Miniemulsion Polymerization Of Styrene Research Articles

Starch nanoparticles as Pickering emulsifiers in miniemulsion polymerization of styrene

AbstractPickering miniemulsion polymerizations of styrene using octenyl succinic anhydride (OSA) and dodecenyl succinic anhydride (DSA) modified starch nanoparticles (SNP) (~20–25 nm) were conducted. The effect of different degrees of substitution (DS), alkyl chain length, concentration of Pickering emulsifier (PE), and pH was correlated to the shelf‐life stability of the styrene Pickering miniemulsions and the particle size distribution (PSD). Interfacial tension values of aqueous dispersions of SNP‐OSA (DS = 0.11) and SNP‐DSA (DS = 0.14) against toluene as low as 14.7 and 11.0 mN/m, respectively, were observed. Average styrene droplet diameters in the miniemulsions (DV(sty)) ranged between 100–600 nm. 2,2′‐Azobisisobutyronitrile (AIBN) and lauroyl peroxide (LPO) were employed as initiators and the effect of the water solubility on the resulting PSD and latex stability was investigated. The resulting polystyrene (PS) latex particles ranged between 70 and 550 nm in diameter. When AIBN was used as initiator, secondary nucleation was observed. The rate of polymerization and conversion of SNP‐OSA and SNP‐DSA stabilized Pickering miniemulsion polymerizations were compared. The SNP‐armoured PS particles were visualized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). At low conversions (<40%), the resulting latexes were relatively uniform when modified SNP were used as PE along with small amounts of hexadecane as a hydrophobe. At higher conversion, however, coagulation occurred which was correlated to a side reaction in which the PS particles grafted together to form large coagulates.

Upconverting Nanoparticles in Aqueous Media: Not a Dead-End Road. Avoiding Degradation by Using Hydrophobic Polymer Shells.

The stunning optical properties of upconverting nanoparticles (UCNPs) have inspired promising biomedical technologies. Nevertheless, their transfer to aqueous media is often accompanied by intense luminescence quenching, partial dissolution by water, and even complete degradation by molecules such as phosphates. Currently, these are major issues hampering the translation of UCNPs to the clinic. In this work, a strategy is developed to coat and protect β-NaYF4 UCNPs against these effects, by growing a hydrophobic polymer shell (HPS) through miniemulsion polymerization of styrene (St), or St and methyl methacrylate mixtures. This allows one to obtain single core@shell UCNPs@HPS with a final diameter of ≈60-70nm. Stability studies reveal that these HPSs serve as a very effective barrier, impeding polar molecules to affect UCNPs optical properties. Even more, it allows UCNPs to withstand aggressive conditions such as high dilutions (5µgmL-1 ), high phosphate concentrations (100mm), and high temperatures (70°C).The physicochemical characterizations prove the potential of HPSs to overcome the current limitations of UCNPs. This strategy, which can be applied to other nanomaterials with similar limitations, paves the way toward more stable and reliable UCNPs with applications in life sciences.

Cationic polymerization of styrene using iron-containing ionic liquid catalysts in an aqueous dispersed medium

This work aims to study the cationic miniemulsion polymerization of styrene catalyzed by iron-containing imidazolium-based ionic liquids. The polystyrenes had very high number-average molar mass around 1300 kg mol-1 at 85 °C, molar-mass dispersity close to 2.0 and glass transition temperature higher than 102 °C with average particle diameter that remained practically unchanged during the reaction, indicating that the monomer droplets correspond to the polymerization locus. First-order kinetics up to a limit conversion, along with the increase in molar mass as the temperature decreases, styrene polymerization at low temperatures and catalyst inability to polymerize monomers that react exclusively via free radical and/or anionic polymerization, indicate the cationic nature of polymerization. 1H-NMR and 13C-NMR spectra suggested the formation of polystyrene, allowing for tacticity distribution quantification: 10% isotactic, 20% atactic and 70% syndiotactic configurations. TEM micrographs confirmed the formation of spherical polymer nanoparticles and the presence of catalysts in the polymer matrix.

Redox-Initiated Reversible Addition-Fragmentation Chain Transfer (RAFT) Miniemulsion Polymerization of Styrene using PPEGMA-Based Macro-RAFT Agent.

