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.     

Preparations and properties of uniform size macroporous polymer beads prepared by two-step swelling and polymerization method utilizing divinyl succinate or divinyl adipate as a crosslinking agent

Uniform size macroporous polymer beads were prepared through a typical two-step swelling and polymerization method utilizing divinyl succinate or divinyl adipate as well as ethylene dimethacrylate as crosslinking agents. Stable macroporous polymer beads with good size monodispersity and a slightly nonspherical shape were obtained by homopolymerization of divinyl succinate in cyclohexanol as porogen. BET measurements indicated that the beads prepared by homopolymerization of divinyl succinate and copolymerization of divinyl succinate with vinyl p-tert-butylbenzoate, as well as homopolymerization of ethylene dimethacrylate had relatively large specific surface area. In contrast, copolymerization of divinyl succinate with methyl methacrylate afforded beads having a very small specific surface area. Similarly, all the beads prepared using divinyl adipate had very small specific surface area, while size exclusion chromatography in tetrahydrofuran suggested that these beads acquired a porous structure as a result of swelling. When used as packing materials for high-performance liquid chromatography, the beads prepared with divinyl adipate showed unexpected molecular recognition toward flat solutes in reversed phase liquid chromatography in contrast to those prepared with ethylene dimethacrylate. Copolymerizations with methyl methacrylate led to a decrease in molecular recognition, while those with vinyl p-tert-butylbenzoate enhanced the selectivity. © 1996 John Wiley & Sons, Inc.     

Synthesis of highly monodisperse quantum dot‐loaded polymer beads by impregnation and precipitation techniques

A novel approach to the synthesis of highly monodisperse quantum dot‐loaded polymer beads by combining impregnation and precipitation techniques was reported. The monodisperse poly(glycidyl methacrylate) (PGMA) beads were first synthesized by dispersion polymerization. Then, the PGMA beads were chemically modified to generate carboxyl groups, and impregnation of cadmium ions (Cd²⁺) inside the beads. Subsequently, the cadmium ions were reacted with thioacetamide to form cadmium sulfide (CdS) quantum dots within the polymer beads. The morphology, structure, and properties of CdS quantum dot‐loaded polymer beads were studied by field emission scanning electron microscope (SEM), transmission electron microscope, fluorescence spectrophotometer, fluorescence microscope, Fourier transform infrared spectroscopy, powder X‐ray diffraction, and thermogravimetric analysis. The results indicated that the CdS quantum dot‐loaded polymer beads had an average size of 1.4 μm, and were highly monodisperse. More interestingly, the CdS quantum dots distributed evenly within the polymer beads, which provide very strong fluorescence intensity. The existence of carboxyl groups on the quantum dot‐loaded polymer beads was measured quantitatively, and was found to be 0.2 mmol/g. These CdS quantum dot‐loaded polymer beads involving functional carboxyl groups would have potential applications in biological immunoassay and photoelectronic fields. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Preparation of micron-size monodisperse polymer particles by seeded polymerization utilizing the dynamic monomer swelling method

Utilizing a new type of monomer swelling method, 6.1 m-size monodisperse polymer particles were prepared by seeded polymerization. 1.8 m-size monodisperse polystyrene (PS) seed particles (1.8 m in size) were prepared by dispersion polymerization in ethanol-water (80/20, v/v) medium in the presence of poly(acrylic acid) as stabilizer with 2,2-azobisisobutyronitrile as initiator. The PS seed dispersion was mixed with ethanol-water (60/40, v/v) solution dissolving styrene (S) monomer, benzoyl peroxide as initiator, and poly(vinyl alcohol) as stabilizer. By slow, continuous, dropwise addition of water with a micro feeder into the mixture, the PS particles absorbed the many S monomers, which were separated from the medium and swelled from 1.8 m to 8.4 m while keeping the monodispersity high. We named this procedure the dynamic swelling method. Then, the seeded polymerization of the absorbed S monomer was carried out in the presence of NaNO₂ as water-solube inhibitor.Part CXXII of the series Studies on Suspension and Emulsion.     

