Final Latex Research Articles

Electrolytes on governing particle coagulation and size distribution in the emulsion polymerization of butyl acrylate

Poly (butyl acrylate) (PBA) latices with controllable particle size (90–350 nm) were synthesized via one-step batch emulsion polymerization in the presence of different species of electrolyte. The evolution of particle size and number as a function of monomer conversion were tracked in order to investigate the effect of electrolyte species on the particle stability. For electrolyte with different anions, the particle size of final latices decreased with increasing pH of the aqueous phase and the sequence was Na2CO3 < NaHCO3 < Na2C2O4 < NaCl, latices with Na2SO4 showed some particular performance and possessed of a particle size up to 347.4 nm; for electrolyte with different valences of counter ion, while achieving the similar particle size (Ca. 120 nm), an obvious variance in ionic strength was found (0.03, 0.016 and 0.0035 mol kg−1 for Na+, Mg2+ and Al3+). It indicate that electrolyte affects the particle stability by adjusting the pH of the aqueous phase and ionic strength, further controls the particle coagulation. As a result, latices with designated final particle size and distribution can be obtained by choosing the appropriate type and concentration of electrolyte.

Facile synthesis of large scale and narrow particle size distribution polymer particles via control particle coagulation during one-step emulsion polymerization

This study is an extension of the previous research results reported by our group (Colloid and Surf. A: Physicochem. Eng. Aspects 452 (2014) 159–164), where a novel approach to prepare large-scale polymer particles with a narrow distribution was reported. However, many important problems such as the visual evidence of particle coagulation, the relationship between particle distribution and particle coagulation, and the reasons of particle coagulation were not addressed in this article. In this manuscript, the polyisoprene latex particles were added to the polymerization systems as the indicator to follow the process of particle coagulation, and the reasons of particle coagulation are also discussed. The experimental results show that the final latex particles possessed a special structure similar to multicores and single-shell structure for the system containing polyisoprene particles and could be considered as a direct evidence of the particle coagulation. In addition, the competitive growth kinetics and reversible particle coagulation were used to analyze the reasons of a narrow particle size distribution of the final latex particles. In the combination with the Derjaguin–Landau–Verwey–Overbeek theory, the effect of the aqueous phase composition and initiator types on the particle coagulation were explained in the view of interaction energy.

Self film‐forming and opaque hollow latexes fabricated via seeded emulsion polymerization followed by alkali post‐treatment

ABSTRACTIn order to obtain novel hollow latexes with both opaque and self film‐forming properties, the four‐layer core/shell latex particles—sequentially consisting of a high carboxyl‐containing soft core, a transition layer, a rigid supporting layer, and an outermost film‐forming layer—are first designed and prepared by emulsion polymerization, and then treated with alkali to fabricate self film‐forming hollow latexes. On the basis of the previous research on the three‐layer core/shell latex, influences of the composition and thickness of the film‐forming layer on the properties and morphologies of the four‐layer core/shell and the final hollow latexes are investigated. Results show that under optimized conditions with butyl acrylate/styrene (BA/St) mass ratio of 2/1, divinyl benzene (DVB) content of 1 wt %, and core/film‐forming layer mass ratio of 1/6 in the film‐forming layer preparation, the final hollow latex particles exhibit best morphology considering both light scattering efficiency and film‐forming capability at room temperature. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42541.

Water Whitening Reduction in Waterborne Pressure‐Sensitive Adhesives Produced with Polymerizable Surfactants

Water whitening resistance of pressure‐sensitive adhesives obtained from high solids content acrylic dispersions is studied. The effect of the pH and surfactant system on the water whitening of the final films is investigated. The pH used throughout the polymerization process and the pH at which the final latex is adjusted just before the application have a substantial influence on the water whitening resistance. The performance of films obtained from latexes stabilized using conventional surfactant is compared to that of latexes stabilized using polymerizable surfactant or polymerizable stabilizer. In the films containing the conventional anionic surfactant, the water whitening phenomenon is affected by two counteracting mechanisms: latex stability and excess of surfactant in the aqueous phase. However, when polymerizable surfactants or stabilizer are used, due to their incorporation into the polymer backbone, no effect of the surfactant excess is observed leading to films with superior performance increasing their concentration.

