Divinylbenzene Content Research Articles

Effects of cosolvent on formation and morphology of microspheres in precipitation polymerization of divinylbenzene in supercritical carbon dioxide

Abstract Precipitation polymerizations of divinylbenzene (DVB) in pure supercritical carbon dioxide, and parallel runs with presence of a cosolvent were carried out. The results showed that use of acetone as the cosolvent contributed greatly to the formation of the monodisperse microspheres. PDVB microspheres, with obviously higher uniformity than reported up to date, were achieved using 6–7 mL of acetone in a reactor of 50 mL with DVB concentration of 0.4 mol/L under 16 MPa, a much lower pressure than previously reported without use of cosolvent.

Correlations for prediction of specific surface area and bulk and apparent densities of porous styrene‐divinylbenzene copolymers

AbstractMacroporous styrene‐divinylbenzene copolymers with different degree of crosslinking were prepared by suspension polymerization in presence of different binary mixtures of toluene and heptane, as diluent. Specific surface area, bulk and apparent densities, and pore volume of the resulting beads were determined experimentally. Applying the least square method to the experimental data, correlations for prediction of these properties were obtained. Effects of divinylbenzene concentration, diluent to comonomer volume ratio, and composition of the diluent mixture were considered in developing the aforementioned correlations. The influence of the reaction recipe on porous structure of the samples was also studied using scanning electron microscope (SEM). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Formation of hyperbranched polymers in atom transfer radical copolymerization of MMA and DVB

Hyperbranched poly(methyl methacrylate)s (HPMMAs) have been successfully prepared by atom transfer radical copolymerization of MMA and divinylbenzene (DVB). Kinetic study shows complete consumption of the initiator in 0.5 h, and relatively low polymerization rate when DVB content in the feed was high. By analyzing MALDI-TOF spectra of the resulting copolymers, the linear A n B* (n = 0, 1, 2, 3) oligomers were formed in 0.5 h of polymerization, and then the oligomers reacted each other to form dimers, further reactions produced HPMMA. The SEC and NMR spectroscopies were used to trace the polymerization, and the results demonstrate that small amount of the branching reactions occur in the initial polymerization, and the branched polymers are significantly generated past a certain conversion depending upon the feed ratios. Raising the content of DVB in the monomer mixture can increase the pendent vinyl groups of the linear oligo-inimers, leading to gelation at low MMA conversion.

Preparation of polydivinylbenzene microspheres in supercritical carbon dioxide using acetone as cosolvent

Monodisperse polydivinylbenzene (PDVB) microspheres with clean surface were prepared by precipitation polymerization without stabilizer in supercritical carbon dioxide using acetone as cosolvent. Effects of the cosolvent, reaction time and pressure, and monomer concentration on the polymerization were studied. It was found that the conversions in all polymerization systems were above 95%. Examination by scanning electron microscopy showed that reaction pressure, divinylbenzene concentration, and level of the cosolvent had pronounced effects on the morphology of the microspheres. When 6 ∼ 7 ml of acetone was used in a reactor of 50 ml, monodisperse PDVB microspheres of around 2.1 μm in diameter were obtained. Thermal gravimetrical analysis showed the products were of good thermostability up to about 400 °C.

Radiolytic preparation of poly(styrene sulfonic acid) – grafted poly(tetrafluoroethylene- co-perfluorovinyl vinyl ether) membranes with highly cross-linked networks

In this study, various amounts of a divinylbenzene (DVB) cross-linking agent (5∼30%) were introduced during a simultaneous irradiation grafting of styrene onto a PFA film of a 25 μm thickness in order to prepare a series of poly(styrene sulfonic acid)-grafted poly(tetrafluoroethylene- co-perfluorovinyl vinyl ether) (PFA) membranes with various degrees of cross-linking and grafting (29∼74%). The effects of the DVB cross-linking agent on the properties of the prepared membranes, such as water uptake, proton conductivity, methanol permeability, and chemical stability, were also investigated in this study. The results indicated that the ion exchange capacity (IEC) slightly decreased with increasing DVB content, whereas the water uptake, proton conductivity, and methanol permeability of the membrane greatly decreased. The chemical stability of the prepared membranes was found to be significantly improved with increasing DVB content. The results indicated that the cross-linked network membranes are promising for application in a direct methanol fuel cell.

