Amount Of Styrene Research Articles

Synthesis of Raspberry-Like Poly(styrene–glycidyl methacrylate) Particles via a One-Step Soap-Free Emulsion Polymerization Process Accompanied by Phase Separation

We herein report a facile method to prepare raspberry-like poly(styrene-glycidyl methacrylate) [P(S-GMA)] particles with controllable structure via a one-step soap-free emulsion polymerization process accompanied by phase separation. In this method, corona particles with a size of 10-20 nm were produced in situ in the later polymerization stage by the migrating of S-enriched polymers from GMA-enriched core particles. The size of the corona particles and the roughness of the raspberry-like particles can be easily controlled by adjusting the amount of styrene (S), glycidyl methacrylate (GMA), and divinylbenzene (DVB). The structure of raspberry-like P(S-GMA) particles was confirmed by transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. A possible mechanism of the formation of raspberry-like particles was proposed.

Comparative Studies on the Mechanical and Thermo-Mechanical Performance of Flax Fiber Reinforced Polyester and Polyester-Biopolymer Blend Resins

Bio-composites made of biopolymer and natural fibers provide good alternative to traditional fiber reinforced composites made of synthetic fibers and non-biodegradable polymers. In order for biocomposites to attain widespread applications and acceptance, compatibility between natural fibers and biopolymers in terms of good interfacial load transfer should be established which could be obtained through fiber surface treatment. Hence, current investigations were focused on the surface treatment of fiber and study its influence on the adhesion between fiber and polymer matrix. Initially, dew retted flax fibers were treated with alkali by varying concentration keeping temperature and time constant. The fibers were treated with 2.5, 5, and 7% of alkali at room temperature for one hour. 2.5% treated fiber showed comparatively better properties than higher concentration. Hence, for further studies, all flax fibers were treated with 2.5% solution of alkali at different temperatures. In the next phase of study, biocomposites were prepared by immersing fiber mats in resin bath and compression molded using a hot press. Two polymers: Polyester and a polyester-biopolymer blend, ENVIREZ® 1807 were used as matrix. Moisture absorption, mechanical and thermomechanical tests were conducted on the composites. It was determined that treated composites showed reduction in moisture uptake compared to untreated. Alkali treated composites showed an increase in flexural properties as well as storage modulus. The improvement of composites properties is attributed to the chemical treatment. Composites made using ENVIREZ® 1807 which has about 18% of natural polymer blend showed comparable properties with those of polyester resin system with potential to reduce amount of styrene used in fabrication.

Sustainable bio-production of styrene from forest waste

A strain of Penicillium expansum was studied for the production of styrene using forest waste biomass as a feeding substrate. The fungal strain was cultivated on bark of various trees supplemented with yeast extract and the volatiles produced were collected on Tenax TA and analyzed by gas chromatography-mass spectrometry. Fungus cultured on grated soft bark of pine (Pinus sylvestris) stems (GPB) and mature bark of oak (Quercus robur) supplemented with yeast extract produced relatively the highest amounts of styrene. The maximum styrene production rate was 52.5 μg/h, 41 μg/h and 27 μg/h from fungus cultivated on 50 mL liquid media with 10 g GPB or mature bark of oak and potato dextrose broth respectively. These promising results suggest that the fungal strain could be used to produce "green" styrene plastics using renewable forest waste biomass.

Nitroxide-Mediated Polymerization-Induced Self-Assembly of Poly(poly(ethylene oxide) methyl ether methacrylate-co-styrene)-b-poly(n-butyl methacrylate-co-styrene) Amphiphilic Block Copolymers

