Styrene Miniemulsion Research Articles

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 ...

Preparation of PLLA/PMMA and PLLA/PS binary blend nanoparticles by incorporation of PLLA in methyl methacrylate or styrene miniemulsion homopolymerization

Miniemulsion homopolymerization reactions of methyl methacrylate (MMA) and styrene (STY) using poly(L-lactide) as co-stabilizer were carried out in order to prepare poly(L-lactide)/poly(methyl methacrylate) (PLLA/PMMA) and poly(L-lactide)/polystyrene (PLLA/PS) binary blend nanoparticles. The effect of PLLA concentration on methyl methacrylate (MMA) and styrene (STY) homopolymerization reactions was evaluated. It was found that the incorporation of PLLA resulted on acceleration of MMA and STY homopolymerization reactions and led to a molar mass increase of up to 70% for PS in PLLA/PS blend nanoparticles in relation to those prepared without PLLA, which can be attributed to an increase of reaction loci viscosity (gel effect). PLLA also acted as an efficient co-stabilizer, since it was able to retard diffusional degradation of droplets when no other kind of co-stabilizer was used. Two isolated Tgs were found in both PLLA/PMMA and PLLA/PS blend nanoparticles which can be associated to blend immiscibility. TEM images corroborate these results, suggesting that immiscible PLLA/PMMA and PLLA/PS blend nanoparticles could be formed with two segregated phases and core-shell morphology.

Effect of hydration layer on the structure of thermo‐sensitive nanocapsules

ABSTRACTA thermo‐sensitive nanocapsule, containing the hydration layer, was synthesized through introducing N‐isopropylacrylamide into the system of styrene miniemulsion polymerization and hexadecane as liquid template. The properties and content of the water in the hydration layer were investigated by differential scanning calorimetry. With dynamic light scattering and transmission electron microscope, the effects of temperature and solvent on the particle size and morphologies were studied. The results showed that the increase of temperature and the ethanol–water mixed solvent could decrease the thickness of hydration layer and caused the polymer chain in the shell coil‐to‐globule transition, which switched on the pathway to loading and releasing substances in the nanocapsules. By using UV‐visible spectroscopy to monitor the tracer, the diffusion coefficients were determined and verified the switching process above. In addition, the ethanol–water molecule cluster can form a stable associative structure around ethanol mole fraction of 0.4, and destroyed the hydration of the hydrophilic group. The solvent interactions were proved to be the main driving force for the coil‐to‐globule transition of poly(N‐isopropylacrylamide). Moreover, an appropriate latex particle size should exclude the hydration layer but stable dispersed in the solvent was suggested. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40589.

Reactive mcl‐PHA: A Sustainable Alternative for Innovative Hybrid Materials

AbstractThe ability to incorporate medium chain length poly(hydroxyalkanoate) (mcl‐PHA) in the styrene miniemulsion polymerization process was investigated. As a result, novel poly(hydroxyalkanoate)‐co‐poly(stryrene) (PHA‐co‐PS) copolymers were synthesized in the form of stable organic–organic hybrid latexes. Evidence of chemical grafting of mcl‐PHA and cross‐linking of the PHA grafts was obtained using NMR, differential scanning calorimetry (DSC), gel extraction, and rheological analysis. A high degree of mcl‐PHA grafting was achieved by maintaining proper miniemulsion polymerization conditions throughout the course of the polymerization. The incorporation of PHA grafts was a function of the level of PHA in the formulations as well as the reaction conditions, as evidenced by solvent extraction and rheological analysis. DSC showed shifts in the Tg of PS towards higher temperatures, indicating chemical interaction of PS‐PHA. magnified image

Rate enhanced nitroxide-mediated miniemulsion polymerization: effect of nitroxide water solubility

