Inverse Emulsion Polymerization Research Articles

Novel microreactors of polyacrylamide (PAM)[sbnd]CdS microgels for admirable photocatalytic H2 production under visible light

Cadmium sulfide, with its narrow band gap, can be used as a photocatalyst in the visible light region for the splitting of water, but its limited number of active sites and tendency to agglomerate are problematic for producing high yields of hydrogen. Therefore, an inverse emulsion polymerization method was used to fabricate polyacrylamide (PAM) microgels as a substrate to immobilize CdS nanoparticles (PAM-CdS). The PAM microgels not only immobilized the CdS nanoparticles, but also prevented aggregation. NCd bonds in the PAM-CdS microgels facilitated electron transfer from the PAM to the CdS resulting in more electrons participating in the H2 production process. The electrostatic interactions between the PAM and CdS also hindered the recombination of electron-hole pairs. These PAM-CdS microgels exhibit admirable photocatalytic H2 production performance with a H2 production rate of up to 5.21 mmol h−1 g−1.

Some insights into the structure and morphology of surfactant‐doped poly(o‐toluidine)

AbstractPoly(o‐toluidine) (POT) doped with dodecylbenzene sulfonic acid (DBSA) was synthesized by inverse emulsion polymerization and characterized systematically for morphological, structural, electrochemical, and thermal properties with scanning electron microscopy (SEM), cyclic voltammetry (CV), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). SEM demonstrated irregular granular morphology of the polymer with high porosity similar to polyaniline (PANI). The size distribution of POT salts was analyzed using Nano Measurer 1.2.5 software from scanning electron micrographs. The semicrystalline nature, with crystallite size and d‐spacing in the range of 21.4–30.2 nm and 4.93–4.99 Å, respectively, was confirmed from XRD. The activation energy (Ea) of degradation was calculated from TGA curves using Coats and Redfern (39.92–47.50 kJ/mol) & Horwitz and Metzger (50.09 ̶ 57.45 kJ/mol) methods, respectively. The small crystallite size, high thermal stability, and high values of the activation energy of degradation reveal that DBSA is an efficient dopant for POT and imparts interesting characteristics to this otherwise less thermally stable polymer. The fast rate of electron transfer of POT, as confirmed by electrochemical impedance spectroscopy, reveals its high electrochemical activity toward electrolyte. Potentiodynamic polarization measurement of POT‐coated stainless steel showed large anodic potential shift as compared to uncoated stainless steel, illustrated good anticorrosion performance. The enhanced anticorrosion performance is due to synergic effect of dopant which increases the contortion of diffusion pathway of corrosive substance.

Synthesis of Fe3O4/PAM superparamagnetic nano-hydrogels in water-in-oil emulsion

In this study, the nano-sized water droplets (NWDs) in water-in-oil (W/O) emulsion were employed as mini-reactors, in which Fe3O4/PAM magnetic nano-hydrogels (MNHs) were obtained based on the coprecipitation and inverse emulsion polymerization. In addition, compound nonionic surfactant was used as the stabilizer of W/O emulsion. The test results showed that Fe3O4/PAM MNHs were quasi-sphere particles with a diameter of about 50–380 nm and had superparamagnetism. The percentage of PAM coating Fe3O4 was about 81%. The saturation magnetization of the Fe3O4/PAM MNHs was 21.6 emu/g (Fe3O4/AM (wt/wt) = 16.63%). The W/O emulsion containing Fe3O4/PAM MNHs (E-2) changed from fluid to solidlike in an external magnetic field. As current intensified or shear rate increased, the shear stress of E-2 increased.

