Preparation Of Polymer Microspheres Research Articles

Preparation of polymer microspheres as oil displacement agent for extra-high temperature and extra-high salinity reservoirs

Based on the difficult problem that conventional polymer and gel can't be used for enhancing oil recovery in extra-high temperature (200 °C) and extra-high salinity (2 ×105 mg/L) reservoirs，an anti-temperature anti-salinity microspheres was prepared with 2,2′-bis[4-(4-aminophenoxy)phenyl] propane (BAPP), 3, 3′, 4, 4′-diphenyl ether dianhydride (ODPA) and phthalic anhydride (PA) as the monomers. The FTIR results showed that the temperature- and salt-resistant polyimide (PI) microspheres were prepared as target product. TGA showed that thermal decomposition of the unaged and aged PI-2 microspheres occurred over 281 °C and 252 °C, respectively; These values greatly exceed those of commercial HPAM, weak gel particles and pre-crosslinked gel particles. After the polyimide microspheres were aged for 120 d, the enhanced oil recovery of the PI-2 microspheres does not decrease significantly, so the long-term stability of two polyimide microspheres are very good at 200 °C and total dissolved solids (TDS) = 2 × 105 mg/L. The PI-2 microspheres had better properties than the conventional polymer and gel as profile control agent and water plugging agent. The microspheres possess the characteristics of being able to inject, block, and move, resulting in excellent oil displacement efficiency. The results of core displacement experiments revealed that PI-2 microspheres are highly efficient in oil displacement and have a strong ability to improve the water injection profile. Therefore, PI-2 microspheres can be used as an oil displacement agent in reservoirs with extremely high temperature and salt content.

Preparation of Hollow-Porous Rosin-Based Polyurethane Microspheres with pH-Responsive Characteristics

Preparation of polymer microspheres from naturally occurring resource is a challenge. Here, a rosin-based polyol (RAG) was used to prepare polyurethane resin (RPU) firstly, and then act as both self-assembled precursor and emulsifier, rosin based polyurethane microspheres (RPUMs) were prepared. In the process of self-emulsification, the RPU formed vesicles by self-assembly. The outer shell of the vesicle consisted of hydrophilic segments, while the inner shell contained the hydrophobic phase. After cross-linking the RPU and removal of the solvent in the core, the porous-hollow microspheres with pH-sensitive were obtained. The microspheres were characterized by optical microscope (OM), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The effect of type and amount of the hydrophilic chain extender, and solvent on the morphology, particle size and distribution, and buffer volume of the microspheres were determined. The best conditions for synthetic RPUMs were as follows: nNCO/nOH = 1, nRAG:n1-(2-hydroxyethyl) piperazine = 4:6, with azodiisobutyronitrile level of 1.0 wt.%, based on reactive monomers, mixing speed of both emulsification and polymerization at 400 r·min−1, the RPUMs synthesized had porous-hollow structure with a buffer volume of 1.6 mL.

Synthesis of oligosiloxanes with 3-aminopropyl groups and their testing as surfactants in the preparation of polymer microspheres

Polydimethyl-co-methyl(3-aminopropyl)siloxanes differing in the content of amino groups and molecular weight were synthesized by two pathways, namely, by hydrosilylation of oligodimethyl-co-methylhydrоsiloxane with N-(trimethylsilyl)allylamine (TMSAA) and by copolymerization of octamethylcyclotetrasiloxane with methyl(3-aminopropyl)cyclosiloxanes. The colloid-chemical properties of the synthesized oligomers were studied. The oligosiloxanes possess high surface activity and can reduce the interfacial tension in the interface surfactant solution in toluene–water to 6.7–4.2 mJ m2. Aggregatively stable polystyrene suspensions with particle of 0.5 and 0.8 μm in diameter were obtained in the presence of the synthesized oligomers.

Preparation of polymer microspheres with reactive epoxy group and amino groups as stabilizers for gold nanocolloids with recoverable catalysis

Narrow disperse poly(divinylbenzene-co-glycidyl methacrylate) (P(DVB-co-GMA)) microspheres with reactive epoxy group were prepared by distillation precipitation copolymerization of divinylbenzene (DVB) and glycidyl methacrylate (GMA) with benzoyl peroxide (BPO) as initiator in neat acetonitrile. The epoxy group was modified with ethylenediamine (EDA) for transferring to amino group, which was used as a stabilizer for the gold metallic nanocolloids during the in situ reduction of gold chloride trihydrate (HAuCl4) with sodium borohydride (NaBH4) as a reductant. The catalytic properties of the microsphere-stabilized gold nanocolloids (P(DVB-co-GMA)-NH2@Au) were investigated by the reduction of aqueous 4-nitrophenol (4-NP) to 4-aminophenol (4-AnP) with NaBH4 as reductant. The resultant microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectra (FT-IR), elemental analysis (EA), Zeta potential, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP) mission spectrum, and ultraviolet–visible spectroscopy.

