Role of liquid crystal in the emulsification of a gel emulsion with high internal phase fraction

A gel emulsion with high internal oil phase volume fraction was formed via an inversion process induced by a water–oil ratio change. The process involved the formation of intermediate multiple emulsions prior to inversion. The multiple emulsions contain a liquid crystal formed by the surfactant with water; this was both predicted by the equilibrium phase diagram as well as observed using polarization microscopy. These multiple emulsions were more stable compared to alternative multiple emulsions prepared in the same way with a surfactant that does not form liquid crystals. While the formation of a stable intermediate multiple emulsion may not be a necessary condition for the inversion to occur, the transitional presence of a liquid crystal proved to be a significant factor in the stabilization of the intermediate multiple emulsions. The resulting gel emulsion contained a small fraction of the liquid crystal according to the phase diagram, and it exhibited excellent stability.     

Preparation of P(AN–MMA) microporous membrane for Li-ion batteries by phase inversion

A novel process was proposed for preparation of microporous poly(acrylonitrile–methyl methacrylate) (P(AN–MMA)) membranes by phase inversion techniques using ultrasonic humidifier. Being prepared by dissolving the polymer (PAN–MMA) in the N,N-dimethylformamide (DMF) solution with mechanical stirring, the homogenous casting solution was cast onto a clean glass plate. Successively, the glass plate was exposed to the water vapor produced by ultrasonic humidifier, inducing the phase inversion. It is found the pore size is much more uniform across the cross-section of the membrane than that of the porous membrane prepared by conventional water bath coagulation technique. The microporous membranes were directly obtained after the washing and drying. It had about 1–5 μm of pores and presented an ionic conductivity of 2.52 × 10⁻³ S/cm at room temperature when gelled with 1 M LiPF₆/EC-DMC (1:1 vol.%) electrolyte solution. The test cells with the gel electrolytes prepared from as-prepared microporous membranes showed stable cycling capacities, indicating that the microporous membrane, which was prepared from cheap starting materials acrylonitrile and methyl methacrylate, can be used for the gel electrolyte of lithium batteries.     

Morphological analysis of bead–string shaped and core–shell attapulgite@polystyrene (ATP@PS) particles via emulsion polymerization

A convenient method for the preparation of bead–string shaped and core–shell attapulgite@polystyrene (ATP@PS) composite particles through emulsion polymerization from needle‐shaped attapulgite is reported. The pretreatment of attapulgite with cetyltrimethylammonium bromide (CTAB) in ultrasonic is essential for successful encapsulation and for creating strong interfacial interaction between attapulgite and polystyrene (PS). The different morphologies of the ATP@PS particles, bead–string shaped and core–shell shaped, obtained with different amounts of styrene charges, were characterized by transmission electron microscopy (TEM). Encapsulation mechanisms of the two morphologies were also developed. Copyright © 2007 John Wiley & Sons, Ltd.     

Ethylene–vinyl acetate semi-batch emulsion copolymerization: Experimental design and preliminary screening experiments

Ethylene–vinyl acetate emulsion copolymers are useful materials for paint, adhesive, and coating applications. The kinetics of their production remain largely unstudied, probably due to the inherent difficulties associated with pressure polymerizations. Polymerizations at elevated pressures are in general more difficult to understand and control, and relatively more expensive since one has to consider the added cost of increased safety precautions. Reported here are the preliminary results of an extensive experimental investigation of the variables which govern the ethylene–vinyl acetate emulsion process. Two redox initiator systems have been identified as more suitable for the polymerization process. Two buffer systems, namely sodium acetate/acetic acid and potassium phosphate, have been used to effectively control pH. The addition of n-hexane has offered an effective method of enhancing the ethylene content in the copolymer produced. Several other important variables including agitation/mixing and emulsifier type and concentration have been identified and are discussed. These screening experimental observations have aided in the selection of suitable design levels for future, more focused experimentation to quantify the effects of reaction variables on the latex and copolymer properties of interest. A review of the existing literature on ethylene–vinyl acetate copolymer properties and processes is also included. © 1993 John Wiley & Sons, Inc.     

Block copolymers prepared by emulsion polymerization with poly(ethylene oxide)–azo-initiators

Poly(ethylene oxide)-b-poly(styrene) block copolymers were prepared in the form of latex particles by emulsion polymerization of styrene with poly(ethylene glycol)–azo-initiators as well as with the redox initiation system poly(ethylene glycol)/Ce⁴⁺. The emulsion polymerization can be carried out in the absence of additional stabilizers if the chain length of the poly(ethylene glycol) is greater than 40. The latex particles as well as the copolymers were characterized by capillary hydrodynamic fractionation, ¹³C-nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy. By ¹³C-NMR spectroscopy a side reaction of the primary radicals arising from the azo-initiator was found which can contribute to the low efficiency of azo-initiators in emulsion polymerization.     

