Surface Of Latex Particles Research Articles

Photoinduced Electron Transfer from Pyrenes to Alkyl Viologens on the Surface of Polystyrene Latex Particles: Effects of Polarities of the Donors and Charge Densities of the Particles

Photoinduced electron transfers (PET) from pyrene (Py), 1-pyrenemethanol (PyM), and 1-Pyrenebutyltrim-ethylammonium bromide (PBTAB) to alkyl viologens, such as methyl viologen (MV 2 + ) and Octyl viologen (OV 2 + ), in polystyrene latex (PSL) aqueous dispersions have been studied by steady-state fluorescence, time-resolved fluorescence, and adsorption/desorption measurements. From steady state fluorescence measurements, it is found that the PET is remarkably enhanced on going from the aqueous homogeneous solution to the latex dispersion. The PET efficiency increases with increasing polarity of the electron donors in the PSL dispersions; PBTAB shows the highest efficiency and Py shows the lowest one. The low PET efficiency of Py in the PSL dispersion is attributed to penetration of Py, as revealed by the I 1 /I 3 ratio in the vibronic fine structure of Py fluorescence spectrum. The PET efficiency of PBTAB in PSL dispersion increases with the increase in the charge density of the particle, but decreases with the increase in alkyl-chain length of the quencher. The alkyl viologen with longer alkyl-chain weakens the PET efficiency by desorbing the donors from the latex surface and/or preventing the donors from effective approach with higher steric hindrance effect.

Synthesis of Polymerizable Anionic Surfactants and Their Emulsion Copolymerization with Styrene

Two polymerizable ionic surfactants sodium 4-(ω-acryloyloxyalkyl)oxy benzene sulfonate (SABS-n, n = 8 or 10) have been synthesized and polymerized. Their critical micelle concentrations (CMC) were determined to be 9.40 × 10-3 M and 2.02 × 10-3 M at 25 °C for SABS-8 and SABS-10, respectively. The rate of micellar polymerization of SABS-8 or SABS-10 was found to be proportional to half an order of the concentration of ammonium persulfate (APS) and first order of the surfactant concentration. Their activation energies of micellar polymerization were relatively low, that is, 58.2 kJ mol-1 for SABS-8 and 45.4 kJ mol-1 for SABS-10. The monomer reactivity ratios for emulsion copolymerization of SABS-8 (M1) and styrene (M2) were determined to be r1 = 0.47 and r2 = 3.91. These emulsion copolymerizations produced small latex particles ranging from 16 to 30 nm in diameter. XPS analysis shows that SABS-8 was significantly enriched on the surface of latex particles, for example, 63.4% surface coverage on latex particl...

Emulsion Polymerization of Styrene Stabilized with an Amphiphilic PEG-Containing Graft Copolymer

The amphiphilic graft copolymer comprising monomeric units of the macromonomer poly(ethylene glycol) acrylate (mPEG acrylate), stearyl methacrylate, and 2-hydroxyethyl methacrylate was synthesized and characterized. The effectiveness of this PEG-containing graft copolymer in stabilizing styrene emulsion polymerization was evaluated. Latex particles are nucleated by the entry of free radicals into the polymeric micelles and monomer droplets only serve as a reservoir to supply the continuously growing latex particles with monomer. The polymerization rate increased with increasing concentration of the graft copolymer due to the increased number of reaction loci (i. e., latex particles). The total amount of scraps produced during the polymerization was greatly reduced when the graft copolymer concentration increased. However, the amount of coagulum was still quite high for the polymerization with the highest level of the graft copolymer (30×critical micelle concentration (CMC)). The poor colloidal stability of the polymerization system is attributed to the retarded molecular diffusion of the graft copolymer from the monomer droplet surface to the growing latex particle surface. Thus, latex particles with a relatively low surface PEG density tend to coagulate with one another. Supporting evidence for this postulation obtained from three independent sets of polymerizations is presented in this work.

Surface Properties of Polystyrene Nanoparticles Coated with Dextrans and Dextran−PEO Copolymers. Effect of Polymer Architecture on Protein Adsorption

Hydrophobically substituted dextran (dextran phenoxy, DexP) and dextran phenoxy−poly(ethylene oxide) copolymers (DexP−PEO) have been used to modify the surface of polystyrene latex particles. To av...

