Preparation and characterization of micron‐sized magnetic microspheres by one‐step suspension polymerization

Micron‐sized magnetic microspheres with different functional groups were prepared by one‐step suspension copolymerization of styrene, divinyl benzene, and methyl methacrylate in the presence of oleic acid‐coated magnetic nanoparticles. In the present work, we used benzoyl peroxide as an initiator and poly(vinyl alcohol) (PVA‐1788; degree of polymerization: 1,700; degree of hydrolysis: 88%) as a stabilizer. We also added acrylamide (AM) monomer in the aqueous phase and methacrylic acid (MAA) in the oil phase. The morphology and properties of the resulting magnetic microspheres were examined by optical micrographs (OMs), vibrating‐sample magnetometer (VSM), and Fourier transform infrared spectrometer (FT IR). The results showed the three products have uniform and spherical form with superparamagnetism and well dispersion. Moreover, we found that monomer AM had a little contribution to the copolymerization, and MAA could strikingly decrease the diameter of the final microspheres. The magnetic microspheres with functional groups could be linked well with the IgG‐FITC. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Preparation and catalytic application of poly 4‐vinylpyridine microspheres

Poly 4‐vinylpyridine (P4VP) microspheres between 170 and 728 nm were synthesized by Emulsifier‐Free Emulsion Polymerization. The monomer concentration, ionic strength, and initiator concentration affected the microsphere size and size distribution. The increasing monomer concentration led to the increase of microsphere size, whereas the size distribution of the resultant P4VP microspheres increased with the increasing ionic strength of the reaction systems. Mo(O₂)₂O·2DMF was successfully anchored onto the P4VP microspheres by ligand exchange, and the heterogeneous catalyst showed high‐catalytic activity for epoxidation of cis‐cyclooctene with environmentally friendly hydrogen peroxide. The size and morphology of the supported microspheres has important influence on the catalytic activity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study on synthesis and morphology control of poly(4‐vinylpyridine‐co‐butyl acrylate)/poly(styrene‐co‐butyl acrylate) composite microspheres

Monodispersed crosslinked cationic poly(4‐vinylpyridine‐co‐butyl acrylate) [P(4VP‐BA)] seed latexes were prepared by soapless emulsion polymerization, using 2,2′‐azobismethyl(propionamidine)dihydrochloride (V₅₀) as an initiator and divinylbenzene (DVB) or ethylene glycol dimethacrylate (EGDMA) as a crosslinker. The optimum condition to obtain monodispersed stable latex was investigated. It was found that the colloidal stability of the P4VP latex can be improved by adding an adequate amount of BA (BA/4VP = 1/4, w/w), and adopting a semicontinuous monomer feed mode. Subsequently, poly(4‐vinylpyridine‐co‐butyl acrylate)/Poly(styrene‐co‐butyl acrylate) [P(4VP‐BA)/P(ST‐BA)] composite microspheres were synthesized by seeded polymerization, using the above latex as a seed and a mixture of ST and BA as the second‐stage monomers. The effects of the type of crosslinker, the degree of crosslinking, and the initiators (AIBN and V₅₀) on the morphology of final composite particles are discussed in detail. It was found that P(4VP‐BA)/P(ST‐BA) composite microspheres were always surrounded by a PST‐rich shell when V₅₀ was used as initiator, while sandwich‐like or popcorn‐like composite particles were produced when AIBN was employed. This is because the polarity of the polymer chains with AIBN fragments is lower than for the polymer with V₅₀ fragments, hence leading to higher interfacial tension between the second‐stage PST‐rich polymer and the aqueous phase, and between PST‐rich polymer and P4VP‐rich seed polymer. As a result, the seed cannot be engulfed by the PST‐rich polymer. Furthermore, the decrease of T_g of the second‐stage polymer promoted phase separation between the seeds and the PST‐rich polymer: sandwich‐like particles formed more preferably than popcorn‐like particles. It is important knowledge that various morphologies different from PST‐rich core/P4VP‐rich shell morphology, can be obtained only by changing the initiator, considering P4VP is much more hydrophilic than PST. The zeta potential of composite particles initiated by AIBN in seeded polymerization shifted from a positive to a negative charge. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1190–1203, 2002     

