Synthesis of hollow polymer microspheres with movable polyelectrolyte core and functional groups on the shell-layer

Hollow polymer microspheres with movable quaternary pyridinium polyelectrolyte (PE) cores and various functional groups on the shell-layers, such as hydroxyl, amide, and carboxyl, were prepared by the selectively etching of mid-silica layer with hydrofluoric acid from the corresponding poly(ethyleneglycol dimethacrylate-co-methacrylic acid)@poly(ethyleneglycol dimethacrylate- co-4-vinylpyridinium benzylchloride)/silica/polymer (P(EGDMA-co-MAA) @P(EGDMA-co-VPyBzCl)/SiO₂/polymer) tetra-layer microspheres. The tetra-layer hybrid microspheres were synthesized by a multi-stage reaction process, which included the combination of distillation precipitation polymerization for the formation of polymer-layers and the hydrolysis of tetraethyl orthosilicate (TEOS) via a modified Stöber sol-gel procedure to afford silica layer. The efficient electrostatic interaction between the cationic pyridinium species on the surface of P(EGDMA-co-MAA)@P(EGDMA-co-VPyBzCl) cores and the negative charges on the silica species was essential to get monodisperse tri-layer P(EGDMA-co-MAA)@P(EGDMA-co-VPyBzCl)/SiO₂ microspheres during the hydrolysis of TEOS. The functional polymer shell was encapsulated over 3-(methacryloxy)propyl trimethacrylate (MPS) modified tri-layer polymer/silica seeds by distillation precipitation copolymerizations of N,N′-methylenebisacrylamide (MBAAm) crosslinker and comonomers with different functional groups, including N-isopropylacrylamide (NIPAAm), 2-hydroxyethylmethacrylate (HEMA) and methacrylic acid (MAA), with 2,2′-azobisisobutyronitrile (AIBN) as an initiator in neat acetonitrile. The morphology and structure of the tetra-layer hybrid microspheres and the corresponding hollow microspheres with movable PE core and functional polymer shell-layer were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), ξ-potential, and dynamic light scattering (DLS).     

Poly(acrylonitrile‐co‐vinyl acetate)/Ag composite microspheres: One‐pot fabrication and application as catalyst

Waxberry‐like poly(acrylonitrile‐co‐vinyl acetate)/Ag composite microspheres have been prepared simply and directly via a one‐step self‐assembly approach. The morphology, formation, and catalytic activity of the as‐prepared composite microspheres are further investigated. The difference in the solubility among different segments of poly(acrylonitrile‐co‐vinyl acetate) is the basis of the formation of poly(acrylonitrile‐co‐vinyl acetate) microspheres, while the ? CN groups on the surface of poly(acrylonitrile‐co‐vinyl acetate) microspheres play an important role in the growth process from poly(acrylonitrile‐co‐vinyl acetate) microsphere to poly(acrylonitrile‐co‐vinyl acetate)/Ag composite microsphere. It is found that bulk quantities of composite microspheres with high density of Ag nanoparticles on the surface can be obtained readily by controlling the concentration of AgNO₃. The as‐prepared composite microsphere exhibits excellent catalytic activity on reduction of p‐nitrophenol. This study may shed some light on the self‐assembly of other metal/polymer composite microspheres. POLYM. ENG. SCI., 50:1767–1772, 2010. © 2010 Society of Plastics Engineers     

Preparation of magnetite and tumor dual-targeting hollow polymer microspheres with pH-sensitivity for anticancer drug-carriers

The hollow poly(N,N′-methylenebisacrylamide-co-methacrylic acid) (P(MBAAm-co-MAA)) microspheres were prepared by the selective removal of poly(methacrylic acid) (PMAA) core from the corresponding PMAA/P(MBAAm-co-MAA) core-shell microspheres, which were synthesized via a two-stage distillation precipitation polymerization. The magnetic Fe₃O₄ nanoparticles onto the surface of hollow P(MBAAm-co-MAA) microspheres via partial oxidation of ferrous salt during the chemical deposition in the presence of potassium nitrate as oxidant with the aid of hexamethylene tetramine and the magnetic hollow microspheres were further functionalized with folic acid (FA) via the chemical linkage with amino groups of 3-aminopropyl triethoxysilane (APS)-modified P(MBAAm-co-MAA)@Fe₃O₄ microspheres to afford the magnetite and tumor dual-targeting hollow microspheres. The resultant dual-targeting hollow polymer microspheres with pH-sensitivity were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared-spectrometer (FT-IR), UV-vis absorption spectroscopy, and vibrating sample magnetometer (VSM). Finally, the drug loading capacities of the magnetite and tumor dual-targeting hollow P(MBAAm-co-MAA) microspheres and their releasing dependence on pH values were investigated with doxorubicin hydrochloride (DXR) as an anticancer drug model.     