Preparation of a hyperbranched polycarbosilane precursor to SiC ceramics following an efficient room-temperature cross-linking process

Room-temperature cross-linking of a hyperbranched polycarbosilane (HBPCS) with divinylbenzene (DVB) in the presence of the cyclohexanone peroxide–cobaltous naphthenate (CHP–CN) initiator system was studied. According to the Fourier transform infrared spectroscopy (FT-IR) and 1H nuclear magnetic resonance (1H NMR) results, the cross-linking reaction occurred via the vinyl polymerization. The GPC analysis confirmed the molecular weight of the cross-linked HBPCS significantly increased. Thermal behaviors of cross-linked HBPCS and original HBPCS were investigated by thermal gravimetric analysis-differential thermal analysis (TGA–DTA). The TGA results indicated that the ceramic yield of HBPCS remarkably increased by the cross-linking treatment. For the HBPCS/10 wt% DVB system, the maximum of reaction degree of HBPCS was obtained, which might be responsible for the highest ceramic yield of 70.1 wt% at 1000 °C. However, the ceramic yield of the non-crosslinked HBPCS was only 45 wt% at 1000 °C. The evolution of crystal structure of SiC as a function of pyrolysis temperature was traced by means of X-ray diffraction (XRD) and FT-IR. With the pyrolysis temperature increasing, the β-SiC peaks became sharper and the grain size also grew larger. As the DVB content increased, the intensity of β-SiC peaks significantly reduced, indicating smaller β-SiC grain size.

Precipitation polymerization in acetonitrile and 1-propanol mixture: synthesis of monodisperse poly(styrene-co -divinylbenzene) microspheres with clean and smooth surface

Precipitation polymerization of styrene (St)–divinylbenzene (DVB) has been carried out using acetonitrile/1-propanol mixture as the reaction media and 2,2′-azobisisobutyronitrile (AIBN) as initiator. Monodisperse micron-sized poly(St-co-DVB) microspheres with clean and smooth surface were synthesized in the absence of any stabilizing agent such as surfactants or steric stabilizers. The effects of various polymerization parameters such as 1-propanol fraction in the reaction media, initiator and total monomer concentration, DVB content, polymerization time and polymerization temperature on the morphology, particle size and size distribution were investigated. It was found that smoothly shaped stable particles were obtained when less than 70 vol% of 1-propanol was used in the media. The particle size increased with the AIBN concentration, whereas the change of uniformity was less obvious. Monodisperse microspheres were obtained when the total monomers loading ranged from 0.5 to 3 vol%. The particle diameter ranged from 2.73 to 1.87 µm with an increasing DVB content and the uniformity was enhanced. In addition, the yield of microspheres increased with the increasing total monomer, initiator, and DVB concentration and polymerization time. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis of a poly(vinylcatechol-co-divinylbenzene) resin and accessibility to catechol units

Poly(vinylcatechol-co-divinylbenzene) resins have been prepared by suspension copolymerization of 3,4-dimethoxystyrene (DMS) with divinylbenzene (DVB) using toluene as the porogen and followed by deprotection of the catechol functions. The ratio of DMS versus DVB was modified and led to a maximum catechol content (determined by elemental analysis) varying from 0.82 to 3.16mmolg−1. Large surface areas were found for copolymers prepared with a divinylbenzene content larger than 35% v/v: from 464 to 658m2g−1. Accessibility (determined by back titration of the hydroxyl groups) was improved by prior contact with ethanol but remained inferior to 20%. This can be the result of the morphology of the resin beads and of the bottle-shape form of the pores, or/and of the embedding of the catechol units inside the polymer network. The sorption capacities were determined for Cu(II) and Cd(II) and reached 101.5 and 81.0μmolg−1 for copper and cadmium, respectively. Moreover, a significant variation of coloration has been observed upon complexation of copper by the resins.