Synthesis and characterization of micron‐sized monodisperse superparamagnetic polymer particles with amino groups

Micron‐sized monodisperse superparamagnetic polyglycidyl methacrylate (PGMA) particles with functional amino groups were prepared by a process involving: (1) preparation of parent monodisperse PGMA particles by the dispersion polymerization method, (2) chemical modification of the PGMA particles with ethylenediamine (EDA) to yield amino groups, and (3) impregnation of iron ions (Fe²⁺ and Fe³⁺) inside the particles and subsequently precipitating them with ammonium hydroxide to form magnetite (Fe₃O₄) nanoparticles within the polymer particles. The resultant magnetic PGMA particles with amino groups were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X‐ray diffractometry (XRD), and vibrating sample magnetometry (VSM). SEM showed that the magnetic particles had an average size of 2.6 μm and were highly monodisperse. TEM demonstrated that the magnetite nanoparticles distributed evenly within the polymer particles. The existence of amino groups in the magnetic polymer particles was confirmed by FTIR. XRD indicated that the magnetic nanoparticles within the polymer were pure Fe₃O₄ with a spinel structure. VSM results showed that the magnetic polymer particles were superparamagnetic, and saturation magnetization was found to be 16.3 emu/g. The Fe₃O₄ content of the magnetic particles was 24.3% based on total weight. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3433–3439, 2005     

Production of micron-sized monodispersed composite polymer particles by seeded polymerization utilizing the dynamic swelling method

 In order to develop the seeded polymerization technique utilizing the dynamic swelling method (DSM) proposed by authors for the production of micron-sized mono-dispersed “composite” polymer particles consisting of two kinds of polymers, the seeded polymerization for the dispersion of ethyl methacry-late (EMA)-swollen PS particles prepared utilizing DSM was carried out. Monodispersed PS/poly(ethyl methacrylate) (PEMA) composite particles having 7 μm in diameter were produced by the addition of NaCl to lower the solubility of EMA in medium and by the addition of CuCl₂ as a water-soluble inhibitor to depress the by-production of submicron-sized PEMA particles. Received: 16 July 1996 Accepted: 10 October 1996     

Model filled polymers. V. Synthesis of crosslinked monodisperse polymethacrylate beads

Monodisperse polymethacrylate beads of varied size and crosslink density are prepared by emulsion copolymerization of methacrylate and divinyl monomers in the absence of emulsifiers. The sizes of polybutyl and polyethyl methacrylate beads decreased with increasing polymerization temperature, while polymethyl methacrylate beads were largely unchanged in size. The molar mass of polymer in polymethyl metnacrylate beads markedly exceeded that in polystyrene beads. The rate of polymerization increased, and bead size decreased, with increasing initiator concentration or decreasing monomer concentration. The polymethacrylate beads are used as filler particles in polymer composites.     

Model filled polymers. XI. Synthesis of monodisperse crosslinked polymethacrylonitrile beads

Monodisperse polymethacrylonitrile beads of varied size and crosslink density are prepared by emulsion copolymerization of methacrylonitrile and allylmethacrylate in the absence of emulsifier. The particle size is very sensitive to polymerization temperature and initiator concentration. Because of a nitrile group effect, the maximum conversion varies with reaction conditions. The highest conversion obtained was 82%. © 1992 John Wiley & Sons, Inc.     

Preparation and control of surface properties of monodisperse micrometer size beads by dispersion copolymerization of styrene and butyl methacrylate in polar media

The dispersion copolymerization of styrene and butyl methacrylate in ethanol-water medium to afford micrometer-size monodisperse beads has been investigated. Hydroxypropyl cel-lulose, poly (acrylic acid), and poly (vinylpyrrolidone) have been used as steric stabilizers, benzoyl peroxide and azobisisobutyronitrile as initiators. A novel steric stabilizing system consisting of a mixture of poly (acrylic acid) and hydroxypropyl cellulose has also been shown to lead to monodisperse beads for which the surface charge can be controlled by the relative ratio of steric stabilizers. The effect of several variables, such as the solvency of the medium, the concentration of co-monomers, the reaction temperature, and the type of steric stabilizer and initiator used on the bead size and size distribution are discussed. © 1995 John Wiley & Sons, Inc.     