Well-defined water-soluble brush-type homopolymers and copolymers entirely composed of poly(ethylene)oxide methacrylate (PEOMA) units with PEO side groups of various chain lengths (Mn = 300 and 950 g mol–1) were synthesized by nitroxide-mediated polymerization (NMP) using a low molar mass unimolecular alkoxyamine initiator (so-called BlocBuilder) and N-tert-butyl-N-(1-diethyl phosphono-2,2-dimethyl propyl) nitroxide (SG1) in the presence of a small amount of styrene. The resulting SG1-capped macroalkoxyamines possessed the predicted molar masses based on the monomer/initiator molar ratio and narrow molar mass distributions. They were then employed to initiate the emulsion polymerization of n-butyl methacrylate with a low amount of styrene under mild conditions (85 °C) leading to amphiphilic block copolymers that in situ self-assembled into sterically stabilized particles. Kinetics study confirmed the living character of the polymerization, while SEC analysis indicated the presence of a small fraction of dead chains formed by irreversible homotermination reactions. Spherical latex particles with diameters comprised between 60 and 300 nm were obtained at pH 4.2 when decreasing the macroinitiator concentration from 7.2 to 1.2 mM in agreement with the in situ formation of block copolymers. As expected, only the macroinitiators with long PEO side groups, and whose cloud points were above the reaction temperature, led to stable latex suspensions. A drastic change in particle morphology with the formation of vesicles and anisotropic objects was observed when increasing the suspension pH from 4.2 to 6.7. As the macroalkoxyamine initiator contained only one terminal methacrylic acid unit, such a strong effect of pH on particles morphology was not expected. The observed results were interpreted in terms of a salting out effect induced by the concomitant increase of ionic strength upon neutralization of the alkoxyamine initiator. Hence, particle morphologies could be tuned from spherical to elongated micelles and vesicles by the addition of increasing amounts of sodium chloride at a fixed pH of 4.2, which confirmed the above hypothesis.

分散聚合制备聚苯乙烯微球及影响因素研究

以聚乙烯吡咯烷酮为分散剂，水及无水乙醇为反应介质，偶氮二异丁腈引发剂，采用分散聚合的方法，制备出了一系列亚微米级的PS微球，分析了单体、引发剂、分散剂的用量，反应介质组成和搅拌速度对产物粒径及粒径分布的影响。结果表明，利用分散聚合，初步实现了PS粒径的可控，反应物组成对微球粒径及分布起主要作用，而搅拌速率只对微球粒径有影响，对粒径分布影响不大。 Polystyrene microspheres sized in sub micron were prepared by a dispersion polymerization with PVP as dispersant, H2O and ethanol as reaction medium, AIBN as initiator. The effects of H2O-ethanol ratio, string speed and amount of styrene, AIBN and PVP on particle size and distribution were discussed. Results show that PS spheres size could be preliminarily control. The component of reactant is the main effect of size and distribution, meanwhile, spin rate only effects sphere size.

Surface functionalized polymer particles and thereby generation of PNIPAAM grafted monoliths by shear aggregation and ATRP

Surface functionalization of the materials to achieve functionalities like thermal responsiveness has found increasing interest. In the current study, such a functionalization with poly(N-isopropylacrylamide) (PNIPAAM) polymer has been reported by controlled grafting from the surface of aggregated particles to form macroporous monoliths. The particles were first modified with a thin polymer shell of a functional monomer 2-(2-bromopropionyloxy) ethyl acrylate, BPOEA (or copolymer with styrene), which also contained a terminal atom transfer radical polymerization (ATRP) moiety. Surfactant free emulsion polymerization was carried out to generate polystyrene seed particles as well as the shell around them. Due to the colloidal unstability of BPOEA polymer chains, stable particles were formed only in presence of excess molar amount of styrene (styrene to BPOEA mole ratio of 3:1) or seed particles. Collapse of the BPOEA polymer chains on the seed particles was also enhanced by the addition of salt in the shell forming monomer batch, which did not allow the formation of stable secondary particles. The surface morphology of the particles was affected both by the kinetic collapse of the BPOEA chains on surface of the particles and subsequent polymerization as well as efficient stirring of the contents. The emulsifier free particles could not be gelated by the addition of salt and were destabilized by shear. The resulting aggregates were stable and porous which allowed simultaneous grafting of PNIPAAM polymer from the surface as well as imparted dimensional stability to the structure during the grafting process. It was also required to optimize the extent of grafting as the excess grafting could reduce the porosity of the structure.

