Dispersion polymerization of methyl methacrylate in supercritical carbon dioxide using a silicone‐containing fluoroacrylate stabilizer

Free radical dispersion polymerization of methyl methacrylate (MMA) was carried out in supercritical carbon dioxide (scCO₂) using poly{(heptadecafluorodecyl acrylate)‐co‐3‐[tris(trimethylsilyloxy)silyl]propyl methacrylate} (p(HDFDA‐co‐SiMA)) as stabilizer. Dry, fine powdered spherical poly(methyl methacrylate) (pMMA) particles with well‐defined sizes were produced. The resulting high yield of spherical and relatively uniform micron‐size pMMA particles was formed utilizing various amounts of p(HDFDA‐co‐SiMA) random copolymer. The particle diameter was shown to be dependent on the weight percent of the stabilizer added to the system. The effects of varying the concentration of stabilizer (1–7 wt%), reaction time (4–12 h) and pressure (15–35 MPa) upon the polymerization yield, molar mass and morphology of pMMA were investigated. Copyright © 2005 Society of Chemical Industry     

Fe‐mediated ARGET atom transfer radical polymerization of methyl methacrylate in ionic liquid‐based microemulsion

Poly(methyl methacrylate) (PMMA) was synthesized by activator regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP) of MMA in ionic liquid‐based microemulsion with polyoxyethylene sorbitan monooleate (Tween 80) as surfactant. The polymerization was carried out at 25°C with CCl₄ as initiator, FeCl₃·6H₂O/N,N,N′,N′‐tetramethyl‐1,2‐ethanediamine (TMEDA) as catalyst complex in the presence of reducing agent ascorbic acid (VC). The polymerization kinetics showed the feature of controlled/″living″ process as evidenced by a linear first‐order plot. The well‐controlled polymers were obtained with narrow polydispersity indices and the ionic liquid‐based microemulsions were transparent with a particle size less than 30 nm. The obtained polymer was characterized by ¹H NMR and gel permeation chromatography. The chain extension was successfully achieved by the obtained PMMA macroinitiator/FeCl₃·6H₂O/TMEDA/VC initiator system based on ARGET ATRP method. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

High‐conversion catalytic chain transfer polymerization of methyl methacrylate

In this work the effects of conversion on the apparent catalyst activity in the catalytic chain transfer polymerization of methyl methacrylate are reported. Several mechanisms are discussed that may explain the experimental observations. The discussion is supported with computer simulations using Predici software. It is shown that the experimental decrease in weight average molecular weight with conversion is smaller than the decrease obtained in simulations. The most likely cause for this discrepancy is slow catalyst deactivation. The half‐life of CoBF under the reported conditions was determined to be about 10 h. Furthermore, the effect of acetic acid (HAc) and benzoyl peroxide (BPO) on the evolution of the molecular weight distribution is investigated. Both HAc and BPO enhance catalyst deactivation. For HAc, catalyst deactivation scales with the square root of its concentration. BPO‐ enhanced deactivation depends linearly on its concentration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1375–1388, 2004     

A kinetic study on polymerization of methyl methacrylate with di‐t‐butyl perfumarate

Di‐t‐butyl perfumarate (DBPF) was found to induce the radical polymerizations of various vinyl monomers at 60°C in benzene, although the initiation activity was considerably lower than those of dimethyl 2,2′‐azobisisobutyrate and benzoyl peroxide. The polymerizations with DBPF showed a tendency of dead‐end polymerization. The polymerization of methyl methacrylate (MMA) with DBPF was kinetically studied in chlorobenzene. The initial polymerization rate (R_p) was given by R_p = k [DBPF]^0.5 [MMA]^1.1. The overall activation energy of the polymerization was 47 kJ/mol, a very low value. Use of this value and activation energies of propagation and termination for MMA gave an unexpectedly low activation energy (65 kJ/mol) to the decomposition of DBPF, a t‐butyl perester, in the polymerization system. An ESR study on the polymerization of di‐2‐ethylhexyl itaconate with DBPF revealed that the observed dead‐end tendency comes from the consumption of DBPF. These results suggest that the initiator efficiency of DBPF is considerably low in the present polymerization systems. Some solvent effect was observed on the polymerization of MMA with DBPF. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 218–224, 2000     

Thermodynamic and kinetic considerations: effect of β-cyclodextrin on methyl methacrylate dispersion polymerization

Effect of β-cyclodextrin (CD) on methyl methacrylate dispersion polymerization forming poly (methyl methacrylate) (PMMA) particles was investigated. The presence of CD showed obviously effects on the polymerization, so as to increase the rate of polymerization and the conversion of monomer, as well as decrease the particle size. These effects were evidenced by the more increase in the CD content. The change of free energy derived from thermodynamic investigation in the present of CD was lower than that in the absence of CD. Also the monomer reactivity in the presence of CD is actually higher than that in the absence of CD. The decrease of free energy would be thermodynamically responsible for the increase of MMA conversion. The increase of monomer reactivity may take charge of increasing the polymerization rate. The dependency of particle size on CD content may be thermodynamically responsible for the change of macromolecular conformations of stabilizer due to the interaction of CD and stabilizer.     