Core–shell biopolymer microspheres for sustained drug release

In this work, a core–shell biopolymer microsphere comprising a carvedilol‐loaded yeast cell wall polysaccharides core surrounded by a silk fibroin shell layer is developed to eliminate the risks of using synthetic polymers for drug encapsulation on human health and to avoid burst release and to prolong the release time. Transmission electron microscopy, Fourier‐transform infrared, confocal laser scanning microscope, and phase contrast microscopy analysis indicate that yeast treated with Tris–HCl containing cetyltrimethylammonium bromide, EDTA, and NaCl could provide much larger space for host drug as compared to plasmolyzed cells because the former can help maintain the original shape of yeast cells. In addition, its permeability barrier is significantly altered and nucleus becomes pyknotic. In contrast, plasmolyzed cells can hardly maintain the rigidity and integrity of their cell walls and will finally end up with cell fragments. SEM observation reveals that the carvedilol‐loaded cells maintain very similar shape and size before and after coating with 0.1% silk fibroin. In vitro release studies show that a drug delivery system using the carvedilol‐loaded cells can achieve a sustained drug release up to 20 days probably due to the electrostatic interaction between the positively charged carvedilol and the negatively charged yeast cells at the pH 7.4 and to the stability of the yeast cell helped by silk fibroin that provides an effective diffusion barrier. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41782.     

苯乙烯-对氯甲基苯乙烯共聚物胶乳微球的制备及表征

以苯乙烯（St）和对氯甲基苯乙烯（VBC）为共聚单体,过硫酸钾（KPS）为引发剂,十二烷基苯磺酸钠（SDBS）为乳化剂,采用乳液聚合法制备了富含氯甲基的苯乙烯-对氯甲基苯乙烯共聚物功能微球。采用红外光谱（FT-IR）、扫描电镜（SEM）、激光粒度仪和X射线光电子能谱（XPS）对样品进行表征,研究了乳化剂用量、单体用量、引发剂用量、反应时间、反应温度等因素对微球粒径、乳液转化率的影响。结果表明,产物微球粒径均一,表面光滑、富含氯甲基功能基团,采用此方法可以制备粒径在100～250 nm的功能高分子微球。     

Synthesis and characterization of air‐stable magnetic Fe composites microspheres of narrow size distribution

Air‐stable Fe magnetic nanoparticles entrapped within carbon and porous crosslinked polystyrene microspheres of narrow size distribution were prepared by the following sequential steps: (1) Polystyrene/poly(divinyl benzene) and polystyrene/poly(styrene‐divinyl benzene) uniform micrometer‐sized composite particles were prepared by a single‐step swelling of uniform polystyrene template microspheres dispersed in an aqueous continuous phase with emulsion droplets of dibutyl phthalate containing the monomers divinyl benzene and styrene and the initiator benzoyl peroxide. The monomers within the swollen polystyrene template microspheres were then polymerized by raising the temperature to 73°C; (2) Porous poly (divinyl benzene) and poly(styrene‐divinyl benzene) uniform crosslinked microspheres were prepared by dissolution of the polystyrene template part of the former composite particles; (3) Uniform magnetic poly(divinyl benzene)/Fe and poly(styrene‐divinyl benzene)/Fe composite microspheres were prepared by entrapping Fe(CO)₅ within the porous crosslinked microspheres, by suction of the Fe complex into the dried porous particles, followed by decomposition of the encapsulated Fe(CO)₅ at 200°C in Ar atmosphere; (4) Uniform magnetic air‐stable C/Fe composite microspheres were prepared similarly, apart from changing the decomposition temperature from 200 to 600°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of novel semi‐interpenetrating 2‐hydroxyethyl methacrylate‐g‐chitosan copolymeric microspheres for sustained release of indomethacin

A novel semi‐interpenetrating (semi‐IPN) graft copolymer of 2‐hydroxyethyl methacrylate (HEMA) with chitosan (CS) has been prepared in the form of microspheres, using water‐in‐oil (W/O) emulsion technique. Microspheres were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X‐ray diffractometry (X‐RD) to confirm the crosslinking and polymorphism of indomethacin (IDM). The X‐RD and DSC techniques indicated a molecular‐level dispersion of IDM in the IPN matrix. Scanning electron micrographs (SEM) taken at the cross section of the microspheres have shown rough surfaces around the microspheres. The sustained release characteristics of the matrices for IDM, an anti‐inflammatory drug, were investigated in pH 7.4 media. Particle size and size distribution of the microspheres were studied by laser light diffraction particle size analyzer. The drug was released in a sustained manner for up to 12 h. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