Picosecond Fluorescence Studies of the Surface Morphology of Charged Polystyrene Latex Particles

Two negatively charged polystyrene latex dispersions with particles of similar diameter (around 100 nm) but different surface charge density (1.7 μC/cm2 for CG18 and 2.3 μC/cm2 for CG5) were compared in terms of their surface morphology. Since they were synthesized in the presence of a redox initiator (potassium persulfate/sodium metabisulfite), particles bore sulfate and sulfonate charged groups at the surface. Fluorescence decay measurements were performed in situ on these latex samples, using a pair of fluorescent cationic dyes adsorbed onto the surface: Rhodamine 6G (R6G) as the energy transfer donor and malachite green carbinol hydrochloride (MG) as the acceptor. Since the kinetics of the direct nonradiative energy transfer process between the dyes is sensitive to the donor and acceptor distributions, fluorescence decay measurements provide information about the binding distribution of the cationic dyes, which reflects the distribution of the negative charges at the latex particle surface. For the h...

Functionalization of latex particle surface by using polymeric inisurfs

In this work the emulsion polymerisation of styrene was carried out in presence of the inisurfs (reactive surfactants). The reaction kinetics was followed by dilatometric and calorimetric measurements. The influence of the inisurf concentration in reaction mixture as well as the reaction temperature on the particle properties were studied. Resulting particles were characterised with FFFF-MALLS and PCS. Viscosity measurements indicate the formation of particle flocks in the solution at certain inisurf concentration in reaction mixture.

Nonaqueous emulsion copolymerization of ethyl methacrylate/lauryl methacrylate in propylene glycol. II. Adsorption of poly(ethylene oxide)-polystyrene-poly(ethylene oxide) triblock copolymer on latex particles

The adsorption behavior of various poly(ethylene oxide)–polystyrene–poly(ethylene oxide) (PEO-PS-PEO) triblock copolymer (TBC) s on acrylic latex particles in propylene glycol was studied. The composition of the PEO-PS-PEO triblock polymers varied from 41 to 106 in each PEO block length and from 18 to 41 in the PS block length. The location of the PEO-PS-PEO TBC was determined by analyzing for the physically adsorbed amount on the latex surface, the anchored mount on the surface, the entrapped amount inside the particle, and the “free” PEO-PS-PEO TBCs in the propylene glycol. A contour graph technique was applied to analyze the experimental data, which showed that a minimum existed for the physically adsorbed portion at a PS block length of about 30 units. When the PS block length was less than 30 units, the adsorption decreased with increasing PS block length, indicating rearrangement of mixed PEO brush and adsorbed PS block. When the PS block was greater than 30 units, the adsorption increased with increasing block length because of the poor solvency of the PS block in the propylene glycol medium, resulting in a collapse of the PS chain. Considering the binding energy between the PS block and the latex particle surface, which governs adsorption, it was hypothesized that a lower block length limit exists, below which no adsorption takes place. The solubility of the PS block in propylene glycol guides the important upper block length limit. The anchored fraction of the block copolymer increased continuously with increasing PS block length in the entire region investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1963–1975, 2001

Capillary zone electrophoresis of sub-μm-sized particles in electrolyte solutions of various ionic strengths: Size-dependent electrophoretic migration and separation efficiency

To gain insight into the mechanisms of size-dependent separation of microparticles in capillary zone electrophoresis (CZE), sulfated polystyrene latex microspheres of 139, 189, 268, and 381 nm radius were subjected to CZE in Tris-borate buffers of various ionic strengths ranging from 0.0003 to 0.005, at electric field strengths of 100-500 V cm(-1). Size-dependent electrophoretic migration of polystyrene particles in CZE was shown to be an explicit function of kappaR, where kappa(-1) and rare the thickness of electric double layer (which can be derived from the ionic strength of the buffer) and particle radius, respectively. Particle mobility depends on kappaR in a manner consistent with that expected from the Overbeek-Booth electrokinetic theory, though a charged hairy layer on the surface of polystyrene latex particles complicates the quantitative prediction and optimization of size-dependent separation of such particles in CZE. However, the Overbeek-Booth theory remains a useful general guide for size-dependent separation of microparticles in CZE. In accordance with it, it could be shown that, for a given pair of polystyrene particles of different sizes, there exists an ionic strength which provides the optimal separation selectivity. Peak spreading was promoted by both an increasing electric field strength and a decreasing ionic strength. When the capillary is efficiently thermostated, the electrophoretic heterogeneity of polystyrene microspheres appears to be the major contributor to peak spreading. Yet, at both elevated electric field strengths (500 V/cm) and the highest ionic strength used (0.005), thermal effects in a capillary appear to contribute significantly to peak spreading or can even dominate it.