Structural changes and crystallization kinetics of polylactide under CO2 investigated using high‐pressure Fourier transform infrared spectroscopy

The structural changes and crystallization kinetics of polylactide (PLA) during cold crystallization under CO₂ at 80 °C were studied using in situ high‐pressure Fourier transform infrared (FTIR) spectroscopy. The FTIR spectra show that PLA can crystallize under air and CO₂, and some differences are observed. In the second‐derivative spectra, the 1220 cm^?1 band is only found for PLA crystallized under CO₂, and the tt conformer of PLA crystallized under CO₂ is located at 1749 cm^?1, while that of PLA crystallized under air is located at 1751 cm^?1. From wide‐angle X‐ray diffraction, only the α′‐crystal is observed when PLA is crystallized under air, whereas the α‐crystal appears when crystallized under CO₂. The crystalline‐sensitive bands at 921 and 1458 cm^?1 were used to analyze the crystallization kinetics of PLA. When PLA crystallizes under air, the 1458 cm^?1 band changes faster than the 921 cm^?1 one; when it crystallizes under CO₂, the result reverses. This suggests that CO₂ hinders interchain interactions while promoting the helix conformation. © 2015 Society of Chemical Industry     

Microemulsion polymerization of methyl methacrylate initiated with γ ray

Polymerization of methyl methacrylate was studied in an oil and water microemulsion stabilized with styrene 12-butinoyloxy-9-octadecenoic acid. During the polymerization the size change of the monomer-swollen particles with conversion was measured with photon correlation spectroscopy, and the hydrodynamic diameter of the final polymer latex was about 50 nm. The polymerization kinetics in this microemulsion were also investigated. The apparent plateau of the polymerization rate was observed at a low dose rate and high emulsifier content. The mechanism leading to this plateau was discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2621–2626, 1999     

Grafting of methyl methacrylate onto Antheraea pernyi silk fiber with the assistance of supercritical CO2

Graft copolymerization of methyl methacrylate (MMA) onto Antheraea pernyi silk fibers, initiated by benzoyl peroxide in the supercritical CO₂ was investigated. The grafting degree was determined as a function of impregnating pressure, impregnating time, monomer concentration, initiator concentration, and reaction time. The structural properties of MMA‐grafted fiber were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Grafted MMA was chemically bonded and/or physically adhered to the surfaces of the fibers. The grafted silk fibers exhibited two steps of weight loss according to the characteristic of each component as demonstrated by the thermogravimetric analysis. The water‐retention values indicated that the hydrophobic nature of the fibers was improved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1299–1305, 2006     

压力瞬态下超临界压力CO2的传热特性

在均匀加热条件下,开展超临界压力二氧化碳在压力瞬态下的传热特性实验研究。实验段内径为10.0mm,实验参数范围：压力P=7.58~9.97MPa,热流密度q _w=64~256kW/m²,质量流速G=660~893kg/(m²·s)。分析了正常传热和传热恶化条件下,瞬间泄压过程对传热的影响规律。实验结果表明,正常传热工况下,壁温随着压力的减小有降低的趋势,传热系数明显增大;传热恶化发生后壁温迅速上升,对应的传热系数减小传热恶化更加严重,且恶化壁温峰值点向着入口方向移动。最后对实验现象进行了解释,正常传热下壁温降低是由于压力的降低增大了比热容,从而改善了传热。传热恶化发生后,压力的降低减小了拟临界焓值i _pc,从而增大了超临界沸腾数SBO,更大的SBO表明膨胀动量力占主导,靠近壁面低密度的vapor-like fluid在不断向外膨胀,从而使得低密度层流体的厚度增加,从而加大了传热热阻,这时壁温升高或者出现更大的恶化。     

Core‐shell ZrO2/PMMA composites via dispersion polymerization in supercritical fluid: Synthesis,characterization and mechanism

