Effects of short chain alcohols on the styrene emulsion polymerization

The effects of a series of short chain alcohols, 1‐butanol (C₄OH), 1‐pentanol (C₅OH), and 1‐hexanol (C₆OH), on the styrene (ST) emulsion polymerization mechanisms and kinetics were investigated. The CMC of the ST emulsions stabilized by sodium dodecyl sulfate (SDS) first decreases rapidly and then levels off when the C_iOH (i = 4, 5, or 6) concentration ([C_iOH]) increases from 0 to 72 mM. Furthermore, at constant [C_iOH], the CMC data in decreasing order is CMC (C₄OH) > CMC (C₅OH) > CMC (C₆OH). The effects of C_iOH (i = 4, 5, and 6) on the ST emulsion polymerization stabilized by 6 mM SDS are significant. This is attributed to the reduction in CMC by C_iOH, the different oil–water interfacial properties, the different concentrations of monomer within latex particles, and the different effectiveness of SDS/C_iOH in stabilizing latex particles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4406–4411, 2006     

Microemulsion copolymerization of vinyl acetate and butyl acrylate using a mixture of anionic and non-ionic surfactants

Monomer mixtures of vinyl acetate (VAc)/butyl acrylate (BuA) were polymerized in batch reactions at 60 °C with potassium persulfate as the initiator in microemulsions consisting of VAc:BuA (85:15 wt/wt)/water/sodium dodecyl sulfate (SDS)/polyoxyethylene (23) dodecyl ether (3:1 wt/wt). The effect of the concentration of the monomer mixture on the kinetics was studied. It was found that, as the total monomers concentration ([M]₀) increases, the polymerization rate increases also, and that the maximum polymerization rate is proportional to [M]₀^1.26. Particle size increases with total monomers concentration. In all cases, final average particle diameter was less than 50 nm. Particle number density is independent of total monomers concentration. A mathematical model that takes into account the partition of monomers between the different phases during polymerization using a minimum of adjustable parameters was applied to simulate the experimental data. A correlation for the radical desorption coefficient, which is a function of the rate of monomer chain transfer and of the probability of desorption, was used in the model. Radical capture by micelles and particles was assumed to occur by diffusion. The model takes into account both micellar and homogeneous nucleation. Good agreement between the model and the experimental results was observed.     

Synthesis of star polymer by means of the living polymerization of [(o-trifluoromethyl)phenyl]acetylene using a MoOCl4-based catalyst and the linking method

A star polymer was synthesized by addition of 1,4-diethynyl-2,5-dimethylbenzene as linking agent (30 °C, 24 h) after living polymerization of [(o-trifluoromethyl)phenyl]acetylene (o-CF₃PA) with MoOCl₄-n-Bu₄Sn-EtOH catalyst (in anisole, 30 °C, 20 min; [Mo]=10 mM, [P^∗]/[Mo]=40%, [o-CF₃PA]₀=200 mM). The M_n values of the living and star polymers were 8.1×10³ and 5.3×10⁴, respectively, according to gel permeation chromatography, while these values determined by multi-angle laser light scattering (MALLS) were 7.8×10³ and 2.5×10⁵. The M_w/M_n and arm number of the star polymer were 1.04 and 29, respectively, according to MALLS. The molecular weight and arm number of star polymer increased with increasing linking agent concentration and polymerization temperature.     

Characteristics of solubilization and encapsulation of fullerene C60 in non-ionic Triton X-100 micelles

The solubilization and encapsulation of monomeric C₆₀ in Triton X-100 micelles were investigated. Characteristic hydrophobic interactions of the type π-π and CH-π between the Triton X-100 micelle and C₆₀ resulted in stable aqueous dispersions of C₆₀ in the micellar medium, as evidenced from UV-vis, fluorescence emission and micro-Raman spectroscopy. Cyclic voltammetry of C₆₀ encapsulated Triton X-100 in aqueous 5 mM LiClO₄ solution revealed a quasi-reversible one-electron reduction peak with E_1/2 = −0.61 V and a reversible reduction peak at E_1/2 = −1.11 V vs. Ag/AgCl reference electrode at a scan rate of 10 mV s⁻¹, a redox behaviour drifting substantially from that of pure C₆₀. An onset concentration of ∼0.025 mM for C₆₀ aggregation in the micellar core was substantiated from the characteristic absorption spectral broadening and quenching of pyrene fluorescence. The molar solubilization capacity of C₆₀ in aqueous Triton X-100 micellar solution was estimated spectrophotometrically to be 0.22.     

