Thermodynamic analysis of the morphology of monomer-adsorbed,cross-linked polymer particles prepared by the dynamic swelling method and seeded polymerization

Thermodynamic simulation of the morphology of monomer-adsorbed, cross-linked polymer particles prepared by the dynamic swelling method which the authors proposed was conducted to clarify its thermodynamic stability from the viewpoint of the total interfacial free energy. By comparing it with experimental results reported in previous articles, it was found that the morphology was controlled thermodynamically. Snowman-shaped composite polymer particles having different morphologies were prepared by seeded polymerization of the monomer-adsorbed, cross-linked polymer particles, in which the polymer particles had different cross-linking densities.     

Monodisperse ultrafine polystyrene nanoparticles prepared by a semicontinuous microemulsion polymerization

Monodisperse ultrafine polystyrene nanoparticles have been successfully prepared under low levels of surfactant through a novel semicontinuous microemulsion polymerization, in which the first part of monomer (St₁) is added dropwise while the subsequent supply to the polymerizing system is delivered in one potion. Polystyrene nanoparticles with number‐average diameter of 17.4 nm and polydispersity index of 1.06 were obtained using low level of surfactant/monomer weight ratio of 0.20. Influencing of parameters including amount of St₁, solid content, initiator, reaction temperature, and cosurfactant on the resultant particle size and size distribution were investigated. The mechanism of nucleation and particle growth was discussed as well. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4522–4528, 2008     

Monodisperse polystyrene microspheres prepared by dispersion polymerization with microwave irradiation

Monodisperse polystyrene microspheres with diameters of 200–500 nm were prepared by dispersion polymerization with microwave irradiation with poly(N‐vinylpyrrolidone) as a steric stabilizer and 2,2′‐azobisisobutyronitrile as a radical initiator in an ethanol/water medium. The morphology, size, and size distribution of the polystyrene microspheres were characterized with transmission electron microscopy and photon correlation spectroscopy, and the formed films of the polystyrene dispersions were characterized with atomic force microscopy. The effects of the monomer concentration, stabilizer concentration, and initiator concentration on the size and size distribution of the polystyrene microspheres were investigated. The polystyrene microspheres prepared by dispersion polymerization with microwave irradiation were smaller, more uniform, and steadier than those obtained with conventional heating. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2368‐2376, 2005     

Influence of the seed polymer on the chromatographic properties of size monodisperse polymeric separation media prepared by a multi-step swelling and polymerization method

Monodisperse polymer particle-based separation media were prepared by a multi-step swelling and polymerization method with two pairs of monomers and two porogenic solvents. Their chromatographic properties were compared to those of beads prepared by a corresponding suspension polymerization method without the use of seed polymer to ascertain the influence of the seed polymer on their porous structures. A large change in porous structure was observed when the swollen particle consisting of monomers and porogenic solvents contained at least one good solvent for the polystyrene seed polymer, allowing it to remain in the polymerizing medium. In contrast, when the polystyrene seed particle was excluded from the swollen oil droplets, due to its poor solubility in the monomers and the porogenic solvents, there was no difference in the chromatographic properties such as pore volume, pore size, pore size distribution, or retention selectivity between the multi-step swelling and polymerization method and the suspension polymerization method. Since the only difference between the multi-step swelling and polymerization method and the suspension method is the use of the seed polymer, it appears that a very small amount (< 1% v/v) of seed polymers in the enlarged swollen droplets plays an important role as a porogen and affects the porous structure as well as the chromatographic properties of the monodisperse polymer particle-based separation media. © 1993 John Wiley & Sons, Inc.     

Titania-coated polystyrene hybrid microballs prepared with miniemulsion polymerization

Hybrid microballs with polystyrene cores coated by titania nanoparticles were prepared in miniemulsion polymerization. Acrylic acid was used as a comonomer to promote locating titania nanoparticles on the polymer's surface. The addition of a hydrophobic agent effectively prevents monomer diffusing into the aqueous phase. The morphology of hybrid particles was examined with the transmission electron microscope, and its change pattern with reactive conditions was observed. The infrared spectra of hybrid nanoparticles showed that there existed a certain interaction between titania nanoparticles and polymers. The crystallization morphology of hybrid particles before and after calcination was characterized with X-ray diffraction.     

Research on gamma-ray irradiation-assisted synthesis of cross-linked polystyrene via bulk polymerization

Journal of Radioanalytical and Nuclear Chemistry - Controlling heat accumulation is one of the major challenges for block materials synthesizing via bulk polymerization. In the paper, cross-linked...     