Starved Semi-Batch Emulsion Polymerization for Polystyrene Nanolatexes Preparation With n-Pentanol as Cosurfactant

In the starved semi-batch emulsion polymerization, the n-pentanol was predissolved in the sodium dodecyl sulfate (SDS) solution as cosurfactant, for the purpose of polystyrene nanolatexes preparation. The effects of styrene (St) monomer feeding rate, n-pentanol dosage and SDS concentration on the monomer conversion (total and instantaneous conversions), the latex particles size (average volume diameter, dv) and the latex particles number in a unit volume (Np) were discussed. The function of n-pentanol not only debased the surface tension of the SDS solution, but also formed the smaller nanolatex particles size. With the 1.5 wt% n-pentanol dosage, 0.8 wt% SDS concentration and 6.0 mL/h St feeding rate for 6 h, the dv and Np of the final latex particles were 45.1 nm and 8.52×1015/ mL, respectively. The final latex solid content was 24.1%. All results were original and available compared to the state of the art.

Evolution of particle morphology during the synthesis of hybrid acrylic/CeO2 nanocomposites by miniemulsion polymerization

ABSTRACTThe evolution of the morphology of an acrylic/CeO2 hybrid latex synthesized by a two step seeded semibatch emulsion polymerization process was investigated. The seed was produced by batch miniemulsion polymerization and in the second step a neat monomer preemulsion was fed to the seed to increase the solids content and encapsulate the inorganic material. The morphology of the hybrid miniemulsion droplets, the seed and the final latex was analyzed by TEM. The morphologies achieved could be explained by theoretical equilibrium morphology maps based on the interfacial tensions of the monomeric, polymeric, inorganic and aqueous phases. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 792–799

RAFT Ab Initio Emulsion Polymerization of Styrene Using Poly(acrylic acid)-b-polystyrene Trithiocarbonate of Various Structures as Mediator and Surfactant

Reversible addition fragmentation chain transfer (RAFT) ab initio emulsion polymerization of styrene using poly(acrylic acid)-b-polystyrene trithiocarbonate (AAx-b-Sty macroRAFT) as both mediator and surfactant was investigated with systematically changed y from 0 to 7 and x from 15 to 30. A well-controlled polymerization in terms of little coagulum, well predicted molecular weight and low polydispersity (PDI) (≈1.2) could only be achieved by using the macroRAFTs of hydrophile-lipophile balance (HLB) values between 13 and 20. The final latex particle size could be tuned from 80 to 172 nm in diameter simply by changing x and y values while the molecular weight was targeted the same (30 K).

Effect of aqueous phase composition on particle coagulation behavior in batch emulsion polymerization of styrene

Previously, we studied the latex particle coagulation in the emulsion polymerization of n-butyl acrylate induced by an electrolyte (Colloid Polym Sci 291 (2013) 2385–2398). However, the evolution of particle size distribution vs. monomer conversion and reaction time, and the possibility for the manipulation of particle coagulation to control particle size and polydispersity were not studied. In this study, we investigated the evolution of particle size distribution vs. monomer conversion and reaction time during the emulsion polymerization of styrene. Moreover, the particle coagulation at different aqueous phase compositions was studied in details. The experimental results indicate that the particle size and polydispersity was controlled by particle coagulation, which was adjusted by varying the content of electrolyte or methanol in the aqueous phase. The final latex particle size increased in the range 89.2–265.9nm with increasing electrolyte or methanol. The effect of aqueous phase composition on the polydispersity index (PDI) of the final latex was also considered. The PDI of the final latex reached 0.005 at an appropriate aqueous phase composition. Interestingly, the demulsification phenomenon easily occurred at electrolyte concentration>1.2wt% or methanol/water ratio>30/70.

Fluorinated Latex Particles Prepared by Semibatch Miniemulsion Polymerization and its Film Surface Properties

Hexafluorobutyl methacrylate (HFMA) was predissolved as sole co-stabilizers in miniemulsions in order to improve the surface properties of films prepared by final latex, and a semibatch polymerization was used for enhancing the HFMA usage efficiency. In miniemulsion polymerization, the effects of the HFMA on the stability of monomer droplet were investigated. The ratio of the final latex particles number to the initial monomer droplets number was used to discuss the nucleation formation process. In a semibatch minimeulsion reaction, the effect of HFMA dropping policy on the size of final latex particles was discussed and morphology of the latex particles observed. Although the HFMA consumption was equal in all semibatch experiments, the surface properties of film prepared by final latex demonstrated a strong difference.

