Surface functionalization of polystyrene latex particles with a liposaccharide monomer

Emulsifier-free latexes with immobilized carbohydrate residues have been prepared by batch or seed (co)polymerization of styrene in the presence of 11-(N-p-vinylbenzyl)amido undecanoyl maltobionamide (LIMA). The critical micelle concentration and the molecular surface area of LIMA were determined by surface tension and fluorescence measurements. Batch polymerization of LIMA with styrene was first performed using potassium persulfate, proving the efficiency of LIMA as emulsifier. Seed copolymerization was then investigated using polystyrene seed particles with varying experimental conditions (especially the LIMA surface coverage). Material balance of LIMA between aqueous phase and particles was obtained by separating both phases by ultracentrifugation and it was found that the surfaceactive monomer is preferentially on or in the particle (nearly 100% in batch and at most 70% in seed copolymerization). The presence of the carbohydrate residues at the particle surface was directly evidenced by ¹H-nuclear magnetic resonance, electron spectroscopy for chemical analysis and electrophoretic mobility.     

Equilibrium encapsulation of polystyrene latex particles

We have performed a series of seeded styrene emulsion polymerizations in which the second stage of growth was initiated only after the second-stage monomer charge had achieved equilibrium saturation with the seed particles. The final particles were observed in the electron microscope by using two means of distinguishing between the first- and second-generation polymer: (a) butadiene tagging and osmium tetroxide staining coupled with ultramicrotomy and (b) tritiated-styrene tagging coupled with autoradiographic detection. We find that the first- and second-generation polymer chains are not uniformly mixed throughout the final latex product; rather, the second-generation polymer overcoats the seed polymer in a core–shell fashion. In order to explain these results, we present the viewpoint that monomer actually concentrates at the periphery of the swollen particle to form a monomer-encapsulated structure, rather than swelling the particle uniformly as has always been envisioned. We believe the encapsulation phenomena to be governed by the microscopic thermodynamic environment of the latex particles which has, in turn, a profound effect upon the conformational behavior of the long-chain polymer molecules as they interact with the particle–water interface.     

Protein adsorption on polystyrene latex particles

Protein adsorption is the net result of various types of interaction between the different components present in the system, i.e. the sorbent surface, the protein(s), the solvent and any other solutes such as low molecular weight electrolyte. In this paper methods and techniques will be discussed to study the mechanism of protein adsorption on, in particular, colloidal particles. The discussion is based on experimental data obtained with relatively simple systems that contain one well-defined protein and well-characterized polystyrene latexes. Thus, the adsorption behavior of lysozyme and α-lactalbumin are compared, emphasizing the role of structural rearrangements in the protein molecule.     

Synthesis of micrometer-sized silica-stabilized polystyrene latex particles

Micrometer-sized silica-stabilized polystyrene latexes have been readily prepared by alcoholic dispersion polymerization using a 13 or 22 nm commercial alcoholic silica sol as the sole stabilizing agent. These resulting surfactant-free polystyrene particles have relatively narrow particle size distributions and contain surprisingly low levels of silica (相似文献   

Adsorption force of polyaniline-coated polystyrene latex particles

Visible polyaniline-latex particles 13 microm in diameter were used for obtaining a quantitative relationship between the adsorption force and the electroactivity at a platinum electrode. An optical cell equipped with wire electrodes was filled with the suspension in hydrochloric acid. When electrode potential was switched between the oxidized and the reduced domains, some adsorbed particles showed color change owing to the electroactivity. The numbers of electroactive and the inactive particles in the suspension were counted, including poly(N-vinylpyrrolidone) (PVP). The ratio of the numbers was proportional to the concentration of PVP, as it was in equilibrium. The adsorbed particles were desorbed mechanically by forced flow. The numbers of the desorbed particles did not decrease with an increase in the flow velocity until threshold values. The threshold value for the electroactive particle was 10 times larger than that for the inactive ones, corresponding to 10 times larger adsorption energy of the electroactive particles than of the inactive ones. The adsorption stress was evaluated from the removal of the electropolymerized polyaniline film from the electrode. Then the adsorption area of the particle was estimated.     

Synthesis of monodisperse,magnetic latex particles with polystyrene core

A novel method for producing monodisperse, submicron-sized magnetic latex particles is described. The method provides coating of polymer particles with surface-modified magnetic particles during soap-free polymerization. Experiments were performed with styrene monomer, potassium persulfate initiator, Fe ₃O ₄ magnetic particles, and silane-coupling reagents of methacryloxypropyltrimethoxysilane (MPTMS) and methacryloxypropyldimethoxysilane (MPDMS). The morphology of the magnetic particles depended on the silane-coupling reagents. Use of the tri-functional coupling reagent MPTMS produced particles having a disk-like or concave-like shape, whereas use of the di-functional coupling reagent MPDMS produced spherical particles that had a coefficient of variation of 4.4%, which was much smaller than the standard criteria of monodispersity, 10%.     