Production of micron-sized monodispersed polymer particles by seeded polymerization for the dispersion of highly monomer-swollen particles prepared with submicron-sized polymer seed particles utilizing the dynamic swelling method

For the purpose of extending the size range of polymer seed particles used in “dynamic swelling method” (DSM), first it was verified theoretically that the submicron-sized polymer particles produced by emulsion polymerization can also absorb a large amount of monomer by DSM in both equilibrium and kinetic control states. Next, on the basis of the theoretical results, experimentally about 2.6 μm-sized styrene-swollen polystyrene (PS) particles were prepared utilizing DSM in the presence of 0.64 μm-sized monodispersed PS seed particles produced by emulsifier-free emulsion polymerization. Moreover, 2.5 μm-sized monodispersed PS particles were produced by the addition of cupric chloride as a water-soluble inhibitor to depress the by-production of submicron-sized PS particles in the seeded polymerization at 30°C with 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) initiator. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2513–2519, 1998     

Solvent dependent friction force response of polystyrene brushes prepared by surface initiated polymerization

Polystyrene (PS) brushes were prepared on oxide passivated silicon by the surface initiated polymerization (SIP) technique. From an AIBN-type free radical initiator, which was silanized and immobilized on silicon wafers, styrene brushes were directly polymerized and grafted from the surface. The formation of the initiator monolayer and, subsequently, the polymer brush on the surface were monitored by X-ray photoelectron spectroscopy (XPS) and ellipsometry. Friction force measurements were performed by atomic force microscopy (AFM), using a 5 microm SiO2 colloidal sphere tip and under systematically varied solvent environments (nonpolar to polar), to demonstrate the dependence of brush lubricity on solvation. The relative uptake of solvents in the PS brush was determined by quartz crystal microbalance (QCM), and it correlates well with friction data. It is surmised that, in poor solvent environments, the polymer brush exists in a collapsed conformation, giving rise to the higher observed friction response.     

Preparation of micron-sized, monodispersed, monomer-adsorbed polymer particles utilizing the dynamic swelling method with loosely cross-linked seed particles

Influence of the water-addition rate (R _w ) (ml/h) on the monodispersity of monomer-adsorbed polymer particles prepared by utilizing the dynamic swelling method (DSM) with 1.9-μm-sized, monodispersed, loosely cross-linked polystyrene/styrene-divinylbenzene copolymer [1/(47.5–2.5), w/w] composite particles was examined theoretically and experimentally. The thermodynamic simulation under a kinetic control state indicates that, at the R _w values below 4, the cross-linked composite particles adsorb all styrenes separated from ethanol/water media. The experimental result at the R _w value of 2.66 supported it. At the R _w values above 5.32 and below 1.33, polydispersed styrene-adsorbed particles were prepared. The former depended on the formation of some pure styrene droplets not containing the composite particle. The latter depended on coalescence among the adsorbed particles by DSM. Received: 5 April 2000 Accepted: 5 October 2000     

Anionic surfactant for silica-coated polystyrene composite microspheres prepared with miniemulsion polymerization

Raspberry-like composite microspheres with polystyrene (PS) cores and silica shell were prepared through miniemulsion polymerization by using the anionic sodium dodecyl sulfate (SDS) as a surfactant and 1-vinylimidazole (1-VID) as an auxiliary monomer. The strong acid–base interaction between acidic hydroxyl groups of silica surfaces and basic amino groups of 1-VID promote the formation of long-term stable PS/SiO₂ nanocomposite microspheres. Transmission electron microscopy TEM studies indicated that the acid–base interaction between silica nanoparticles and auxiliary monomer was strong enough for the formation of colloidally stable composite microspheres, which have raspberry-like morphology. Influences of several synthetic parameters, such as initial silica amount, the amount of auxiliary monomer 1-VID, and SDS concentration on the polymerization stability, diameters, and morphology of the composite microspheres were studied. A tentative mechanism of the formation of nanocomposite particles was proposed.     