Synthesis of Structurally Stable Colloidal Composites as Magnetically Recyclable Acid Catalysts

In this study, we provide a simple and reproducible method for the preparation of highly active and recyclable colloidal acid catalysts. First, 16-heptadecenoic acid-functionalized magnetite nanoparticles were encapsulated in monodisperse cross-linked polymer spheres. This was achieved by emulsion copolymerization technique in an aqueous phase of styrene and divinylbenzene (DVB). Different ratios of styrene and DVB were used to tune the structural stability and surface morphology of the composites. With increase in DVB content, the surfaces of the colloidal composites become increasingly rougher. The obtained colloids were functionalized with sulfonic acid groups to obtain magnetically recyclable catalysts with H+ contents in the range of 2.2−2.5 mmol g−1 and surface areas of 45−120 m2 g−1. For the condensation reaction of benzaldehyde and ethylene glycol, magnetic acid catalyst prepared only from DVB precursor was found to be active and with high selectivity and long-term stability.

Modifications in the morphology of poly(styrene-co-divinylbenzenes) induced by gamma-ray irradiation

Abstract The possibility of increasing the apparent specific surface area of macroreticular styrenic polymers crosslinked to different extent by gamma-ray irradiation was investigated. In order to overcome the protective action of benzene rings and simultaneously minimize the negative effect of chain scission competing with the desired additional crosslinking, it was necessary to optimize both the irradiation dose and the content of divinylbenzene. The best conditions for the radiation-induced post-crosslinking of polymers were assessed on the basis of the resultant apparent BET surface area. Useful morphological changes both in the dry and swollen state were possible to be generated.

Synthesis of Temperature-Responsive Poly(N-isopropyl acrylamide)/Poly(methyl methacrylate)/Silica Hybrid Capsules from Inverse Pickering Emulsion Polymerization and Their Application in Controlled Drug Release

Poly(N-isopropylacrylamide)/poly(methyl methacrylate)/silica hybrid capsules were prepared from inverse Pickering emulsion polymerization. A N-isopropylacrylamide aqueous solution was emulsified into an oil phase containing methyl methacrylate and divinyl benzene by sonication to obtain a W/O Pickering emulsion using modified silica nanoparticles as stabilizers. After the emulsion was polymerized, the hybrid capsules were obtained. The capsule wall contained two layers--a solid particle monolayer and a polymer layer--and the wall thickness could be controlled by adjusting the methyl methacrylate and divinyl benzene concentrations in the continuous oil phase before polymerization. The as-synthesized capsules exhibited temperature-responsive properties. The controlled release experiments showed that the release rate of a model drug from the hybrid capsules could be controlled by adjusting the wall thickness of the capsule or the temperature of the release medium.

Influence of the matrix porosity on the synthesis and adsorption behavior of dithiocarbamate styrenic resins toward zinc(II) and cadmium(II) ions

AbstractThe dependence of the adsorption behavior toward Zn2+ and Cd2+ on the synthesis conditions of dithiocarbamate styrenic resins was investigated. We synthesized styrene–divinylbenzene copolymers with different kinds of porous structures by varying the divinylbenzene (DVB)‐to‐styrene ratio and the dilution degree of the monomers with n‐heptane. The porous structure of these materials was characterized. The introduction of the dithiocarbamate moiety on the copolymers followed a synthetic pathway based on the nitration reaction, reduction of the nitro group to the amino one, and finally, the addition of the amino group to CS2. All of the synthesis steps were monitored by Fourier transform infrared spectroscopy. Only the addition reaction to CS2 was greatly influenced by the copolymer porosity. The effect of the dilution degree on the reaction extension was more pronounced than the effect of the DVB content. The more porous materials with higher dithiocarbamate contents adsorbed a higher amount of ions in a faster way, with Zn2+ being preferable over Cd2+ ions. The difference between the Zn2+ and Cd2+ adsorption rates was enhanced with the copolymer porosity, and also enhanced was the difference between the amounts of ions adsorbed by the copolymer; this suggested that the selectivity toward these ions could be controlled by the copolymer porous structure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Simultaneous Estimation of the Binding Constant of Saccharide to Sodium Ion and the Swelling Pressure of Cation-exchange Resin