Reversible addition–fragmentation chain transfer polymerization of methyl methacrylate in emulsion

Theoretical simulations showed that for controlled/living radical polymerization in an emulsion system, some of the earliest born particles could be superswollen to a size close to 1 μm. We hypothesized that the superswelling of these particles would lead to colloidal instability. Under the guidance of the simulation results, reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization of methyl methacrylate (MMA) was carried out. Experimental results showed that increasing the initiation rate, surfactant level, and targeted molecular weight could improve the colloidal stability of the RAFT polymerization of MMA in an emulsion. The experimental results were in full accord with the theoretical predictions. The poor control of the molecular weight and polydispersity index was found to have a close relationship with the colloidal instability. For the first time, we demonstrated that RAFT polymerization could successfully be implemented with little coagulum, good control of the molecular weight, and a low polydispersity index with the same process used for traditional emulsion polymerization but with higher surfactant levels and initiation rates. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44:2837–2847, 2006     

Formulation of unrestricted and restricted Hartree–Fock–Bogoliubov equations

The Hartree–Fock–Bogoliubov (HFB) method, dealing with Bogoliubov orbitals, which consist of particle and hole part, can provide states with pair correlations associated with Cooper pairs. The dimension of HFB Fock matrices can be reduced by restrictions of spin states of Bogoliubov orbitals similarly to ordinary Hartree–Fock (HF) equations such as restricted HF (RHF), unrestricted HF (UHF), and generalized HF (GHF). However, there are few studies of moderate restricted HFB equations such as UHF‐based HFB equations. In this article, formulation and calculations of restricted HFB equations are described. The solutions of general and restricted HFB equations are compared. Pair correlations taking account of restricted and general HFB equations are discussed. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Untersuchungen zum Zustandsdiagramm EuCl2–EuCl3

Investigations on the Phase Diagram EuCl₂–EuCl₃ The phase diagram EuCl₂–EuCl₃ was determined by difference‐thermoanalysis and the barogram of the system was determined by total pressure measurements of different compositions in function of temperature. By the results the phase diagram was precised. Eu₅Cl₁₁ decomposes at 565 °C in to EuCl_2,s and Eu₄Cl_9,s and shows a transition at 510 °C. Eu₄Cl₉ decomposes at 603 °C in to EuCl_2,s and Eu₁₄Cl_33,s. Eu₁₄Cl₃₃ decomposes at 612 °C peritectically in EuCl_2,s and a EuCl₃‐rich melt. Eu₁₄Cl₃₃ shows two high temperature transition points at 570 °C and 580 °C. The endothermal effect of compositions near Eu₁₄Cl₃₃ was interpreted as an endothermal formation of this compound. The eutectikum was detected between Eu₁₄Cl₃₃ and EuCl₃ to 60 ± 1 Mol‐% EuCl₃ at 530 °C.     

Investigation of various polymeric materials for set-point temperature calibration in pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS)

The precision and long-term stability of pyrolysis probe set-point temperature calibration of a commercially available coiled-filament pyrolyzer were assessed for a variety of polymers, including Kraton^® D1107, high-density polyethylene (HDPE), and low-density polyethylene (LDPE). While plots of peak area ratios for Kraton^® and HDPE versus pyrolysis set-point temperatures produced statistically significant linear curves at the 95% confidence level, poor precision was observed at each of the set-point temperatures. Plots of peak area ratios for LDPE, in particular for n-C₁₆ alkyldiene/n-C₁₆ alkene peak area ratios, also exhibited good linearity but showed significant improvements in precision at each set-point temperature. In addition, replicate analysis over a 10-month period of peak area ratios for polymers pyrolyzed at a set-point temperature of 900 °C confirmed the improved method precision obtained from pyrolysis of LDPE and analysis of the n-C₁₆ alkyldiene/n-C₁₆ alkene ratio when compared to the precision obtained from pyrolysis of Kraton^® D1107 or high-density polyethylene.     

Thermal Polymerization of Styrene,Part 2 – (Mini)emulsion Polymerization

An experimental and theoretical study on the thermal (spontaneous) polymerization of styrene in compartmentalized systems is presented. Experimental data on thermally polymerized miniemulsions varying temperature and droplet size is provided. This data is used to test a new model approach to describe the thermal polymerization process of a disperse phase. The mathematical model is based on a chemical master equation balancing radical species that are capable of desorption (monomeric radicals) and ones that cannot leave a particle. Reasonable agreement between theory and experiment for the data provided here and for literature data can be achieved. Part 1 of this series is a review on the thermal bulk polymerization of styrene.