High gel-strength hybrid hydrogels based on modified starch through surface cross-linking technique

Modification of starch with a microgel latex has been suggested as a novel method for preparing a hybrid hydrogel. The microgel latex, (poly (NaAA–AA–AM–AMPS)), was synthesized through inverse emulsion polymerization and used for modification of starch. The maximum absorbency of distilled water was achieved as 87 g/g for the hybrid hydrogel. A key advantage of this hybrid hydrogel is a high percentage (about 70%) of natural component. Since hybrid hydrogels are mechanically weak, the surface cross-linking technique was carried out to increase the gel strength and the absorbency under load (AUL), by employing 3-(2,3-epoxypropoxy) propyl trimethoxysilane. The AUL of hydrogels was increased from 6.5 to 17 g/g after surface cross-linking. The current hydrogels have overcome two limitations of hybrid hydrogels (i.e., low gel strength and low contribution of the natural part) which caused them not be commercial yet. Therefore, the current hydrogels have the potential to be used in agricultural applications, due to their high AUL and low acrylamide content.

Ternary composites of polyaniline with polyvinyl alcohol and Cu by inverse emulsion polymerization: A comparative study

AbstractAddition of inorganic particles and insulating polymeric materials to conducting polymers allows the alteration and modification of physical properties of the conducting polymer. An inverse emulsion polymerization technique was employed for the synthesis of polyaniline (PANI), composites of PANI with copper (PANI‐Cu), polyvinyl alcohol (PANI‐PVA), as well as composites of PANI with Cu and PVA (PANI‐Cu‐PVA) under comparable experimental conditions. The FTIR and UV/Vis, spectra were employed to determine the chemical structure. The morphology of the synthesized composites was studied by SEM technique. The XRD pattern illustrates good crystallinity of the composites with improved conductivity at room temperature. The TGA results show an increase in the thermal stability of the composites. The results show that co‐addition of PVA and Cu into PANI greatly affects the properties of PANI as well as the solubility as the composites were soluble in a number of commonly used organic solvents such as DMSO, NMP, chloroform, 2:1 mixture of chloroform and 2‐propanol, and 2:1 mixture of toluene and 2‐propanol.

Thermoviscosifying polymers based on polyether prepared from inverse emulsion polymerization

ABSTRACTThermoviscosifying polymers are attractive for enhancing oil recovery owing to their exceptional thickening power as temperature increases. However, the polymers reported to date show inadequacies including obligatory high polymer concentration to get the thermothickening ability because of their low molecular weight (MW), and inconvenient post‐treatment due to the high viscosity after manufacturing. To overcome these drawbacks, inverse emulsion polymerization was used here for preparing polyether‐based thermoviscosifying polymers (TVP‐Ps) by grafting acrylic monomers onto triblock copolymers PEO–PPO–PEO. It was found the MW of final products could reach 8 million Daltons, making them thermoviscosifying at 0.2 wt %. The viscosity of polymerized inverse emulsions was as low as 175 mPa·s, leading to direct dispersing. The TVP‐Ps containing Pluronic F127, F108, F68 all exhibited significant thermothickening behaviors in both aqueous solutions and brines, and the critical thermoassociative temperature could be tuned by changing the nature or amount of Pluronics. After aging at 45 °C for 60 days with equal initial viscosity, TVP‐Ps shows 21% higher viscosity retention than the reference polymer without Pluronic, PAMA, and preliminary core flooding test demonstrated TVP‐Ps can get 2.1% higher incremental oil recovery than PAMA. This work paves a new avenue for scaled‐up preparation and potential use of TVP‐Ps. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 134, 46696

A novel silica aerogel microspheres loaded with ammonium persulfate gel breaker for mid-deep reservoirs

As one of the important additives in the process of petroleum’s exploitation, the gel breaker is a key factor to determine whether the exploitation can be completed successfully. Here, a novel porous SiO2 aerogel microsphere loaded with ammonium persulfate (aAPS) with obvious delay-releasing performance under higher temperature and pressure was synthesized by the process of sol–gel and water-in-oil (W/O) inverse emulsion polymerization. The obtained gel breaker was characterized by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The releasing rate of ammonium persulfate of gel breakers under different conditions was determined by pH meter method. The results show that the loading of APS is about 53 wt% and the releasing rate is significantly affected by temperature and time.

