A novel type of microencapsulated phase change material (MPCM) with a phase change heat storage capability was prepared in this paper through the suspension polymerization method using methyl palmitate (MP) derived from waste cooking oil as core materials. Meanwhile, the response of foamed concrete containing MPCM to ambient temperature change was investigated. According to the experimental findings, the MPCM's phase change temperature, phase change enthalpy, and decomposition temperature are respectively 20 °C, 68 J/g, and 215 °C, which is extremely suitable for the external walls of buildings to adjust the indoor temperature. Moreover, the particle size of the MPCM is about 100 μm-220 μm, which can fill part of the voids in foam concrete to increase its strength. Additionally, the infrared thermal imaging experiment indicates that the foam concrete containing 10 wt% MPCM can maintain 4 °C-5 °C gap with the ambient temperature, which demonstrates that the MPCM can significantly mitigate the impact of ambient temperature on buildings. The findings of the study contribute to the intellectualization of building materials and the recycling of waste resources.

Efficient continuous-flow synthesis of diacyl peroxide in a microreactor and the post-processing of its effluent

Di-(3,5,5-trimethylhexanoyl) peroxide (TMHP) is a low-temperature diacyl peroxide in liquid form, which is widely used as an initiator for the polymerization of vinyl monomers, especially for the production of polyvinyl chloride by suspension polymerization. However, the high reaction heat and the extreme instability of the product of the peroxidation reaction to synthesize TMHP often lead to safety concerns, therefore, the batch reaction processes often sacrifice efficiency in return for better safety. In this work, continuous-flow microreaction technology is utilized to realize an efficient and safe synthesis of TMHP. Under the conditions of T2 = 30°C, NaOH eq. = 1.05, and H2O2 eq. = 1.20, 94% yield could be obtained within 2.80 min, while batch reactors require hours to perform the same yield. It proves that, compared with batch processes, the efficiency is significantly improved by microreaction technology. Besides, a post-processing method for microreactor effluent is also proposed. After four post-processing steps of aging, washing, drying, and formulation, commercial TMHP product could finally be obtained. This work first reports the efficient and safe synthesis of TMHP based on microreaction technology and a post-processing method for microreactor effluent, which not only develops an efficient route from raw material to TMHP commercial products but also provides a basis for the process development of synthesizing other similar organic peroxides in a more efficient and safer manner.

Interfacial insight of core@double‐shell Mo@MoO3@PS/PVDF composites towards prominently meliorative dielectric performances

AbstractPolymer dielectrics with synergistically large dielectric permittivity (ε') and breakdown strength (Eb) but prohibited loss is of crucial applications in the electronic devices and power equipment. In this study, we aim to elevate the integrated dielectric performances of molybdenum (Mo)/polyvinylidene fluoride (PVDF) by constructing a semiconducting molybdenum oxide (MoO3) shell and insulating polystyrene (PS) shell on the Mo surface through high‐temperature oxidation followed by suspension polymerization. The resulting core@double‐shell Mo@MoO3@PS particles were compounded with PVDF to achieve high ε' and Eb while minimizing the loss. The results reveal that the Mo@MoO3@PS/PVDF composites indicate simultaneously ameliorative ε' and Eb along with restrained loss owing to the existence of the MoO3@PS double‐shell, which not only prominently enhances the interfacial compatibility and interactions between fillers and PVDF, but significantly inhibits the conductivity and loss through impeding the long‐distance motion of carrier charges. The dielectric capabilities could be improved by adjusting the thickness of the PS interlayer. The Havriliak‐Negami equation was used to fit the experimental results, which showed the impact of the PS shell on the polarization mechanism and how it inhibits carrier migration. The Mo@MoO3@PS/PVDF with high ε' and Eb yet exceptionally low loss exhibit potential applications in microelectronics and electrical industries.