In this study, the polyester (PET) fabric was hydrolyzed with alkali to increase the surface activity and enhance the nano titanium dioxide (nano-TiO₂) adsorption to produce higher functionality. The PET fabric was first treated with sodium hydroxide along with cetyl trimethyl ammonium bromide as a cationic surfactant and then dipped into an ultrasound bath containing nano-TiO₂ followed by curing at high temperature. The weight loss, vertical wicking, and water droplet adsorption time were evaluated and are reported. The photocatalytic activity of TiO₂ nanoparticles deposited on the PET fabric was examined by the degradation of methylene blue as a model stain under daylight irradiation. The residual TiO₂ on the fabric surface after 1 and 10 successive washings was determined to indicate the washing durability of the finished fabric. Also, the UV protection was assessed by UV reflectance spectroscopy. The scanning electron microscopy pictures and energy-dispersive X-ray spectra of some fabrics are also reported. The surface hydrolysis of the PET fabric with sodium hydroxide created some voids and hydrophilic groups on the fabric surface; this led to the higher adsorption of nano-TiO₂ particles and enhanced the wettability, vertical wicking, and higher durability against repeated washings of the nano-TiO₂ treated fabric. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

超临界二氧化碳流体萃取大黄蒽醌动力学模型

通过对萃取固定床层进行质量衡算建立了超临界CO₂流体萃取动力学模型.然后采用BP神经网络拟合实验条件下的萃取动力学曲线,并将之与动力学模型试差法求解所得的萃出曲线进行对照确定模型参数k_La.结果表明,BP神经网络能很好地模拟大黄蒽醌的萃取动力学曲线,网络训练误差和预测误差分别为1.5%和3.5%.确定参数后的动力学模型可用于对萃取床层作较为精确的定量描述：模拟所得萃取穿透曲线与大黄蒽醌萃取实验结果相比AARD误差在10%左右.与前人模型相比,该模型具有精度好,获取参数时的实验条件相对宽松等优点.     

Copper‐based reverse ATRP process for the controlled radical polymerization of methyl methacrylate

A series of copper‐based reverse atom transfer radical polymerizations (ATRP) were carried out for methyl methacrylate (MMA) at same conditions (in xylene, at 80°C) using N,N,N′,N′‐teramethylethylendiamine (TMEDA), N,N,N′,N′,N′‐pentamethyldiethylentriamine (PMDETA), 2‐2′‐bipyridine, and 4,4′‐Di(5‐nonyl)‐2,2′‐bipyridine as ligand, respectively. 2,2′‐azobis(isobutyronitrile) (AIBN) was used as initiator. In CuBr₂/bpy system, the polymerization is uncontrolled, because of the poor solubility of CuBr₂/bpy complex in organic phase. But in other three systems, the polymerizations represent controlled. Especially in CuBr₂/dNbpy system, the number‐average molecular weight increases linearly with monomer conversion from 4280 up to 14,700. During the whole polymerization, the polydispersities are quite low (in the range 1.07–1.10). The different results obtained from the four systems are due to the differences of ligands. From the point of molecular structure of ligands, it is very important to analyze deeply the two relations between (1) ligand and complex and (2) complex and polymerization. The different results obtained were discussed based on the steric effect and valence bond theory. The results can help us deep to understand the mechanism of ATRP. The presence of the bromine atoms as end groups of the poly(methyl methacrylate) (PMMA) obtained was determined by ¹H‐NMR spectroscopy. PMMA obtained could be used as macroinitiator to process chain‐extension reaction or block copolymerization reaction via a conventional ATRP process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Free‐radical copolymerization and kinetic treatment of methyl methacrylate with N‐P‐tolylmaleimide

The free‐radical copolymerization of methyl methacrylate (MMA) with N‐P‐tolylmalemide (NPTMI) at 77°C in cyclohexanone solution initiated by AIBN was studied. The copolymer composition was calculated from the nitrogen content estimated by the Mico–Kijedldahl's method and by elemental analysis. The reactivity ratios have been calculated by Fineman and Ross method. The monomer reactivity ratios were r_NPTMI = 1.24, r_MMA = 2.1. The glass transition temperature (T_g) of the copolymers were determined by torsion braid analysis (TBA). The thermal stability was determined by thermogravimetric analysis (TGA). T₅₀, temperature at which the weight loss reaches 50%, was abstained. The results showed that the M _n and M _w increased, whereas the NPTMI feed content increased. The T_g and T₅₀ increased dramatically. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 867–870, 2004     

A new investigation with the salting‐out effect on emulsifier‐free emulsion polymerization of methyl methacrylate

The effects of the various salts onto the emulsifier‐free emulsion polymerization of methyl methacrylate (MMA) were investigated. It was found that the kind and amount of the salts were very effective on the polymerization even onto the polymeric products. It is known that the ionic strength of the electrolyte is effective for the polymerization. However, our investigation with the same ionic strength of different electrolyte produced the different effect on the polymerization. It was found that the Stokes radiuses of ions are very important for the reaction kinetics and type of the product. At the same electrolyte concentration, as increased Stokes radii of cation of salts that not react (the fragments of initiator, ions, etc.) in polymerization, polymerization rate and average molecular weight of polymer decreased, polymer particle diameter increased. In the case of Br^? and SO₄⁼ the anions of the salt are also demonstrated some unexpected reactions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2494–2500, 2007     