Genotoxicity of styrene-7,8-oxide and styrene in Fisher 344 rats: A 4-week inhalation study

The cytogenetic alterations in leukocytes and the increased risk for leukemia, lymphoma, or all lymphohematopoietic cancer observed in workers occupationally exposed to styrene have been associated with its hepatic metabolisation into styrene-7,8-oxide, an epoxide which can induce DNA damages. However, it has been observed that styrene-7,8-oxide was also found in the atmosphere of reinforced plastic industries where large amounts of styrene are used. Since the main route of exposure to these compounds is inhalation, in order to gain new insights regarding their systemic genotoxicity, Fisher 344 male rats were exposed in full-body inhalation chambers, 6h/day, 5 days/week for 4 weeks to styrene-7,8-oxide (25, 50, and 75ppm) or styrene (75, 300, and 1000ppm). Then, the induction of micronuclei in circulating reticulocytes and DNA strand breaks in leukocytes using the comet assay was studied at the end of the 3rd and 20th days of exposure. Our results showed that neither styrene nor styrene-7,8-oxide induced a significant increase of the micronucleus frequency in reticulocytes or DNA strand breaks in white blood cells. However, in the presence of the formamidopyridine DNA glycosylase, an enzyme able to recognize and excise DNA at the level of some oxidized DNA bases, a significant increase of DNA damages was observed at the end of the 3rd day of treatment in leukocytes from rats exposed to styrene but not to styrene-7,8-oxide. This experimental design helped to gather new information regarding the systemic genotoxicity of these two chemicals and may be valuable for the risk assessment associated with an occupational exposure to these molecules.

Oxidation of gaseous styrene by electron beam irradiation

In this research, the absorbed dose, background gases, relative humidity, and initial concentrations were selected as control factors to discover decomposition characteristics of styrene using electron beam irradiation. It was confirmed that a considerable amount of styrene was removed by primary electrons as well as radicals and ions, which were produced after the electron beam irradiation. Moreover, the removal efficiencies of styrene were observed to rise when the initial concentration was lower, moisture content was higher, and the absorbed dose increased. For instance, 50ppmv styrene showed extremely high removal efficiency (over 98%) at a condition of 2.5kGy. A small amount of styrene oxide, benzaldehyde, aerosol, CO, and CO2 were produced as by-products after EB irradiation.

Effect of styrene–acrylonitrile content on 0.5 M NaI/0.05 M I2 liquid electrolyte encapsulation for dye-sensitized solar cells

The effect of a gel polymer electrolyte (GPE) as the redox electrolyte used in dye-sensitized solar cells was studied. A GPE solution consisting of 0.5 M sodium iodide, 0.05 M iodine, and ethylene carbonate/propylene carbonate (1:1 w/w) binary solvents was mixed with increasing amounts of styrene–acrylonitrile (SAN). Bulk conductivity measurements show a decreasing trend from 4.54 to 0.83×10−3 S cm−1 with increasing SAN content. The GPE exhibits Newtonian-like behavior and its viscosity increases from 0.041 to 1.093 Pa s with increasing SAN content. A balance between conductivity (1.3 × 10−3 S cm−1) and viscosity (1.4 Pa s) is observed at 19 wt.% SAN. Fourier transform infrared spectroscopy detects elevated ring torsion at 706 cm−1 upon the addition of SAN into the liquid electrolyte. This indicates that SAN does not bond with the liquid electrolyte. Finally, the potential stability window of 19 wt.% SAN, which ranges from −1.68 to 1.38 V, proves its applicability in solar cells.

Synthesis of additive-free cationic polystyrene particles with controllable size for hollow template applications

Studies on the synthesis of organic particles for template applications for facilitating the production of hollow particles have attracted tremendous attention. The unavailability of the commercial templates with a positive zeta charge is the main reason for this demand of study. The purpose of this study was to spotlight the synthesis of pure and cationic polystyrene (PS) particles with controllable size (from 30 to 300nm) using a single step and relatively simple and cheap process and to demonstrate their application as the template in the production of hollow inorganic particles. Different from other methods, the synthesis method was based on the polymerization of styrene monomer in an aqueous solution system in the absence of any additional components (polymers, surfactants, chemicals, etc.) under 2,2-azobis (isobutyramidine) dihydrochloride (AIBA) as a cationic initiator to facilitate the creation of PS with a positive zeta charge. Precise control of the PS particle size in the nanometer range was achieved by the adjustment of reaction parameters (i.e. temperature, and styrene and AIBA concentrations). The size of the PS particles was proportional to the composition of styrene and the amount of initiator but had an inverse-proportional trend to the temperature. In addition, we also found that the styrene amount had more effect than the initiator (more than 4 times) on controlling PS size. Since an FTIR pattern and a micro-Raman spectrum results detected that the prepared PS particles had pure composition and homopolymer in spite of varying reaction parameters, the change of the particle size was due to changes in nucleus formation and particle growth rates. Flexibility of the process in the nanometer size control also drove to the devise of an equation to predict the particle size, which would be important for further scale-up development. Finally, the loaded positive zeta charge in the PS made it possible to assist the production of hollow inorganic particles (e.g. tungsten oxide, zirconia, and silica), in which this production could not be achieved when using commercial PS particles, verified by the particle formation mechanism hypothesis.