     

A ternary phase diagram of the Mn–Te–O system at 950 K

A ternary phase diagram of the Mn–Te–O system at 950 K has been established in the composition range in and around the MnO–TeO₂ pseudo binary line. Various preparation methods were employed to confirm the co-existence of different ternary phases. The results of these phase equilibration studies were revalidated by the invariancy of partial pressures at constant temperature during high temperature mass spectrometric vaporization experiments. The following three-phase regions have been identified: MnO+Mn₃O₄+Mn₆Te₅O₁₆ (phase region 1; PH1), Mn₃O₄+Mn₆Te₅O₁₆+MnTeO₃ (phase region 2; PH2), Mn₃O₄+MnTeO₃+Mn₃TeO₆ (phase region 3; PH3), and MnTeO₃+Mn₂Te₃O₈+Mn₃TeO₆ (phase region 4; PH4). The complex nature of the Mn–Te–O ternary system was revealed by the interesting results obtained by us with regard to preparation of samples and mass spectrometric vaporization experiments.     

Self‐emulsion polymerization of amphiphilic monomers—a green route to synthesis of polymeric nanoscaffolds

Self‐emulsion polymerization (SEP), a green route developed by us for the polymerization of amphiphilic monomers, does not require any emulsifier or an organic solvent except that the water‐soluble initiators such as 2,2′‐azobis[2‐(2‐imidazolin‐2‐yl)propane]dihydrochloride (VA‐044) and potassium persulfate (KPS) are only used. We report here the polymer nanoscaffolds from a number of amphiphilic monomers, which can be used for in situ encapsulation of a variety of nanoparticles. As a demonstration of the efficacy of these nanoscaffolds, the synthesis of a biocompatible hybrid nanoparticle (nanohybrid), prepared by encapsulating Fe₃O₄ magnetic nanoparticle (Fe₃O₄ MNPs) in poly(2‐hydroxyethyl methacrylate) in water, for MRI application is presented. The nanohybrid prepared following the SEP in the form of an emulsion does not involve the use of any stabilizing agent, crosslinker, polymeric emulsifier, or surfactant. This water‐soluble, spherical, and stable nanohybrid containing Fe₃O₄ MNPs of average size 10 ± 2 nm has a zeta potential value of ?41.89 mV under physiological conditions. Magnetic measurement confirmed that the nanohybrid shows typical magnetic behavior having a saturation magnetization (Ms) value of 32.3 emu/g and a transverse relaxivity (r2) value of 29.97 mM^?1 s^?1, which signifies that it can be used as a T2 contrast agent in MRI. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019     

Synthesis and characterization of fluorine‐containing polyacrylate latex with core–shell structure by UV‐initiated seeded emulsion polymerization

A core–shell fluorine‐containing polyacrylate emulsion was successfully prepared by UV‐initiated seeded emulsion polymerization in two stages in the presence of two photoinitiators. The water‐soluble photoinitiator for the core polymerization and the oil‐soluble photoinitiator was used for the shell polymerization. Both of the two stage polymerizations could be completed within 15 min and displayed a conversion above 94%. The emulsion and the films were characterized by Fourier transformed infrared spectrometry, transmission electron microscopy, dynamic light scattering, X‐ray photoelectron spectroscopy (XPS), contact angle (CA), and thermogravimetry analysis, respectively. The analysis results indicated that the fluorine‐containing latex particles had very small particle size (40 nm) with a core–shell structure and a narrow particle size distribution. XPS analysis revealed that a gradient concentration of fluorine excited in fluorine‐containing emulsion film from the film–air interface to the film–glass interface. In addition, the film formed from the fluorine‐containing emulsion exhibited not only higher thermal stability but also better hydrophobicity than that of the fluorine‐free emulsion. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of high oil‐absorption resins of poly(methyl methacrylate‐butyl methacrylate) by suspended emulsion polymerization

The synthesis of high oil‐absorption resins by suspended emulsion polymerization process for the first time with butyl methacrylate (BMA) and short‐chain methyl methacrylate (MMA) as the monomers was studied. And the effects of different polymerization technological parameters, such as the comonomer, initiator, crosslinker, emulsifier, dispersant agent, and the agitation rate, on the oil absorbency of high oil‐absorption resins were discussed in detail. The optimum polymerization conditions were obtained. With the increasing contents of these factors, the oil absorbency increased first, and then decreased. The highest oil absorbency to toluene was 17.6 g/g. The particle morphology of the high oil‐absorption resins was observed by scanning electron microscopy (SEM). The resins were determined by FTIR spectrometry. Compared with the high oil‐absorption resins prepared by suspension polymerization process and emulsion polymerization process, the high oil‐absorption resins prepared by suspended emulsion polymerization process had the higher oil absorbency, faster oil‐adsorbing rate, better oil‐retention, and regeneration property. Copyright © 2010 John Wiley & Sons, Ltd.     