Alkylation of polyethyleneimine for homogeneous ligands in ATRP

Ethylated and butylated polyethyleneimine ligands were synthesized and employed in copper catalyzed atom transfer radical polymerization of styrene and methyl methacrylate with suitable initiators in order to obtain homogeneous polymerizations, resulting in well defined polymers with low polydispersities. Linear curves drawn from kinetics and conversion-molecular weight plots indicate that all the polymerizations were successfully controlled. In ATRP reactions of S and MMA, the apparent rate of polymerization, k_p^app, exhibits a plateau at [Ligand]/[CuBr] ≥ 0.5 ratio for both ligands. The apparent rate constant also decreases by increasing the alkyl chain length of the alkylated polyethyleneimine ligand. Ethylated and butylated polyethyleneimine ligands in ATRP of S and MMA were found to be faster than the existing ATRP ligands.     

乳化剂浓度对苯乙烯乳液聚合成核机理的影响

以苯乙烯（St）为单体、十二烷基硫酸钠（SDS）为乳化剂、过硫酸钾（KPS）为引发剂,重点研究了该乳液聚合体系中乳化剂浓度（[S]）对胶束成核和沉淀成核的影响规律。结果表明,当SDS浓度高于CMC时（[S]≥ 8mmol/L）,体系的成核以胶束成核为主;当[S]=2mmol/L时,体系的成核以沉淀成核为主;当2mmol/L<[S]< 8mmol/L时,体系同时以沉淀成核和胶束成核两种方式成核,且胶束成核所占的比例随着SDS浓度的增加而增大。研究了聚合反应过程中SDS浓度对单位体积水中乳胶粒个数（Np）的影响规律：当[S]≥8mmol/L时,Np∝[S]0.9;当[S]<8mmol/L时,Np∝[S]0.8。     

PEG-directed microwave-assisted hydrothermal synthesis of spherical α-Ni(OH)2 and NiO architectures

Spherical α-Ni(OH)₂ architectures were synthesized by the microwave-assisted hydrothermal technique using PEG-6000 as the surfactant. NiO architectures with similar morphology were obtained by a simple thermal decomposition process of the precursor α-Ni(OH)₂ at 400 °C for 2 h and were confirmed by the X-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) revealed that the synthesized spherical α-Ni(OH)₂ and NiO architectures were composed of stacked lamellar sheets and transmission electron microscopy (TEM) showed that the α-Ni(OH)₂ and NiO architectures were polycrystalline. The effect of the PEG-6000 concentration on particle size was investigated and it was found that the average particle size of α-Ni(OH)₂ architectures decreased from 4.689 μm at C_PEG=2 mmol L⁻¹ to 3.907 μm at C_PEG=4 mmol L⁻¹, and the corresponding average particle size of NiO decreased from 2.818 μm to 2.492 μm. The optical absorption band gap of NiO architectures was determined to be about 2.7–3.0 eV by UV–vis spectroscopy.     

Electrocrystallization of Au nanoparticles on glassy carbon from HClO4 solution containing [AuCl4]

The mechanism and kinetics of electrocrystallization of Au nanoparticles on glassy carbon (GC) were investigated in the system GC/1 mM KAuCl₄ + 0.1 M HClO₄. Experimental results show that the gold electrodeposition follows the so-called Volmer-Weber growth mechanism involving formation and growth of 3D Au nanoparticles on an unmodified GC substrate. The analysis of current transients shows that at relatively positive electrode potentials (E ≥ 0.84 V) the deposition kinetics corresponds to the theoretical model for progressive nucleation and diffusion-controlled 3D growth of Au nanoparticles. The potential dependence of the nucleation rate extracted from the current transients is in agreement with the atomistic theory of nucleation. At sufficiently negative electrode potentials (E ≤ 0.64 V) the nucleation frequency becomes very high and the nucleation occurs instantaneously. Based on this behaviour is applied a potentiostatic double-pulse routine, which allows controlled electrodeposition of Au nanoparticles with a relatively narrow size distribution.     