Random Poly(methyl methacrylate‐co‐styrene) Brushes by ATRP to Create Neutral Surfaces for Block Copolymer Self‐Assembly

AbstractRandom copolymer brushes of styrene and methyl methacrylate (MMA) on silicon wafers by atom transfer radical polymerization (ATRP) are synthesized using CuCl/CuCl2/HMTETA. It is found that with increasing amount of styrene the thickness of the brush layer could no longer be well controlled by the amount of free (sacrificial) initiator in the reaction. At constant concentration of free initiator a constant thickness is obtained for various ratios of MMA to styrene. Within 30–70% MMA in the monomer feed the composition of the free polymer corresponds well to the monomer feed ratio, displaying a water contact angle in agreement with the theoretical value for a random copolymer. These copolymers are shown to create a neutral surface directing spin‐coated poly(styrene‐b‐MMA) into a perpendicular lamellae orientation.

Dielectric study of Poly(styrene-co-butadiene) Composites with Carbon Black, Silica, and Nanoclay

Dielectric spectroscopy is used to measure polymer relaxation in styrene–butadiene rubber (SBR) composites. In addition to the bulk polymer relaxation, the SBR nanocomposites also exhibit a slower relaxation attributed to polymer relaxation at the polymer–nanoparticle interface. The glass transition temperature associated with the slower relaxation is used as a way to quantify the interaction strength between the polymer and the surface. Comparisons were made among composites containing nanoclay, silica, and carbon black. The interfacial relaxation glass transition temperature of SBR–clay nanocomposites is more than 80 °C higher than the SBR bulk glass transition temperature. An interfacial mode was also observed for SBR–silica nanocomposites, but the interfacial glass transition temperature of SBR–silica nanocomposite is somewhat lower than that of clay nanocomposites. An interfacial mode is also seen in the carbon black filled system, but the signal is too weak to analyze quantitatively. The interfacial polymer relaxation in SBR–clay nanocomposites is stronger compared to both SBR–carbon black and SBR–silica composites indicating a stronger interfacial interaction in the nanocomposites containing clay. These results are consistent with dynamic shear rheology and dynamic mechanical analysis measurements showing a more pronounced reinforcement for the clay nanocomposites. Comparisons were also made among clay nanocomposites using different SBRs of varying styrene concentration and architecture. The interfacial glass transition temperature of SBR–clay nanocomposites increases as the amount of styrene in SBR increases indicating that styrene interacts more strongly than butadiene with clay.

Preparation of Monodisperse Cationic Microspheres by Dispersion Polymerization of Styrene and a Cation-Charged Monomer in the Absence of a Stabilizer

Cationic polystyrene (PS) microspheres with monodispersity were prepared by dispersion polymerization of styrene and [2-(methacyrloyloxy) ethyl] trimethylammonium chloride (METMAC) in methanol/water system. The effects of METMAC, styrene, and initiator concentration as well as solvent composition on the diameters and size distribution of PS microspheres were systematically investigated. The results indicated that monodisperse cationic PS microspheres could be generated at METMAC concentration less than 2 mol% relative to styrene amount, and too high or low styrene amount was unfavorable to produce cationic PS microspheres. Moreover, it was found that with initiator concentration increasing, the average diameter and the size distribution of cationic PS microspheres also markedly increased. Solvent composition played a significantly important role in the preparation of cationic PS microspheres by dispersion polymerization of styrene and METMAC. Finally, the possible growth and stabilization mechanism of cationic PS microspheres was proposed. The electrostatic repulsion derived from positive charge on the surface of PS microspheres was responsible for the stabilization during dispersion polymerization in the absence of a stabilizer.