Emulsifier‐free,organotellurium‐mediated living radical emulsion polymerization (emulsion TERP): Effect of monomer hydrophilicity

Emulsifier‐free, organotellurium‐mediated living radical emulsion polymerizations (emulsion TERPs) of methyl methacrylate (MMA) and n‐butyl methacrylate (BMA) with dimethyl ditelluride were carried out at two different stirring rates (220 rpm and 1000 rpm). In the emulsion TERP of MMA as a hydrophilic monomer, the molecular weight distribution (MWD) controls with both stirring rates were good with high polymerization rate (100% conversion at 1.5 h). On the other hand, in the emulsion TERP of BMA as a hydrophobic monomer, at 220 rpm the polymerization rate was much slow (～50% conversion at 22 h) and the MWD control was bad, but at 1000 rpm the polymerization was completed within 7 h and MWD control was good. These results suggest that monomer transportation from droplets to polymerizing particles via aqueous medium is important for good MWD control and steady polymerization in the emulsion TERP. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Determining the temperature dependence of the emulsion particle size of polyacrylate core–shell and polystyrene by photon correlation spectroscopy

The dependence of the particle size of a polyacrylate core-shell emulsion on temperature has been investigated in the temperature range of 10–55°C by photon correlation spectroscopy. To compare, the dependence of the particle size of an aqueous suspension of a polystyrene standard on temperature has been also investigated under the same conditions. This showed that as the temperature increases, the particle size of both samples decreases, but the rate of size decrease of the polystyrene standard is larger than that of the polyacrylate core–shell emulsion. By linear regression analysis, two regression equations of both samples have been set up. Furthermore, the apparent moving activation energy has been worked out from the size–temperature data.     

Synthesis of polymeric nanocapsules by radical UV‐activated interface‐emulsion polymerization

A new methodology is reported that allows a better control of the synthesis of polymeric core–shell nanocapsules. These nanocapsules were made of biocompatible polymers, obtained from poly(ethylene glycol)diacrylate and poly(ethylene glycol) methyl ether methacrylate, and were used as carrier for curcumin as therapeutic agent. The impact of manufacturing factors (time of sonication, time of UV irradiation, and type of monomer) was investigated in relation to the average size of nanocapsules, their distribution, shape, composition, stability, and their capability to deliver curcumin. We successfully synthesized core–shell nanocapsules in various sizes, ranging from 80 nm to 300 nm, by acting either on the process conditions or on the composition of the monomer mixture. This wide range of sizes makes the method here proposed very promising for the production of nanocarriers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3357–3369     

Properties of acrylic–polyurethane hybrid emulsions synthesized by the semibatch emulsion copolymerization of acrylates using different polyurethane particles

Aqueous acrylic–polyurethane hybrid emulsions were prepared by the semibatch emulsion copolymerization of methyl methacrylate and butyl acrylate in the presence of eight polyurethane dispersions. The polyurethane dispersions were synthesized with isophorone diisocyanate, 1000 and 2000 molecular weight polyester polyols, 1000 molecular weight polyether polyol, butanediol, and dimethylol propionic acid. Acrylic monomers were added in the monomer emulsion feed. We studied the effect of the use of different polyurethane seed particles and the effect of different weight ratios of methyl methacrylate to butyl acrylate on the emulsion properties, microphase structure, and mechanical properties of hybrid films. The average particle size and distribution were determined by photon correlation spectroscopy. The rheological properties of polyurethane dispersions and hybrid emulsions were tested under destructive conditions by an examination of flow curves and under nondestructive conditions of oscillatory shear in a range of linear viscoelastic responses. Differential scanning calorimetry was performed to characterize the thermal‐response properties of polymeric films. The relative average molecular weights were determined by gel permeation chromatography. The interactions between the acrylic and polyurethane components in hybrid particles and particle structure were studied with infrared spectroscopy and nuclear magnetic resonance spectroscopy. Mechanical properties such as the Koenig hardness, tensile strength, elongation at break, and Young's modulus were measured. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4050–4069, 2005