Mobility of SDOSS Powered by Ionic Interactions in Sty/n-BA/MAA Core−Shell Latex Films. 21. A Spectroscopic Study

While molecular level interactions between sulfonate groups of sodium dioctylsulfosuccinate (SDOSS) and COOH groups in styrene/n-butyl acrylate/methacrylate acid (Sty/n-BA/MAA) copolymer particles have been the subject of our earlier studies, the main focus of this work is to establish how MAA groups affixed to polymer latex particle surfaces will affect SDOSS mobility in Sty/n-BA/MAA latex films. The ultimate objective is to develop a series of model systems simulating the degree of neutralization of polymer surfaces and how it may alter polymer contractions and release of entropically attached molecules to interfacial regions. These studies show that the release of SDOSS molecules from MAA containing Sty/n-BA particles is attributed to two factors: (1) entropic effect due to increased compatibility resulting from surfactant penetration into latex particle surfaces and (2) enhanced particle out-layer glass transition temperature (Tg). The SDOSS release is inhibited when surface neutralization levels are...

Novel STY/nBA/GMA and STY/nBA/MAA Core−Shell Latex Blends: Film Formation, Particle Morphology, and Cross-Linking. 20. A Spectroscopic Study

These studies focus on behavior of sodium dioctylsulfosuccinate (SDOSS) surfactant molecules in styrene/n-butyl acrylate/glycidyl methacrylate (Sty/nBA/GMA) and styrene/n-butyl acrylate/methacrylic acid (Sty/nBA/MAA) blended latexes during their film formation process. Using a combination of Fourier transform infrared (FT-IR) microanalysis and FT-Raman techniques, not only stratification of SDOSS surfactant molecules during film formation process can be assessed but also the effect of latex particle structures and cross-linking reactions during coalescence can be determined. For Sty/nBA/GMA and Sty/nBA/MAA blended copolymer latexes, SDOSS exhibit nonuniform distributions at the film air (F−A) interface. However, for core/shell Sty/nBA-GMA and Sty/nBA-MAA blended latexes, SDOSS is distributed uniformly near the F−A interface, and its concentration levels are lower as compared to copolymer latex blends. At elevated coalescence temperatures, SDOSS migration to the F−A interface is prohibited due to cross-linking reactions between epoxy and acid groups. Microanalysis results show that SDOSS migration to the F−A interface is initiated after the majority of H2O (>95%) evaporates from the film. Furthermore, these studies show that latex particle surface morphology, particle−particle interdiffusion, and cross-linking reactions play a significant role in controlling mobility of low molecular weight species in latex films.

Development of a simple and rapid latex test for rotavirus in stool samples.

In the fields of infectious diseases, a variety of immunoassay methods has been reported. More simple, rapid and cost-effective manual tests for infectious diseases are needed. For the purpose of simple diagnosis of rotavirus infection, a rapid test against human rotavirus was developed. As for the preparation of the reagent, clinically isolated human rotavirus was cultured using MA-104 cells. Then, the cultured virus was purified by an ultracentrifugation method. The purified virus was inactivated with formaldehyde for use as antigen for immunization of rabbits. The antibody was purified and applied to sensitize the surface of latex particles to react with rotavirus in diarrheal stools. The latex agglutination test showed that the sensitivity was 98.2% and the specificity was 94.8%, in comparison with electron microscopy as the gold standard. Furthermore, to measure the virus concentration in stool samples, an automated latex photometric immunoassay system (LPIA) was used, which has been developed for quantitative measurement of agglutination. The range of the reactive viruses detected by the LPIA system was 3 x 10(7)-10(9) virions/mL. The rotavirus-positive and rotavirus-negative subjects were clearly discriminated. The results were in good accordance with electron microscope results. Those results showed that the latex agglutination test is a good tool for the simple and rapid detection of rotavirus in stool samples.

