The properties of amphiphilic triblock copolymer particles, which consist of a hydrophobic polystyrene (PS) core and a thermo-sensitive double hydrophilic block copolymer shell made of polyacrylic acid (PAA) and poly-N-isopropylacrylamide (PNIPAM) sequences, differ significantly depending on the sequence of the hydrophilic blocks from the core to the shell-either PS-PNIPAM-PAA or PS-PAA-PNIPAM. These triblock copolymer particles were prepared via reversible addition-fragmentation chain transfer polymerization (RAFT) following the PISA approach, using the corresponding double hydrophilic block copolymer macro-RAFT agents. The macro-RAFT agents (MRA) were synthesized through sequential polymerization of the corresponding monomers, using 4-cyano-4-(propylsulfonyl thiocarbonyl) sulfonyl pentanoic acid as the RAFT agent. These two different MRAs result in remarkable differences in the course of styrene emulsion polymerization (EP). Furthermore, the two types of polystyrene latexes behave differently in two key aspects: firstly, in terms of particle size and latex stability, which depend on both temperature and ionic strength, and secondly, in their capacity to disperse laponite disks within the particle shell when present during styrene emulsion polymerization.

AbstractThis article is an overview of heterophase polymerization techniques in liquid continuous media to prepare polymer dispersions. The common feature of heterophase polymerizations is the distinctive role that interfaces play during all stages and in all aspects of these processes. Accordingly, the heterogeneous nature and its influence on polymerization kinetics and product properties is emphasized rather than a successive treatment of various types of heterophase polymerization techniques such as suspension or emulsion polymerization. Thus, the focus is on colloid chemical and kinetic consequences of the compartmentalization during the polymerization processes.

This chapter shows that a surfactant can act in emulsion polymerization in two basic ways: either entirely physical or additionally chemical. It summarizes the chain-transfer constants of some frequently employed monomers to various molecules, which represent important building blocks of surfactant molecules such as aryl, alkyl and ethoxy groups. The physical actions of surfactants are much more important as they are essential for emulsion polymerization, i.e. that means for the creation and stabilization of the heterogeneous reaction system. Thus, the consequences of physical actions of surfactants on the kinetics and mechanism of emulsion polymerization during the period of main monomer consumption are mainly partitioning effects between the continuous, aqueous and the dispersed, organic phase. The chapter also summarizes the actions of surfactants in emulsion polymerization into four categories: solubilization; stabilization; suitability; and sustainability and support. All individual parts of this S-series are linked to the surface or the interfacial areas in the emulsion polymerization system.

ABSTRACT Poly(methyl methacrylate‐co‐butyl acrylate) (PMMA‐ co ‐PBA) and poly(sytrene‐ co ‐butyl acrylate) (PSt‐ co ‐PBA) latexes in which solid content (SC) varied from 20% up to 40 wt % armored with laponite clay have been successfully synthesized using a simple method, which does not require modification of the clay particles prior to polymerization. Incorporation of quite high amounts of laponite nanoparticles into PMMA‐ co ‐PBA and PSt‐ co ‐PBA latexes with a certain amount of solids content was achieved. The nanocomposite latexes and polymer samples were characterized using Fourier transform infrared (FTIR) spectroscopy in attenuated total reflectance (ATR) mode, dynamic light scattering (DLS), X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), contact angle, zeta potential, viscosimetry and analytical ultracentrifuge (AUC). Zeta potential values showed that stable latex was obtained and precipitation problem of the nanoparticles in the latex was not seen during the storage. Obtained nanocomposite latex showed fine particle size between 88 and 160 nm. TEM images and XRD results pointed out that the exfoliated nanocomposite structure for latexes was obtained. DSC analyzes showed that the glass‐transition temperature ( T g ) values of nanocomposite films decreased slightly compared with those of pure (PMMA‐ co ‐PBA) films. Mechanical properties of laponite clay armored PMMA‐co‐PBA were tested and compared with those of pure PMMA‐ co ‐PBA, indicating that incorporated the Young's modulus and tensile strength are also improved to a noticeable extent after the incorporation of laponite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47423.

