Polymer-clay nanocomposites prepared via in situ emulsion polymerization

A series of novel polystyrene and poly(butyl methacrylate) montmorillonites (MMT-Na) nanocomposite latexes have been successfully prepared by emulsion polymerization. First of all, chemical modification of MMT-Na with a reactive coupling agent (MMT-QS) has been employed for the synthesis of hybrids. Subsequently, in situ seeded emulsion polymerization of hydrophobic vinyl monomers, such as butyl methacrylate and styrene, using sodium dodecyl sulfate (SDS) and ammonium persulfate (APS) as surfactant and initiator, respectively, were used for nanocomposite preparation. This technique allowed preparing of stable nanocomposite latexes with high (30–45 wt.%) solids contents and with loading of inorganic particles up to 5 wt.%. The prepared wet dispersions were subsequently characterized by light scattering method. In order to characterize the microstructure of the clay layers, and that of the organoclay in polystyrene and poly(butyl methacrylate) nanocomposites, wide and small angle X-ray analyses (WAXS, SAXS) and transmission electron microscopy (TEM) techniques were used.     

Entry in emulsion polymerization using a mixture of sodium polystyrene sulfonate and sodium dodecyl sulfate as the surfactant

A mixture of sodium polystyrene sulfonate (NaPSS) and anionic surfactant, sodium dodecyl sulfate (SDS), was used as the emulsifier in the emulsion polymerization of styrene at 60 °C. The latexes prepared were stable, bearing the better resistance to the addition of electrolyte, and have the larger values in particle size and the higher polymerization rates than those counterparts prepared using SDS only. The NaPSS was prepared by a series of process: a concentrated cyclohexane solution of an anionically polymerized polystyrene (PS) was sulfonated with sulfuric acid at 80 °C, and then neutralized and purified through dialysis. The data of average polymer number per particle (n_p) were found useful in investigating the surfactant content effect on the entry of radicals into particles, where the latex particle size plays an important role.     

Facile Preparation of Crosslinked Polymeric Nanocapsules via Combination of Surface-Initiated Atom Transfer Radical Polymerization and Ultraviolet Irradiated Crosslinking Techniques

A facile approach for the preparation of crosslinked polymeric nanocapsules was developed by the combination of the surface-initiated atom transfer radical polymerization and ultraviolet irradiation crosslinking techniques. The well-defined polystyrene grafted silica nanoparticles were prepared via the SI-ATRP of styrene from functionalized silica nanoparticles. Then the grafted polystyrene chains were crosslinked with ultraviolet irradiation. The cross-linked polystyrene nanocapsules with diameter of 20–50 nm were achieved after the etching of the silica nanoparticle templates with hydrofluoric acid. The strategy developed was confirmed with Fourier transform infrared, thermogravimetric analysis, and transmission electron microscopy.     

Uniform star‐polystyrene nanoparticles prepared by emulsion atom transfer radical polymerization

Pentaerythritol (PT) was converted into four‐arm initiator pentaerythritol tetrakis(2‐chloropropionyl) (PT‐Cl) via reaction with 2‐chloropropionyl chloride. Uniform (monodisperse) star‐polystyrene nanoparticles were prepared by emulsion atom transfer radical polymerization of styrene, using PT‐Cl/CuCl/bpy (bpy is 2,2′‐dipyridyl) as the initiating system. The structures of PT‐Cl and polymer were characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The morphology, size and size distribution of the star‐polystyrene nanoparticles were characterized by transmission electron microscopy, atomic force microscopy and photon correlation spectroscopy. It was found that the average diameters of star‐polystyrene nanoparticles were smaller than 100 nm (30–90 nm) and monodisperse; moreover, the particle size could be controlled by the monomer/initiator ratio and the surfactant concentration. The average hydrodynamic diameter (D_h) of the nanoparticles increased gradually on increasing the ratio of styrene to PT‐Cl and decreased on enhancing the surfactant concentration or increasing the catalyst concentration. Copyright © 2011 Society of Chemical Industry     