A comprehensive investigation of polymer microspheres (PMs) migration in porous media: EOR implication

A type of polymer microspheres (PMs) with superior dispersity, swelling, elasticity, and saline and temperature resistance was prepared in this work through inverse emulsion polymerization. It was observed that these PMs experienced elastic deformation and obstructed micro-pores by means of complete, single and bridge plugging, and thus causing additional flow resistance. The migration modes of the PMs in porous media could be defined as smooth pass, elastic plugging-remigration incorporating low-efficiency and high-efficiency plugging, and complete plugging, on the basis of matching coefficients between the PMs and pore geometry. The plugging capability of the PMs was largely dependent on the matching coefficients. Interestingly, it was found that if appropriate matching coefficients was obtained, the PMs with higher elastic modulus showed an enhanced plugging capability even with smaller particle size. In addition, the results of adsorption and desorption behaviors of the PMs implied that the adsorbed PMs partially detached as a result of caused flow fluctuation and decline/disappearance of secondary adsorption potential well. It is believed that the proposed PMs could be a viable, robust and promising candidate for conformance control and oil recovery improvement.

Polyaniline@CuNi nanocomposite: A highly selective, stable and efficient electrode material for binder free non-enzymatic glucose sensor

We present an efficient, highly selective and binder free non-enzymatic glucose sensor based on polyaniline@copper-nickel (PANI@CuNi) nanocomposite. PANI@CuNi nanocomposites with different loading ratio of nanoparticles (1: 025, 1: 0.33, 1: 05 and 1: 1) were prepared by mixing solution of PANI, synthesized through inverse emulsion polymerization method, and CuNi nanoparticles, synthesized through polyol process. The as prepared PANI@CuNi nanocomposites were coated on glassy carbon substrate without binder for non-enzymatic glucose sensing. A considerable increase in the active surface area of the electrode occurred after coating of this material. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry demonstrated that PANI@CuNi nanocomposite with 1: 0.5 ratio could be a good choice to be used as electrode material for non-enzymatic glucose sensing. The PANI@CuNi modified electrode exhibited high sensitivity (1030 μA mM−1 cm−2), good lower detection limit (0.2 μM) and a linear range of 5.6 mM (R2 = 0.992) with additional advantage of excellent selectivity, high stability and effective detection in real blood samples.

A Novel Magnetic Separation Agent Prepared by Inverse Emulsion Polymerization and Magnetic Separation Performance for Dye in Solution

The discharge of industrial wastewater containing dyes is a matter of concern because dyes have harmful effects on the environment and human health. In this work, a novel magnetic separation agent of Fe3O4/poly (acrylamide-acryloyloxyethyl thimethylammonium chloride) [MCPAM] was designed for high-performance removal dyes by taking advantage of magnetic separation property of Fe3O4 nanoparticles. MCPAM was synthesized through inverse emulsion polymerization and the optimal reaction conditions were obtained by orthogonal experiments. The shape and size of MCPAM was detected by transmission electron microscopy (TEM). The chemical bonds and functional groups of MCPAM were measured by fourier transform infrared spectroscopy (FT-IR). The magnetic properties of MCPAM was surveyed by Superconducting Quantum Interference Device (SQUID MPMSXL). The magnetic separation performance of MCPAM was studied through detecting the removal efficiency of reactive red dye X-3B. The results showed that the MCPAM had core-shell structures and good magnetic properties. And the MCPAM has great potential in accelerating solid-liquid separation and improving removal efficiency of pollutants such as dye colloid in wastewater.

Anticorrosion Activity of a Polyacrylamide with High Molecular Weight on C-Steel in Acidic Media: Part 1