The apparent distribution coefficients, Kapp, of some mono-, di- and trisaccharides onto cation-exchange resins in the sodium-ion form and having the divinylbenzene (DVB) contents of 4, 6 and 8% were measured at 25°C. A method for simultaneously estimating the swelling pressures of the resins and the binding constants, B, of the saccharides to the sodium ion was proposed. By applying the method to the Kapp values of mono- and disaccharides, the swelling pressures of the resins having the DVB contents of 4, 6 and 8% were estimated to be 18.9, 30.8 and 37.8 MPa, respectively, and the B values of the mono- and disaccharides were also estimated simultaneously. The B values of the trisaccharides were calculated using the estimated swelling pressures. The B values ranged from 0.24 to 2.2 L/mol. The tri-, di- and monosaccharides had higher B values in this order. There was a tendency that the solute, which can form a tridentate complex with the sodium ion, contains high numbers of axial-equatorial and equatorial-equatorial complexing hydroxyl groups.

Synthesis of butyl acrylate grafted polypropylene fibre and its applications on oil-adsorption in floating water

AbstractPolypropylene oil-absorption fibre (PP-g-BA) was prepared by radiationinduced graft polymerization of butyl acrylate (BA) onto polypropylene (PP) using divinylbenzene (DVB) as cross-linking agent. The original and grafted PP fibres were characterized by Fourier transform infrared (FT-IR) spectrometer and Scanning Electron Microscopy (SEM), and the result indicated that butyl acrylate was successfully grafted onto PP fibre. The factors that influenced the grafting degree of PP were discussed, such as the concentration of monomer and crosslinking agent. When the concentration of DVB was 2% and the concentration of BA was 10%, the maximum grafting degree reached 20.53%. The oil absorption properties of PP and PP-g-BA fibre were investigated and the results showed that the maximum adsorption capacity of PP-g-BA reached 19.74 g/g for toluene and 18.8 g/g for kerosene. Simulating absorption in the oil floating on the surface of water showed that the oil could be absorbed quickly and completely in three minutes. PP-g-BA exhibited quicker adsorption rate and higher adsorption capacity than PP fibre did.

Synthesis of monodisperse poly(styrene-co-divinyl benzene) microspheres by precipitation polymerization in acetonitrile and n-butanol mixture

AbstractNarrow disperse poly(styrene-co-divinylbenzene) microspheres were prepared by precipitation polymerization using acetonitrile/n-butanol mixture as the reaction medium and 2,2’-azobis(2-methylpropionitrile) (AIBN) as initiator. The resulting particles have smooth surfaces due to the absence of any additional stabilizer. Effects of the reaction parameters such as n-butanol fraction in the reaction medium, monomer and initiator concentration, and divinylbenzene content were investigated. It was found that the particle size increased with an increasing concentration of monomer and initiator, while the uniformity was kept constant. The number-average particle diameter ranged from 2.36 to 1.63 μm and decreased with an increasing divinylbenzene concentration. In addition, the uniformity was enhanced as the concentration of divinylbenzene increased. On the basis of the DSC and TGA data, the microspheres prepared by the precipitation polymerization possessed a highly crosslinked structure and the thermal stability improved with the DVB concentration.

Highly crosslinked micron‐sized, monodispersed polystyrene particles by semicontinuous dispersion polymerization. II. Semicontinuous, delayed addition and seeded semicontinuous processes

AbstractA highly crosslinked, monodispersed polystyrene (PS) particle was prepared by the seeded semicontinuous dispersion polymerization using ready‐made monodispersed PS seed particles. The effects of Styrene (in 2nd stage)/Styrene (in PS seed) ratio, addition point and feeding time of divinylbenzene (DVB), concentration of DVB and polymerization temperature on the particle size, size distribution and morphology of the resulting particles were investigated. Monodispersed PS particles with 15 wt % of the DVB were prepared at 1/1 in St/St ratio, In comparison, highly crosslinked monodispersed and smooth‐surfaced PS particles containing up to 70 wt % of the DVB were effectively prepared at 0/1. 5% weight loss of the PS particles determined by TGA occurred from 353.3 to 389.6°C and the degree of swellability in toluene decreased from 113 to 101% as the DVB concentration increased from 10 to 70 wt %, implying increased thermal stability and solvent resistance due to the increase of the crosslink density. This study demonstrates that the seeded semicontinuous process, primarily with the starved condition at the second stage, is an efficient way to obtain highly crosslinked, monodispersed PS particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Preparation and characterization of molecularly imprinted polymers for the selective separation of 2,4-dichlorophenoxyacetic acid

