Preparation of Poly(methyl methacrylate) Nanoparticles 15–50 nm in Diameter from Submicrometer-Sized Latex Particles

Russian Journal of Applied Chemistry - A procedure was developed for preparing poly(methyl methacrylate) nanoparticles of 15–50 nm size from coarser (200–300 nm) polymer latex particles...     

Surfactant-free emulsion copolymerization of styrene and methyl methacrylate for preparation of water-redispersible polymeric powders

Poly(methyl methacrylate), polystyrene, and poly(styrene-co-methyl methacrylate) cationically stabilized latexes with up to 25% solid content were prepared by surfactant-free emulsion polymerization (SFEP) employing 1 mol % 2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044) as an initiator and stabilizer (inisurf) with respect to monomer at 70 °C. The latexes had 200–500 nm z-diameter and a very narrow size distribution (PDI < 0.05). The stabilizing amidinium moieties from VA-044 were covalently bound to the particles. After drying in air, poly(styrene-co-methyl methacrylate), PS-co-PMMA latexes were easily redispersible in water simply by addition of water and a few minutes of gentle stirring. The redispersed latex particles had colloidal characteristics very similar to the original latex particles in terms of polydispersity, size, and zeta potential. In contrast, latexes prepared with a similar formulation but using a conventional cationic surfactant (CTAB) that was not covalently bound to the particles were not redispersible. This is the simplest method reported so far for the preparation of redispersible latexes that do not use high stabilizer concentrations. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2376–2381     

Size tuned electrophoretic pyrazoline nanoparticles prepared through dispersion-polymerization

Highly monodispersed electrophoretic particles of size ranging from 550 to 160 nm could be prepared through dispersion-polymerization of methyl methacrylate and ethylene glycol dimethacrylate in presence of pyrazoline nanoparticles in a methanol-water mixture. The size of the fabricated electrophoretic particles could be controlled by adjusting the concentration of surfactant. Stearic acid, used as surfactant during the polymerization process also acts as charge controlling additive to control the electrophoric mobility of the particles. Maximum electrophoric mobility (-7.513×10(-5) cm(2)/Vs) was obtained for the 400 nm electrophoretic particles prepared with 1.5 wt.% of stearic acid surfactant. The electrophoric display cells prepared with our electrophoretic particles reveal good current voltage characteristics and color change under applied bias voltage.     

Ultrasonically initiated emulsion polymerization of methyl methacrylate

The ultrasonically initiated emulsion polymerization of methyl methacrylate (MMA) was investigated. Experimental results show that sodium dodecyl sulfonate (SDS) surfactant plays a very important role in obtaining a high polymer yield, because in the absence of SDS, monomer conversion is near zero. Thus, the surfactant serves as an initiator and as interfacial modifier in this system (MMA/H₂O), and the monomer conversion increases significantly with increasing SDS concentration. An increase in the reactor temperature also leads to an increase in the monomer conversion. An appropriate increase in the N₂ purging rate also leads to higher conversion. The conversion of MMA decreases with increasing monomer concentration because of the higher viscosity of the system. With the experimental results, optimized reaction conditions were obtained. Accordingly, a high monomer conversion of about 67% and a high molecular weight of several millions can be obtained in a period of about 30 min. Furthermore, transmission electron micrographs show that the latex particles prepared are nanosized, indicating a promising technique for preparing nanoscale latex particles with a small amount of surfactant. In conclusion, a promising technique for ultrasonically initiated emulsion polymerization has been successfully performed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3356–3364, 2001     

Stabilization of miniemulsion droplets by cerium oxide nanoparticles: a step toward the elaboration of armored composite latexes