Redox-initiated reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerizations are successfully conducted with an employment of trithiocarbonate-based macro-RAFT agents and surfactant. Two macro-RAFT agents-hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA27 ) and amphiphilic poly(poly(ethylene glycol) methyl ether methacrylate)-b-polystyrene (PPEGMA27 -b-PS33 )- are examined for the miniemulsion polymerization of styrene. The use of PPEGMA27 (in the presence of sodium dodecyl sulfate (SDS)) results in a slow polymerization rate with a broad particle size. In the absence of SDS, the use of PPEGMA27 -b-PS33 results in a broad particle size distribution due to its inability to form uniform initial droplets whereas the same amphiphilic block copolymer in the presence of SDS yields resulting products with a uniform particle size distribution. The latter exhibits a fashion of controlled polymerization with a high consumption of monomer (98% in 100min) and a narrow molecular weight distribution throughout the polymerization. This is attributed to the formation of uniform droplets facilitated by SDS in a miniemulsion. The amphiphilic macro-RAFT agent is able to anchor efficiently on the monomer droplet or particle/water interface and form stabilized particles of well-defined PPEGMA27 -b-PS block copolymer, confirmed using dynamic light scattering and transmission electron micrographs.

Miniemulsion polymerization of styrene using carboxylated graphene quantum dots as surfactant

Carboxylated graphene quantum dots (cGQDs) were synthesized from dextrose and sulfuric acid via a hydrothermal process, and subsequently used as sole surfactant in miniemulsion polymerization of styrene.

Designed Amphiphilic Polystyrene as Surfactant for Oligo(p-phenylenevinylene)-Incorporated PS Nanobeads and Visual Detection of Bilirubin in Human Blood Serum

Amphiphilic polystyrene having pendant glucuronic acid (PS-DGlu) was designed and systematically synthesized to be used as a stabilizing agent in styrene miniemulsion polymerization, while covalently incorporating oligo(p-phenylenevinylene) (OPV)-based fluorophore to prepare PSG-OPV-n. This OPV fluorophore was incorporated with an aim to work as a signal transducer, while glucuronic acid on the surface of PS nanobeads would act as the water solubilizing moiety for PS to enable it to function as surfactant and also serve as an interaction site for free bilirubin to facilitate noncovalent interaction via hydrogen bonding. Efficient energy transfer from OPV to bilirubin was observed, owing to the appreciable spectral overlap between emission of OPV and absorption of bilirubin. Visual color change from blue to bluish green was observed under an UV lamp after the addition of bilirubin into the polymer. Selectivity of the sensor was checked among the pool of other interferences, such as glucose, sucrose, metal ...

Modeling of Miniemulsion Polymerization of Styrene with Macro-RAFT Agents to Theoretically Compare Slow Fragmentation, Ideal Exchange and Cross-Termination Cases.

A 5-dimensional Smith-Ewart based model is developed to understand differences for reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization with theoretical agents mimicking cases of slow fragmentation, cross-termination, and ideal exchange while accounting for chain length and monomer conversion dependencies due to diffusional limitations. The focus is on styrene as a monomer, a water soluble initiator, and a macro-RAFT agent to avoid exit/entry of the RAFT leaving group radical. It is shown that with a too low RAFT fragmentation rate coefficient it is generally not afforded to consider zero-one kinetics (for the related intermediate radical type) and that with significant RAFT cross-termination the dead polymer product is dominantly originating from the RAFT intermediate radical. To allow the identification of the nature of the RAFT retardation it is recommended to experimentally investigate in the future the impact of the average particle size (dp) on both the monomer conversion profile and the average polymer properties for a sufficiently broad dp range, ideally including the bulk limit. With decreasing particle size both a slow RAFT fragmentation and a fast RAFT cross-termination result in a stronger segregation and thus rate acceleration. The particle size dependency is different, allowing further differentiation based on the variation of the dispersity and end-group functionality. Significant RAFT cross-termination is specifically associated with a strong dispersity increase at higher average particle sizes. Only with an ideal exchange it is afforded in the modeling to avoid the explicit calculation of the RAFT intermediate concentration evolution.