Nitroxide-mediated radical polymerization of styrene in miniemulsion based on in situ surfactant generation of potassium oleate has been conducted at 130 °C for three nitroxides of vastly different water solubilities; 4-stearoyl-TEMPO, TEMPO and 4-hydroxy-TEMPO. These miniemulsions contain high levels of surfactant (120 wt% relative to styrene) and have particle diameters of <20 nm, and as such compartmentalization effects are important. The TEMPO-based system proceeded with extraordinarily high polymerization rate (initial rate ∼30 times higher than in the corresponding bulk system), much faster than ever before achieved, while control/livingness remained satisfactory. The results for the other two nitroxides were consistent with the propensity (or lack thereof) of the free nitroxide to exit to the aqueous phase – the 4-stearoyl-TEMPO system (negligible nitroxide exit) exhibited a polymerization rate similar to the corresponding bulk system with good control/livingness, whereas the 4-hydroxy-TEMPO system polymerized much faster than the corresponding bulk system, accompanied by loss of control. Consumption of free nitroxide caused by the presence of oleic acid may also influence these polymerizations.

Styrene Miniemulsion Polymerization: Incorporation of N‐Alkanes

AbstractSummary: In this work, the incorporation of alkane hydrocarbons in poly(styrene‐co‐methacrylic acid) particles via miniemulsion polymerization was investigated. The reactions were performed at 80 °C for 4 hours, using benzoyl peroxide as oil‐soluble initiator. The effects of different concentrations of a hydrophilic co‐monomer (methacrylic acid) and different types and concentrations of alkanes, namely n‐hexadecane, n‐octane and n‐heptane were evaluated. Miniemulsion stability at room temperature and reaction kinetics were monitored, as well as the particles size and morphology. Results show the viability of encapsulation of alkanes in miniemulsion polymerizations, especially of alkanes with intermediate chain lengths (e.g. n‐hexadecane). When short chain alkanes are incorporated the miniemulsions become less stable, due to their lower hydrophobicity. Based on monomer droplet size distribution data, it was determined that the best concentration of hydrophilic co‐monomer for the studied system was 1.0 wt%.

Controlled radical polymerization of styrene in miniemulsion mediated by PEO-based trithiocarbonate macromolecular RAFT agents

Poly(ethylene oxide) (PEO) based macroRAFT agents with various chemical structures have been used as both stabilizer and control agent for the polymerization of styrene in miniemulsion conditions. Trithiocarbonate (PEO-DTTC (Z = thiododecyl), PEO-PTTC (Z = thiopropyl)) functional groups were attached to a commercial monomethyl ether PEO (Mn = 2000 g mol−1). PEO-DTTC and PEO-PTTC allowed the formation of stable miniemulsions of styrene in water. Our previous results (A. M. Dos Santos, T. Le Bris, C. Graillat, F. D'Agosto, M. Lansalot, Macromolecules, 2009, 42, 946) showed that PEO-based dithiobenzoate (PEO-DB) led to controlled polymerization but also to broad molar mass distribution (PDI = 1.9) and multipopulated polymer chains. The switch from PEO-DB to PEO-DTTC greatly improved the molar mass distribution (PDI = 1.6). This was ascribed to the ability of PEO-DTTC to be localized at the water/monomer droplets interface. An increase in PEO-DTTC concentration improved the control of the polymerization. However, the concomitant formation of micelles favored secondary nucleation. This was attenuated by the use of PEO-PTTC, less prone to form micelles in water which greatly improved both the quality of control (PDI = 1.3) and the particle size distribution and showed that the particles were constituted of well-defined PEO-b-PS polymer chains. These results could be attributed to a more efficient anchoring of PEO-PTTC at the monomer droplet or particle/water interface showing the crucial role of the macroRAFT structure in these systems.

Miniemulsion polymerisation in pseudo-bulk regime: Mathematical modelling, prediction and optimal strategy of operation

A dynamic mathematical model based on pseudo-bulk kinetics was developed for styrene miniemulsion polymerisation and validated using experimental data. Key findings are that the developed model match reasonably with experimental data and is able to predict the polymerisation attributes and product properties such as fractional conversion, average molecular weight, molecular weight distribution (MWD), average particle size and particle size distribution (PSD) in miniemulsion polymerisation. Optimal strategy of semibatch operation was developed using reaction temperature and monomer feed rate as process variables with specified initial conditions.