Preparation of polymer/silica/polymer tri-layer hybrid materials and the corresponding hollow polymer microspheres with movable cores

Tri-layer poly(methacrylic acid-co-ethyleneglycol dimethacrylate)/silica/poly(ethyleneglycol dimethacrylate) (P(MAA-co-EGDMA)/SiO₂/PEGDMA) and P(MAA-co-EGDMA)/SiO₂/polydivinylbenzene hybrid microspheres were prepared by distillation precipitation polymerization of ethyleneglycol dimethacrylate (EGDMA) and divinylbenzene (DVB) in the presence of 3-(methacryloxy)propyl trimethoxysilane (MPS)-modified P(MAA-co-EGDMA)/SiO₂ microspheres as the seeds. The polymerization of EGDMA and DVB was performed in neat acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator to coat the MPS-modified P(MAA-co-EGDMA)/SiO₂ seeds through the capture of EGDMA and DVB oligomer radicals with the aid of vinyl groups on the surface of modified seeds in the absence of any stabilizer or surfactant. Monodisperse P(MAA-co-EGDMA)/SiO₂ core-shell microspheres were synthesized by coating of a layer of silica onto P(MAA-co-EGDMA) microspheres via a sol-gel process, which were further grafted by MPS incorporating the reactive vinyl groups onto the surface to be used as the seeds for the construction of hybrid microspheres with tri-layer structure. Hollow poly(ethyleneglycol dimethacrylate) (PEGDMA) and poly(divinylbenzene) (PDVB) microspheres with movable P(MAA-co-EGDMA) core were subsequently developed after the selective etching of the silica mid-layer from the tri-layer hybrid microspheres in hydrofluoric acid. The morphology and structure of the tri-layer polymer hybrids and the corresponding hollow polymer microspheres with movable P(MAA-co-EGDMA) core were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra and X-ray photoelectron spectroscopy (XPS).     

Synthesis of pH-sensitive hollow polymer microspheres and their application as drug carriers

The pH-sensitive hollow poly(N,N′-methylene bisacrylamide-co-methacrylic acid) (P(MBAAm-co-MAA)) microspheres were prepared by a two-stage distillation precipitation polymerization to afford a core-shell poly(methacrylic acid)/poly(N,N′-methylene bisacrylamide-co-methacrylic acid) (PMAA/(P(MBAAm-co-MAA))) microsphere with subsequent removal of poly(methacrylic acid) (PMAA) core. PMAA/P(MBAAm-co-MAA) core-shell microspheres were synthesized by the second-stage copolymerization of N,N′-methylene bisacrylamide (MBAAm) as crosslinker and the functional methacrylic acid (MAA) comonomer in acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator. The pH-responsive properties of hollow P(MBAAm-co-MAA) microspheres were investigated by dynamic laser scattering (DLS). The loading and controlled-release behavior of the drug for hollow P(MBAAm-co-MAA) microspheres was strongly dependent on the pH values with doxorubicin hydrochloride (DXR) as a model molecule. The core-shell and hollow polymer microspheres were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectra (FT-IR), DLS and elemental analysis.     

Monodispersed thermoresponsive hydrogel microspheres with a volume phase transition driven by hydrogen bonding

We report the synthesis and characterization of monodispersed thermoresponsive hydrogel microspheres with a volume phase transition driven by hydrogen bonding. The prepared microspheres, composed of poly(acrylamide-co-styrene) (poly(AAM-co-St)) cores and poly(acrylamide)/poly(acrylic acid) (PAAM/PAAC) based interpenetrating polymer network (IPN) shells, were featured with high monodispersity and positively thermoresponsive volume phase transition characteristics with tunable swelling kinetics, i.e. the particle swelling was induced by an increase rather than a decrease in temperature. The monodisperse poly(AAM-co-St) seeds were prepared by emulsifier-free emulsion polymerization, the PAAM or poly(acrylamide-co-butyl methacrylate) (poly(AAM-co-BMA)) shells were fabricated on the seeds by free radical polymerization, and the core-shell microspheres with PAAM/PAAC based IPN shells were finished by a method of sequential IPN synthesis. The microsphere size increased with increasing both AAM and BMA dosages. The increase of hydrophilic monomer AAM dosage resulted in a better monodispersity, but the increase of hydrophobic monomer BMA dosage led to a worse monodispersity. With increasing the crosslinker methylenebisacrylamide (MBA) dosage, the mean diameter of the microspheres decreased and the monodispersity became better. An equimolar composition of AAC and AAM in the IPN shells of the microspheres resulted in a more complete shrinkage for the microspheres at temperatures lower than the upper critical solution temperature. Both BMA and MBA additions depressed the swelling ratio of the hydrodynamic diameter of the microspheres.     