Stable methyl methacrylate (MMA) miniemulsions were successfully prepared using for the first time cerium oxide (CeO(2)) nanoparticles as solid stabilizers in the absence of any molecular surfactant. The interaction between MMA droplets and CeO(2) nanoparticles was induced by the use of methacrylic acid (MAA) as a comonomer. Both MAA and CeO(2) contents played a key role on the diameter and the stability of the droplets formed during the emulsification step. Cryo-transmission electron microscopy (TEM) images of the suspensions formed with 35 wt % of CeO(2) showed the presence of polydisperse 50-150 nm spherical droplets. More surprisingly, some nonspherical (likely discoidal) objects that could be the result of the sonication step were also observed. The subsequent polymerization of these Pickering miniemulsion droplets led to the formation of composite PMMA latex particles armored with CeO(2). In all cases, the conversion was limited to ca. 85%, concomitant with a loss of stability of the latex for CeO(2) contents lower than 35 wt %. This stability issues were likely related to the screening of the cationic charges present on CeO(2) nanoparticles upon polymerization. TEM images showed mostly spherical particles with a diameter ranging from 100 to 400 nm and homogeneously covered with CeO(2). Besides, for particles typically larger than 200 nm, a buckled morphology was observed supporting the presence of residual monomer at the end of the polymerization and consistent with the limited conversion. The versatility of these systems was further demonstrated using 35 wt % of CeO(2) and replacing MMA by n-butyl acrylate (BA) either alone or in combination with MMA. Stable monomer emulsions were always obtained, with the droplet size increasing with the hydrophobicity of the oil phase, pointing out the key influence of the wettability of the solid stabilizer. The polymerization of Pickering miniemulsion stabilized by CeO(2) nanoparticles proved to be an efficient strategy to form armored composite latex particles which may find applications in coating technology.     

Emulsion polymerization of styrene and methyl methacrylate using a hydrophobically modified inulin and comparison with other surfactants

The use of a new class of graft polymer surfactants, based on inulin, in emulsion polymerization of poly(methyl methacrylate) (PMMA) and polystyrene (PS) particles is described. PS and PMMA were synthesized by emulsion polymerization, and stable particles with a high monomer content (50 wt %) were obtained with a very small amount of polymeric surfactant ([surfactant]/[monomer] = 0.0033). The latex dispersions were characterized by dynamic light scattering and by transmission electron microscopy to obtain the average particle size and the polydispersity index, and the stability was determined by turbidimetry measurements and expressed in terms of critical coagulation concentration. The last section gives a comparison of PMMA particles prepared by emulsion polymerization using classical surfactants from different types as emulsifiers with that obtained using the copolymer surfactant. It shows the superiority of INUTEC SP1 as it is the only one that allows stable particles at 20 wt % monomer content, with a smaller ratio [surfactant]/[monomer] = 0.002.     

Dispersion polymerization of methyl methacrylate in supercritical CO2 in the presence of non-fluorous random copolymers

A series of non-fluorous random copolymers, composed of 3-[tris(trimethylsilyloxy)silyl] propyl methacrylate and 2-dimethylaminoethyl methacrylate, poly(SiMA-co-DMAEMA) with different comonomer ratios were prepared and utilized as stabilizers for the free radical dispersion polymerization of methyl methacrylate (MMA) in supercritical carbon dioxide (scCO₂). It was demonstrated that the composition and concentration of the stabilizer have a dramatic effect on the morphology of resulting poly methyl methacrylate (PMMA) latex. When the copolymeric stabilizer poly(SiMA-co-DMAEMA) (71:29) was employed, free-flowing spherical PMMA particles were produced in high yield. As the concentration of stabilizer increases, the resulting size of colloidal particles decreases. In addition, the monomer concentration and initial pressure affected the particle diameter of PMMA.     

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.     

Developing a hybrid emulsion polymerization system to synthesize Fe3O4/polystyrene latexes with narrow size distribution and high magnetite content

A hybrid emulsion polymerization was formulated for synthesizing Fe₃O₄/polystyrene composite latex. This system, containing binary droplets that are magnetic (Mag)‐droplets with a diameter of 100–200 nm and styrene (St)‐droplets with a diameter of 3–4 μm, was obtained by mixing Mag‐miniemulsion and St‐macroemulsion. With extremely low surfactants concentration (?critical micelle concentration, CMC), the nucleated loci are selectively controlled in the Mag‐droplets, as the result of smaller droplet size and larger surface ratio. Both water‐soluble potassium persulfate (KPS) and oil‐soluble 2,2′‐azobis(2‐isobutyronitrile) was adopted to initiate the polymerization. In the presence of KPS, magnetic polystyrene latices with particles size of 60–200 nm, narrow size distribution, and high magnetite content (86 wt % measured by TGA) were attained successfully. The synthesized magnetic Fe₃O_4/polystyrene latices assembled into well‐ordered hexagonal structure in the surface of a carbon supported copper grid. The influence of various parameters on various aspects of the as‐synthesized Fe₃O₄/polystyrene was investigated in detail: type of initiator on composite morphology, feed ratio of Mag‐miniemulsion and St‐macroemulsion on magnetite content, and hydrophobic agent or amount of surfactant on size and size distribution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5285–5295, 2007     