Fine control of the porous structure and chromatographic properties of monodisperse macroporous poly(styrene-co-divinylbenzene) beads prepared using polymer porogens

The porous structure of monodisperse macroporous beads can be controlled by using soluble polymers with well-defined structural characteristics as part of the porogenic mixture. In general, the use of linear polystyrene as a porogen in the preparation of poly (styrene-co-divinylbenzene) beads shifts the pore size distribution towards larger pores. While a direct correlation between pore size and molecular weight of the porogen has been established, the chemical composition of the polymer porogen has no effect on the porous and chromatographic properties of the beads. These findings suggest that the average molar volume of the porogenic system is important while the miscibility of the polymer porogen with the crosslinked polymer that is formed is of little relevance. © 1994 John Wiley & Sons, Inc.     

Narrow‐disperse,cross‐linked polymer microspheres by one‐step dispersion polymerization with a chain transfer agent

The increasing demand for monodispersed cross‐linked polymers in high‐quality applications requires continuous improvement in their preparation process. In this study, an appropriate amount of a chain transfer agent was added to a traditional cross‐linking system, resulting in the preparation by one‐step dispersion polymerization of cross‐linked polystyrene (PS) microspheres with a particle size of 3.867 μm and a diameter coefficient of variation of 0.011. The particles were characterized using scanning electron microscopy (SEM) and an Ubbelohde viscometer. The results show that the tertiary dodecyl mercaptan (TDDM) chain transfer during nucleation increases the oligomer concentration, promotes the aggregation of the oligomers, increases the primary particle size, and reduces the cross‐linking effect. This controls the volume of cross‐linked chains in the primary particles, thus avoiding the problem of poor dispersion of the polymer microspheres due to the introduction of divinylbenzene (DVB). This study produces a preparation method for cross‐linked microspheres.     

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.     

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     

Preparation and characterization of monodisperse CdS quantum dot‐polymer microspheres

A novel and effective method for the preparation of monodisperse CdS quantum dot‐polymer microspheres was proposed. The monodisperse hollow polymer microspheres were firstly swelled in chloroform. Then, the reaction precursor composed of CdO and sulfur, was impregnated into the hollow polymer microspheres. Subsequently, the CdS quantum dots were synthesized directly within the polymer microspheres by thermal decomposition. The morphology, structure, and fluorescence properties of CdS quantum dot‐polymer microspheres were studied by scanning electron microscope, transmission electron microscope, fluorescence microscope, and flow cytometry. The results indicate that the fluorescent CdS quantum dots are successfully synthesized in the monodisperse hollow polymer microspeheres, which provide very strong fluorescence intensity, and offer excellent photostability due to the compact structure of the polymer matrix. These CdS quantum dot‐polymer microspheres have potential applications in biotechnology and biomedicine. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 751–755, 2010     

Producing bimodal molecular weight distribution polymers through facile one‐pot/one‐step RAFT polymerization

Well‐defined bimodal molecular weight distribution (MWD) polystyrene and polystyrene‐b‐poly(acrylonitrile) were successfully synthesized using a pair of mono/difunctional trithiocarbonate RAFT agents 1 and 2 via one‐pot RAFT polymerization. The kinetics of RAFT polymerization for styrene in bulk with a molar ratio of [St]₀:[AIBN]₀:[ 1 ]₀:[ 2 ]₀ = 1200:1:2.5:2.5 was studied at 75°C. The results indicated that the system showed excellent controllability and “living” characteristics to both higher and lower molecular weight fractions, providing an efficient and facile way to producing bimodal MWD (co)polymers with both controlled molecular weight (MW) and MWD in molecular level, and the plausible mechanism was discussed in this work. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preparation of monodisperse poly(St‐co‐PETEA) microspheres by precipitation polymerization using ethanol as solvent