Kinetics of styrene miniemulsion polymerization using poly[(stearyl methacrylate- co-( N, N-dimethylamino)ethyl methacrylate] as surfactant

Two comb-like amphiphilic copolymers have been prepared via conventional free-radical random copolymerization of stearyl methacrylate (SMA) and 2-( N, N-dimethylamino)ethyl methacrylate (DMAEMA) with different feed ratios. The resultant copolymers, poly(SMA- co-DMAEMA), were then characterized by 1H NMR and gel permeation chromatography (GPC) measurements. The surface activity of these copolymers in aqueous solution with different pH values was studied by surface tension measurements. Finally, these amphiphilic cationic copolymers were used as polymeric surfactants in the miniemulsion polymerization of styrene. The hydrophobic stearyl side chains of SMA could be strongly adsorbed onto the monomer droplets or propagating particles during the miniemulsion polymerization, while the hydrophilic and protonated PDMAEMA units at low pH media could stabilize the latexes. Moreover, the influences of the composition and amounts of the polymeric surfactants on the kinetics of the miniemulsion polymerization and colloidal stability have been investigated. The reaction rate of miniemulsion polymerization was found to increase with increasing amounts of polymeric surfactants and decrease with the increase of pH values of aqueous solution.

A kinetic Monte Carlo study on the nucleation mechanisms of oil‐soluble initiators in the miniemulsion polymerization of styrene

AbstractThe use of oil‐soluble initiators in free‐radical miniemulsion polymerization has increased due to their ability to generate radicals primarily within monomer droplets. Existing theories concerning the nucleation mechanism for oil‐soluble initiators suggest that a single radical must be formed within a particle for propagation to occur, despite the fact that an oil‐soluble initiator molecule decomposes to form two radicals. According to existing theories, the primary source of nucleating radicals may be either within the particle or from the small amount of initiator in the aqueous phase. At the nanometer size of miniemulsion particles, concentration variables do not adequately describe the reactions in a particle, and use of such variables may lead to the inaccurate description of mechanisms within a particle. Application of the kinetic Monte Carlo algorithm allows for the simulation of individual reactive events, such as propagation or termination, while tracking macroscopic observables, such as conversion and molecular weight. Comparison of the simulation results to experimental data for styrene miniemulsion polymerization indicates that desorption of radicals may be more significant at smaller particle sizes and lower reaction temperatures. Oil‐soluble initiator radicals generated in the aqueous phase are found to be insignificant under typical conditions in the miniemulsion polymerization of styrene. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6114–6128, 2008

Kinetics of Miniemulsion Polymerization of Styrene in the Presence of Organoclays

AbstractThe impacts of nanoclays on the miniemulsion polymerization kinetics of styrene were studied. It was found that both RP and the fractional conversion decreased upon increasing the organoclay content in the miniemulsion system. In the presence of nanoclay the molecular weight of polystyrene nanoclay composite is lower and the particle size polydispersity of the final composite latex is greater than that of pure styrene miniemulsion polymerization. The effect of the nanoclays is mainly caused by the destabilization of the miniemulsion by the organoclay particles. The increase in the monomer viscosity and the decrease in the diffusion rate of the monomer and the living polymer inside the monomer droplet also accounts for the reduction in the polymerization rate.magnified image

Surface modification of iron oxide nanoparticles by a phosphate‐based macromonomer and further encapsulation into submicrometer polystyrene particles by miniemulsion polymerization