The chemical structure of a polyacrylamide (PA), synthesized by inverse emulsion polymerization, was confirmed by FTIR and 1H NMR. The experimental conditions were conducted to produce high molecular weight of 1.4 × 106 g mol−1 determined by both gel permeation chromatography and viscosity average molecular weight methods. The efficiency of PA was evaluated, on corrosion inhibition of C-steel in 1.0 M HCl solution, by means of electrochemical impedance spectroscopy, potentiodynamic polarization (PP), and mass-loss (ML) measurements, and a very good concordance was obtained from the three techniques. The inhibiting efficiency increased up to 4 × 10−6 mol L−1 and dropped down afterward. The PP curves revealed that PA was of mixed-type, influencing predominantly the anodic process. The electrochemical interface was satisfactorily modeled with the electrical circuit (RS + Qdl/Rct) using CPE(α,Q) reflecting one-time constant. This fact, testifying the dominant character of charge transfer control of the C-steel corrosion process, was well described in both Nyquist along with Bode diagrams which take into account the frequency dependence, justifying the suitable choice of the electrical circuit. The adsorption of PA involved both physical and chemical interactions of non-protonated and protonated molecules with a deeper discussion on the suitable sites of protonation. The performance of PA was maintained if not slightly ameliorated in a more aggressive medium such as 0.5 M H2SO4 at 298 K. Two-time constants were needed to model the electrochemical interface (RS + Qdl/(Rct + RL/L)).

Investigation of synthesized polymer on the rheological and filtration performance of water-based drilling fluid system

Based on the molecular structure requirement of the synthesized polymer resistant to higher temperature and the lower cost demand of water-based drilling fluid system, a kind of synthesized polymer Poly(SSS/AM/AMPS) was prepared by using 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide (AM) and sodium p-styrenesulfonate (SSS) through inverse emulsion polymerization. Firstly, the molecular structure, molecular weight distribution and thermal stability were studied. Secondly, the Poly(SSS/AM/AMPS) was introduced into water-based drilling fluid system. As a result, when adding amount is 1.2 wt%, it was found that the water drilling fluids is more fitted to the Herschel - Bulkley flow model. Besides, before and after thermal aging test, the FLAPI of drilling fluid system is 9.20 and 9.40 mL, respectively. Moreover, it was shown that the higher temperature resistance of drilling fluid system was also improved, and the operation cost was decreased. Furthermore, the results of adsorption analysis, zeta potential method and morphology analysis shows that Poly(SSS/AM/AMPS) improves the filtration properties of drilling fluid system by absorption and physical plugging.

Fabricating core (Au)-shell (different stimuli-responsive polymers) nanoparticles via inverse emulsion polymerization: Comparing DOX release behavior in dark room and under NIR lighting.

Different core-shell nanoparticles with Au as core and stimuli-responsive polymers such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), poly(N-isopropylacrylamide) (PNIPAAm), poly(N,N'-methylenebis(acrylamide)) (PMBA), poly(2-hydroxyethyl methacrylate) (PHEMA) and poly((2-dimethylamino)ethyl methacrylate) (PDMAEMA) as shells were fabricated via inverse emulsion polymerization. Dynamic light scattering (DLS) was used to investigate particles sizes and particle size distributions and transmission electron microscopy (TEM) was applied to observe the core-shell structure of Au-polymer nanoparticles. Also, surface charge of all samples was studied by measurement of zeta potentials. Synthesized core-shell nanoparticles were utilized as nanocarriers of DOX as anti-cancer drug and drug release behaviors were investigated in dark room and under irradiation of near-infrared (NIR) light. Results showed that all core-shell samples have particle sizes less than 100 nm with narrow particle size distributions. Moreover, amount of drug loading decreased by increasing zeta potential. In dark room, lower pH resulted in higher cumulative drug release due to better solubility of DOX in acidic media. Also, NIR lighting on DOX-loaded samples led to increasing cumulative drug release significantly. However, DOX-loaded Au-PAA and Au-PMAA showed higher drug release at pH = 7.4 compared to 5.3 under NIR lighting.