Helical structures are ubiquitous in biological materials and often serve a structural purpose. Bioinspired helical materials can be challenging to synthesize and rarely reach the degree of hierarchy of their natural counterparts. Here we report the first example of particles synthesized by direct emulsification of polypeptides found to display spiral morphologies in the dry state. The polypeptides were alpha-helical homo- and copolypeptides of gamma-benzyl glutamate and allylglycine. The chirality of the spirals was controlled by the chirality of the alpha-helices. Notably, right-handed alpha-helical polypeptides (rich in 1, residues) produced clockwise spirals, whereas left-handed alpha-helical polypeptides (rich in D residues) produced the enantiomorphs, i.e., counterclockwise spirals. The disruption of the alpha-helical conformation by the introduction of chiral defects led to less regular spirals and in some cases their suppression. A hypothesis for the transmission of helicity and chirality from a molecular to a higher hierarchical level, involving fibril bundling of coiled alpha-helices, is proposed.

The traditional way of making emulsions is via the input of extra mechanical energy, but there is another mechanism of emulsification that is entirely thermodynamically controlled. Experimental results are presented elucidating the consequences of this spontaneous emulsification for heterogeneous reaction systems. Special emphasis is placed on aqueous heterophase polymerization. We present the results of unusual experiments in oil-water systems that fundamentally changed our view of the mechanism of emulsion polymerization.

The objective of this investigation is to find a less‐expensive and less‐toxic environmentally benign route for the preparation of magnetic PANI nanocomposite particles. For this citric acid, a weak organic tricarboxylic acid has been used during seeded chemical oxidative polymerization of aniline in presence of variable amounts of Fe3O4 nanoparticles. Nanosized Fe3O4 particles are first prepared by co‐precipitation of Fe2+ and Fe3+ from their alkaline solutions. Then in the second step, magnetic nanocomposite particles—named as Fe3O4/PANI—are prepared by seeded chemical oxidative polymerization of aniline using ammonium persulfate (APS) as oxidant. Independent of Fe3O4 content, Fe3O4/PANI nanocomposite particles possessed comparable high electrical conductivity having the same magnitude as HCl‐doped PANI particles (2.13 × 10−3 S/cm). This result suggested that addition of citric acid during seeded chemical oxidative polymerization not only promoted solubilization of aniline but also functioned as stabilizer and doping agent. Iron oxide content critically influenced the stability, morphology, and magnetic properties of the produced nanocomposite particles. The saturation magnetization and magnetic susceptibility increased with the increase of Fe3O4 content. The nanocomposite particles prepared with core/shell ratio of 0.6/1 (w/w) exhibited the strongest paramagnetism and aligned into fiber‐like structure. The analysis of electromagnetic properties and spectral data from FTIR, X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and thermogravimetry (TG) confirmed the complete coverage of Fe3O4 nanoparticles by PANI layer. POLYM. COMPOS., 39:4628–4636, 2018. © 2017 Society of Plastics Engineers

Porous γ-alumina (γ-Al2O3) is one of widely used ceramic materials. To maximize the application potentials attempt was made to prepare multifunctional γ-Al2O3 ceramic composite particles following magnetization and then seeded polymerization with epoxide functional glycidyl methacrylate (GMA). γ-Al2O3 particles were first prepared by a modified sol-gel approach and then doped with variable content Fe3O4 nanoparticles. At higher Fe3O4 content the magnetite nanoparticles were oriented into needle like hairy structure basically grown from the surface of γ-Al2O3 particles. Before the seeded polymerization the magnetic γ-Al2O3 particles were modified with SiO2 layer to improve the compatibility with the PGMA layer. The produced multifunctional ceramic particles were named as γ-Al2O3/Fe3O4/SiO2/PGMA nanocomposite because one of the phases constituting Fe3O4 was in nano-size range. The produced nanocomposite particles possessed superparamagnetic properties and could be isolated from the dispersion medium by external magnetic field. Fourier Transform IR (FTIR) and X-ray photoelectron spectroscopic (XPS) data revealed that final nanocomposite particles contained reactive epoxide groups on or near the surface. The produced multifunctional γ-Al2O3 ceramic nanocomposite particles can be useful in biotechnology, catalysis and adsorbents for pollutant removal.