乳液法聚苯乙烯纳米微球的制备

采用十二烷基硫酸钠为乳化剂、过硫酸盐为引发剂、苯乙烯为单体,在低水油比的条件下,采用乳液聚合方法合成了聚苯乙烯纳米微球,探讨了乳化剂用量、乳化时间、反应温度、引发剂用量和反应时间对单体转化率及产物分子量的影响.结果表明:在低水油比条件下,反应参数对苯乙烯的转化率和聚苯乙烯的分子量具有一定的影响.在最优条件下苯乙烯的转化率达到98%、聚苯乙烯的分子量达到32万.激光粒度分布测试结果显示,所得产物为单分散纳米微球.     

Effects of crosslinking time and amount of sulfophthalic acid on properties of the sulfonated poly(vinyl alcohol) membrane

A proton‐exchange membrane for a direct methanol fuel cell was prepared by modifying the chemical structure of poly(vinyl alcohol) (PVA) via a sulfonation. The sulfonation was carried out by using sulfophthalic acid (sPTA) as a sulfonating agent. The sulfonated PVA membranes, with a variety of degrees of substitutions, were obtained by varying the crosslinking time and the amount of sulfonating agents. The chemical structure and thermal stability of the sulfonated PVA were characterized by using FTIR and thermogravimetric analysis techniques, respectively. The ion‐exchange capacity (IEC) and water uptake of the sulfonated membranes was evaluated by titration and gravimetry techniques, respectively. It was found that the IEC of the membrane increased with the amount of sPTA. Water uptakes of the membranes could either decrease or remain unchanged with the crosslinking time, depending on the amount of the sulfonating agent used. Methanol permeability values of the membranes treated with 10% sPTA were relatively low, comparing with that of the Nafion 115 membrane. Proton conductivity values of the sulfonated PVA membranes ranged between 0.024 and 0.035 S/cm and they did not remarkably change with the crosslinking time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1931–1936, 2006     

Polystyrene nanoparticles as surfactant carriers for enhanced oil recovery

It is well known that oil recovery processes can be increased by surfactant solution injections in the reservoir. However, the high adsorption of this type of compounds on the reservoirs rocks surface is one of the factors that have been preventing the Enhanced Oil Recovery (EOR) development and the economicity of the process. This work presents the synthesis of cross‐linked polystyrene nanoparticles (PSNP) and their evaluation as surfactant carriers, able to percolate through the reservoirs pores and to deliver it at the water/oil interface. The nanoparticles were synthesized by emulsion polymerization of styrene and divinylbenzene in the presence of nonylphenol ethoxylate‐10 (NF‐10EO) or sodium dodecyl sulphate. Photon Correlation Spectroscopy and Interfacial Tension results gave support to the initial supposition that the nanoparticles would swell when in contact with the oil phase, releasing the surfactant at the interface. The nanoparticles obtained with NF‐10EO were able to reduce the water/oil interfacial tension to values that were similar to the ones obtained with the aqueous solution of NF‐10EO. The results suggest that the PSNP have a great potential to be used as surfactant carriers in EOR. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43789.     

Synthesis of Polystyrene/Hydrophobic SiO2 Composite Particles via Oil‐in‐Water Pickering Emulsion Polymerization

The aim of this work is to present a facile Pickering emulsion polymerization method for the synthesis of submicron polystyrene/SiO₂ core/shell composite particles. The commercial hydrophobic SiO₂ nanoparticles were used as stabilizing agent for creating a stable oil‐in‐water emulsion. Although the adsorption of hydrophobic SiO₂ nanoparticles in the emulsion system was unfavorable in terms of thermodynamics, by ultrasound treatment, self‐assembly of hydrophobic SiO₂ nanoparticles effectively stabilized oil‐in‐water Pickering emulsions during polymerization. Using 3 wt.% SiO₂ nanoparticles (based on styrene monomer) and 1:10 volume ratio of styrene monomer:water, the composite particles having average size of 790 nm and relatively narrow particles distribution were produced. With decreasing the volume ratio, smaller composite particles were created. Results from scanning electron microscope revealed that SiO₂ nanoparticles were located exclusively at the surface of the polystyrene latex particles. The SiO₂ content, determined by thermogravimetric analysis, was 12.6 wt.% in the composite particles. The route reported here may be used for the preparation of other composite nanostructures. POLYM. ENG. SCI., 59:E195–E199, 2019. © 2018 Society of Plastics Engineers     

