Production of micron-sized polystyrene particles containing PEG near the particles surface

Polystyrene (PS) particles in the size range of 1-7 µm, containing poly(ethylene glycol) or PEG on the particles surface, were prepared by multi-step seeded polymerizations. Micron-sized PS particles were first prepared by dispersion polymerization using 2,2'-azobisisobutyronitrile as initiator and polyvinyl pyrrolidone as stabilizer. Conventional swelling method was then used to increase the size of the PS particles with a large amount of styrene in presence of oil soluble initiator, benzoyl peroxide. In the final step, the PS particles have been used to carry out seeded polymerization with small amount of styrene in presence of poly(ethylene glycol)-azo or PEGA initiator with average molecular weights of the PEG chains of 200 and 3000 g mol^-1 , respectively. The average size, size distribution, and surface morphology indicate that seeded polymerization in the final step with small amount of styrene in presence of PEGA is the best way to produce monodisperse polystyrene particles containing PEG near the particles surface.     

Rapid spectroscopic confirmation of the presence of polystyrene in polymer particles of mixed composition

A technique for rapid determination of the presence of polystyrene in individual micron-diameter polymer particles of mixed composition is presented. This technique is based upon observation of visible emission from conjugated regions of the polymer backbone, generated photochemically, while the particle is held in an optical trap. Particle emission characteristics are dependent upon particle size and suspending solvent. Emission spectra are provided for single component polystyrene particles and mixed polymer particles containing poly(methyl methacrylate), poly(N-vinyl pyrrolidone), and polystyrene. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 999–1004, 1998     

Nanotechnological evaluation of protein adsorption on dialysis membrane surface hydrophilized with polyvinylpyrrolidone

Hydrophilizing synthetic polymer dialysis membranes with polyvinylpyrrolidone (PVP) play an important role for inhibition of protein adsorption on membrane surface. In the present study, the effect of PVP on protein adsorption was evaluated from a nano-scale perspective. Swelling behavior of PVP present on wet polysulfone (PS)/PVP film surfaces was observed by atomic force microscopy (AFM). Fibrinogen and human serum albumin (HSA) were immobilized on the tip of AFM probes, with which a force-curve between protein and wet PS/PVP film surface was measured by AFM while scanning in order to visualize two-dimensional protein adsorbability on film surfaces. Furthermore, HSA adsorbability on non-PVP containing PEPA dialysis membrane (FLX-15GW) and PVP containing PEPA dialysis membrane (FDX-150GW) was evaluated by the AFM force-curve method. As a result, PS/PVP film surface was completely covered with hydrated and swollen PVP at 5 wt% or more PVP content. Protein adsorbability on PS/PVP film surfaces decreased greatly with increasing content of PVP. The adsorption of HSA was inhibited by the presence of PVP on film surfaces more significantly than that of more hydrophobic fibrinogen. HSA adsorbability on wet FLX-15GW dialysis membrane surface was 428 ± 174 pN whereas that on wet FDX-150GW dialysis membrane surface was 42 ± 29 pN.     

Accumulation of monomolecular polystyrene particles from a water surface onto a substrate

Monomolecular particles of polystyrene (M_w/M_n = 1.04, M_w = 3.84 ? 10⁶) formed by spreading of a dilute solution in benzene over a water surface were successfully accumulated onto a hydrophobic substrate by the horizontal lifting method. The accumulation was quantitative (up to 66 layers) to give a multilayer film. The substrates used were silicon single crystals, quartz coated with an iron(III) stearate monolayer, and poly(methylmethacrylate) plates. The film contained voids amounting to 20-30 vol%. The surface structure observed by transmission electron microscopy clearly showed a multilayer, particle structure. These facts indicate that the molecules exist as monomolecular particles in the film. The film should be a suitable material to study properties of polymeric monomolecules in a very unusual state as compared with the ordinary solid.     

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.     

Laser surface treatment of high‐speed steel: presence of TiC particles at the surface

Laser treatment of a high‐speed steel surface is carried out and metallurgical and morphological changes in the laser‐treated layer are examined using SEM, EDS and XRD. A carbon film of 50 µm thickness and containing 5% TiC particles is formed at the workpiece surface prior to the laser treatment process. The carbon film formed at the surface enhances the absorption of laser irradiation and retains TiC particles at the workpiece surface. The residual stress formed at the laser‐treated surface is determined using the XRD technique while the indentation tests are carried out to measure microhardness and fracture toughness of the resulting surface. It is found that ε‐Fe₃N, and ε‐Fe₃ (N,C) compounds are formed at the laser‐treated surface, which are attributed to the presence of carbon film and high‐pressure nitrogen‐assisting gas. The fracture toughness of the laser‐treated surface reduces because of the increased hardness and dense layer formed at the surface vicinity. Copyright © 2011 John Wiley & Sons, Ltd.     

Spectrophotometric determination of zirconium with alizarin red S in the presence of polyvinylpyrrolidone

The absorbance of the microcolloidal zirconium/alizarin red S/polyvinylpyrrolidone complex is measured at 525 nm in acetate buffered medium at pH 4.75. The molar absorptivity is 3.8 × 10⁴ l mol^?1 cm^?1, which is much greater than that of the classical method. Sulphate and fluoride do not interfere.     