Dispersion polymerization of MMA in supercritical CO2 stabilized by random copolymers of 1H,1H–perfluorooctyl methacrylate and 2‐(dimethylaminoethyl methacrylate)

A series of random copolymers, composed of 1H,1H‐perfluorooctyl methacrylate (FOMA) and 2‐dimethylaminoethyl methacrylate (DMAEMA) were prepared as stabilizers for the dispersion polymerization of methyl methacrylate in supercritical CO₂ (scCO₂). Free‐flowing, spherical poly(methyl methacrylate) (PMMA) particles were produced in high yield by the effective stabilization of poly(FOMA‐co‐DMAEMA) containing 34–67 w/w % (15–41 m/m %) FOMA structural units. Less stabilized but micron‐sized discrete particles could be obtained even with 25 w/w % (10 m/m %) FOMA stabilizer. The result showed that the composition of copolymeric stabilizers had a dramatic effect on the size and morphology of PMMA. The particle size was controllable with the surfactant concentration. The effect of the monomer concentration and the initial pressure on the polymerization was also investigated. The dry polymer powder obtained from dispersion polymerization could be redispersed to form stable aqueous latexes in an acidic buffered solution (pH = 2.1) by an electrostatic stabilization mechanism due to the ionization of DMAEMA units in the stabilizer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1365–1375, 2008     

Influence of hexadecane on the formation of droplets and growth of particles for methyl methacrylate miniemulsion polymerization

The evolution of monomer droplets and latex particles of methyl methacrylate miniemulsions, initiated by an oil‐phase initiator, stabilized by a cationic surfactant mixture, and costabilized by different amounts of hexadecane, was investigated. With an increasing hexadecane concentration, the ultrasonication time required for the miniemulsions to reach a critically stabilized state was reduced, and a unimodal size distribution of the droplets with a decreasing average diameter was obtained. For lower hexadecane concentrations, a bimodal size distribution of the latex particles, with a significant increase in the volume fraction of the smaller latex particles, was achieved after the polymerization. The enhanced growth of the volume fraction of the smaller latex particles came from both nucleation of the shrinking droplets due to Ostwald ripening and homogeneous and/or micellar nucleation, if micelles existed, triggered by radicals in the aqueous phase. For high hexadecane concentrations, Ostwald ripening was effectively retarded, and the miniemulsions were sufficiently stabilized against the degradation of molecular diffusion. The size distributions of the droplets and latex particles were almost identical. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4603–4610, 2006     

Preparation and clinical application of immunomagnetic latex

Magnetic poly(methyl methacrylate) (PMMA)/poly(methyl methacrylate‐co‐methacrylic acid) [P(MMA–MAA)] composite polymer latices were synthesized by two‐stage soapless emulsion polymerization in the presence of magnetite (Fe₃O₄) ferrofluids. Different types and concentrations of fatty acids were reacted with the Fe₃O₄ particles, which were prepared by the coprecipitation of Fe(II) and Fe(III) salts to obtain stable Fe₃O₄ ferrofluids. The Fe₃O₄/polymer particles were monodisperse, and the composite polymer particle size was approximately 100 nm. The morphology of the magnetic composite polymer latex particles was a core–shell structure. The core was PMMA encapsulating Fe₃O₄ particles, and the shell was the P(MMA–MAA) copolymer. The carboxylic acid functional groups (COOH) of methacrylic acid (MAA) were mostly distributed on the surface of the composite polymer latex particles. Antibodies (anti‐human immunoglobulin G) were then chemically bound with COOH groups onto the surface of the magnetic core–shell composite latices through the medium of carbodiimide to form the antibody‐coated magnetic latices (magnetic immunolatices). The MAA shell composition of the composite latex could be adjusted to control the number of COOH groups and thus the number of antibody molecules on the magnetic composite latex particles. With a magnetic sorting device, the magnetic immunolatices derived from the magnetic PMMA/P(MMA–MAA) core–shell composite polymer latex performed well in cell‐separation experiments based on the antigen–antibody reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1342–1356, 2005     