Effect of the crosslinking agent on porous networks formation of hema-based copolymers

New copolymers of ethylene glycol dimethacrylate/2-hydroxyethyl methacrylate [poly(EGDMA-co-HEMA)],2,2′,2″-nitrilotriethyl triacrylate/2-hydroxyethyl methacrylate [poly(NTETA-co-HEMA)] and pentaerythritol tetraacrylate/2-hydroxyethyl methacrylate [poly(PETA-co-HEMA)] were obtained by suspension polymerization at 70 or 85 °C, using cyclohexane (Cyc) as porogen. In this work, the influence of the crosslinking agent (di, tri, or tetravinyl monomer) on the morphology of the polymeric networks was investigated. Swelling studies, Fourier Transform Infrared (FTIR) and mercury intrusion porosimetry, demonstrated that when both the vinyl groups number and molecular chain length between double bonds of the crosslinking agent decreased, networks with high porosity and crosslinking degree were generated.     

Synthesis of pH-sensitive hollow polymer microspheres with movable magnetic core

The pH-sensitive hollow poly(N,N′-methylenebisacrylamide-co-methacrylic acid) (P(MBAAm-co-MAA)) microspheres with movable magnetic/silica (Fe₃O₄/SiO₂) cores were prepared by the selective removal of poly(methacrylic acid) (PMAA) layer in ethanol/water from the corresponding Fe₃O₄/SiO₂/PMAA/P(MBAAm-co-MAA) tetra-layer microspheres, which were synthesized by the distillation precipitation copolymerization of N,N′-methylenebisacrylamide (MBAAm) and methacrylic acid (MAA) in the presence of Fe₃O₄/SiO₂/PMAA tri-layer microspheres as seeds in acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as the initiator. The Fe₃O₄/SiO₂/PMAA tri-layer microspheres were afforded by the distillation precipitation polymerization of MAA with 3-(methacryloxy)propyl trimethoxysilane (MPS)-modified Fe₃O₄/SiO₂ core-shell particles as the seeds. The functional multi-layer inorganic/polymer microspheres and the corresponding hollow polymer microspheres with movable magnetic cores were characterized with transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectra, dynamic light scattering (DLS), and vibrating sample magnetometer (VSM).     

Controlled release of doxorubicin from amphiphilic depsipeptide–PDO–PEG-based copolymer nanosized microspheres

Novel biodegradable amphiphilic ABA triblock copolymers, i.e. poly(3(S)-methyl-morpholine-2,5-dione-co-p-dioxanone)-block-poly(ethylene glycol)-block-poly(3(S)-methyl-morpholine-2,5-dione-co-p-dioxanone) [P(MMD-co-PDO)-b-PEG-b-P(MMD-co-PDO)], were successfully prepared by ring-opening polymerization of 3(S)-methyl-morpholine-2,5-dione (MMD) and p-dioxanone (PDO) in the presence of poly(ethylene glycol) 6000 as an initiator. These triblock copolymers were characterized by ¹H NMR, ¹³C NMR, Fourier transform infrared, gel permeation chromatography and differential scanning calorimetry measurements. P(MMD-co-PDO)-b-PEG-b-P(MMD-co-PDO) could self-assemble into stable nanosized microspheres with critical micellar concentrations of 0.41–0.66 μg/mL. The microspheres showed high hydrolytic degradation. In addition, doxorubicin (DOX) was chosen as a model drug and successfully encapsulated into the microspheres by hydrogen-bond interaction and hydrophobic effect. The transmission electron microscopy and dynamic light scattering measurements revealed that these microspheres were ellipsoidal nanoparticles with diameters ranged from 50 to 100 nm. These copolymer microspheres exhibited high loading capacity (LC), encapsulation efficiency (EE) of DOX and sustained drug release behavior in phosphate buffered solution (PBS). Moreover, the release rate of DOX from those microspheres in pH 4.0 PBS was faster than that in pH 7.4 due to pH sensitivity of the polymer–drug systems and the degradation of the matrix polymers. These amphiphilic depsipeptide multiblock copolymers would be potential promising carriers for anti-tumour drug delivery.     