Atom transfer radical polymerization of methyl methacrylate with low concentration of initiating system under microwave irradiation

Homogeneous atom transfer radical polymerization of methyl methacrylate (MMA) under microwave irradiation (MI) with low concentration of initiating system [ethyl 2-bromobutyrate (EBB)/CuCl/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA)] was successfully carried out in N,N-dimethylformamide (DMF) at 69 °C. Plots of ln ([M]₀/[M]) vs. time and molecular weight evolution vs. conversion showed a linear dependence. A 27.3% conversion for a polymer with number-average molecular weight (M_n) of 57,280 and a polydispersity index (PDI) of 1.19, was obtained under MI (360 W) with the ratio of [MMA]₀/[EBB]₀/[CuCl]₀/[PMDETA]₀=2400/1/2/2 in only 150 min; but 963 min was needed under conventional heating (CH) process to reach a 26.0 % conversion (M_n=63,990 and PDI=1.14) under identical polymerization conditions, indicating a significant enhancement of the polymerization rate under MI.     

Study on kinetics and electrochemical properties of low-Co AB5-type alloys for high-power Ni/MH battery

The structure and electrochemical kinetics properties of La_0.90−xCe_xPr_0.05Nd_0.05Ni_3.90Co_0.40Mn_0.40Al_0.30 (x = 0.10, 0.20, 0.30, 0.40, 0.50) hydrogen storage alloys have been investigated. XRD shows that the alloys consist of LaNi₅ phase with hexagonal CaCu₅ structure. With increase in Ce content, the parameter a and cell volume decrease remarkably, but the parameter c increases slightly. The limiting current density I_L and the hydrogen diffusion coefficient D increase, and the exchange current density I₀ increases firstly from 201.4 mA/g (x = 0.10) to 277.9 mA/g (x = 0.30) and then decreases to 208.5 mA/g (x = 0.50). Meanwhile, high rate dischargeability (HRD) at 1440 mA/g increases from 44.1% (x = 0.10) to 59.9% (x = 0.30), and then decreases to 44.2% (x = 0.50). As the amount of Ce increases, the plateau pressure of P-C isotherms increases gradually, the capacity retention of the alloys increases firstly and then decreases, the alloy with x = 0.30 has the higher capacity retention and cycling stability, but the maximum discharge capacity of alloys decreases. Ce is a vital element in favor of kinetics properties of rare earth-based AB₅-type alloys, and the substitution of La with Ce in suitable amount could improve the HRD by increasing kinetics.     

Effect of particle size distribution of metakaolin on hydration kinetics of tricalcium silicate

The focus of this study is to elucidate the role of particle size distribution (PSD) of metakaolin (MK) on hydration kinetics of tricalcium silicate (C₃S–T₁) pastes. Investigations were carried out utilizing both physical experiments and phase boundary nucleation and growth (pBNG) simulations. [C₃S + MK] pastes, prepared using 8%_mass or 30%_mass MK, were investigated. Three different PSDs of MK were used: fine MK, with particulate sizes <20 µm; intermediate MK, with particulate sizes between 20 and 32 µm; and coarse MK, with particulate sizes >32 µm. Results show that the correlation between specific surface area (SSA) of MK's particulates and the consequent alteration in hydration behavior of C₃S in first 72 hours is nonlinear and nonmonotonic. At low replacement of C₃S (ie, at 8% _mass), fine MK, and, to some extent, coarse MK act as fillers, and facilitate additional nucleation and growth of calcium silicate hydrate (C–S–H). When C₃S replacement increases to 30% _mass, the filler effects of both fine and coarse MK are reversed, leading to suppression of C–S–H nucleation and growth. Such reversal of filler effect is also observed in the case of intermediate MK; but unlike the other PSDs, the intermediate MK shows reversal at both low and high replacement levels. This is due to the ability of intermediate MK to dissolve rapidly—with faster kinetics compared to both coarse and fine MK—which results in faster release of aluminate [Al(OH)₄⁻] ions in the solution. The aluminate ions adsorb onto C₃S and MK particulates and suppress C₃S hydration by blocking C₃S dissolution sites and C–S–H nucleation sites on the substrates’ surfaces and suppressing the post-nucleation growth of C–S–H. Overall, the results suggest that grinding-based enhancement in SSA of MK particulates does not necessarily enhance early-age hydration of C₃S.     