AbstractA new strategy relying on the use of a phosphate‐based macromonomer (PAM200) to modify the surface of iron oxide nanoparticles was developed for the synthesis of submicrometer polystyrene (PS) magnetic particles. First, iron oxide nanoparticles were synthesized using the coprecipitation of ferrous and ferric salts in alkaline medium. Besides the classical oleic acid (OA)/octane‐based ferrofluid, styrene‐based ferrofluids were elaborated with either OA or PAM200 as the stabilizer. In all cases, maghemite (γ‐Fe2O3) was clearly identified, with nanoparticles rather spherical in shape but exhibiting broad particle size distribution (PSD). Both OA and PAM200 led to stable maghemite‐based ferrofluids showing superparamagnetic properties. Further use of these ferrofluids in styrene miniemulsion polymerization resulted in inhomogeneous distribution of maghemite among and inside the polymer particles with OA‐based ferrofluids, whereas PAM200/styrene‐based ferrofluids led to magnetic particles with homogeneous distribution of maghemite inside PS particles. Broad PSD and small nonmagnetic particles were however observed. The true mechanisms operating in these systems are still to elucidate, but this study validates PAM200 as an efficient compatibilizing agent between hydrophilic maghemite and hydrophobic PS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 327–340, 2008

Encapsulation of Organic Pigment Particles Via Miniemulsion Polymerization

AbstractDifferent organic yellow, magenta, and blue pigment nanoparticles can be efficiently encapsulated by cosonicating pigment dispersions and monomer miniemulsions in the pigment to monomer weight ratio of 80:20, followed by polymerization. As polymers polystyrene, different polyacrylates or copolymers could be used. Efficient encapsulation was proven by means of ultracentrifugation, electron microscopic methods, and streaming potential titration. Comparing the reaction kinetics of a typical styrene miniemulsion polymerization with the corresponding “ad‐miniemulsion polymerizations” proceeding on the surface of pigment particles, an influence of the pigments' molecular structure was observed.magnified image

Compartmentalization in TEMPO-Mediated Styrene Miniemulsion Polymerization

TEMPO-mediated styrene miniemulsion polymerizations were conducted at varying particle sizes (∼50, 90, and 180 nm) to study possible effects of compartmentalization. Polymerizations were initiated using a TEMPO-terminated polystyrene macroinitiator that also acted as costabilizer for the miniemulsion. A bulk polymerization was conducted as a control. Conversion, molecular weight distribution, and the chain livingness were measured to assess the effects of particle size. Decreasing particle size resulted in lower rates of polymerization; after 6 h of polymerization, conversions were 59% for ∼180 nm particles and 43% for ∼50 nm particles. More importantly, large differences in the polymer chain livingness were observed, with smaller particles exhibiting superior livingness at equivalent conversions. Minor effects were also observed on molecular weight; decreasing particle size resulted in higher Mn at a specified conversion, signifying lower chain concentrations in smaller particles.

Reverse Iodine Transfer Polymerization (RITP) in Emulsion

AbstractReverse iodine transfer polymerization (RITP) is a new controlled radical polymerization technique based on the use of molecular iodine I2 as control agent. This paper aims at presenting the basics of RITP and the strategy that we have followed for the development of this process in the past three years, from the validation in homogeneous solution polymerization up to recent results in heterogeneous aqueous polymerization processes. Typical examples of RITP of butyl acrylate in emulsion and RITP of styrene in miniemulsion are discussed.

Nanocolorants: A novel class of colorants, the preparation and performance characterization

Anthraquinone-based solvent red, yellow (or green), and blue dyes used as essential ingredients were completely dissolved in styrene miniemulsion system, and a set of nanocolorants were successfully prepared by using a modified miniemulsion polymerization process. In architecture, the obtained nanocolorants belong to a class of nanocomposite entities, in which a fraction of dye molecules are attached with crosslinked macromolecular chains and more dye being embedded in the interior of crosslinked polymer owed to the high hydrophobicity of dyes and phase separation between dye and polymer during the polymerization process. The performance characterization of the obtained nanocolorants indicated that they exhibited excellent chromatic properties attributed to the nanoscale effects of homogeneous nanocolorants, and really achieved superior migration fastness, light fastness, thermal stability, and good processibility. These nanocolorants are very applicable for aqueous ink-jet inks, color resistance, high-performance coloration for polymers, and for electrophotographic toners.