The inverse emulsion polymerization of acrylamide using poly(methyl methacrylate)‐graft‐polyoxyethylene as the stabilizer

Inverse emulsion polymerization of an aqueous solution of acrylamide (AM) in toluene is carried out using poly(methyl methacrylate)‐graft‐polyoxyethylene (PMMA‐g‐PEO) as an emulsifier. The kinetics of polymerization, morphology of the particle, and particle size of the inverse emulsion have been investigated. The rates of polymerization are found to be proportional to the initiator concentration, the monomer concentration, and the emulsifier concentration. The morphology of particles shows a spherical structure. The mechanism of inverse emulsion polymerization using amphipathic graft copolymer as the emulsifier is proposed. The resulting molecular weights of polyacrylamide are extremely high, and relate to the amphipathic graft copolymer structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 528–534, 2001     

A kinetic model of nano‐CaO reactions with CO2 in a sorption complex catalyst

This article describes the reactive kinetics of nano‐CaO with CO₂ in a sorption complex catalyst. Based on an observation of nano‐CaO reaction with CO₂ has a fast surface reaction regime and followed by a slow diffusion‐controlled regime, a criterion has been proposed to divide the fast surface reaction regime and the slow diffusion‐controlled reaction regime. The kinetics of the fast surface reaction was studied, and a new ion reaction mechanism was proposed. A surface reaction‐controlled kinetic model with a Boltzmann equation, X = X_u?X_u/[1+exp((t?t₀)k/X_u)], was developed. Experiments using nano‐CaO to react with CO₂ in a fast surface reaction regime within a sorption complex catalyst were performed using thermogravimetric analysis at 773–873 K under a N₂ atmosphere with 0.010–0.020 MPa CO₂. The activation energy of the kinetic model for carbonation is 30.2 kJ/mol, and the average relative deviation of the sorption ratio is less than 9.8%. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Synthesis of new phase transfer‐catalyzed free radical polymerization of ethyl methacrylate: A kinetic study

In this study, a new phase transfer catalyst has been synthesized and characterized, which is used for the study of kinetics and mechanism of the free radical polymerization of ethyl methacrylate. The reactions were carried out using peroxodisulfate as initiator in inert and unstirred condition at 60°C ± 1°C. The order with respect to monomer, initiator, and catalyst were found to be 1, 0.7, and 0.5, respectively. The rate of polymerization is independent of ionic strength and pH. Based on the results obtained, a mechanism has been proposed for the polymerization reactions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Determination of kinetics of CO2 absorption in solutions of 2‐amino‐2‐methyl‐1‐propanol using a microfluidic technique

The kinetics for the reactions of carbon dioxide with 2‐amine‐2‐methyl‐1‐propanol (AMP) and carbon dioxide (CO₂) in both aqueous and nonaqueous solutions were measured using a microfluidic method at a temperature range of 298–318 K. The mixtures of AMP‐water and AMP‐ethylene glycol were applied for the working systems. Gas‐liquid bubbly microflows were formed through a microsieve device and used to determine the reaction characteristics by online observation of the volume change of microbubbles at the initial flow stage. In this condition, a mathematical model according to zwitterion mechanism has been developed to predict the reaction kinetics. The predicted kinetics of CO₂ absorption in the AMP aqueous solution verified the reliability of the method by comparing with literatures’ results. Furthermore, the reaction rate parameters for the reaction of CO₂ with AMP in both solutions were determined. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4358–4366, 2015     

Comparison of the kinetics of conventional and microwave methyl methacrylate polymerization

A comparative investigation of the conventional and microwaves kinetics of methyl methacrylate (MMA) polymerization was performed. A method for determining the increase of the reaction rate in the microwave field (β) was presented. It was found that at all of the investigated temperatures and powers the polymerization rates increased in the presence of microwave energy by up to 8.9 times compared with conventional polymerization. Isothermal kinetics of the conventional MMA polymerization was investigated and its parameters were determined using isoconversion method. It was found that the calculated kinetics parameters changes complexly with degree of MMA conversion (α) and are in the mutual linear functional relationship, which is so called “compensation effect.” The complex changes of the kinetics parameters with α are explained with the postulated model for the mechanism of the MMA polymerization. The kinetics of the MMA polymerization under the microwave field (MWF) with different input power was investigated and its parameters were determined on the basis of the conversion‐temperature curves and Arrhenius equation. The values of the kinetics parameters for MMA polymerization in the MWF are dependent on α and are from 1.2 to 12 times lower than that for conventional MMA polymerization. A new method for the determination of activation energy (E_a) of the investigated process in the MWF was described. Decreased E_a value of the polymerization process in the MWF compared with the conventional polymerization is explained with the formation of the nonequilibrium energetic distribution of the reactants due to the rapid transfer of energy in the reaction system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1775–1782, 2007