Isothermal emulsion polymerization of n-butyl methacrylate with KPS and redox initiators: Nucleation

Nucleation is a very important stage of emulsion polymerization due to its significant influence on the latex particle diameter, particle diameter distribution, and molecular weight. In this study, we evaluated the effect of thermal and redox initiators on the nucleation and reaction kinetics with a model emulsion system comprised of n-butyl methacrylate, sodium lauryl sulfate, water, initiators, and other additives. Our previous study has demonstrated that a micellar nucleation mechanism plays a role in both initiator systems. In the present study, we further explored secondary nucleation using these two types of initiator systems, that is, homogeneous nucleation, which exists in the redox-initiated process, and micellar nucleation which is the main nucleation mechanism for the thermal-initiated system. The investigation also illustrates that coagulative nucleation in the redox-initiated emulsion system results in a greater extent of monodispersed particle diameter distributions, much smaller particle diameters, and lower molecular weights for the final latex. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48275.     

Preparation of ZnO/Eu mixed films by electrochemical precipitation

The electrochemical preparation of europium doped zinc oxide and europium oxide/hydroxide as thin films is investigated. First, a thermodynamic study of the Eu-Cl-H₂O system has been carried out at 25 and 70 °C in order to predict the electrochemical behaviour of Eu(III) dissolved in aqueous solution containing chloride ions. A comparison of the Eu-Cl-H₂O and Zn-Cl-H₂O systems indicates the possible coprecipitation of ZnO and Eu(OH)₃ from deposition solutions containing well-adjusted Eu(III)/Zn(II) concentrations ratio. The thermodynamic predictions have been confirmed experimentally by the electrochemical co-deposition of ZnO/Eu thin films on conducting electrode substrates at −1.4 V versus MSE. The presence of europium in the film is detected for Eu(III)/Zn(II) concentration ratio at (0.6 mM/5 mM) which is lower than the predicted value. Increasing Eu(III) concentration leads to the rapid appearance of two phases: dispersed zinc oxide nanorods and, at the bottom of the rods, a covering layer containing Eu(OH)₃ and zinc. The density of ZnO rods decreases and the rod size increases with increasing Eu(III) concentration in the bath. Above 1 mM EuCl₃, a dramatic fall in the current density is observed with the formation of a less conducting ZnO/Eu mixed deposit.     

Reverse ATRP of acrylonitrile with diethyl 2,3-dicyano-2,3-diphenyl succinate/FeCl3/iminodiacetic acid

The reverse atom transfer radical polymerization (RATRP) technique using FeCl₃/iminodiacetic acid (IMA) complex as a catalyst was applied to the living radical polymerization of acrylonitrile (AN). A hexa-substituted ethane thermal initiator, diethyl 2,3-dicyano-2,3-diphenylsuccinate (DCDPS), was firstly used as the initiator in this iron-based RATRP system. The polymerization in N,N-dimethylformamide not only shows the best control of molecular weight and its distribution but also provides rather rapid reaction rate with the ratio of [AN]:[DCDPS]:[FeCl₃]:[IMA] at 500:1:2:4. The rate of polymerization increases with increasing the polymerization temperature and the apparent activation energy was calculated to be 49.9 kJ mol⁻¹. The polymers obtained were end-functionalized by chlorine atom, and they were used as macroinitiators to proceed the chain extension polymerization in the presence of FeCl₂/IMA catalyst system via a conventional ATRP process. The resultant polyacrylonitrile fibers were obtained with the fineness at 1.16 dtex and the tenacity at 6.01cN dtex⁻¹.     

On the role of an unconventional rigid rodlike cationic surfactant on the styrene emulsion polymerization. Kinetics, particle size and particle size distribution

An unconventional amphiphile (1-[ω-(4′-methoxy-4-biphenylyloxy)octyl]pyridinium bromide, PC8) was used as surfactant in the emulsion polymerization of styrene. At low surfactant concentration (6, 12 or 36 mmol l⁻¹), curves of polymerization rate versus conversion obeyed the typical behavior characterized by intervals I, II and III. However, at high concentration (48 or 72 mmol l⁻¹) the interval II was not observed. The particle size distribution curves showed two families of polymer particles, indicating the participation of at least two mechanisms of particle formation, one being the simple micellar nucleation and the other probably the coagulative nucleation of precursor particles. The latter was considered to occur during the nucleation interval.     