Progress in membrane liquid–liquid reactor—a review

Liquid–liquid reactions are crucial in chemical synthesis and industries, such as hydrolysis, oxidation, reduction, nitration, and sulfonation of organic compounds. In recent years, membrane liquid–liquid reactors have drawn great attentions due to the elevated conversion, selectivity, yield, and efficiency. Membrane liquid–liquid reactors can be divided into membrane dispersive reactor and membrane non-dispersive reactor. The membrane dispersive reactor has been employed in the preparation of polymer microspheres and microcapsules. The non-dispersive membrane reactors are widely used in chemical reactions (e.g. consecutive, reversible, and irreversible reactions) and biochemical reactions (e.g. resolution of racemic compounds, and reaction of non-chiral substrate). The feature, applications, advantages, and limits of the membrane liquid–liquid reactors are briefly reviewed.

Polymeric microspheres preparation by membrane emulsification-phase separation induced process

Uniform Polyethersulfone (PES) microspheres of target size in the range of 30–60µm were successfully prepared by combining membrane emulsification technology and phase separation induced process in one step. An emulsion is generated by injecting the polymeric solution through a microporous membrane into the continuous phase which allows also the phase separation induced process and precipitation of the polymer (coagulation bath). Therefore, the droplets formation and solidification occur in a single step. Furthermore, the preparation of non-aqueous (O/O) emulsions by membrane emulsification as well as the preparation of polymeric microspheres by non-solvent induced phase separation has never been reported previously. The effect of continuous phase-coagulation bath composition, hydrophobic emulsifier, dispersed phase flux and shear stress on size and uniformity of PES microspheres has been investigated. Key factors in microspheres production by membrane emulsification and phase separation induced process mechanism include the solvent/non-solvent system type, non-solvent composition and O/O interface composition. Polymeric microspheres with spherical morphology have been produced by tailoring such key factors.

Biodegradable paclitaxel‐loaded microparticles prepared from novel block copolymers: influence of polymer composition on drug encapsulation and release

This study covers the preparation of microspheres for the controlled and targeted release of paclitaxel, using novel degradable polymers as carrier materials. Paclitaxel-loaded microspheres were prepared by oil-in-water single-emulsion solvent extraction/evaporation technique by using a series of polyurethanes and a block copolymer; the physicochemical properties of these polymers were modulated by changing nature and composition of their structural units. The obtained microparticles showed a regular morphology and properties (diameter: 1-100 µm; resuspension index: 18.8-100%; encapsulation efficiency: 26.6-97.2%) depending on polymer hydrophilicity and emulsifier used. In vitro release curves showed in all cases almost zero-order kinetics after an initial low burst effect (from 1 to 8.4%), which is required to minimize the drug side effects. This work also proposes a novel strategy to combine a controlled and a targeted release through the functionalization of the polymer matrix with peptide sequences. An RGD-functionalized polyurethane was used to successfully prepare paclitaxel-loaded microparticles. Studies on the preparation of polymer microspheres are reported.

Preparation of Polymeric Microspheres for Controlled Release of Acetamiprid

Preparation of Polymeric Microspheres for Controlled Release of Acetamiprid

Rapid Synthesis of Non-Crosslinked and Monodisperse Polystyrene Microspheres

Non-crosslinked and monodisperse polystyrene (PS) microspheres showing uniform size were synthesized by using a dispersion polymerization technique in the presence of the Fenton reagent (FeSO4/H2O2) as an initiator. The effects of stabilizer dosage, monomer concentration, volume ratio of dispersion medium and reaction time on both the morphology and dispersity of PS microspheres were investigated. The results of transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM) indicated that the obtained PS microspheres are perfect with uniform size of about 170 nm under the optimum experimental condition. On the basis of the experimental results, the mechanism of PS polymerization was proposed, which should be helpful to guide the preparation of polymer microspheres with desired uniform size. In comparison with the conventional emulsion polymerization, this new synthesis technique with the Fenton reagent exhibits some advantages such as being a simple and fast polymerization process without deoxygenation.