Fluorescence Quenching of 1-Pyrenemethanol by Serotonin on the Surface of Polystyrene Latex Particles

Abstract The fluorescence quenching of 1-pyrenemethanol (PyM) by serotonin (Ser) in polystyrene latex dispersions has been studied by steady-state and time-resolved fluorescence spectroscopy. From steady state fluorescence measurements, it is found that the quenching is remarkably enhanced on going from an aqueous homogeneous solution to a latex dispersion. This is attributed to that both PyM and Ser are effectively adsorbed onto the latex particles, as evidenced by measurements of the adsorption isotherms. Fluorescence decay curves of PyM in polystyrene latex dispersions have been successfully analyzed in terms of double exponential functions. The analysis reveals that the quenching of PyM fluorescence by Ser on polystyrene latex surfaces is mainly operated by a static mechanism, although the contribution of a dynamic mechanism is not negligible.

Photoinduced Electron Transfer from 3-(9-Anthracene)propyltrimethyl Ammonium Bromide and Pyrene to Methyl viologen on the Surface of Polystyrene Latex Particles

Photoinduced electron transfer from anthracene (An), 3-(9-anthracene)propyltrimethylammonium bromide (APTAB), and pyrene (Py) to methyl viologen (MV2+) in polystyrene (PS) latex dispersions has been studied by steady-state fluorescence, time-resolved fluorescence, and diffuse reflectance flash photolysis spectroscopy. Steady-state fluorescence measurements showed that the photoinduced electron transfer from APTAB and Py to MV2+ is remarkably enhanced on going from the aqueous homogeneous solution to the latex dispersion, whereas no such significant latex effect is observed for the An−MV2+ pair. This seems to be because An molecules deeply penetrate into the latex particles in contrast to APTAB, Py, and MV2+. The fluorescence decay curves of APTAB in PS latex dispersions are conformed to double-exponential functions. The analysis reveals that quenching of APTAB fluorescence by MV2+ (i.e., photoinduced electron transfer from the former to the latter) on PS latex surfaces is performed by both static and dyna...

Analysis of Surfactants Adsorbed onto the Surface of Latex Particles by Small-Angle X-ray Scattering

A comprehensive study of the process of adsorption of a nonionic surfactant C18E112 onto poly(styrene) (PS) latex particles by small-angle X-ray scattering (SAXS) is presented. The PS latexes (particle radii 35 and 71 nm) employed in this investigation bear no chemically bound surface charges. The analysis of the process of adsorption by SAXS demonstrates that the point of saturation of the surface may be determined directly from the scattering curves. Free micelles are formed beyond saturation, and no second layer of the surfactant is built up at higher concentrations of the surfactant. Any association of the micelles with the covered latex particle can be ruled out as well. Moreover, an analysis of the radial structure of the surface layer in terms the zeroth and the second moment of the electron density of the layers along the radial direction is given. Both moments can directly be obtained from the SAXS data. The zeroth moment of the excess electron density corroborates the finding that the surfactant is firmly adsorbed onto the surface of the particles. The average extension of the adsorbed layer (2−4 nm) as express through the second moment increases with the amount of adsorbed surfactant. This points to a stretching of the chains due to their mutual interaction when the point of saturation of the surfaced is approached.

PEO−PPO−PEO Block Copolymers at the Emulsion Droplet−Water Interface

ζ potential measurements were used to determine the adsorbed layer thickness of poly(ethylene oxide)−polypropylene oxide−poly(ethylene oxide) (PEO−PPO−PEO) block copolymers at the surfaces of poly(dimethylsiloxane) emulsion droplets, silica particles, and polystyrene latex particles. The adsorbed layer thickness (δ) was shown to depend on the copolymer structure, the surface chemistry of the adsorbent, and the level of cross-linking within droplets. For a wide range of copolymers, δ values are in the range 2−20 nm and directly proportional to the PEO block length. For copolymers with PEO segment lengths > PPO segment lengths, the plateau δ values for PDMS, latex, and silica correspond to ∼35%, 20%, and 7% of the fully extended PEO segment length. Equivalent values for copolymers with PEO segment lengths < PPO segment lengths are significantly greater but follow the same dependence on the type of adsorbent. As the level of internal cross-linking within the PDMS droplets was increased, the interface became less deformable and the adsorbed copolymer layer thickness significantly decreased. Findings are discussed with respect to the adsorbed copolymer conformations, which result from different adsorption mechanisms and the influence of interfacial penetrability.