Surface immobilisation of fluorinated polystyrene‐acrylate latex nanoparticles with core–shell structure by crosslinking

Fluorinated polystyrene‐acrylate (PSA) latex nanoparticles with core–shell structure were synthesised by two‐stage seeded emulsion polymerisation method in the presence of reactive emulsifier DNS‐86. Diallyl phthalate (DAP) and Vinyltriethoxysilicone (VTES) were used as crosslinking agent to immobilise the fluorinated copolymer on the surface of the latex film. Fourier transform infrared spectroscopy (FTIR) spectra show that fluorine and siloxane monomers were effectively involved in the emulsion copolymerisation. Transmission electron microscope (TEM) observation shows that the prepared emulsion particles had a core–shell structure with fluorinated copolymer in the shell. X‐ray photoelectron spectroscopy (XPS) analysis reveals that fluorine atom has the tendency of migrating to the film–air interface and the incorporation of VTES helps the migration of fluorine atom towards the film–air interface. Water contact angle (WCA) test proved that DAP and VTES as crosslinking agent can immobilise the fluorinated copolymer on the surface of the latex films. © 2011 Canadian Society for Chemical Engineering     

Ultrasound assisted in situ emulsion polymerization for polymer nanocomposite: A review

This review covers an ultrasound assisted synthesis of polymer nanocomposites using in situ emulsion polymerization. First of all, surface modification of core nanoparticles with a coupling agent and surfactant has been employed for the synthesis of core–shell polymer nanocomposites. In addition to application of ultrasound for the synthesis of core–shell polymer nanocomposites, due to its influential efficiency, sonochemistry has been extensively used not only as an aid of dispersion for inorganic nanoparticles and organo-clay, but also acts as an initiator to enhance polymerization rate for synthesis of polymer nanocomposites. In situ emulsion polymerization of hydrophobic monomers, such as methyl methacrylate, butyl acrylate, aniline, vinyl monomers and styrene, using surfactant and water soluble initiator were carried out for a synthesis of core–shell polymer nanocomposite. This technique assists in preparation of stable and finely dispersed polymer nanocomposite with the loading of inorganic particles up to 5 wt.%. Recent developments in the preparation of core–shell polymer nanocomposites using an ultrasound assisted method with their physical characteristics such as morphology, thermal, and rheological properties and their potential engineering applications have been discussed in this review.     

The tough microcapsules of acrylic acid–styrene–isoprene–styrene quadrablock copolymer shell via Pickering emulsion technique

Pickering emulsion technique has been demonstrated a simple method to fabricate the microcapsules. However, the resulted microcapsules are often fragile. This limits their applications. Here, we report that the microcapsules with the nanostructured shell of poly(acrylic acid‐b‐styrene‐b‐isoprene‐b‐styrene) (ASIS), which is of high toughness and elasticity, could be fabricated via Pickering emulsions using ASIS nanoparticles as stabilizing particles. The surfactant‐free ASIS latex (with theoretical molecular weight for each block: 1.5k–15k–55k–10k) was synthesized by reversible additional fragmentation transfer (RAFT) emulsion polymerization using amphiphilic macro‐RAFT agent [poly(acrylic acid)₂₀‐b‐polystyrene₅ trithiocarbonate] as both reactive surfactant and polymerization mediator. It was found that the ASIS nanoparticles were able to self‐assemble on oil/water interface to stabilize Pickering emulsion of hexadecane in the pH range from 8 to 12. The droplet diameter was finely tuned from 17 to 5 µm by increasing the ASIS particle levels from 0.13 to 12 wt % based on the mass of the ASIS aqueous dispersions. With toluene as a coalescing aid, the capsules with a coherent and nonporous shell were obtained with the dispersed phase volume percentage as high as 50%. The toluene treated capsules were so mechanically strong to survive the utrasonic treatment. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46700.     