One‐Pot Preparation of Organic–Inorganic Composite Microspheres Comprising Silica Nanoparticles and End‐Functionalized Polymers

Colloidal assemblies of inorganic nanoparticles dispersed in liquid media hold particular promise for the creation of a unique class of functional materials with innovative applications. In the present report, “compound‐eye”‐like core–shell and Janus‐type silica and amino‐terminated 1,2‐polybutadiene (PB‐NH₂) and polystyrene (PS) composite microspheres are successfully prepared by simply mixing an aqueous dispersion of silica particles into a tetrahydrofran (THF) solution of PB‐NH₂, and PB‐NH₂ and PS blends, followed by evaporation of the THF. This co‐precipitation process provides a new approach for producing organic–inorganic composite particles without the need for surface modification of the inorganic nanoparticles.

     

Emulsifier‐free emulsion copolymerization of styrene with methacrylic acid

The study on batch emulsifier‐free emulsion copolymerization of styrene with methacrylic acid was conducted. The copolymerization process was followed by gravimetry, infrared, and transmission electron microscopy. The copolymerization mechanism differs from that of styrene with acrylic acid. The effect of solid content on particle size was examined, and it was found that the particle size was increased as the solid content was increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1747–1751, 2003     

Preparation of inner asymmetric composite microspheres

Novel inner asymmetric composite microspheres were prepared by encapsulating surface‐modified magnetic particles via mini‐emulsion polymerization. Most of the surface‐modified magnetic particles encapsulated into the polymer matrix aggregate in one side of each microsphere, while only a few particles randomly disperse in the remaining part. The magnetic content of these novel asymmetric composite microspheres is 46.7% and the saturation magnetization is 23.8 emu g^?1. Copyright © 2012 Society of Chemical Industry     

Preparation and characterization of novel self cross‐linking fluorinated acrylic latex

Self crosslinking fluorinated acrylic latex (SCLFAL) has been successfully prepared via starved seeded semibatch emulsion polymerization of butyl acrylate (BA), methyl methacrylate (MMA), 2‐(perfluoro‐(1,1‐bisisopropyl)‐2‐propenyl)oxyethyl methacrylate (POMA), and N‐methylolacrylamide (NMA). The resultant SCLFAL is characterized by Fourier transform infrared (FTIR) spectrometry and nuclear magnetic resonance (NMR). Influences of the added amount of NMA on the crosslinking degree, contact angle, particle size, and glass transition temperature (T_g) of the film are investigated. Results show that the crosslinking degree, contact angle, and T_g of the film can be improved when the moderate amount of NMA is introduced into the mixed monomers. However, the added amount of NMA has no marked effect on the particle size of SCLFAL. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and evaluation of poly(3‐hydroxybutyrate) microspheres containing bovine serum albumin for controlled release

The utility of the Poly(3‐hydroxybutyrate) (PHB) to encapsulate and control the release of bovine serum albumin (BSA), via microspheres, was investigated. Various preparing parameters, including polymer concentration in oil phase, emulsification concentration in external water phase, volume ratio of inner water phase to oil phase, and volume ratio of primary emulsion to external water phase were altered during the microspheres production. The effects of these changes on the morphological characteristics of the microspheres, size of the microspheres, drug loading, encapsulation efficiency, and drug release rates were examined. The diameter of the microspheres ranged from 6.9 to 20.3 μm and showed different degrees of porous structure depending on the different preparation parameters. The maximum and minimum BSA encapsulation efficiency within the polymeric microspheres were 69.8 and 7.5%, respectively, varying with preparation conditions. The controlled release characteristics of the microspheres for BSA were investigated in pH 7.4 media. The initial BSA burst release from 8.9 to 63.1% followed by constant slow release for 28 days was observed for BSA from BSA‐loaded microspheres and followed the Higuchi matrix model. So, the release behavior of microspheres showed the feasibility of BSA‐loaded microspheres as controlled release devices. Pristine BSA, pristine PHB microspheres, and BSA‐loaded microspheres were analyzed by Fourier transform infrared spectrophotometer, which indicated no interaction between BSA and PHB. Differential scanning calorimetry on BSA‐loaded microspheres indicated a molecular level dispersion of BSA in the microspheres. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of monodisperse fluorescent core–shell polymer microspheres with functional groups in the shell layer by two‐stage distillation–precipitation polymerization