Differences between ab initio emulsion and miniemulsion polymerization of styrene mediated by an alkenyl-functionalized amphiphilic RAFT agent

An alkenyl (butene)-functionalized amphiphilic macromolecular reversible addition fragmentation chain transfer (macro-RAFT) agent was designed as both surfactant and polymerization mediator for ab initio emulsion and miniemulsion polymerization of styrene (St), intending to synthesize polymer nanoparticles with alkenyl-enriched surfaces. However, the pendent alkenyl units exhibited unexpectedly higher reactivity in ab initio emulsion polymerization than they did in solution polymerization. Their copolymerization with St resulted in depletion of alkenyl groups, positive deviation of molecular weights, broad molecular weight distributions, and limiting conversions. Miniemulsion polymerization was superior to ab initio emulsion polymerization in its ability to prepare alkenyl-functionalized nanoparticles. Consumption of alkenyl groups happened, but only within the nucleation period. In spite of positive deviation of molecular weights and broad molecular weight distributions, the final particles were characteristics of alkenyl functionalities confined to the particle surfaces. Thus, PSt nanoparticles with alkenyl-enriched surface were obtained via miniemulsion polymerization.

Heteromorphic Polymer Nanoparticles in Response to Rotational Magnetic Fields for Stirring inside Living Cells

Heteromorphic polymer nanoparticles containing iron oxide particles were prepared to obtain a nanometer-sized magnetic stir bar that remotely responds to external magnetic fields. The polymer nanoparticles were prepared by the mini-emulsion polymerization of styrene with small amounts of a cross-linker, and the spherical nanoparticles obtained were incorporated into a poly (vinyl alcohol) (PVA) film. The PVA film was stretched and deformed at 160°C to make the nanoparticles heterogeneous. The dimensions of the polymer nanoparticles with a heterogeneous morphology and rugby ball-like shape were about 210 nm ×100 nm with an average aspect ratio greater than 2.0. The dispersion ability of the nanoparticles was sufficient to use in aqueous circumstances. When an external magnetic field was applied to an aqueous suspension of the nanoparticles, the particles aggregated quickly. Also, on the application of a rotational magnetic field, the polymer nanoparticles began rotating with a velocity proportional to the rate of the external magnetic field rotation. Therefore, it was concluded that the heteromorphic polymer nanoparticles have the potential to stir a micrometer-scale reaction vessel, such as living cells.

Cationic miniemulsion polymerization of styrene mediated by imidazolium based ionic liquid

For the first time, it was shown the cationic miniemulsion polymerization of styrene using an ionic liquid as catalyst. The ionic liquid (BMI·Fe2Cl7) was tolerant to the presence of high amount of water, being effective for polymerization of styrene in the evaluated temperatures range from 70 to 90 °C. The polymerization was considerably slower than conventional cationic polymerization, indicating that this process is easier to control than the conventional ones. In addition, quite high molecular weights were reached, while the particle size, between 150 and 175 nm, was within the typical range for miniemulsion polymerization.

Miniemulsion Polymerization Monitoring Using Off‐Line Raman Spectroscopy and In‐Line NIR Spectroscopy

Miniemulsion polymerization has been extensively studied in the last decade due to its advantages when compared with conventional emulsion polymerization. In this work, monomer conversion and particle size are monitored during miniemulsion polymerization of styrene using in‐line near‐infrared (NIR) spectroscopy and at‐line Raman spectroscopy. Gravimetric analysis and dynamic light scattering have been used as off‐line reference measurements. Good agreement has been found between off‐line data and the values predicted by NIR and Raman spectroscopy for conversion. The values of average particle size are well predicted from the NIR spectra with the respective calibration model, but the predictions from Raman spectra present some slight discrepancies for particle size. The results show a decrease of the average particle size during the initial period of the polymerization, indicating the occurrence of nucleation mechanisms other than the classical droplet nucleation. These results indicate that insightful information can be obtained by monitoring miniemulsion polymerizations with the use of spectroscopic techniques. image

Polystyrene latex particles containing europium complexes prepared by miniemulsion polymerization using bovine serum albumin as a surfactant for biochemical diagnosis

Luminescent particles have been attracting significant attention because they can be used in biochemical applications, such as detecting and imaging biomolecules. In this study, luminescent polystyrene latex particles were prepared through miniemulsion polymerization of styrene with dissolved europium complexes in the presence of bovine serum albumin (BSA) and poly(ethylene glycol) monomethoxy methacrylate as surfactants. The solubility of the europium complex in styrene has a strong effect on the yield of the particle. Europium tris(2-thenoyl trifluoroacetonate) di(tri-n-octyl phosphine oxide), which has a high solubility in styrene, was sufficiently incorporated into the polystyrene particles compared to europium tris(2-thenoyl trifluoroacetonate), which has a low solubility in styrene. The luminescence property of the europium complex could remain intact even after its incorporation through the miniemulsion polymerization. In the aqueous dispersion, the resulting particles could emit strong luminescence, which is a characteristic of the europium complex. The antibody fragments were covalently attached to BSA-covered particles after a reaction with a bifunctional linker, N-(6-maleimidocaproyloxy)succinimide. The time-resolved fluoroimmunoassay technique showed that 3.3pg/mL of human α-fetoproteins (AFP) can be detected by using the resulting luminescent particles. An immunochromatographic assay using the resulting particles was also performed as a convenient method to qualitatively detect biomolecules. The detection limit of AFP measured by the immunochromatographic assay was determined to be 2000pg/mL. These results revealed that the luminescent particles obtained in this study can be utilized for the highly sensitive detection of biomolecules and in vitro biochemical diagnosis.