Dependence of morphological changes of polymer particles on hydrophobic/hydrophilic additives

Fairly uniform microspheres of poly(styrene‐co‐methyl methacrylate) were prepared by employing a microporous glass membrane [Shirasu porous glass (SPG)]. The single‐step SPG emulsification, the emulsion composed mainly of monomers, hydrophobic additives, and an oil‐soluble initiator, suspended in the aqueous phase containing a stabilizer and inhibitor, was then transferred to a reactor, and subsequent suspension polymerization followed. The droplets obtained were polymerized at 75°C under a nitrogen atmosphere for 24 h. The uniform poly(styrene‐co‐methyl methacrylate) microspheres with diameters ranging from 7 to 14 μm and a narrow particle‐size distribution with a coefficient of variation close to 10% were prepared by using SPG membrane with a pore size of 1.42 μm. The effects of the crosslinking agent and hydrophobic additives on the particle size, particle‐size distribution, and morphologies were investigated. It was found that the particle size decreased with a narrower size distribution when the additives were changed from long‐chain alkanes to long‐chain alcohols and long‐chain esters, respectively. Various microspheres with different morphologies were obtained, depending on the composition of the oil phase. The spherical poly(styrene‐co‐methyl methacrylate) particles without phase separation were obtained when using an adequate amount of the crosslinking agent and methyl palmitate as an additive. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1013–1028, 2000     

Preparation of poly(divinylbenzene‐co‐N‐isopropylacrylamide) microspheres and their hydrogen‐bonding assembly behavior for raspberry‐like core‐corona polymer composite

Narrowdisperse poly(divinylbenzene‐co‐N‐isopropylacrylamide) (poly(DVB‐co‐NIPAM)) functional microspheres with the diameter in the range of 630 nm and 2.58 μm were prepared by distillation–precipitation polymerization in neat acetonitrile in the absence of any stabilizer. The effect of N‐isopropylacrylamide (NIPAM) ratio in the comonomer feed on the morphology of the resultant polymer particles was investigated in detail with divinylbenzene (DVB) as crosslinker and 2,2′‐azobisisobutyronitrile (AIBN) as initiator. The monodisperse poly(DVB‐co‐NIPAM) microspheres with NIPAM fraction of 20 wt % were selected for the preparation of raspberry‐like core‐corona polymer composite by the hydrogen‐bonding self‐assembly heterocoagulation with poly(ethyleneglycol dimethacrylate‐co‐acrylic acid) [poly(EGDMA‐co‐AA)] nanospheres. Both of the functional poly(DVB‐co‐NIPAM) microspheres and the core‐corona particles were characterized with scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), and elemental analysis (EA). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1350–1357, 2007     

Core-shell nanohydrogel structures as tunable delivery systems

Poly(acrylonitrile-co-N-isopropylacrylamide) (p(AN-co-NIPAM)) core-shell hydrogel nanoparticles were synthesized by microemulsion polymerization and their feasibility as a drug carrier was investigated. Highly monodispersed nanoparticles with desired size range - i.e., 50-150 nm - were prepared by adjusting the reaction conditions. The hydrophobic core of the composite which consists primarily of poly(acrylonitrile), can be easily made highly hydrophilic by converting the nitrile groups to the corresponding amidoxime groups. This provides a level of tunability in the hydrophobicity/hydrophilicity balance of the composite nanoparticle. The thermo-responsive feature of the shell was utilized for the release of a model drug, propranolol (PPL). It is shown that the loading/release capacity of nanoparticles was increased almost two-fold by the amidoximation of the core material.     