Preparation and characterization of poly(MMA-M12-BPMA)/TiO2 composite particles

In this paper, poly(MMA-M12-BPMA)/TiO₂ composite particles were prepared by the copolymerization of a reactive surfactant sodium sulfopropyl-laurylmaleate (M12) and a reactive UV-stabilizer 2-hydroxy-4-(3-methacryloxy-2-hydroxylpropoxy) benzophenone (BPMA) with methyl methacrylate (MMA) in the presence of TiO₂. The structure and performance of composite particles were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, gel permeation chromatography, ultraviolet–visible absorption spectroscopy, differential scanning calorimeter, and scanning electron microscope.The measurement results indicate that the percentage of grafting and the grafting efficiency can reach 336.87% and 36.38%, respectively, and the glass transition temperature of poly(MMA-M12-BPMA)/TiO₂ composite particles is higher than that of poly(MMA-M12-BPMA); the size of the composite particles is about 130–200 nm. The poly(MMA-M12-BPMA) grafted from the surface of TiO₂ keeps the excellent characteristic of BPMA that possesses high absorbance of ultraviolet light, which is very important for improving UV-resistant performance of the polymethyl methacrylate. These research results are very useful for preparing polymethyl methacrylate with resistance to UV light.     

Studies on the Preparation of Stable and High Solid Content Emulsifier-Free Poly(MMA/BA/HEA) Latex with the Addition of AMPS and Characterization of the Obtained Copolymers

The 2-acrylamido -2-methylpropane sulfonic acid (AMPS) was used as a reactive comonomer for the methyl methacrylate (MMA), n-butyl acrylate (BA) and 2-hydroxyethyl acrylate (HEA) emulsifier-free emulsion copolymerization system to obtain latices of stable and high-solid content (50 wt%).The polymerization and storage process is very stable, and the emulsion could store at room temperature for more than six months with the addition of AMPS. Properties of the latices, such as stability, flow behavior, particles diameter and morphology were studied. In addition, physical properties of the obtained copolymers, such as water resistance, glass transition temperature (T_g) were also investigated. The final size of the latex particles is 200～300 nm in diameter. Compared with the copolymers that were prepared by surfactant emulsion polymerization water resistance is greatly improved.     

Semibatch Emulsion Polymerization of Butyl Acrylate: Effect of Functional Monomers

Abstract

The concentration of sodium lauryl sulfate (SLS) in the initial reactor charge is the most important parameter in determining the latex particle size during semibatch emulsion polymerization of butyl acrylate in the presence of acrylic acid (AA), methacrylic acid, or hydroxyethyl methacrylate. The final latex particle size decreases with increasing concentration of SLS, NP-40, or functional monomer. The carboxylic monomer AA is the most efficient functional monomer to nucleate and then stabilize the latex particles. The plot of log N _f vs log SLS shows a slope of 0.4–0.8, which is more consistent with Feeney's analysis based on the coagulative nucleation mechanism. Experimental data also show that the particle size first decreases to a minimum and then increases with an increase in the concentration of the neutralizing agent NaHCO₃. The optimal concentration NaHCO₃ for achieving the smallest latex particle size occurs at a point close to 0.15–0.29%. Experimental data of the particle size distribution and molecular weight distribution show that the aqueous phase reaction can play a very important role during the particle nucleation period.     

Preparation of poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) core–shell nanoparticles

Poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) (PMMA–NBR) core–shell structured nanoparticles were prepared using a two‐stage semibatch microemulsion polymerization system with PMMA and NBR as the core and shell, respectively. The Gemini surfactant 12‐3‐12 was used as the emulsifier and found to impose a pronounced influence on the formation of core–shell nanoparticles. The spherical morphology of core–shell nanoparticles was observed. It was found that there exists an optimal MMA addition amount, which can result in the minimized size of PMMA–NBR core–shell nanoparticles. The formation mechanism of the core–shell structure and the interaction between the core and shell domains was illustrated. The PMMA–NBR nanosize latex can be used as the substrate for the following direct latex hydrogenation catalyzed by Wilkinson's catalyst to prepare the PMMA–HNBR (hydrogenated NBR) core–shell nanoparticles. The hydrogenation rate is rapid. In the absence of any organic solvent, the PMMA–HNBR nanoparticles with a size of 30.6 nm were obtained within 3 h using 0.9 wt % Wilkinson's catalyst at 130 °C under 1000 psi of H₂. This study provides a new perspective in the chemical modification of NBR and shows promise in the realization of a “green” process for the commercial hydrogenation of unsaturated elastomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Incorporation of titanium dioxide particles into polymer matrix using block copolymer micelles for fabrication of high refractive and transparent organic–inorganic hybrid materials