The Synthesis of Amphiphilic Luminescent Graphene Quantum Dot and Its Application in Miniemulsion Polymerization

Although emulsion applications of microscale graphene sheets have attracted much attention recently, nanoscale graphene platelets, namely, graphene quantum dots (GQDs), have been rarely explored in interface science. In this work, we study the interfacial behaviors and emulsion phase diagrams of hydrophobic-functionalized graphene quantum dots (C18-GQDs). Distinctive from pristine graphene quantum dots (p-GQDs), C18-GQDs show several interesting surface-active properties including high emulsification efficiency in stabilizing dodecane-in-water emulsions. We then utilize the C18-GQDs as surfactants in miniemulsion polymerization of styrene, achieving uniform and relatively small polystyrene nanospheres. The high emulsification efficiency, low production cost, uniform morphology, intriguing photoluminescence, and extraordinary stability render C18-GQDs an attractive alternative in surfactant applications.

Regularities of the kinetics of miniemulsion polymerization of styrene in the presence of dithiobenzoates as reversible chain transfer agents

The results of comparative kinetic study of the miniemulsion controlled radical polymerization of styrene in the presence of reversible chain transfer agents (benzyl dithiobenzoate and polystyrene dithiobenzoate) and bulk polymerization of similar systems are presented. The influence of the reactant nature and dithiobenzoate concentration of the kinetics of the process is discussed.

Visible-Light-Regulated Controlled/Living Radical Polymerization in Miniemulsion.

The implementation of photopolymerization processes in aqueous dispersed systems has the potential to afford greener approaches to the preparation of polymeric materials and has motivated researchers to perform photopolymerization in emulsion. However, these previous works have employed UV irradiation to induce photodegradation of a photoinitiator in addition to specialized equipment setups, thus limiting widespread use of these approaches. In this work, we aim to remedy these drawbacks via the implementation of photoredox catalysis in the regulation of a controlled/living radical polymerization under visible light. Utilizing the photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) process, we report the miniemulsion polymerization of styrene mediated by a household grade blue LED (λmax = 460 nm, 0.73 mW/cm2). The polymerization rate can be easily manipulated by light intensity and catalyst concentration. Finally, temporal control was demonstrated via ON/OFF experiments, which shows that no significant detriment is caused by prolonged interruptions to the light exposure.

Poly(3‐hydroxybutirate‐co‐3‐hydroxyvalerate)–Polystyrene Hybrid Nanoparticles via Miniemulsion Polymerization

Hybrid polymer nanoparticles were obtained by miniemulsion polymerization of styrene with poly(3‐hydroxybutirate‐co‐3‐hydroxyvalerate) (PHBV). Lower polymerization rates were obtained with the gradual addition of PHBV. These results were represented by simulations using a mathematical model that takes into account grafting reactions between the growing polymeric chains and PHBV double bonds (reduced molar mass). Hybrid nanoparticles presented average diameters of up to 113 nm and grafting yield of 94.4%. The hybrid fractions obtained by Selective Soxhlet Extraction were characterized with Fourier Transform Infrared Spectroscopy, Differential Scanning Calorimetry and Transmission Electron Microscopy. Blend nanoparticles were used to confirm the hybrid formation.

Monodisperse cross-linked polystyrene nanospheres by emulsifier-free miniemulsion polymerization

AbstractCross-linked cationic polystyrene (CCPS) nanospheres with monodispersity were successfully generated by soap-free miniemulsion polymerization of styrene and divinylbenzene with 2,2′-azobis (2-amidinopropane) dihydrochloride as a water-soluble initiator. The effects of output power of the homogenizer and the concentration of the initiator and cross-linking agent on the particle size and coefficient of variation of CCPS nanospheres were systematically investigated and discussed. The weight percent of N element on the particle surface and the ζ potential were determined as different initiator concentrations were employed for the preparation of CCPS nanospheres. Furthermore, the technique of nitrogen adsorption/desorption was applied to characterize the specific surface area and the total pore volume of the CCPS nanospheres, which were generated from different amounts of divinylbenzene. Overall, the present study provides a simple route for producing cross-linked polymer nanospheres with monodispersity.