Preparation of polymer microspheres with a rosin moiety from rosin ester, styrene and divinylbenzene

AbstractRosin was reacted with hydroxyethyl methacrylate to produce a macromonomer. This macromonomer was used to partly replace styrene for the novel preparation of polymer microspheres with divinylbenzene via suspension polymerization. Orthogonal experiments were conducted to analyze the factors influencing the particle size, particle size distribution, swelling ratio and degree of crosslinking of the polymer microspheres. Fourier transform IR spectroscopy, thermogravimetry and scanning electron microscopy were used to examine the structures, thermal properties and morphologies, respectively, of the polymer microspheres. The results showed that the amount of dispersant had the greatest influence on particle size and distribution. On the other hand, the monomer ratio greatly influenced the swelling ratio and degree of crosslinking of the polymer microspheres. The decomposition temperature of the polymer microspheres increased upon introduction of the rosin moiety into the product. Open pores were abundant on the surface of the polymer microspheres due to the existence of the porogen, which provided a base for adsorption and separation. The present study opens a novel route for using naturally occurring rosin. Copyright © 2012 Society of Chemical Industry

Preparation of polymer microspheres in supercritical carbon dioxide and their evaluation as cold‐flow improvers in diesel

AbstractPolymeric microspheres were synthesized by the precipitation copolymerization of methacrylic acid and styrene in supercritical carbon dioxide. Scanning electron microscopy showed that the products were spherical microparticles. The mean diameter of the particles was 0.2–2 μm. The synthesis conditions affecting the particle size and morphology were examined in detail. The well‐distributed copolymer microspheres were applied as low‐temperature improvers for diesel. The results showed excellent performance for high‐paraffin diesel at low temperatures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Preparation of polymeric microspheres with high content of sulphonate groups

Poly(styrene-co-sodium styrene sulphonate) (P(St-NaSS)) latex particles were prepared using the mixture of ethanol and water as continuous phase in the presence of surfactant by dispersion–emulsion combined polymerization. The influence of recipes on polymerization process as well as the content of sulphonate group in the purified products was investigated. Results showed that the copolymerization could be performed smoothly. When the mole ratio of NaSS/St/divinyl benzene (DVB) was 25/75/2 and the weight ratio of ethanol/water was 2/11, the product showed a low weight loss in methanol extraction purification, and the NaSS unit ratio in the purified product reached 20.6 mol%, which was close to its theoretical value of 24.9 mol%.

Influence of Rheology of Dispersion Media in the Preparation of Polymeric Microspheres through Emulsification Method

Chitosan microspheres as drug delivery system have attained importance and attracted the attention of researchers in last few years. This study was aimed toward the elucidation of the effect of viscosity of external oil phase on the properties of microspheres prepared by emulsification method. Chitosan microspheres were prepared utilizing oil phase of different viscosity viz. castor oil, heavy liquid paraffin, light liquid paraffin and mixture of light paraffin, and petroleum ether (1:1 v/v ratio). Microspheres prepared in highly viscous castor oil exhibited an average size of 11.52+/-0.57 microm with a percentage drug entrapment of 43.12+/-2.14. On the other hand, very small microspheres of 3.15+/-0.04 microm and 68.87+/-1.03% drug entrapment were obtained when mixture of liquid paraffin and petroleum ether was utilized as oil phase. Effect of viscosity on percent mucoadhesion, percent drug entrapment, zeta potential, percent process yield, etc. of microspheres has been observed. In vitro drug release in phosphate buffer pH 7.4 was determined for different batch of microspheres. The results revealed a difference in the drug release pattern of the different microspheres prepared as a function of viscosity of different oil phase. Use of low viscose oil resulted in the formulation of spherical and small size microspheres. This work was a part of our ongoing thrust and project to develop microparticulate drug delivery system.

Preparation of Polymer Microspheres by Phase-Separation/Aggregation (PSA) Technique for Color Toner Applications

A particle formation method related to controlled phase separation of organic and aqueous phases, and limited aggregation/coalescence is reported. The method can be applied effectively to form microspherical polymer particles for use as electrophotographic toners. An organic solution containing a polymer resin dissolved in a solvent and an aqueous phase containing an anti-aggregation agent are prepared. The aqueous solution is added to the organic solution during vigorous stirring to facilitate aggregation of gel colloids and diffusion of solvent into the aqueous phase due to the partial aqueous solubility of the solvent. As opposed to the case when the organic phase is added to the aqueous phase under an extremely high speed of agitation (>10,000 rpm), this phase-separation/aggregation process only requires an agitation speed of 1,000∼1,500 rpm. Furthermore, removal of solvents due to diffusion into the aqueous phase is in process at the same time as the formation of gel particles. The depletion of solvents in the organic phase results in solid particle formation. Fine control of particle size distribution can be achieved by careful adjustments of the viscosity values of both the organic and the aqueous solutions. This phase-separation/aggregation method offers numerous advantages for preparation of toners including fast production run and extremely sharp particle size distribution, with mean volume-averaged diameter to mean number-averaged diameter ratios dv/dn smaller than 1.1. The particle shape can also be tuned by the selection of different aqueous solubility of the solvents. Both styrene/acrylate based and polyester based materials can be applied for formation of microspherical particles by using the phase-separation/aggregation technique.