Synthesis of silver-polystyrene nanocomposite particles using water in supercritical carbon dioxide medium and its antimicrobial activity

A novel method based on ex situ dispersion of silver nanoparticles within the monomers and subsequent emulsion polymerization using water-in-sc-CO₂ medium is introduced in this paper. Silver nanoparticles were synthesized by chemical reduction of silver nitrate using sodium borohydrate as a reducing agent and polydimethylsiloxane (PDMS) as a stabilizer in the water-in-sc-CO₂ medium. The stable dispersion of silver nanoparticles was added slowly during the polymerization of styrene in the water-in-sc-CO₂ maintaining the temperature at 70 °C and pressure at 20.68 MPa, respectively. The silver nanoparticles encapsulated within polymer particles were characterized by UV-visible spectroscopy, XRD, TGA, SEM and TEM. The silver/polystyrene nanocomposite particles exhibited antimicrobial activity against a number of bacteria. The current work represents a simple, reproducible and universal way to prepare a variety of metal-polymer nanocomposite particles.     

Synthesis and property of polystyrene particle with smart surface by emulsion polymerization using “giant” surfactant

The colloidal particles with switchable surfaces (i.e. smart surfaces) have attracted great attention for numerous potential industrial applications. We report here a novel approach for the fabrication of polymeric particles with smart surfaces by emulsion polymerization using “giant” surfactant. Specifically, the “giant” surfactant was obtained by incorporating poly(4-vinylpyridine) chains onto the one bulb of snowman-shaped polystyrene particles, and then used as emulsifier for the emulsion polymerization at pH = 2.00. The nearly monodisperse waxberry-like polystyrene particles were prepared with dual-size roughness surfaces, and the particulate film exhibited reversibly pH-switchable superhydrophobic property due to the pH-sensitivity of P4VP chains and the surface topology. This property enabled the particles could be used to effectively sequester hazardous anions from the wastewater.     

The effect of TiO2 nanoparticles on the properties of sulfonated block copolymers

Block copolymers composed of styrene and different elastomeric blocks were sulfonated to high ion exchange capacities (IECs). Titanium dioxide (TiO₂) nanoparticles were added to these polymers to improve their mechanical and thermal stabilities, while influencing their transport properties for direct methanol fuel cell (DMFC) applications. Materials properties as proton exchange membranes (PEMs) were analyzed using: FT‐IR, water absorption, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), IEC, methanol permeability, and proton conductivity studies. Although there was no effect of TiO₂ nanoparticles on the thermal stability of the membranes, significant changes were observed in the mechanical properties of both sulfonated block copolymers studied. Water absorption increased at low TiO₂ content, but was then reduced with the incorporation of more nanoparticles. To enhance the interaction between the inorganic fillers and the polymers, sulfonic and amino groups were attached to the surface of the titania nanoparticles. The effect of sulfonated nanoparticles on the properties of the materials was more significant than the effect of the amino functionalized nanoparticles on all the properties evaluated, suggesting enhanced chemical interactions with the ionic domains of the polymer membranes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42651.     

高分子表面活性剂存在下超声辐照引发苯乙烯乳液聚合的研究

采用高分子表面活性剂(CMC-A9)和十二烷基硫酸钠(SDS)做乳化剂,用超声辐照乳液聚合方法制备了相对分子质量高(>106)的寡链聚苯乙烯纳米粒子。研究结果表明,在适当的反应条件下,CMC-A9的加入使反应速率大大提高,反应60min单体转化率能达到85%,制得直径30～60nm的聚苯乙烯胶乳粒子,乳胶粒子中含平均分子链数为3～20。CMC-A9或SDS质量浓度提高,能降低乳胶粒径和乳胶中所含的平均分子链数,增加聚合物相对分子质量。超声波输出功率对乳胶粒径影响不大。     