Monodisperse crosslinked core–shell micrometer‐sized microspheres bearing a brightly blue fluorescent dye, carbazole, and containing various functional groups in the shell layers were prepared by a two‐stage distillation–precipitation polymerization in acetonitrile in the absence of any stabilizer. Commercial divinylbenzene (DVB), containing 80 vol.% of DVB, was polymerized by distillation–precipitation in acetonitrile without any stabilizer using 2,2′‐azobisisobutyronitrile (AIBN) as the initiator for the first stage of polymerization which resulted in monodisperse polyDVB microspheres used as the core. Several functional monomers, including 2‐hydroxyethyl methacrylate and acrylonitrile together with N‐vinylcarbazole blue fluorescent comonomer, were incorporated into the shell layers with AIBN as initiator during the second stage of polymerization. The resultant core–shell polymer microspheres were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, UV‐visible spectroscopy and fluorescence spectroscopy. Copyright © 2006 Society of Chemical Industry     

Preparation,characterization, and drug‐release properties of poly(N‐isopropylacrylamide) microspheres having poly(itaconic acid) graft chains

An inverse suspension polymerization method for the preparation of thermoresponsive hydrogel microspheres based on N‐isopropylacrylamide was described in this article. The polymerization reaction was carried out at 200 rpm stirring rate and the microspheres obtained were in the size range of 71–500 μm in the swollen states. The particles were sieved by using ASTM sieves. The selected fraction (180–250 μm) of poly(N‐isopropylacrylamide) (PNIPAAm) microspheres was used for radiation‐induced modification with itaconic acid (IA) to obtain PNIPAAm/poly(itaconic acid) graft copolymer. Viagra and lidocaine were used as model drugs for the investigation of controlled‐release behavior of the microspheres. Incorporation of IA graft chains onto microspheres enhanced significantly the uptake of both drugs and further controlled release at specific pH values. The release studies showed that some of the basic parameters affecting the drug‐loading and ‐release behavior of the microspheres were pH, temperature, particle size, and chemical nature of drug. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1115–1124, 2005     

Preparation and characterization core‐shell particles and application for E‐Ink

the core‐shell particles were prepared by dispersion copolymerization. The core‐shell particles were characterized with Fourier‐transform infrared spectroscopy, Transmission electron microscope and scanning electron microscope. The dispersion stability and electrophoretic performance of core‐shell particles were studied in the mixed medium of tetrachloroethylene and cyclohexance. Microcapsules containing the core‐shell particles were prepared by coacervation. Results showed that the core‐shell particles had good dispersion stability and it had no electric response, which could be used as grounding particles for E‐Ink. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1195–1199, 2007     

Preparation and characterization of epoxy resin modified with alkoxysilane‐ functionalized poly(urethane‐imide) by the sol–gel process

The sol–gel process has been frequently employed for preparation of high performance silica/polymer composites. In this paper, novel sol–gel precursor triethoxysilane‐terminated poly(urethane‐imide) (PUI‐Si), combining the advantages of polyurethane (PU) and polyimide, was synthesized and characterized. Then PUI‐Si was incorporated into the epoxy resin matrix to prepare a series of EP/PUI‐Si organic‐inorganic hybrids through an in situ sol–gel process and crosslinking reactions. The thermal stability of EP/PUI‐Si hybrids was evaluated by thermogravimetric analysis and the results show that the PUI‐Si could significantly improve the thermal properties of epoxy resin. The initial decomposition temperature of composites with 50 wt% PUI‐Si reached 347.1 °C, 157.3 °C higher than that of neat epoxy resin. Furthermore, the tensile strength and breaking elongation can also be clearly improved by adding a suitable amount of PUI‐Si. Similarly, the water contact angle increased to 97.4° with 70 wt% PUI‐Si, showing a hydrophobic surface. The morphology was investigated by transmission electron microscopy and the results reveal that the silica particles are smaller than 20 nm and have a strong interaction with the epoxy resin matrix, resulting in the above‐mentioned high performance properties. Copyright © 2011 Society of Chemical Industry     