Metal nanoparticles on polymer surfaces: 6. Probing of non-glassy polystyrene surface layer

Peculiarities of the state of the surface layer of the amorphous glassy polymer polystyrene are studied with a specially developed experimental approach. The essence of the method consists in the observation via atomic force microscope for the depth and rate of embedding of gold nanoparticles in a polymer after their preliminary adsorption on the polymer surface from hydrosol. It is shown that the polymer glass-transition temperature near the boundary with air is substantially lowered relative to its bulk value. “Equilibrium” thickness of the non-glassy (“melted”) surface layer is determined through analysis of the data on the kinetics of nanoparticle embedding, and it is revealed that the layer thickness increases with temperature, reaching, near the “bulk” glass-transition temperature, the magnitude that is close to the diameter of the macromolecular coil. The results obtained are analyzed with allowance for published data, and the semi-empirical formula describing variations in the thickness of the non-glassy surface layer as a function of temperature in the interval between the “surface” and “bulk” glass-transition temperatures of a polymer is proposed.     

Infrared dielectric mirrors based on thin film multilayers of polystyrene and polyvinylpyrrolidone

Thin film polymer multilayers were prepared by spin coating alternating layers of polystyrene and polyvinylpyrrolidone. Samples with 10, 20, 30, 40, and 50 layers were prepared with individual layer thickness values in the range 223–508 nm. These samples were measured using a Fourier transform infrared spectrometer and were found to display narrow photonic band gaps (～ 0.04 to 0.06 μm wide) in their spectral response over the wavelength range 1.6 ? 2.6 μm. The position of the photonic band gaps was controlled by varying the thickness of the individual layers within the multilayer structures. This was achieved by varying the spin speed used during the deposition of the polymer layers. The peak reflectance of the multilayers was controlled by varying the number of layers within the multilayer samples giving values in the range 20–80% (corresponding to transmittances of 80–20%). Calculated transmittance spectra were also obtained using an optical transfer matrix method. These calculated spectra were shown to be in good agreement with the experimental data obtained. These experiments demonstrate a facile approach to the production of low cost dielectric mirrors that have tailored photonic properties over a range of wavelengths that are currently important for applications in fibre optic based telecommunications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

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.     

Preparation of monodisperse ellipsoidal polystyrene particles

A method is described for the preparation of monodisperse ellipsoidal particles of polystyrene in the colloidal size range. Monodisperse polystyrene particles were dispersed in a solution of polyvinyl alcohol. This dispersion was then allowed to form, by evaporation, a thin film of polyvinyl alcohol containing spherical polystyrene particles. Strips of this film were clamped into a metal frame, heated rapidly in an oil bath to 200°C and stretched to a predetermined extent in order to convert the spherical particles into ellipsoids; the film was then cooled. A wide range of axial ratios for a variety of initial particle sizes was obtained by this method.     

Catalytic degradation of polystyrene in the presence of active charcoal

To obtain useful products from polystyrene degradation waste, the catalytic degradation of polystyrene over an active charcoal catalyst was carried out. By controlling the reaction conditions, the selective recovery of styrene dimer derivatives, a promising sourse of useful industrial additives, was investigated. Cis- and trans-l,3-diphenyl-2-butene. 1,3-diphenyl-1-butene and 1,3-diphenylbutane were detected as the main products. The yield of styrene dimer derivatives was about 15 wt.% of the total liquid products recovered. Also. selective recovery of the styrene dimer derivatives by the catalytic reaction of polystyrene in the presence of a catalyst was possible by controlling the contact time and activity of the catalyst.     

Bulk polymerized polystyrene in the presence of multiwalled carbon nanotubes

The in situ bulk polymerization method was applied to synthesize composites of multiwalled carbon nanotubes (MWNTs) and polystyrene (PS) under ultrasonication to open π-bonds in the MWNTs. Morphology of the composite products was studied by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thermal properties and molecular weight of the PS synthesized in the presence of the MWNTs were examined by thermogravimetric analysis (TGA) and gel permeation chromatography (GPC), respectively. The MWNTs were observed to play an important role as initiator consumers during the polymerization reaction. Electrical conductivity of a film-type sample of the PS/MWNT nanocomposite was found to increase with increased amount of MWNTs added, following the percolation theory.     

A facile method to prepare CdS/polystyrene composite particles

Nano-CdS/polystyrene composite particles were prepared via surfactant-free emulsion polymerization. 2-(Dimethylamino)ethyl methacrylate (DMEMA) was used as auxiliary monomer which co-polymerized with styrene (St) and provided the location for coordinating with Cd²⁺. By the coordination of Cd²⁺ ions to DMEMA, mono-disperse polystyrene with the Cd²⁺ ions on the particles surface were prepared successfully. With the release of S²⁻ ions from the thioacetamide (TAA), cadmium sulfide (CdS) was formed. Nano-CdS/PS composite particles could be synthesized via this facile method. The order of materials addition and the amount of initiator both are playing important roles to the final morphologies of the composite particles. In the method proposed in this study, no surfactant was used, and the stable emulsion was successfully obtained. UV–vis absorption and fluorescence measurement indicated the quantum dot effect in the resulted nano-CdS/PS composite particles. The possible composite particle formation mechanism was presented.     

Porous polystyrene microspheres having dimpled surface structures prepared within micellar assemblies of amphiphilic silica particles in water

Production of porous polystyrene microspheres having dimpled surface structures was demonstrated using amphiphilic and hydrophobic silica particles as structure-directing agents.