Effect of Surface Segregation of Ionic End Groups on Polystyrene Latex Early-Time Interdiffusion

Using a direct energy transfer method, ionic end groups on polystyrene were found to increase the early-time apparent interdiffusion coefficients during film formation. The early-time apparent diffusion coefficients of polystyrene with varying end groups were found to follow the ordering of SO4 > COOH > H. The higher apparent diffusion coefficients are presumably due to the surface segregation of the end groups caused by the polar, aqueous environment during latex synthesis. By titration, 60% of the sulfate end groups and 30% of the carboxyl end groups were found on the latex particle surfaces. The apparent diffusion coefficients at very early times are separable into two additive values: that arising from the polymer chains with chain ends on the latex surface, and that caused by polymer with chain ends buried in the latex interior. The present experiments suggest that the location of the end group is the critical factor determining the initial apparent diffusion coefficients of the polymers rather than...

Seeded emulsion polymerization of styrene: Incorporation of acrylic acid in latex products

Seeded batch emulsion polymerization of styrene and acrylic acid was studied. The influence of pH and acrylic acid content on the polymerization rate and the amount of carboxylic acid groups incorporated in the final latex products was investigated. The distribution of the functional groups over the aqueous phase, the latex particle surface, and the interior of the latex particle was determined using aqueous conductometric titration and nonaqueous potentiometric titration at intermediate and complete overall conversions. Combined with kinetic results, the carboxylic acid group distribution history provided valuable information about the process of incorporation of acrylic acid in latex products. Two-step processes in which a shot of acrylic acid was performed in the last stage of the emulsion polymerization reaction were investigated as a strategy to increase the surface incorporation efficiency.

Characterizing the surface of latex particles with a microcollider

Although latex particles are often used as model colloidal systems, evidence from a variety of sources suggests that latex particles suspended in water are often `hairy', presumably because charged polymer chains protrude from the surface. We will discuss here a novel technique for characterizing the surface of latex particles, based on an accurate determination of the force distance relation between two spherical particles. From the difference between the theoretical forces for smooth spheres and the observed forces for real spheres, information about the surface structure can be obtained.

Hemiesters and hemiamides of maleic and succinic acid: synthesis and application of surfactants in emulsion polymerization with styrene and butyl acrylate

Hemiesters and hemiamides of maleic acid with different chain lengths of the hydrophobic alkyl group (R = C8H17, C10H21, C12H25, C16H33) have been synthesized and used as surfactants in the emulsion polymerization of styrene and butyl acrylate. The same polymerization experiments were also carried out using nonreactive surfactants with an analogous succinic structure. The chemical structure of the surfactants was confirmed by 1H nuclear magnetic resonance. The melting point and critical micelle concentration of the reactive surfactants described herein were measured. All of the surfactants studied provided good stability of styrene/butyl acrylate latexes, when compared with a reference latex of a styrene/butyl acrylate copolymer prepared with a surfactant sodium dodecyl sulfate. The amount of surfactant grafted onto the particles of the final latex was estimated by conductimetric titration. Between 33 and 68% of surfactant used in emulsion polymerization was found on the surface of latex particles. Electrolyte addition at high concentration and freeze/thaw cycle cause flocculation of latexes. Copyright © 1999 John Wiley & Sons, Ltd.

Adsorption of Anions on the Surface of Charge-Free Latex Particles as Revealed by Turbidimetric Measurements

The preferential adsorption of anions on the surface of latex particles without permanent charges is investigated. The latex consists of particles of 83 nm diameter stabilized by a thin layer (1.3 nm) of polyethylene oxide chains. The serum of the latex is adjusted to an ionic strength of 0.001 by adding different salts (KCl, KI, LiF, LiI, NaI). The structure of the latex particles has been studied by small-angle X-ray scattering and by dynamic light scattering whereas the interaction of the particles was investigated by turbidimetry. The latter method gives clear indication that the particles repel each other due to the electrostatic repulsion. The effect is much more pronounced in the presence of I−anions than in the presence of Cl−or F−. Since all other mechanisms of long-range repulsive interactions can be ruled out, the results presented herein demonstrate the preferential adsorption of anions, in particular of I−onto the latex surface.