Substitution effects on the catalytic activity of Mn(III)-porphyrins in epoxidation of alkenes with iodosylbenzene: A comparison between the electron-rich and electron-deficient porphyrins

Oxidation of different olefins with iodosylbenzene in the presence of Mn(III) complexes of meso-tetra( para-tolyl)porphyrin, meso-tetra( ortho-tolyl)porphyrin, meso-tetra(thien-2-yl)porphyrin and β-hexaboromo- meso-tetra(thien-2-yl)porphyrin as catalyst has been studied. Oxidation of cis- and trans-stilbene in a competitive reaction strongly suggests the involvement of a high valent (porphyrin)Mn O as the active oxidant intermediate, in the case of each catalyst. Clear observation of the band relevant to a (porphyrin)Mn(IV) O species in the presence of excess amounts of styrene shows the stability of this moiety towards reaction with olefins. Although, the stability of metalloporphyrins towards oxidative degradation decreases in the order MnT( o-tolyl)P(OAc) > MnT(thien-2-yl)PBr 6(OAc) > MnT( p-tolyl)P(OAc) ⩾ MnT(thien-2-yl)P(OAc), a complex pattern of catalytic activity and product (epoxide) selectivity has been found for the Mn-porphyrins in oxidation of various alkenes.

High Solids Nitroxide-Mediated Microemulsion Polymerization of MMA with a Small Amount of Styrene and Synthesis of (MMA-co-St)-block-(BMA-co-St) Polymers

We report the first nitroxide-mediated microemulsion polymerization of methyl methacrylate-co-styrene as well as the synthesis of (MMA-co-St)-block-(n-BMA-co-St) polymers using a one-pot, two-stage differential monomer addition technique. These microemulsion polymerizations were conducted with commercially available materials and do not require a preliminary synthesis step. The latexes are optically translucent with monomodal particle size distributions, mean particle diameters ranging from 20 to 30 nm, low surfactant-to-monomer ratios (0.13−0.28 w/w), and solids contents up to 40 wt %. The polymerizations exhibited fast reaction rates, resulting in well-controlled reactions yielding high molecular weight polymer (>100 000 g mol−1). The styrene content and duration of the first stage were particularly important for obtaining narrow molecular weight distributions, with 30 mol % styrene in the first stage (∼8−10 mol % styrene overall in the polymer), resulting in the best controlled polymerizations. The overall styrene content in the latexes can be as low as 8 mol % while maintaining excellent control. The MMA-co-St microemulsion latexes can readily be chain extended with n-BMA-co-St while preserving monomodal particle size distributions.

Rubbers Based on Conjugated Soybean Oil: Synthesis and Characterization

AbstractA range of bio‐based rubbery thermosets have been synthesized by the cationic copolymerization of conjugated soybean oil, styrene, and 1,5‐hexadiene or isoprene as flexible crosslinkers. The thermal, and mechanical properties, as well as the wear behavior, of these new bio‐rubbers are reported. The amount of styrene and the type of diene incorporated have the greatest influence on the properties of the final materials. The largest variations are found in glass transition temperature, storage modulus, tan δ values, crosslink density, and abrasive wear depth, while thermal degradation and extraction analyses showed minimal variations with changes in composition. magnified image

Nitroxide-Mediated Controlled/Living Radical Copolymerization of Methyl Methacrylate with a Low Amount of Styrene in Ionic Liquid.

An ionic liquid, 1-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide ([C1C4Im]NTf2) was used as the polymerization medium for the SG1-mediated free-radical solution copolymerization of methyl methacrylate with a low percentage of styrene, initiated by the BlocBuilder alkoxyamine at 90 °C. Control over the polymer molar mass and molar mass distribution was good, slightly better than that obtained in bulk or classical organic solvent solutions for the same system. Compared to the results of nitroxide-mediated polymerizations in ionic liquids previously reported in the literature, the quality of control was significantly better. It seems that the ionic liquid did not influence the activation−deactivation mechanism but played a role on the polymerization kinetics only. Indeed, the overall polymerization rate was found to be larger and the final conversion higher, in good agreement with the increase of kp and the decrease of kt, which are key features of free-radical polymerization in ionic liquids.