Synthesis,characterization, and antimicrobial activity of silver nanoparticles on poly(GMA‐co‐EGDMA) polymer support

Poly(glycidyl methacrylate‐co‐ethylene glycol dimethacrylate) (poly(GMA‐co‐EGDMA) macroporous copolymer decorated with silver nanoparticles was prepared by a modification of poly(GMA‐co‐EGDMA) in the reaction with arginine, and consequent reduction of silver ions with amino groups. The mercury intrusion porosimetry, transmission electron microscopy, X‐ray diffraction, UV–vis reflection spectroscopy, and inductively coupled plasma atomic emission measurements were used to characterize obtained composite. The coordination of silver nanoparticles to the poly(GMA‐co‐EGDMA) copolymer was studied using infrared spectroscopy. Time dependence and concentration dependence of the antimicrobial efficiency of composite were tested against Gram‐negative bacteria Escherichia coli , Gram‐positive bacteria Staphylococcus aureus , and fungus Candida albicans . The composite ensured maximum reduction of both bacteria, while the fungi reduction reached satisfactory 96.8%. Preliminary antimicrobial efficiency measurements using laboratory flow setup indicated potential applicability of composite for wastewater treatment. POLYM. COMPOS., 38:1206–1214, 2017. © 2015 Society of Plastics Engineers     

Initiation of surface graft polymerization by ceric ions on polymer microspheres

The surface graft polymerization of acrylamide on poly(styrene‐co‐acrylonitrile) copolymer microspheres by the initiation of ceric ions was studied. The grafting was verified by IR spectra and X‐ray photoelectron spectroscopy measurements. The resultant microspheres with surface‐grafted polymer chains were employed in the preparation of polymer‐microsphere‐supported palladium composite particles. The composite particles were then studied by transmission electron microscopy and X‐ray diffraction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 936–940, 2003     

Temperature-tunable catalytic property of Pd–M (Ag,Cu) bimetallic nanoparticles stabilized by thermal-sensitive PDEAm-g-PAN/PSt polymeric microspheres

Thermal-sensitive poly(N,N-diethylacrylamide) grafted poly(acrylonitrile/styrene) (PDEAm-g-PAN/PSt) polymeric microspheres were prepared from PDEAm macromonomer, St and AN by dispersion copolymerization. The polymeric microspheres had raspberry-like morphology with large surface area. Palladium–metal (Pd–M) (M: copper, Cu, silver, Ag) bimetallic nanoparticles were stabilized on the surface of the PDEAm-g-PAN/PSt microspheres via the coordinate interaction between amide groups in PDEAm and metal ions with the reduction of the corresponding ions. Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and thermogravimetry analysis (TGA) results confirmed the size and composition of the immobilized Pd–M nanoparticles. The Pd–M bimetallic nanoparticles showed superior catalytic efficiencies for the reduction of 4-nitrophenol (4-NP) than the monometallic nanoparticles. The catalytic activity of the Pd–M bimetallic catalysts could be controlled by the molar ratio of Pd and M ions and composition of Pd–M nanoparticles. Moreover, the catalytic property of the Pd–M nanoparticles could be regulated by temperature and increased with increasing the temperature above lower critical solution temperature (LCST). Furthermore, the Pd–M nanoparticles could be easily recycled and reused to catalyze 4-NP for five times without loss of activity. These bimetallic nanoparticles possess great potential in future practical application in catalytic technology.     

Preparation of poly[dl-lactide-co-glycolide]-based microspheres containing protein by use of amphiphilic diblock copolymers of depsipeptide and lactide having ionic pendant groups as biodegradable surfactants by W/O/W emulsion method

To develop the preparative method for poly(dl-lactide-co-glycolide)-based microspheres containing proteins, we prepared microspheres from mixture of poly(dl-lactide-co-glycolide) and polydepsipeptide-block-poly(dl-lactide) having cationic or anionic pendant groups. Since the latter amphiphilic copolymers consisting of hydrophobic poly(dl-lactide) segment and hydrophilic polydepsipeptide segment with amino or carboxyl groups could be converted to cationic or anionic block copolymers, they could act as biodegradable surfactants on the preparation of poly(dl-lactide-co-glycolide)-based microspheres by water-in-oil-in-water emulsion method. The amphiphilic block copolymers were established to stabilize primary emulsions on the preparation of microspheres by scanning electron microscopy. We investigated the effects of the addition of the block copolymers on the entrapment efficiency of protein, the release behavior of protein from microspheres and the stability of protein.     