Compromise between dominant polymerization mechanisms in preparation of polymer microspheres

A system consisting of uniform-sized styrene monomer droplets dispersed in an aqueous phase was employed to study the compromise between dominant polymerization mechanisms in the preparation of polymer microspheres. Monomer droplets were prepared by a microporous membrane emulsification technique, with negligible size distribution. Two polymerization mechanisms were identified—polymerization in micro-sized monomer droplets and nano-sized secondary nuclei, even in the presence of a hydrophobic initiator. Factors affecting the compromise between these two dominant mechanisms were investigated. Increasing the amount of hydrophobic additive (hexadecane) and/or adding water-soluble inhibitor in the aqueous phase suppressed the polymerization in the secondary nuclei, while adding a relatively hydrophilic monomer in the styrene feed and/or increasing the amount of the initiator and the size of the monomer droplets promoted the polymerization in the secondary nuclei. Under the condition where a hydrophilic monomer was added, hollow microspheres were formed when polymerization in the secondary nuclei was dominant, while one-hole microspheres resulted when polymerization occurred only inside the larger monomer droplets, indicating that the compromise between dominant mechanisms is critical to the polymerization process.

A one-step method to prepare monodisperse polymer particles in the micron size range

Micron-sized, monodisperse PMMA microspheres were produced in TEOS, under static condition by one step. The mechanism of this novel self-formation method was studied based on experiment results; it was found that the growth of PMMA microspheres was in two ways. The properties of the intermediate particles were studied by several methods. The size of finally obtained polymer particles could be controlled by adjusting the content of monomer in initial polymerization solution. The influence of the polymerization temperature on the preparation of polymer microspheres was also investigated.

Preparation of polymer microspheres from solutions

AbstractPolymer microspheres are obtained by the dropwise addition of a precipitant, containing a polymeric stabilizer, into a polymer solution, containing a polymeric stabilizer. The polymer and stabilizer concentrations, the stirring speed, and the precipitation temperature determine the size and size uniformity of the microspheres. Seven polymer microspheres of polyimide, poly(ether imide), poly(ether ketone), poly(phenylene oxide), polysulfone, poly(vinylidene fluoride), and cellulose diacetate have been prepared with dimethylacetamide as the solvent, with water as the precipitant, and with poly(vinyl alcohol) as the stabilizer. The size and size uniformity of the obtained microspheres are d = 2.3–25.7 μm and ϵ = 0.15–0.50, respectively (ϵ = σ/d, where ϵ is the dispersion coefficient, d is the average diameter, and σ is the standard deviation of the diameter). © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 159–165, 2003

Preparation of polymeric microspheres by the solvent evaporation method using sucrose stearate as a droplet stabilizer

Polymeric micro spheres containing nicardipine hydrochloride (HCI) as a reference drug were prepared with the acrylic polymers Eudragit RS and L by the solvent evaporation method. Different concentrations of sucrose stearate as a droplet stabilizer were used. Sucrose stearate affected the diffusion rate of the solvent from the preliminary emulsion droplets to the outer phase for the formation of microspheres. Increasing concentrations of sucrose stearate in the formulations caused increasing porosity on the surface of the microspheres. However, a correlation between the concentrations of sucrose stearate and diameters of micro spheres could not be assessed. From this point of view, during processing, applied stirring rate was important.

Ultrastructure Synthesis and Nonlinear Spectroscopy of Photonic Materials

Abstract A brief progress report is provided on (1) the fabrication and integration with high speed VLSI circuitry of high frequency organic electro-optic modulators and (2) preparation of polymer microspheres, containing one or more layers of covalently coupled chromophores, capable of supporting morphological resonances.

Polymeric microspheres by radiation copolymerization of acrolein and various monomers at low temperatures

The preparation of polymeric microspheres having aldehyde groups by radiation polymerization of acrolein solution containing various monomers at low temperatures was studied, in which the monomer solution was dispersed with polyvinyl alcohol in order to obtain monomeric microspheres and then irradiated. The particle size of the microspheres from acrolein — 2-hydroxyethyl methacrylate system varied with polymerization and dispersion condition, in which the particle size increase of the concentration of 2-hydroxy ethyl methacrylate and its particle size distribution was broadened. In acrolein — polyethyleneglycol dimethacrylate system, the effect of the molecular structure of monomers on the particle size was studied, and it was found that the particle size decreased with number of oxyethylene units in monomers.