Emulsifier-free, organotellurium-mediated living radical emulsion polymerization of Styrene: Initial stage of polymerization

Behavior of the particle formation based on self-assembling in emulsifier-free, organotellurium-mediated living radical emulsion polymerization (emulsion TERP) of styrene was studied from the molecular weight distributions (MWDs) of polystyrene (PS) formed in an initial stage of the polymerization at different temperatures from 50 °C to 70 °C. As the polymerization temperature was decreased, the larger number of poly(methacrylic acid) (PMAA; degree of polymerization, 30)-methyltellanyl (TeMe) (PMAA₃₀-TeMe) participated in the polymerization, resulting in amphiphilic PMAA₃₀-b-PS-TeMe oligomers. Almost all control agents were consumed and a self-assembly nucleation occurred in the initial stage of the polymerization at 50 °C, which lead to depress of particle formation of a homogeneous nucleation. The consumption rate of PMAA₃₀-TeMe affected directly the particle formation. From these results, it is concluded that it is important for the emulsion TERP of styrene with excellent control/livingness that the self-assembly nucleation proceeds without the homogeneous nucleation in the initial stage of the polymerization.     

Electrochemical activity, stability and degradation characteristics of IrO2-based electrodes in aqueous solutions containing C1 compounds

In this paper, we investigate the electrocatalytic behavior and degradation characteristics of IrO₂-based electrodes in Na₂SO₄ solutions containing C₁ compounds (CH₃OH, HCHO and HCOOH). Decreases are generally observed in the electrochemically active area, electrochemical stability and durability of the electrodes in aqueous solutions in the presence of these organic substrates. The following sequence holds for the influence of C₁ compounds on the electrode properties (i.e. activity and stability): CH₃OH > HCHO > HCOOH. The corrosion characteristics of electrode are studied by X-ray diffraction measurements. For the first time, the decomposition and dissolution of active oxide layers are quantitatively characterized from the decreases in cell volume of rutile-structured IrO₂ crystallite and from the increases in texture coefficient of (0 0 2) planes, respectively, as a result of the accelerated lifetime tests.     

Entry in emulsion polymerization using a mixture of sodium polystyrene sulfonate and sodium dodecyl sulfate as the surfactant

A mixture of sodium polystyrene sulfonate (NaPSS) and anionic surfactant, sodium dodecyl sulfate (SDS), was used as the emulsifier in the emulsion polymerization of styrene at 60 °C. The latexes prepared were stable, bearing the better resistance to the addition of electrolyte, and have the larger values in particle size and the higher polymerization rates than those counterparts prepared using SDS only. The NaPSS was prepared by a series of process: a concentrated cyclohexane solution of an anionically polymerized polystyrene (PS) was sulfonated with sulfuric acid at 80 °C, and then neutralized and purified through dialysis. The data of average polymer number per particle (n_p) were found useful in investigating the surfactant content effect on the entry of radicals into particles, where the latex particle size plays an important role.     

The effect of the interlayer anions on the electrochemical performance of layered double hydroxide electrode materials

Both high energy density and high power density are vitally required for new applications such as electric vehicles. Here we present a comparison of two well-crystallised layered double hydroxides, [Ni₄Al(OH)₁₀]OH and [Ni₄Al(OH)₁₀]NO₃, which shows that the former can maintain a better discharge capacity, 294-299 mAh g⁻¹, than the latter, 233-287 mAh g⁻¹ at a current density of 2000 mA g⁻¹ within about 300 cycles, although both electrodes deliver a similar capacity of 326 mAh g⁻¹ at 200 mA g⁻¹ initially. It is believed that both the more watery interlayer space in [Ni₄Al(OH)₁₀]OH than in [Ni₄Al(OH)₁₀]NO₃ and the morphologic changes induced by anion exchange of NO₃⁻ by OH⁻ during electrochemical cycles play key roles in their behaviour.