We report a novel strategy for incorporation of titanium dioxide (TiO₂) particles into poly(methyl methacrylate) (PMMA) to exploit high refractive and transparent organic–inorganic hybrid materials. Formation of TiO₂ particles of around 20 nm was conducted within hydrophilic core of block copolymer micelles of poly(methyl methacrylate‐block‐acrylic acid) (PMMA‐b‐PAA) in toluene via sol–gel process from titanium isopropoxide and hydrochloric acid. Subsequently, incorporation of TiO₂ particles into PMMA matrix was carried out by casting toluene solution of TiO₂ precursor‐loaded copolymer micelles, prepared from PMMA₃₅₀‐b‐PAA₉₃ and the precursor of mole ratio Ti⁴⁺/carboxyl 4.0, and PMMA. Hybrid films of TiO₂/PMMA exhibited high transparency to achieve transmission over 87% at 500 nm at 30 wt % of TiO₂ content. The refractive index of resulting hybrid films at 633 nm linearly increased with TiO₂ content to attain 1.579 at 30 wt % TiO₂, which was 0.1 higher than that of PMMA. Cross‐sectional transmission electron microscope images of TiO₂/PMMA hybrid films showed existence of TiO₂ clusters less than 100 nm, which were probably formed by aggregation or agglutination of TiO₂ particles during a drying process. It was also observed that decomposition temperature of the hybrid films elevated with increasing TiO₂ content. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Seeded semicontinuous emulsion copolymerization of methyl methacrylate,butyl acrylate,and phosphonated methacrylates: Kinetics and morphology

A series of methyl methacrylate, butyl acrylate, and phosphonated methacrylate (MAPHOS) copolymers were prepared by seeded semicontinuous emulsion polymerization under monomer‐starved conditions by varying the amount and nature of phosphonated methacrylates (diester, monoacid, and diacid). The effects on the kinetics, molecular weight distribution, and particle size distribution were investigated. The molecular weights and particle growth were affected by the amount of acidic MAPHOS in the recipe. Secondary nucleation occurred above a critical concentration of acidic MAPHOS (5 wt %). Characterization of the latices by elemental analysis provided information on the phosphonic acid location and showed that phosphonic oligomers were formed in the aqueous phase. Particle size data and electrophoretic behavior of the latex afforded a discussion on the particle surface morphology. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2469–2480, 2003     

Synthesis of high molecular weight polymer nanoparticles by [Cp2ZrCl2] catalyzed emulsion polymerization

An early transition metal metallocene compound, Cp₂ZrCl₂, with an anionic surfactant, sodium n‐dodecyl sulfate (SDS) as emulsifier and NaBPh₄ as cocatalyst has been found to be an effective catalytic system for polymerization and copolymerization of monomers like styrene and methyl methacrylate in aqueous medium. The diameters of the latex particles were found to be in between 20 and 40 nm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Structures and thermal properties of chitosan-modified poly(methyl methacrylate)

The emulsion polymerization of methyl methacrylate in the presence of chitosan with potassium persulfate (KPS) as an initiator was examined in a previous article. The free radicals that dissociated from KPS not only initiated the polymerization but also degraded the chitosan molecules. Therefore, in addition to its role as a cationic surfactant, chitosan also participated in the polymerization reaction. When the polymerization was complete, the latex polymer consisted of poly(methyl methacrylate) (PMMA) homopolymer and chitosan–PMMA copolymer. In this article, the structures and thermal properties of latex polymers are examined. Gel permeation chromatography was used to measure the molecular weight of the PMMA homopolymer, with the copolymer composition determined by an elemental analyzer. Scanning and transmission electronic microscopes were used to measure the size of latex particles from different reaction systems. The surface charges of latex particles at several different pH values were determined by the measurement of the ζ potential. All results agreed with the reaction mechanism proposed in the previous article. Finally, the presence of rigid chitosan increased the glass-transition temperature of the final latex polymers. Thermogravimetric analysis showed that the degradation behavior of latex polymers was similar to the unzipping mechanism of PMMA, yet the presence of chitosan units hindered the unzipping of the main chains in chitosan–PMMA copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1646–1655, 2001