Graft polymerization from pore wall of three-dimensionally ordered macroporous cross-linked polystyrene via atom transfer radical polymerization

The surface-initiated atom-transfer radical polymerization (ATRP) technique was applied to the graft polymerization of methyl methacrylate (MMA) and N-isopropylacrylamide (NIPAm) from three-dimensionally ordered macroporous cross-linked polystyrene (3DOM CLPS) on which the initiator, halogen atom was immobilized onto the pore wall of 3DOM CLPS by chloromethylation. FT-IR and TG-DWA analyses confirm that the graft polymerization of MMA and NIPAm via ATRP had been taken place at the pore wall of 3DOM CLPS. The initiating efficiency of chloromethyl groups was calculated according to the data of TGA-titration, revealed that the benzyl chloride is not only distributed on the surface of the pore walls but also must be present throughout the inner of the cross-linked polystyrene matrix. SEM analyses show that the grafted layers are smooth and homogeneous, and the ordered structure is well preserved after polymerization. By the adjustment of the graft polymerization time, the thickness of grafted polymer layers can be controlled. The max thickness of grafted PMMA layer is 85 nm and the max thickness of grafted PNIPAm layer is 35 nm.     

High-impact polystyrene/halloysite nanocomposites prepared by emulsion polymerization using sodium dodecyl sulfate as surfactant

In this work, we report on the phase behavior of 1-ethyl-3-methyl-imidazolium-ethylsulfate ([emim][etSO(4)])/limonene/polyethylene glycol tert-octylphenyl ether (Triton X-114 or TX-114) microemulsions as a function of ionic liquid (IL) content and temperature. Phase diagrams, conductivity measurements, and small angle X-ray scattering (SAXS) experiments will be presented. A hydrophilic IL, instead of water is used with the goal to enlarge the temperature range on which stable microemulsions can be formed. Indeed, the system shows remarkably large temperature stability, in particular down to -35 °C. We will emphasize on a comparison with a recently published work about microemulsions composed of [emim][etSO(4)], limonene, and Triton X-100 that to some extent are stable at temperatures well below the freezing point of water. The key parameter responsible for the difference in phase behavior, microstructure, and temperature stability is the average repeating number of ethylene oxide units in the surfactant head group, which is smaller for Triton X-114 compared to Triton X-100. Among the fundamental interest, how the amphiphilicity of the surfactant influences the phase diagram and phase behavior of IL-based microemulsions, the exchange of Triton X-100 by Triton X-114 results in one main advantage: along the experimental path the temperature where phase segregation occurs is significantly lowered leading to single phase microemulsions that exist at temperatures beneath 0 °C.     

Uniform-sized molecularly imprinted polymer for metsulfuron-methyl by one-step swelling and polymerization method

Uniform-sized molecularly imprinted polymer (MIP) beads for metsulfuron-methyl (MSM) were firstly prepared by one-step swelling and polymerization method using 4-vinylpyridine (4-VPY) and ethylene glycol dimethacrylate (EDMA) as functional monomer and cross-linker, respectively. The preparation was optimized by varying the ratio of MSM to 4-VPY. The chromatographic behaviors of MSM and other structurally related sulfonylureas (SUs) on the resultant MIP column were evaluated. The imprinted polymer revealed specific affinity to the template and the fair resolution of SUs was also obtained. Furthermore, the uniform-sized MSM-MIP was used as the solid phase extraction (SPE) material to enrich MSM in real water samples before reversed-phase HPLC (RP-HPLC) analysis. The recovery of MSM from 100 mL of drinking water at a 50 ng/L spike level was 99.59% with R.S.D. of 1.13%. The detection limit was about 6.0 ng/L of MSM when enriching a 100 mL water sample.     

Direct radical polymerization of 4-styryldiphenylphosphine: preparation of cross-linked and non-cross-linked triphenylphosphine-containing polystyrene polymers

We report herein a simple synthesis of 4-styryldiphenylphosphine and the radical copolymerization of it with styrene, both with and without a cross-linker, to directly form cross-linked and non-cross-linked polystyrene supported triphenylphosphine in which the level of phosphine incorporation can be easily and accurately controlled. The utility of these polymers is demonstrated by their use in Mitsunobu and alcohol bromination reactions.     