CdS nanodots preparation and crystallization in a polymeric colloidal nanoreactor and their characterizations

Cadmium sulfide (CdS) nanodots in polymeric colloidal reactors were prepared by seeded inverse emulsion polymerization and then crystallized solvothermally. The cadmium sulfate (CdSO4)-polyacrylamide (PAM) seeds were synthesized by inverse miniemulsion polymerization with CdSO4 solution as a co-stabilizer. The prepared CdSO4-PAM particles were used as polymeric colloidal reactors for the formation of CdS-PAM by feeding the mixed solution of sodium sulfide (Na2S) and acrylamide. The effects of the feeding rate on the size, distribution and morphologies of particles were investigated. The influences of the solvothermal treating temperature and time on the crystallite size were characterized. The CdS was well formed and then crystallized in the PAM colloidal reactors. The crystals growth mechanism was taken under consideration. The crystallite size was calculated by the X-ray diffraction (XRD) data, and their morphologies were observed by transmission electron microscopy (TEM). The small CdS crystals showed a blue-shift on the spectra of ultraviolet visible absorption and fluorescence emission. The small CdS crystals displayed the desired property of photocatalytic degradation.

Tunable poly(methacrylic acid-co-acrylamide) nanoparticles through inverse emulsion polymerization.

Environmentally responsive biomaterials have played key roles in the design of biosensors and drug delivery vehicles. Their physical response to external stimuli, such as temperature or pH, can transduce a signal or trigger the release of a drug. In this work, we designed a robust, highly tunable, pH-responsive nanoscale hydrogel system. We present the design and characterization of poly(methacrylic acid-co-acrylamide) hydrogel nanoparticles, crosslinked with methylenebisacrylamide, through inverse emulsion polymerization. The effects of polymerization parameters (i.e., identities and concentrations of monomer and surfactant) and polymer composition (i.e., weight fraction of ionic and crosslinking monomers) on the nanoparticles' bulk and environmentally responsive properties were determined. We generated uniform, spherical nanoparticles which, through modulation of crosslinking, exhibit a volume swelling of 1.77-4.07, relative to the collapsed state in an acidic environment. We believe our system has potential as a base platform for the targeted, injectable delivery of hydrophilic therapeutics. With equal importance, however, we hope that our systematic analysis of the individual impacts of polymerization and purification conditions on nanoparticle composition, morphology, and performance can be used to expedite the development of alternate hydrophilic nanomaterials for a range of biomedical applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1677-1686, 2018.

Synthesis of hybrid microspheres from zirconium butoxide and an ionic–non-ionic copolymer

This work presents the synthesis and characterization of hybrid microspheres made of hydrated zirconium oxide and an organic copolymer. The synthesis was carried out in a two-stage procedure. First, the polymer microspheres were synthesized via the inverse emulsion polymerization of 4-vinyl benzyl trimethyl ammonium chloride (ClVBTA) and 2-hydroxy ethyl methacrylate (HEMA), and second, the copolymeric beads were impregnated with an inorganic precursor (Zr(ButO−)4) to form the hybrid through a sol-gel reaction. Several experimental variables were controlled in both stages of the synthesis, such as the formulation of the emulsion, concentration of the surfactant, molar ratio of the monomers, concentration of the inorganic precursor, and soak time. Well-defined microspheres with low polydispersity were obtained with a volume ratio of 0.2 and a low Span 80 surfactant concentration. While an increase in the ClVBTA/HEMA molar ratio enhanced the hydrophilicity of the particles, it did not necessarily increase the incorporation of oxide. Additionally, an increase in ClVBTA/HEMA decreased the resistance of the composite microspheres to the osmotic shock, resulting in rupturing of the beads. This polymer hybrid microspheres can be used in applications where surface processes are involved.

Understanding the semicontinuous‐heterophase, surfactant‐supported, acrylamide inverse polymerization

In this work, a simple comprehensive mathematical model, to understand the main mechanisms occurring in the semicontinuous heterophase inverse polymerization of acrylamide, is reported. A Mayo‐Lewis extended model, including nucleation and coagulation, is assessed with experimental conversion, particle density and inferred average number of radicals versus time‐data at 60°C, at three monomer addition rates. It was found that: (1) the average number of radicals is much smaller than 0.5 contrary to most of inverse emulsion and microemulsion polymerization reports, this number increased steadily along the experiments, (2) coagulation does exist in this process, and (3) the exit rate coefficient was found to present a high value, agreeing with other authors that claim a large exit rate. Conversion, the bell‐shaped number of particles' evolution and number average radicals' concentration, versus time data, are well described by the proposed model. POLYM. ENG. SCI., 58:2219–2226, 2018. © 2018 Society of Plastics Engineers