Thermoset–thermoplastic hybrid nanoparticles and composite coatings

Structured thermoset–thermoplastic hybrid nanoparticles and composite coatings were successfully synthesized through a novel one-pot approach. Both the polyaddition of epoxy curing and the free radical polymerization of various vinyl monomers were performed in sequence in miniemulsion droplets. Benefiting from the precise control of the compatibility between thermoset phase (epoxy monomer/amine curing agent) and vinyl phase (vinyl monomers/polymers), colloidally stable, core–shell structured thermoset–thermoplastic hybrid nanoparticles between 100 and 200 nm were obtained through chemically induced phase separation. The influence of the compositions on the colloidal stability and morphology of the final hybrid latexes and films was studied in detail. Meanwhile, the mechanical properties of thermoset–thermoplastic coatings and corresponding thermoplastic coatings were investigated. It is found that the thermoset–thermoplastic composite coatings showed significantly improved film properties in terms of hardness compared to the analogous thermoplastic coatings. Furthermore the thermoset–thermoplastic hybrid films were highly transparent even with 33 wt% of epoxy thermoset domains embedded.

Hydrophilicity of polymer effects on controlled particle coagulation in batch emulsion polymerization

The poly(methyl methacrylate-co-styrene) was prepared by batch emulsion polymerization to clarify the effect of characteristics of polymer on particle coagulation. Experimental results showed that the size of final latex particle increased with increasing methyl methacrylate in initial recipe, ranged from 84 to 193 nm, which was attributed to the particle coagulation. With the methyl methacrylate increased, the hydrophilicity of polymeric particle improved, thus led to the surfactant molecules packed loosely on the polymer surface, further, enhanced particle coagulation occurred. On the contrary, the surfactant molecules adsorbed on tightly the polymeric particle surface (methyl methacrylate content low) surface led to the electrostatic repulsion energy of polymer particle improved, and polymer particle stability was also improved. Thus, combined with the results previously reported by us (Colloid Polym Sci 291: 2385–2398, 2013 and Colloid Polym Sci 292: 519-525, 2014), the particle coagulation depended not only on the aqueous phase such as electrolyte concentration and methanol content, but also on the nature of polymer such as hydrophilicity.

A Facile Route toward Structured Hybrid Particles Based on Liquid–Solid Assembly

Structured hybrid particles with strongly improved colloidal stability are synthesized through a facile fabrication method based on the assembly of miniemulsion droplets containing liquid monomeric precursors onto solid nanoparticles. Classical heterocoagulation experiments between solid particles with similar compositions are performed for comparison and result in coagulated samples. A two-step mechanism is proposed which involves polymerization to fixate the final hybrid particle morphology after electrostatically driven self-assembly. Negatively charged polyacrylonitrile (PAN) nanoparticles with a high degree of semicrystallinity are utilized as solid core and combined with positively charged monomer droplets of varying compositions. A simple adjustment of miniemulsion composition enables the tailored synthesis of raspberry or core–shell structured hybrid particles. While the ζ-potential strongly affects the colloidal stability, adjusting the Tg of the polymer and/or the cross-linking degree after polymerization is an efficient tool to determine the final latex morphology. As-prepared hybrid dispersions can form transparent films with embedded PAN domains with an undisturbed high degree of semicrystallinity and thus show potentials in a wide variety of applications, e.g., for coatings and adhesives with reinforced mechanical properties and improved barrier performance.

Particle nucleation and growth in seeded semibatch miniemulsion polymerization of hybrid CeO2/acrylic latexes

CeO2/acrylic hybrid coatings with high solids content and with nanoparticle percentages up to 5 wt% have been successfully synthesized by seeded semibatch miniemulsion polymerization process. The droplet nucleation efficiency has been assessed by Capillary Hydrodynamic Chromatography and TEM analysis. The effect of the stability of the miniemulsion, the type of initiator and the number of particles of the seed on the efficiency of the nucleation of the nanodroplets fed has been investigated. It was found that the less stable the hybrid miniemulsion, the higher the diffusion of the monomer out of the droplets and hence, the seed latex particles grew in size. However, the CeO2 nanoparticles did not diffuse out with the monomer and remained in very small droplets that eventually nucleate leading to a bimodal population. When stable miniemulsions were produced by using a polymer as hydrophobe, droplet size increased reducing the number of particles in the seed and monomer diffusion was minimized enhancing nucleation of droplets with larger sizes that produced broad PSDs. Coalescence of droplets was negligible because the size distribution of the nanoceria particles did not change from the seed particles to the final latex. The UV–Vis absorption capacity of the films prepared with increasing the amount of CeO2 increased, but scattering effects were observed at high loading of CeO2 due to the large size of the CeO2 aggregates.