Reversible addition fragmentation transfer (RAFT) polymerization of styrene in a miniemulsion: A mechanistic investigation

The RAFT polymerization of styrene in miniemulsion using 1-phenylethyl phenyl-dithioacetate (PEPDTA) as a RAFT agent was investigated, in attempt to reveal the mechanism for the often observed inferior performance such as low polymerization rate, broad molecular weight distribution and particle size distribution in the RAFT miniemulsion polymerization with regular levels of surfactant and co-stabilizer (1 wt% sodium dodecyl sulfate and 2 wt% hexadecane). It is strongly evident that a few of large oligomer particles consisting of oligomer, RAFT agent (RAFT agent refers to the original RAFT agent), and monomer would be formed in the early stage of the polymerization due to the superswelling of the first nucleated droplets. With the regular levels of surfactant and co-stabilizer, the observed low polymerization rate, broadened molecular weight distribution, slow conversion of the RAFT agent, lower N p, and broadened particle size distribution could be well explained by the formation of these large oligomer particles and their prolonged existence. When the formation of the oligomer particles was suppressed by increasing surfactant and co-stabilizer levels and wise selection of types of RAFT agent, the molecular weight distribution could be narrowed to around 1.3 and particle size distribution could be close to that of the conventional non-living miniemulsion polymerization.

Low temperature TEMPO‐mediated styrene polymerization in miniemulsion

AbstractThe 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)‐mediated stable free radical polymerization of styrene in miniemulsion at 100 °C is demonstrated. Although this temperature is 20–35 °C lower than typical temperatures used for TEMPO‐mediated polymerizations, reasonable reaction rates were achieved by the addition of ascorbic acid or a free radical initiator. More importantly, the living character of the chains was preserved; the degree of polymer “livingness” was comparable to polymerizations conducted at 135 °C. Polydispersities were broader than that observed in well‐controlled systems, ranging from ∼1.4–1.6, and consistent with expectations for systems having a low activation rate. The results are significant for two reasons. They will facilitate TEMPO‐mediated minemulsion polymerizations in nonpressurized (or minimally pressurized) reactors, and they reveal the potential to expand the traditional temperature range of TEMPO and possibly other nitroxides in bulk, solution, and miniemulsion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 232–242, 2006

Reversible addition–fragmentation transfer (RAFT) copolymerization of methyl methacrylate and styrene in miniemulsion

AbstractIn the reversible addition–fragmentation transfer (RAFT) copolymerization of two monomers, even with the simple terminal model, there are two kinds of macroradical and two kinds of polymeric RAFT agent with different R groups. Because the structure of the R group could exert a significant influence on the RAFT process, RAFT copolymerization may behave differently from RAFT homopolymerization. The RAFT copolymerization of methyl methacrylate (MMA) and styrene (St) in miniemulsion was investigated. The performance of the RAFT copolymerization of MMA/St in miniemulsion was found to be dependent on the feed monomer compositions. When St is dominant in the feed monomer composition, RAFT copolymerization is well controlled in the whole range of monomer conversion. However, when MMA is dominant, RAFT copolymerization may be, in some cases, out of control in the late stage of copolymerization, and characterized by a fast increase in the polydispersity index (PDI). The RAFT process was found to have little influence on composition evolution during copolymerization. The synthesis of the well‐defined gradient copolymers and poly[St‐b‐(St‐co‐MMA)] block copolymer by RAFT miniemulsion copolymerization was also demonstrated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6248–6258, 2004

Magnetic polymer nanospheres with high and uniform magnetite content

Magnetic polymer nanospheres with high and uniform magnetite content were synthesized using a new process based on miniemulsion polymerization, where a stable water-based dispersion of sodium dodecyl sulfate (SDS)/oleic acid bilayer coated magnetite aggregates was first synthesized and mixed with monomer styrene miniemulsion. Then another miniemulsification was performed for the full encapsulation of magnetite into monomer droplets. Subsequent polymerization generated magnetic polymer nanospheres. Extensive characterization of magnetic polymer particles by transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA) and Vibrating Sample Magnetometer (VSM) showed that up to 40 wt% of 8 nm superparamagnetic magnetite particles could be uniformly encapsulated into polystyrene nanospheres with an average diameter of 80 nm.