十二烷基三甲基溴化铵在聚苯乙烯胶乳粒子上的吸附

实验测得C~1~2TAB在PS胶乳粒子表面的吸附等温线呈L型的二阶段吸附特征,这表明初始的C~1~2TA^+离子是将其季铵正电性头基吸引在PS链的负电性硫酸根端基上,并将碳氢链通过疏水相互作用吸附在PS链上。结合光子相关谱测得胶乳粒子流体力学半径R~H的变化,表明第I阶段围绕着这些初始吸附位的聚集吸附,产生平均聚集数为4.0的松散小聚集体,此时对应的浓度c/cmc=0.32是文献通常所指的临界表面胶团浓度csmc。其后的进一步聚集吸附最终生成了附着在PS链端基处且平均聚集数为19.5的球形吸附胶团。这一饱和吸附的结果增加了胶乳粒子在水溶液中的分散稳定性。     

Structure of polystyrene latex particles determined by electron microscopy

The structures of individual polystyrene microspheres obtained in the presence of organosilicon surfactants were studied by transmission electron microscopy. The density of the macro-molecule distribution over the cross section of particles was determined. The synthesized latex particles have a core—shell structure.

     

Effect of pressure on electrophoretic mobility of polystyrene latex particles

A capillary electrophoresis system that can apply arbitrary helium gas pressures at both inlet and outlet reservoirs was constructed. The system was used to investigate the effect of pressure on electrophoretic behavior of polystyrene latex particles. The electrophoretic mobility of latex particles was increased with the application of pressure (< 3.0 kgf/cm2). The shrinkage of particle diameter under pressurization was observed using a microscope, however, the magnitude of shrinkage was not enough to explain the increase in electrophoretic mobility. Therefore, the application of pressure might increase the electric charge of the latex particle. Since methanol inhibited the enhancement in the electrophoretic mobility of the latex particles, water might play an important role in increasing mobility.     

Film formation from nano‐sized polystyrene latex particles

This work reports on the steady state fluorescence (SSF) technique for studying film formation from surfactant‐free, nano‐sized polystyrene (PS) latex particles prepared via emulsion polymerization. The latex films were prepared from pyrene (P)‐labeled PS particles at room temperature and annealed at elevated temperatures in 5, 10, 15, 20 and 30 min time intervals above the glass transition temperature (T_g) of PS. During the annealing processes, the transparency of the film was improved considerably. Monomer and excimer fluorescence intensities, I_P and I_E respectively, from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of the latex films was monitored by using photon transmission intensity, I_tr. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 10.3 and 50.3 kJ mol⁻¹. Void closure temperatures, T_v, were determined from the minima of I_tr value. Copyright © 2005 John Wiley & Sons, Ltd.     

Surface modification of polystyrene latex particles via atom transfer radical polymerization

The atom transfer radical polymerization (ATRP) technique using the copper halide/ N,N′,N′,N″,N″‐pentamethyldiethylenetriamine complex was applied to the graft polymerization of methyl methacrylate and methyl acrylate on the uniform polystyrene (PS) seed particles and formed novel core‐shell particles. The core was submicron crosslinked PS particles that were prepared via emulsifier‐free emulsion polymerization. The crosslinked PS particles obtained were transferred into the organic phase (tetrahydrofuran), and surface modification using the chloromethylation method was performed. Then, the modified seed PS particles were used to initiate ATRP to prepare a controlled poly(methyl methacrylate) (PMMA) and poly(methyl acrylate) (PMA) shell. The final core‐shell particles were characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, thermogravimetric analysis, and elementary analysis. The grafting polymerization was conducted successfully on the surface of modified crosslinked PS particles, and the shell thickness and weight ratio (PMMA and PMA) of the particles were calculated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 892–900, 2002; DOI 10.1002/pola.10160     

Preparation of polystyrene latex particles by γ-rays-induced emulsifier-free emulsion polymerization

Monodisperse polystyrene latex particles were prepared by ⁶⁰Co-γ-ray radiation-induced emulsifier-free emulsion polymerization with the use of surfactant monomer at room temperature. The surfactant monomer 10(9)-hydroxyl-9(10)-allyl ether octadecanoic acid (HAEOA) was synthesized and characterized by FT-IR and ¹H-NMR spectra. TEM was used to characterize the polystyrene latex particles. HAEOA acted as not only a comonomer but also a stabilizer to copolymerize with styrene and stabilize the polystyrene latex particles. Kinetics analysis shows that there is no constant rate stage which seems to indicate a droplet nucleation mechanism.     