Semi-continuous emulsion copolymerization of vinyl acetate and butyl acrylate in presence of AMPS

The emulsifier-free emulsion polymerization of vinyl acetate (VAc) and butyl acrylate (BA) in the presence of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) was carried out by a semi-continuous process. AMPS was a reactive surfactant in the aqueous emulsion, due to its amphiphilic structure and the unsaturated double bonds. Potassium persulfate (KPS) was used as initiator. The following factors were mainly examined: quantity of AMPS, BA and KPS concentrations, which could significantly affect the particle size and its distribution, conversion, gel content, minimum film-forming temperature, etc. The particle size and its distribution were characterized by dynamic laser particle size analyzer, and morphology of the latex particles was characterized by transmission electron microscopy (TEM). Fourier transform infrared spectroscopy was used to characterize chemical structure of copolymers. The results indicated that AMPS was successfully reacted onto the resulted copolymer of vinyl acetate and butyl acrylate. A hydrophilic sulfonic acid group in the molecular structure of AMPS tended to be distributed in particles surface after polymerization. As a result, an electrostatic repulsion between the particles was produced in order to maintain stability of the system. Thermogravimetric analysis curves suggested that as BA content increased, thermal stability of the polymer increased accordingly. The conversion-time plots with varying AMPS and initiator contents were obtained, which illustrated that the initiator concentration could greatly influence the polymerization rate and the final conversion. The TEM micrographs of the final emulsifier-free latex particles for P(VAc/BA/AMPS) system revealed small particle size in monodisperse polymer latex. The particles of the latex were measured as about 150 nm.

Morphological Control of Multihollow Polymer Latex Particles through a Controlled Phase Separation in the Seeded Emulsion Polymerization

In this work, we first reported that the phase separation can take place both inside and outside of a multihollow-structured cross-linked seed microspheres swollen by styrene monomers in water during the radiation-induced seeded emulsion polymerization. The phase separation process in these two opposite directions will determine the morphology of final latex particles. First, sulfonated cross-linked polystyrene (SCPS) seed microspheres were swollen by styrene in water. Water will permeate into the SCPS seed microspheres during the swelling process, forced by the osmotic pressure produced by the strong hydrophilicity of the sulfonic acid groups. New aqueous phases are created and stabilized by the hydrophilic -SO3H groups, resulting in a multihollow structure of swollen SCPS seed microspheres. When the polymerization of styrene is induced by (60)Co γ-ray radiation, the phase separation of newly formed polystyrene phase will occur at the seed microsphere-water interface inside and/or outside of the SCPS seed microspheres through adjusting the diameter of seed microsphere, the content of cross-link agent, and the sulfonation degree of SCPS seed microspheres. As a result, SCPS latex particles with a variety of special morphologies, such as spherical multihollow, plum-like, and walnut-like latex particles were obtained. The results of this study provide not only a simple and interesting way to design and synthesize multihollow polymer latex particles with controllable surface morphologies but also a better understanding on phase separation mechanism during the swelling and polymerization of monomers in cross-linked amphiphilic polymer networks.

Encapsulation of a Biobased Lignin–Saponite Nanohybrid into Polystyrene Co-Butyl Acrylate (PSBA) Latex via Miniemulsion Polymerization

In this study, lignin recovered from a biorefinery waste stream was used to modify a clay saponite to form a lignin–clay nanohybrid. Approximately 32 wt % of lignin was associated into a lignin–clay nanohybrid, which could be well dispersed into an organophilic monomer phase. This nanohybrid was then encapsulated into polystyrene co-butyl acrylate (PSBA) particles to form stable latex via in situ miniemulsion polymerization. The final latex had a broad size distribution and a narrow window of the nanohybrid (1.9–5.3 wt %) loading level. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) analysis of latex films indicated successful encapsulation of intercalated nanohybrids inside a co-polymer matrix. The introduction of lignin–clay nanohybrids greatly improved PSBA properties. The nanocomposite with a 5.3% nanohybrid had a 13.75 times increase in tensile strength, an approximate 50 °C increase in degradation temperature, and a 42% decrease in oxygen permeability.