As a method of preparing ligand-selective cavities in a synthetic polymer matrix, molecular imprinting technique has been attracting significant interest from a large number of areas in chemistry and analytical sciences. In this study, molecularly imprinted polymers (MIPs) were prepared with styrene, 4-vinylpyridine (4-VPy), and divinylbenzene (DVB) for the separation of hazardous 2,4-dichlorophenoxyacetic acid (2,4-D), and the selectivity of MIPs as adsorbed 2,4-D and structurally similar materials was evaluated. The template was removed through the swelling process of toluene/ethanol, and the removal ratio was about 95–99%, respectively. MIPs synthesized in this study had good adsorption selectivity in the presence of other materials, although there was a difference of adsorption quantities (uptake) in the functional monomer (4-VPy contents) and the cross-linker (DVB contents). The results exhibit that the selectivity of MIPs was improved significantly by controlling the cross-linker. We expect that molecular imprinting technique will serve as a novel method for selective separation of specific materials in various fields, especially in the fields of environment and pharmaceutics.

Rheological Behavior of Acid-Swellable Cationic Copolymer Latexes

2-Vinylpyridine (2VP) was copolymerized with four different cross-linker densities ranging from 0.05 to 0.31 wt % divinylbenzene (DVB) via aqueous emulsion polymerization to produce a series of submicrometer-sized, lightly cross-linked P2VP latexes. Protonation of the 2VP residues leads to a latex-to-microgel transition due to interchain electrostatic repulsion, as confirmed by dynamic light scattering. The DVB content of these pH-responsive copolymer particles strongly affects their rheological behavior. The particle size and viscosity of the swollen cationic microgels exhibit a maximum at approximately 0.11 wt % DVB. Static light scattering results confirm this density as the minimum amount of DVB required to ensure that all P2VP chains are cross-linked (i.e. that there is no soluble fraction), thus allowing optimal swelling of the microgels. Viscosity studies shows that the solution viscosity of a P2VP microgel at low pH follows two models, depending on its concentration. For volume fractions below 0.30, the P2VP microgels behave as hard spheres, as predicted by the Batchelor equation. For more concentrated P2VP microgels (volume fractions above 0.30), the rheological behavior can be predicted using the Krieger-Dougherty model for strong particle-particle interactions; thus, this semiempirical approach provides a useful description of the aqueous solution behavior of microgel.

A novel non-catalytic approach for fabrication of bamboo-like carbon nanotubes

Bamboo-like carbon nanotubes (BCNTs) were synthesized via pyrolysis of PMMA@PDVB core–shell spheres in argon atmosphere at 900 °C without any metallic catalyst. TEM and HRTEM observations show the carbon nanotubes with bamboo-like structure. The content of polymerized divinylbenzene (PDVB) in the core–shell nanostructures plays a very important role for the formation of BCNTs. The possible growth mechanism for BCNTs is proposed.

Influence of Network Structure on Dynamic Mechanical Properties of Cross-Linked Polystyrene / Glass Fiber Composites

The cross-linked polystyrene prepolymer was synthesized with divinylbenzene (DVB) as crosslinker via free-radical crosslinking copolymerization (FCC) and used as the matrix materials for E-glass fiber reinforced composites. The surface modification was performed by treatment of E-glass fiber with γ-methacryloylpropyl trimethoxysilane (MPS) solution. Fourier transform infrared spectroscopy (FTIR) was used to identify the functional groups on the surface modified glass fibers. Dynamic mechanical thermal analysis (DMTA) of these composites revealed that the dynamic storage modulus (E′) was gradually enhanced with the increasing content of DVB (0~3.0 wt %) whereas the damping parameter (tanδ) peaks are lower and broader, indicating better load bearing capacity. Moreover, the Tg was shifted to higher temperature corresponding to the increasing of crosslinking density. Morphology of fracture surfaces for these composites showed different fiber-matrix interfacial adhesion which was mainly attributed to the variation of crosslinking network structure in the interface.