High molecular weight monodisperse polystyrene microspheres prepared by dispersion polymerization,using a novel bifunctional macromonomer

A novel bifunctional vinyl‐terminated polyurethane macromonomer was applied to the dispersion polymerization of styrene in ethanol. Monodisperse polystyrene (PS) microspheres were successfully obtained above 15 wt % of macromonomer relative to styrene. The steep slope from the reduction of the average particle size reveals that the macromonomer can efficiently stabilize higher surface area of the particles when compared with a conventional stabilizer, poly(N‐vinylpyrrolidone). The stable and monodisperse PS microspheres having the weight‐average diameter of 1.2 μm and a good uniformity of 1.01 were obtained with 20 wt % polyurethane macromonomer. The grafting ratio of the PS calculated from ¹H NMR spectra linearly increased up to 0.048 with 20 wt % of the macromonomer. In addition, the high molecular weights (501,300 g/mol) of PS with increased glass transition and enhanced thermal degradation temperature were obtained. Thus, these results suggest that the bifunctional vinyl‐terminated polyurethane macromonomer acts as a reactive stabilizer, which gives polyurethane‐grafted PS with a high molecular weight. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3566–3573, 2005     

Slightly surface-functionalized polystyrene microspheres prepared via Pickering emulsion polymerization using for electrophoretic displays

Europium (III) (Eu(3+))-doped nanoporous silica spheres were synthesized, and the states of Eu(3+) ions in the silica framework structure were investigated. The ordered nanopores were preserved with the doping at the Eu(3+) molar concentration to Si up to 10 mol%, and the O-Si-O and Si-OH groups in the structures were clearly rearranged with the doping, indicating the interaction of Eu(3+) with the O atoms. The significant morphological changes in the spheres were observed with the doping. The photoluminescence spectral shapes due to the transitions of (5)D(0)-(7)F(1) and (5)D(0)-(7)F(2) were indicative of the presence of the Eu(3+) in an environment of a low symmetry. It was found that the Eu(3+) was located inside the silica framework to electrostatically interact with the environmental O atoms, which would prevent the aggregation among Eu(3+) ions to show the efficient luminescence. Therefore, the interactions between the Eu(3+) ions and silica framework structures in the spheres were successfully clarified.     

Preparation of molecularly imprinted polymer for vanillin via seed swelling and suspension polymerization

Molecularly imprinted polymer (MIP) for vanillin was synthesized successfully by multi-step swelling suspension polymerization using polystyrene (PS) as the “seed”. The PS-MIP was characterized by scanning electron microscopy and equilibrium adsorption method. The results showed that the PS-MIP microsphere had regular spherical morphology and can selectively separate the target analytes. The PS-MIP had two kinds of binding sites, while the non-imprinted polymer using PS as the “seed” (PS-NMIP) only had one kind of binding sites by Scatchard analysis which indicated that specific and non-specific binding interactions existed there. The PS-MIP had proven to show improved binding capacity in comparison with the MIP synthesized by bulk polymerization.     

Influence of the swelling state of seed polymer particles with monomer on the morphology of micron-sized monodispersed composite polymer particles produced by seeded polymerization utilizing the dynamic swelling method

 Micron-sized mono-dispersed polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) composite particles (PS/PBMA=2/1 by weight) having a heterogeneous structure in which many fine PBMA domains dispersed in a PS matrix near the particle surface were produced by seeded polymerization of n-butyl methacrylate (BMA) of which almost all had been absorbed by 1.8 μm-sized monodispersed PS seed particles utilizing the dynamic swelling method. The morphology was varied by changing the PS/BMA ratio and polymerization temperature. It was concluded that the swelling state of 2 μm-sized BMA-swollen PS particles in the seeded polymerization process is one of the important factors to control the morphology of the composite particles. Received: 27 November 1996 Accepted: 21 March 1997     

Narrowly dispersed molecularly imprinted microspheres prepared by a modified precipitation polymerization method

A modified precipitation polymerization (MPP) method was established to prepare narrowly dispersed molecularly imprinted polymeric microspheres. MPP was stabilizer and surfactant free and needed only small amount of porogen (about 50 wt.%). Only part of alcohols and all the alkanes tested formed particles. Using a mixture of alkane and toluene as porogen, the carbon numbers of alkanes and solubility parameter of porogenic solvents were important factors in controlling particle morphology. Nearly mono-dispersed microspheres with diameter of about 2-3 μm were synthesized by MPP using mineral oil:toluene = 2:3 as porogen. Template did not affect the formation of globe microspheres in MPP. Microspheres prepared under the lowest reaction temperature had the highest binding capability. When used as sorbents of high performance liquid chromatography (HPLC), the microspheres prepared by MPP using bisphenol A, estradiol, and tebuconazole as template had similar binding selectivity and higher binding capability compared to microspheres synthesized by classical precipitation polymerization. Photoinitiation and low reaction temperature were important factors attributed to better binding capability of microspheres prepared by MPP.