Full factorial design‐of‐experiments for preparation of crosslinked dextran microspheres

This work describes full factorial design‐of‐experiment methodology for exploration of effective parameters on physical properties of dextran microspheres prepared via an inverse emulsion (W/O) technique. Microspheres were prepared by chemical crosslinking of dextran dissolved in internal phase of the emulsion using epichlorohydrin. The input parameters were dextran concentration in the aqueous phase, crosslinking ratio, and concentrations of sodium hydroxide and span 80 as the reaction catalyst and surfactant, respectively. Chemical structure of the resulting microspheres was analyzed spectroscopically using Fourier‐transform infrared technique. Final decomposition temperature, mean particle size and its distribution and equilibrium swelling ratio were selected as output responses. Microspheres with smooth surface were obtained according to scanning electron micrographs. It was found that an increase in dextran concentration in the aqueous internal phase increases mean particle diameter of the resulting microspheres, significantly. Moreover, water uptake capacity for the microspheres was dependent on both the dextran concentration and crosslinking ratio. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and characterization of acrylic latex/nano‐SiO2 composites

Acrylic/nano‐silica composite latexes were prepared by blending via high shear stirring (SS) or ball milling (BM) and in situ polymerization (IS). For comparison, composites filled with micro‐silica were also prepared. The mechanical and optical properties of the polymers formed by the composite latex filled with nano‐ or micro‐silica were investigated using an Instron testing machine, by dynamic mechanical analysis, ultraviolet–visible spectrophotometry and transmission electron micrography. The results showed that SS and BM methods could obtain better nanocomposite latex and polymers than the IS method, characterized by better dispersion of nanoparticles, higher tensile strength and T_g for SS and BM than for IS. The increase in absorbance and reduction in transmittance of UV (290–400 nm wavelength) were observed as nano‐silica content increased, whereas the UV absorbance or transmittance basically were kept unchanged for the composites filled with micro‐silica. © 2002 Society of Chemical Industry     

Preparation and characterization of poly‐DL‐lactide–poly(ethylene glycol) microspheres containing λDNA

Polylactide (PLA) and a block copolymer, poly‐DL ‐lactide–poly(ethylene glycol) (PELA) were synthesized by bulk ring‐opening polymerization initiated by stannous chloride. A linear DNA molecule, λDNA, was used as the model DNA. PLA, PELA, λDNA‐loaded PLA and PELA microspheres were prepared by the solvent‐extraction method based on the formation of multiple w₁/o/w₂ emulsion. The particle‐size distribution, surface morphology, and DNA loading characterized the microspheres. The mean diameter of λDNA‐loaded PELA microspheres was proved to be 3.5 μm. The integrity of the λDNA molecules, after preparing the microspheres, was determined by agarose gel electrophoresis. The result suggested that most of the λDNA molecules could retain their integrity after being encapsulated by PELA. The PELA microspheres could also prevent λDNA from being degraded by DNase. The in vitro degradation and release of PLA, PELA, and λDNA‐loaded PELA microspheres were carried out in a pH 7.4 buffer solution at 37°C. Quantitatively, evaluating the molecular weight reduction, the mass loss, the particle‐size changes, and the particle‐size distribution changes also monitored the degree of degradation. The release profile was assessed by measurement of the amount of λDNA present in the release medium at determined intervals. The degradation profiles of the PELA microspheres were quite different from those of the PLA microspheres. The introduction of the hydrophilic poly(ethylene glycol) domain in PLA and the presence of λDNA within the microspheres exhibit the apparent influence on the degradation and release profiles. A biphasic release profile was proved, that is, an initial burst release during the first days, then a gradual release. It was demonstrated that the PELA microspheres could be used potentially as a controlled release‐delivery system for λDNA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2557–2566, 2002     

硅烷化胺基磁性微球的合成与表征

采用溶液聚合法制备具有良好悬浮性和磁响应性的硅烷化胺基磁珠,对胺基磁性微球的形貌、结构、悬浮稳定性和磁响应性进行表征.研究结果显示,硅烷化胺基磁性微球的平均粒径为15nm,粒径分布比较均匀,近似为球形的壳核结构,核为磁性基质,壳为3-胺基丙基三乙氧基硅烷;将硅烷化胺基磁珠用于悬浮稳定性研究表明,磁微球具有较好的悬浮稳定...