Nitroxide-Mediated Surfactant-Free Emulsion Polymerization of n-Butyl Methacrylate with a Small Amount of Styrene

Nitroxide-mediated emulsion polymerization of n-butyl methacrylate (BMA) can produce highly living and well-controlled polymer chains when polymerized in the presence of 10 mol % styrene (St) using a one-pot, differential monomer addition technique. When n-BMA-co-St is polymerized in the presence of a surfactant above the critical micelle concentration, bimodal particle size distributions are obtained, likely as a result of combined micellar and aggregative nucleation mechanisms. This phenomenon is not observed for the more hydrophilic monomer system of methyl methacrylate and styrene. In the absence of surfactant, however, it is possible to prepare stable, monomodal latexes. Using N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide (SG1), we report the first nitroxide-mediated polymerization of n-butyl methacrylate with a small amount of styrene in a facile surfactant-free emulsion polymerization system. The surfactant-free system requires no separate macroinitiator synthesis step and produces highly living polymers with monomodal particle size distributions. The initiator efficiency can be increased by the addition of methyl acrylate or by the addition of surfactant at concentrations below the critical micelle concentration in the absence of methyl acrylate.

Estimation of absorption of aromatic hydrocarbons diffusing from interior materials in automobile cabins by inhalation toxicokinetic analysis in rats

Aromatic hydrocarbons, as well as aliphatic hydrocarbons, diffusing from interior materials in automotive cabins are the most common compounds contributing to interior air pollution. In this study, the amounts of seven selected aromatic hydrocarbons absorbed by a car driver were estimated by evaluating their inhalation toxicokinetics in rats. Measured amounts of these substances were injected into a closed chamber system containing a rat, and the concentration changes in the chamber were examined. The toxicokinetics of the substances were evaluated on the basis of the concentration-time course using a nonlinear compartment model. The amounts absorbed in humans at actual concentrations in automobile cabins without ventilation were extrapolated from the results obtained from rats. The absorbed amounts estimated for a driver during a 2 h drive were as follows (per 60 kg of human body weight): 30 microg for toluene (interior median concentration, 40 microg m(-3) in our previous study), 10 microg for ethylbenzene (12 microg m(-3)), 6 microg for o-xylene (10 microg m(-3)), 8 microg for m-xylene (11 microg m(-3)), 9 microg for p-xylene (11 microg m(-3)), 11 microg for styrene (11 microg m(-3)) and 27 microg for 1,2,4-trimethylbenzene (24 microg m(-3)). Similarly, in a cabin where air pollution was marked, the absorbed amount of styrene (654 microg for 2 h in a cabin with an interior maximum concentration of 675 microg m(-3)) was estimated to be much higher than those of other substances. This amount (654 microg) was approximately 1.5 times the tolerable daily intake of styrene (7.7 microg kg(-1) per day) recommended by the World Health Organization.

Control of methyl methacrylate radical polymerization via Enhanced Spin Capturing Polymerization (ESCP)

The nitrone mediated polymerization of methyl methacrylate (MMA) via the enhanced (termination) spin capturing polymerization (ESCP) process is made possible via the addition of small amounts of styrene (between 5 and 10 vol.%) to the reaction mixture. Efficient control over the molecular weight between 7000 and 57,000 g mol−1 (at 60 °C) yields macromolecules that feature a mid-chain alkoxyamine functionality and are rich in methyl methacrylate. The collated kinetic and molecular weight data allow for a deduction of the spin capturing constant, CSC, in the range between 0.15 and 0.30. During the ESCP process, the number average molecular weight, Mn, of the formed mid-chain functional polymer is constant up to high monomer to polymer conversions (i.e. 80%). The high degree of alkoxyamine mid-chain functionality present in the generated polymeric material is evidenced via a subsequent nitroxide-mediated polymerization process employing the formed ESCP polymer, indicating a chain extension from 37,700 to 118,000 g mol−1 with a concomitant reduction in polydispersity (from 2.3 to 1.5).