Homogeneous aragonite flowers with controlled surface structures can be synthesized by using a thermosensitive polymer, i.e. poly (ethylene glycol)-poly(N-isopropyl acrylamide)-poly(acrylamido methyl propane sulfonate) (PEG-PNIPAM-PAMPS), as a crystal growth modifier in the mineralization of calcium carbonate.

The crystallization of calcium carbonate in a continuous organic medium using the classic ammonium carbonate gas diffusion system was recorded with an optical microscope.Surprisingly, dendritic structures were obtained consistently when the product gas mixture combined with calcium chloride already dissolved in the organic medium.Characterization studies revealed these crystals to be composite mixtures of calcium carbonate and ammonium chloride. ObjectiveTo study calcium carbonate crystallization in a continuous organic medium containing dissolved calcium chloride while using ammonium carbonate gas diffusion method to feed the reaction precursors.

A solid mixture of reactants undergoes composition inversion to form calcium carbonate.

A new class of polymeric colloids, multiple suspension particles (MSP), with a size of several micrometers consisting of many small polystyrene particles with a diameter below 100 nm grown in a poly (N-iso-propyl acrylamide) precursor scaffold is obtained, as reported in our previous paper. Herein, the unique MSP are applied as template for silica nanocasting and hierarchically organized porous silica with raspberry-like aggregation structure is obtained. The aggregates with a diameter of about 1 mm are composed of thousands of hollow silica particles, which are with a size of about 70 nm originating from polystyrene particles and with mesopores of about 5.8 nm on the shell from PNIPAM chains. The aggregates have high specific surface area and pore volume. With the advantage of high mass transport contributed by macropores and of high specific surface area due to mesopores, the hierarchically organized structure has great potential application in catalysis field. (C) 2017 Elsevier Ltd. All rights reserved.

A non-ionic surfactant system is synthesized by standard grafting of poly(ethylene oxide) from renewable lignin fragments and used for the emulsion polymerization of styrene. The lignin precursors are formed by hydrogenolysis and utilized as initiator for the oxyanionic polymerization of ethylene oxide leading to amphiphilic polymers, very similar to standard nonionic surfactant synthesis. Subsequently, the formed amphiphilic polymers are employed as stabilizers in the heterophase polymerization of styrene with various initiators. Poly (styrene) latexes with solids contents of up to 21% depending on stabilizer concentration have been obtained. Stabilizer efficiencies and performances were nicely comparable with those of nonylphenol-based, non-ionic industrial performance surfactants.

Experimental evidence is presented showing that the direct formation of anisotropic colloidal polymer particles via aqueous heterophase polymerization is essentially controlled by the entropy gain of the linear fraction in the semi-interpenetrating network of the seed particles during swelling. Anisotropic particles are produced via photoinitiated polymerization, allowing swelling and polymerization to take place at the same temperature. These experiments prove that the temperature effect on rubber elasticity is, if at all, only of minor importance for the formation of anisotropic polymer particles. The major significance of swelling of the seed particles for the whole process is underlined by additional studies with optical microscopy and model simulations.

This study describes the effects of nitrilotriacetic acid (NTA) and ethylenediaminotetraacetic acid (EDTA) on the mineralization of calcium phosphate from bulk aqueous solution. Mineralization was performed between pH 6 and 9 and with NTA or EDTA concentrations of 0, 5, 10, and 15 mM. X-ray diffraction and infrared spectroscopy show that at low pH, mainly brushite precipitates and at higher pH, mostly hydroxyapatite forms. Both additives alter the morphology of the precipitates. Without additive, brushite precipitates as large plates. With NTA, the morphology changes to an unusual rod-like shape. With EDTA, the edges of the particles are rounded and disk-like particles form. Conductivity and pH measurements suggest that the final products form through several intermediate steps.