常温交联苯——丙乳液建筑密封胶的研制

本文研制了含固量为60～65％的苯—丙四元共聚乳液,以此乳液为基料,以金属离子为交联剂,并加入填料,助剂制得了常温交联建筑密封胶。探讨了聚合过程中丙烯酸(M)的用量,以及胶中交联剂的用量对胶耐水性的影响;考察了填料对密封胶力学性能的影响。     

Castor-oil-based interpenetrating polymer networks: Synthesis and characterization

Castor oil was polymerized and crosslinked with sulfur or diisocyanates to form the vulcanized and urethane derivatives, respectively. Both types were swollen with a plastic-forming monomer plus crosslinker, and a second polymerization was carried out in situ. Polyblends were also made by emulsion polymerization of styrene and methyl methacrylate employing hydrolyzed castor oil as the soap. In all three polymerizations, a wide range of compositions was obtained. The resulting interpenetrating polymer networks were characterized using electron microscopy, modulus–temperature measurements, and stress–strain analysis. The polystyrene phase size of the castor oil–urethane/polystyrene IPN was shown to decrease with increased crosslinking of the castor oil component and with increased polystyrene contents. The modulus–temperature study showed two distinct glass transitions in all cases, with evidence of significant mixing of the two components in many cases. The stress–strain results show that some of the IPN's behave as reinforced, highly extensible elastomers at low polystyrene levels, and a rubber-toughened plastics at high levels of polystyrene or crosslinking.     

Effect of reaction time and temperature on the morphology and ion-exchange capacity of polystyrene beads sulfonated using different sulfonating agents

Monodisperse polystyrene (PS) beads 2.5 μm in size were synthesized by dispersion polymerization. The PS beads were chemically modified by three different sulfonating agents, namely, concentrated sulfuric acid, acetyl sulfate, and chlorosulfonic acid. When they were sulfonated using chlorosulfonic acid, the concentration of sulfonic acid (SO₃ ⁻) groups on the PS beads increased from 0.5 to 2.25 meq/g as the treatment time was increased from 10 to 360 min at 0 °C. As the reaction temperature was increased, the ion-exchange capacity (IEC) of the sulfonated PS beads increased. However, it can be seen that they lost their spherical shape. The PS surface was modified by the introduction of the SO₃ ⁻ groups to give an IEC of up to 2.28 meq/g, which provides 1.1 × 10¹⁰ SO₃ ⁻ groups per bead, without any deformation of their spherical shape.     

Preparation of transparent polystyrene nano-latexes by an UV-induced routine emulsion polymerization

Transparent polystyrene (PS) latexes were prepared by photo-polymerization of a routine styrene (St) emulsion with a surfactant concentration of 0.4 wt% and a monomer concentration of 10 wt%, by using UV light as well as a hydrophilic photo-initiator. The entire polymerization could be performed within 1-2 h and display a conversion higher than 90%. The particle sizes could be tuned in the range of 20-40 nm. The formation mechanism for these of nano-sized latex particles was attributed to an in situ formation of PS chains with terminal hydroxyl groups. The presence of the hydroxyl-functionalized polymer chains seemed to promote a colloidal stability of the small latex particles and prevent coagulation even at low surfactant concentrations.     

Study on emulsion and suspension in situ polymerization

A novel and simple method of emulsion and suspension in situ polymerization was designed for preparing a composite of polystyrene containing core–shell emulsion particles. The advantage of this method was that it did not need a complex process, such as emulsion breaking, washing, drying, and so on, during transforming from emulsion polymerization to suspension polymerization. First, the core–shell particles of poly(styrene/bisphenol A dimethyl methacrylate)/polystyrene [P(St/BPADA)/PS] with crosslinking structure were synthesized by emulsion polymerization. Then the latex was broken with electrolyte dripping and the emulsion particles became swollen and transformed into the monomer in the suspension polymerization system. Thus the emulsion and suspension in situ polymerization could be carried out successfully. The mechanism of the process was investigated in detail. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 404–412, 2005