Enhancement of electrochemical activity by small-sizing the vinylferrocene-immobilized polystyrene latex particles

Voltammetry of vinylferrocene (VFc)-immobilized polystyrene(PS)-based latex particles was carried out in aqueous suspensions by changing the size of latex particles in order to investigate the dependence of the electroactivity of the particles on their size. The anodic peak current was controlled by diffusion of the latex. The voltammetric peak currents increased with an increase in the diameter of PS latex particles for a given analytical concentration of the particles, exhibiting the dependence on 1.5 powers of the diameter of the particles. The increase can be explained in terms of combination of the uniform distribution of VFc in the particle, the partial charge transfer, and the Stokes-Einstein equation for diffusion coefficients. The oxidation of VFc occurs in the restricted domain (0.07 microm) from a contact point of the particle with the electrode. The overall reaction mechanism is diffusion of the particle to the electrode, partial oxidation to VFc+, release of VFc+ from the particle to the solution, and reduction of the released VFc+.     

Surface heterogeneity of polystyrene latex particles determined by dynamic force microscopy

Atomic force microscopy (AFM) was employed to characterize the surface chemistry distribution on individual polystyrene latex particles. The particles were obtained by surfactant-free emulsion polymerization and contained hydrophilic quaternary ammonium chloride, sodium sulfonate, or hydroxyethyl groups. The phase shift in dynamic force mode AFM is sensitive to charge/chemical interactions between an oscillating atomic force microscope tip and a sample surface. In this work, the phase imaging technique distinguished phase domains of 50-100 nm on the surfaces of dried latex particles in ambient air. The domains are attributed to the separation of ion-rich and ion-poor components of the polymer on the particle surface.     

Synthesis of temperature responsive polymer brushes from polystyrene latex particles functionalized with ATRP initiator

Thermally responsive poly(N-isopropylacrylamide) (PNIPAAM) brushes were grafted from polystyrene particles synthesized with surfactant free emulsion polymerization and functionalized with a thin shell of ATRP initiator on the surface. The ATRP initiator was present in the shell either alone or along with copolymerized styrene and also a crosslinker. The grafted brushes were characterized with transmission electron microscopy before and after negative staining with uranyl acetate. Cryo-scanning electron microscopy confirmed the growth of extremely long PNIPAAM layers from the surface, which otherwise looked shrunken in the transmission electron microscope owing to dehydration and possibly the effect of staining agent. The amount of grafted polymer also increases proportionally to the increase of the monomer concentration in the initial reaction system. The change in character from hydrophilic to hydrophobic with temperature and salt was found to be reversible and fast. The adsorption of protein complexes (tobacco mosaic virus) could be readily achieved at higher temperatures indicating the potential of the grafted particles to be used as stationary phases in temperature regulated chromatographic separations.     

Preparation and characterization of cationic polystyrene latex particles of different aminated surface charges

Functionalized polystyrene latex particles were obtained either by seed particle functionalization or by the shot-growth procedure using 2,2′-azobis (2-amidino-propane) dihydrochloride as an initiator and vinylbenzylamine hydrochloride as a cationic monomer. The capabilities of both processes to produce functionalized particles in terms of functionalization yields coming from surface amino group titrations were compared. Different titration methods were performed and a new technique was introduced using fluorescamine.     

SANS study of the interactions among DNA, a cationic surfactant, and polystyrene latex particles

The compaction of DNA by a cationic surfactant both in the bulk and adsorbed on the surface of latex particles was followed for the first time by SANS. In the bulk, a decrease in the overall size of the DNA coil in the presence of the cationic surfactant was observed at a negative-to-positive charge ratio far below the phase separation region, at a negative-to-positive charge ratio of 18. Additionally, large surfactant aggregates seem to form within the DNA-surfactant complex. On the other hand, DNA adsorbs onto the surface of latex particles, forming a thick layer, as evidenced by the fitting of the SANS data to a core-shell form factor. Addition of a cationic surfactant to the DNA-coated latex particles at a negative-to-positive charge ratio of 38 induces a slight decrease in the size of the particle layer, where the cationic surfactant is evenly distributed within the adsorbed layer. A further decrease of the negative-to-positive charge ratio to 18 induces a dramatic change in the SANS data that suggests significant compaction of the adsorbed layer and the formation of large surfactant aggregates, similar to those detected in the bulk.