Precipitation polymerization of styrene (St) was carried out with pentaerythritol tetraacrylate (PETEA) to produce monodisperse crosslinked microspheres. A much safer ethanol replaced acetonitrile as a solvent in precipitation polymerization of monodisperse crosslinked poly(St‐co‐PETEA) microspheres. Monodisperse crosslinked microspheres with high monomer conversion were achieved within 4 hr. Uniform and well‐separated monodisperse were obtained in ethanol when PETEA concentration varied from 30 vol% to 90 vol% and the particle diameter decreased from 0.75 to 0.58 µm. The particle yield increased from 36.51 to 64.38% by increase in the initiator loading from 1 to 8 wt%. No coagulum occurred between particles when the polymerization time varied from 2 to 10 hr. Copyright © 2010 John Wiley & Sons, Ltd.     

Acrylonitrile-divinylbenzene copolymer beads: influence of pre-polymerization step, stirring conditions and polymerization initiator type on the polymer particle characteristics

Cross-linked acrylonitrile-divinylbenzene copolymer beads have been synthesized by suspension polymerization in presence of an inert diluent (toluene). In this study a set of experiments has been performed to evaluate the physical features of the beads. The influence of the pre-polymerization step, process stirring conditions and type of polymerization initiator on the polymer particle size distribution, apparent density and visual appearance by optical microscopy was investigated.     

Preparation of micron-size monodisperse poly(2-hydroxyethyl methacrylate) particles by dispersion polymerization

Dispersion polymerization of 2-hydroxyethyl methacrylate using four categories of polymeric stabilizers in a mixture of good and poor solvents was performed to produce polymeric particles. The stabilizers employed were methyl methacrylate and styrene homopolymers, methacryloyl-terminated poly(methyl methacrylate) and polystyrene macromonomers, an amphiphilic poly(methyl methacrylate-co-methacrylic acid-graft-styrene), and polybutadiene derivatives containing reactive vinyl groups. Dispersion copolymerization with a small amount of the macromonomer gave micron-size particles with relatively narrow size distribution. The amphiphilic graft copolymer and the polybutadiene derivatives also afforded monodisperse particles. The mixed ratio between good and poor solvents greatly affected the particle size and size distribution. © 1996 John Wiley & Sons, Inc.     

Water-soluble ionic liquids as novel stabilizers in suspension polymerization reactions: engineering polymer beads

Aqueous solutions of ionic liquids have been used as novel and environmentally friendly reaction media to synthesize and "control" the size of different cross-linked polymer beads by suspension polymerization reactions. It was found that the investigated ionic liquids can act as novel stabilizing agents of the suspensions as a result of their surface-active properties. The results have demonstrated that the average size of polymer beads can be varied from the macro- to the nanoscale and their surface area can also be "adjusted" by this synthetic approach. Furthermore, the use of a combination of ionic liquids and water for the synthesis of polymers, the simple isolation of the products formed in this polymerization procedure, as well as the recycling of the continuous medium for further reactions open up possibilities for the development of "new and green" polymerization processes.     

Facile one‐pot/one‐step technique for preparation of side‐chain functionalized polymers: Combination of SET‐RAFT polymerization of azide vinyl monomer and click chemistry

An azido‐containing functional monomer, 11‐azido‐undecanoyl methacrylate, was successfully polymerized via ambient temperature single electron transfer initiation and propagation through the reversible addition–fragmentation chain transfer (SET‐RAFT) method. The polymerization behavior possessed the characteristics of “living”/controlled radical polymerization. The kinetic plot was first order, and the molecular weight of the polymer increased linearly with the monomer conversion while keeping the relatively narrow molecular weight distribution (M_w/M_n ≤ 1.22). The complete retention of azido group of the resulting polymer was confirmed by ¹H NMR and FTIR analysis. Retention of chain functionality was confirmed by chain extension with methyl methacrylate to yield a diblock copolymer. Furthermore, the side‐chain functionalized polymer could be prepared by one‐pot/one‐step technique, which is combination of SET‐RAFT and “click chemistry” methods. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012