Dual thermo-responsive and ion-recognizable monodisperse microspheres

A novel type of dual stimuli-responsive microspheres that simultaneously exhibit ion-recognition property based on the supramolecular host-guest complexation of crown ether receptors (benzo-18-crown-6-acrylamide) (BCAm) with specific ions and thermo-sensitivity based on the phase transition of poly(N-isopropylacrylamide) (PNIPAM) is fabricated in this study. The prepared poly(N-isopropylacrylamide-co-benzo-18-crown-6-acrylamide) (P(NIPAM-co-BCAm)) microspheres are characterized by FT-IR spectroscopy, UV-vis absorption spectroscopy, scanning electron microscopy (SEM), and dynamic light scattering (DLS). SEM images and DLS data show that the synthesized microspheres exhibit nearly perfect spherical shape and high monodispersity. Moreover, according to the DLS results, P(NIPAM-co-BCAm) microspheres exhibit satisfactory thermo-responsive behavior and ion-recognition property. In K⁺ solutions, due to the formation of crown ether/K⁺ complexes, the LCST of P(NIPAM-co-BCAm) microspheres shifts to a higher temperature and the colloidal stability is increased. The P(NIPAM-co-BCAm) microspheres undergo a volume change from shrunken state to swollen network isothermally at a certain temperature by the addition of metal ions. Due to dual thermo-responsive and ion-recognition behaviors, this kind of microspheres would serve as promising candidates for sensors, controlled drug delivery systems and possibly new biomaterials.     

Crosslinkable functional moiety for the formation of highly crosslinked stable microspheres in the precipitation polymerization

The highly crosslinked stable spherical microspheres were successfully synthesized using styrene and three crosslinking agents having different number of crosslinkable functional moiety in comonomer using the precipitation polymerization. The crosslinking agents are ethylene glycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA) and pentaerythritol tetraacrylate (PETRA). The maximum and minimum concentrations for forming the stable spherical particles were ranging at 20-90 mol% for EGDMA, 15-80 mol% for TMPTMA, and 5-40 mol% for PETRA, respectively. The number-average diameter of stable poly(S-co-EGDMA), poly(S-co-TMPTMA), and poly(S-co-PETRA) particles varied 4.1-3.06, 3.94-3.03 and 2.77-1.66 μm, respectively. Since the prepared microspheres are highly crosslinked, no glass transition temperature was observed. The TGA onset point of the thermal degradation temperature increased with the concentration of crosslinking agent and the number of crosslinkable functional moiety, which is EGDMA < TMPTMA < PETRA. As a result, the minimum and maximum concentrations for the formation of stable spherical particles of poly(S-co-EGDMA), poly(S-co-TMPTMA), and poly(S-co-PETRA), the particle size and its distribution, CV, yield and the TGA onset point are significantly affected by the number of the crosslinkable functional moiety. Thus, the number of the crosslinkable functional moiety and the different reactivity as well as the different copolymerization parameters of styrene with (meth)acrylates would influence the composition as well as the rate of formation of stable microspheres.     

Monodisperse magnetic composite poly(glycidyl methacrylate)/La0.75Sr0.25MnO3 microspheres by the dispersion polymerization

Monodisperse magnetic poly(glycidyl methacrylate) microspheres were prepared by dispersion polymerization of glycidyl methacrylate in cyclohexane in the presence of La_0.75Sr_0.25MnO₃ nanoparticles, surface of which was modified with penta(propylene glycol) methacrylate phosphate (PPGMAP). However, only agglomerates were formed by the dispersion polymerization in toluene. Sterical stabilizer was poly(styrene-block-hydrogenated butadiene-block-styrene) and initiators investigated were 2,2′-azobisisobutyronitrile (AIBN) and 4,4′-azobis(4-cyanovaleric acid) (ACVA). Effects of initiators and other reaction conditions on properties of the composite microspheres were evaluated. The phase composition of the magnetic polymer composite microspheres and the size of magnetic cores were determined by X-ray powder diffraction. The characterization was completed by magnetization measurements, atomic absorption spectroscopy, TEM, SEM and ATR FTIR spectroscopy.     

Preparation of core-shell emulsion polymer and optimization of shell composition with respect to opacity of paint film

A series of core-shell latexes comprising a poly(n-butyl acrylate-co-methyl methacrylate-co-methacrylic acid) (PBA/MMA/MAA) core and a poly(styrene-co-acrylonitrile) (PS/AN), poly(butyl acrylate-co-methyl methacrylate) (PBA/MMA) shell were prepared at different shell composition ratios. These core-shell binders were used for preparation of decorative coatings. The latexes were synthesized by a semi-continuous sequential emulsion polymerization and characterized by using transmission electron microscopy (TEM), particle size analyser, viscometry and opacity of paint film. The core-shell emulsion with styrene/acrylonitrile ratio 60/40 as shell composition shows the best optical properties.