Hybrid copolymer latex of MMA-BA-zonyl TM-PDMS by mini-emulsion polymerization

Stable, coagulum free fluoro-silicone-acrylic latex (FSAL) of methyl methacrylate (MMA)-co-butyl acrylate (BA)-co-Zonyl TM-hyb-Polydimethylsiloxane (PDMS) is prepared through mini-emulsion polymerization. Apart from this, three more latexes/emulsions acrylic latex (AL) of methyl methacrylate (MMA)-co-butyl acrylate (BA), silicone-acrylic latex (SAL) of methyl methacrylate (MMA)-co-butyl acrylate (BA)-hyb- PDMS, and fluoro acrylic latex (FAL) of methyl methacrylate (MMA)-co-butyl acrylate (BA)-co-Zonyl TM are prepared for systematic understanding of the preparation and properties of the emulsions. The emulsions are prepared with almost uniform size of monomer droplets (mini-emulsions). The prepared latexes were characterized by IR, C13 NMR and 1H NMR. A systematic understanding of the effect of initial droplet size on final latex particle, the properties of the latex particles such as swelling ratio, MFFT, contact angle, distribution of particle size, rheological behavior, DSC/DMA thermograms, SEM images of the films and film topography are reported. The fluoro-silicone-acrylic latex (FSAL) exhibit, stable, low MFFT, narrow particle size distribution, and high contact angle for water, and hence it can be a great candidate as a hydrophobic binder in coating products.

High Solid Contents Copoly (Styrene/Butyl Acrylate)-Cloisite 30B Nanocomposites

Higher solid contents (20 % and 40 %) nanocomposites of poly (styrene-co-butyl acrylate) including higher content of Cloisite 30B (7 wt% and 10 wt %) were prepared via miniemulsion polymerization. Stability of the final latexes proved outstanding combination of polymerization procedure and surfactants. Morphological studies revealed by TEM, SAX and XRD showed three structures of coreshell, armored and individual dispersion of clay layers within the polymer particles. The effect of Cloisite 30B content on the barrier properties presents excellent and wide use of these films for packaging and nanocoatings industries.

The formation of asymmetric polystyrene/saponite composite nanoparticles via miniemulsion polymerization

AbstractThe synthesis of asymmetric spherical nanoparticles has attracted great interest because their anisotropic structure can be used as unique building blocks for constructing advanced materials. In this article, we report the formation of hemispherical or truncated polystyrene/nanosaponite composite particles via one‐pot miniemulsion polymerization. It was found that the morphology of final composite latex particles strongly depends on the size of the nanoclay and its surface properties. Hemisphere or truncated sphere is the dominant morphology if the size of the nanoclay is larger than 100 nm. With the increase of the nanoclay content (up to 30 wt %), the fraction of hemispherical or truncated polystyrene/nanosaponite composite latex particles increased accordingly. The formation of hemispherical particles is possibly attributed to either the asymmetric growth of polymer chains on one side of the hydrophobically modified clay or the mechanical peeling‐off of large spherical particles between polymer and saponite. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

An Emulsifier‐Free RAFT‐Mediated Process for the Efficient Synthesis of Cerium Oxide/Polymer Hybrid Latexes

Hybrid latexes based on cerium oxide nanoparticles are synthesized via an emulsifier-free process of emulsion polymerization employing amphiphatic macro-RAFT agents. Poly(butyl acrylate-co-acrylic acid) random oligomers of various compositions and chain lengths are first obtained by RAFT copolymerization in the presence of a trithiocarbonate as controlling agent. In a second step, the seeded emulsion copolymerization of styrene and methyl acrylate is carried out in the presence of nanoceria with macro-RAFT agents adsorbed at their surface, resulting in a high incorporation efficiency of cerium oxide nanoparticles in the final hybrid latexes, as evidenced by cryo-transmission electron microscopy.