Remarkable hydrogen storage properties and mechanisms of the shell–core MgH2@carbon aerogel microspheres

Carbon aerogel (CA) microspheres with highly crumpled graphene–like sheets surface and network internal structure have been successfully prepared by an inverse emulsion polymerization routine, subsequently ball milled with Mg powder to fabricate Mg@CA. The Mg change into MgH2 phases, decorating on the surface of the CA forming MgH2@CA microspheres composite after the hydrogenation process at 400 °C. The MgH2@CA microspheres composite displays MgH2–CA shell–core structure and shows enhanced hydrogenation and dehydrogenation rates. It can quickly uptake 6.2 wt% H2 within 5 min at 275 °C and release 4.9 wt% H2 within 100 min at 350 °C, and the apparent activation energy for the dehydrogenation is decreased to 114.8 kJ mol−1. The enhanced sorption kinetics of the composite is attributed to the effects of the in situ formed MgH2 NPs during the hydrogenation process and the presence of CA. The nanosized MgH2 could reduce the hydrogen diffusion distance, and the CA provides the sites for nucleation and prevents the grains from agglomerating. This novel method of in situ producing MgH2 NPs on zero–dimensional architecture can offer a new horizon for obtaining high performance materials in the hydrogen energy storage field.

Hybrid hydrogel based on pre-gelatinized starch modified with glycidyl-crosslinked microgel

Hybrid hydrogels based on pre-gelatinized starch were synthesized by inverse emulsion polymerization through modifying the starch with a glycidyl-crosslinked microgel. Glycidyl-crosslinked microgel is a special latex with high ability to impart hydrophilic characteristics to various substrates. Glycidyl-crosslinked microgel latexes with various structures were synthesized, and the effect of latex type on swelling capacity of the hybrid hydrogels based on pre-gelatinized starch was investigated. The highest swelling capacity was achieved for a pre-gelatinized starch modified with a glycidyl-crosslinked microgel latex based on poly(acrylic acid, sodium acrylate, acrylamide, 2-acrylamide-2 methyl propane sulfonic acid) (AA–SA–AM–AMPS). The swelling values of this hybrid hydrogel in distilled water and saline solution were 52.4 and 28.8 g/g, respectively. A key advantage of these hybrid hydrogels is that starch constitutes 64% of their structure. Given the fact that such hybrid hydrogels display low absorbency under load (AUL), they were surface crosslinked using microwave heating instead of conventional heating. Ethylene glycol diglycidyl ether was used as surface crosslinker. The AUL of the surface crosslinked hybrid hydrogels was increased by 85%. The hydrogels were characterized using FTIR, thermogravimetric analysis, scanning electron microscopy, and rheological measurements.

Investigation into the migration of polymer microspheres (PMs) in porous media: Implications for profile control and oil displacement

To reduce the unwanted water and further enhance oil recovery, a profile control agent, named polymer microspheres (PMs), was synthesized by inverse emulsion polymerization and its physical properties including morphology, particle size distribution, dispersibility strength and hydration swelling property were thoroughly examined. The main goal of this paper was to investigate the migration behaviors of the PMs in porous media using visual micromodel, nuclear magnetic resonance (NMR) and core displacement tests. The visual images indicated the PMs could plug the high permeability area and divert the subsequently injected fluid to lower permeability area. Moreover, the PMs could re-migrate in the high permeability area and displace residual oil due to elastic deformation. The NMR results revealed that the PMs with low expansion rate and high elasticity generated higher swept volume and displacement efficiency, thus leading to higher oil recovery, compared to those having high expansion rate and low elasticity. It can be observed from oil-water relative permeability curves that compared with water flooding (WF), the oil-water isotonic point was shifted into higher water saturation and disproportionate permeability reduction (DPR) occurred during PMs flooding (PMF). Finally, the profile control and displacement mechanisms of PMs were proposed based on the experimental observations.