Nonionic surfactant-stabilized raspberry-like polymer/silica nanoparticles latex with film formability

Raspberry-like P(St-BA)/SiO2 nanoparticle latexes were prepared via miniemulsion polymerization of styrene (St) and butyl acrylate (BA) in the presence of 20 nm glycerol-modified SiO2 sol as a Pickering emulsifier and octaphenyl polyoxyethylene (CA-897) as a nonionic surfactant, using 2,2-azobis (isobutyronitrile) (AIBN) as an initiator. 2-(Methacryloyl) ethyltrimethylammonium chloride (MTC) was introduced to act as an auxiliary monomer to enhance the attraction of SiO2 sol onto latex nanoparticles (NPs) via increasing their electrostatic interaction with negative-charged SiO2 sol. The average particle sizes of the latex particles can be well controlled from 200 to 360 nm by variation of the SiO2 sol content as well as soft monomer BA component. The latex NPs displayed a good colloidal stability with excellent resistance to both strong acidic and basic environment. Furthermore, the nanosized latexes exhibited good film formability. The influence of reaction parameters, e.g., the initial silica amount and soft monomer BA content was systematically investigated on the film performances, such as hardness, abrasive resistance, water absorption, gloss. The results indicated that the increase of SiO2 sol content can contribute to the increase of the film hardness and water absorption ability, while increasing BA component is beneficial to the improvement of the film gloss.

Kinetics of reversible addition–fragmentation transfer (RAFT) miniemulsion polymerization of styrene using dibenzyl trithiocarbonate as RAFT reagent and costabilizer

AbstractThe roles of dibenzyl trithiocarbonate (DBTTC) as both costabilizer and reversible addition–fragmentation transfer (RAFT) reagent in RAFT miniemulsion polymerizations of styrene were investigated. The effectiveness of DBTTC costabilizer in retarding Ostwald ripening involved in the storage stability of miniemulsion is comparable to that of conventional low‐molecular‐weight costabilizers such as cetyl alcohol, but inferior to that of hexadecane. The major variables chosen for studying kinetics of RAFT miniemulsion polymerizations include the type of initiators and levels of DBTTC and surfactant. At a constant level of DBTTC, the rate of polymerization for benzoyl peroxide (BPO)‐initiated polymerization is slower than that for sodium persulfate (SPS)‐initiated polymerization. Furthermore, the polymerization rate decreases with increasing level of DBTTC for polymerizations initiated by BPO (or SPS). It is the monomer droplet nucleation that governs BPO‐initiated polymerizations. In contrast, for SPS‐initiated polymerizations, the probability for homogeneous nucleation to take place is greatly increased, especially for polymerizations with lower levels of DBTTC and higher levels of surfactant. © 2015 Society of Chemical Industry

Magnetic microcapsules with inner asymmetric structure: Controlled preparation, mechanism, and application to drug release

Magnetic microcapsules with inner asymmetric structure are prepared by miniemulsion polymerization of styrene in presence of oleic acid-modified Fe3O4 as magnetic nanoparticles and n-heptane (HP) as core. The resultant microcapsules with novel structure exhibit magnetic anisotropy and cavity anisotropy. The formation mechanism of the microcapsule is illustrated in detail. The obtained results showed that the polymerization process is associated with phase-separation between polystyrene, oleic acid (OA) and HP. Based on this formation mechanism, a kind of highly asymmetric magnetic microcapsules are prepared, which is further verified the presented phase-separation mechanism. Meanwhile, four kinds of magnetic microcapsules with inner asymmetric structure, which show different shell thickness and cavity volume, are prepared for application to carrying and releasing drugs. The results reveal that the microcapsules exhibit excellent controlled drug release property and the release speed can be controlled by adjusting the thickness of the thinner-side capsule-wall. Drug loading and drug release of inner asymmetric magnetic microcapsules were from the thinner side of capsule-wall. This kind of novel microcapsule shows potential application value in unilateral or contact point controlled and concentrated release.