Soapless emulsion polymerization of butyl methacrylate through microwave heating

Soapless emulsion polymerization of n‐butyl methacrylate (BMA) was carried out through microwave heating with potassium persulfate (KPS) as an initiator at 73 ± 2°C. The influence of the monomer amount, the initiator amount, and the addition of ethanol on the monomer conversion, the particle size, and its distribution were studied. The results indicate that microwave polymerization had a much higher rate and produced smaller particles with a slightly broader size distribution compared with normal polymerization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2455–2459, 2001     

Synthesis of poly(methyl methacrylate)/silica nanocomposite through emulsion polymerization using dimethylaminoethyl methacrylate

Polymer/Silica nanocomposite latex particles were prepared by emulsion polymerization of methyl methacrylate (MMA) with dimethylaminoethyl methacrylate (DM). The reaction was performed using a nonionic surfactant and in the presence of silica nanoparticles as the seed. The polymer‐coated silica nanoparticles with polymer content and number average particle sizes ranged from 32 to 93 wt % and 114–310 nm, respectively, were obtained depending on reaction conditions. Influences of some synthetic conditions such as MMA, DM, surfactant concentration, and the nature of initiator on the coating of the silica nanoparticles were studied. Electrostatic attraction between anionic surface of silica beads and cationic amino groups of DM is the main driving force for the formation of the nanocomposites. It was demonstrated that the ratio of DM/MMA is important factor in stability of the system. The particle size, polymer content, efficiency of the coating reaction, and morphology of resulted nanocomposite particles showed a dependence on the amount of the surfactant. Zeta potential measurements confirmed that the DM was located at the surface of the nanocomposites particles. Thermogravimeteric analysis indicated a relationship between the composition of polymer shell and polymer content of the nanocomposites. The nanocomposites were also characterized by FTIR and differential scanning calorimetry techniques. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Different composition poly(methyl methacrylate-co-butyl methacrylate) copolymers through seeded semi-batch emulsion polymerization

In the present work the synthesis and the chemical and thermal characterization of poly(methyl methacrylate-co-butyl methacrylate) copolymer, in three different macromolecular compositions, are reported. The aim of the present work was the identification of a standard method to obtain copolymers with controlled macromolecular composition, molecular weights and particle size distribution, together with the identification of the effect of the macromolecular composition on the material properties. A monomer-starved seeded semi-batch emulsion reaction was carried out and optimized, monitoring the kinetic of the copolymerization through the evaluation of residual monomer amounts. Then, an evaluation of the macromolecular composition was performed by Fourier transform infrared spectroscopy analysis. Molecular weight, molecular weight distribution, latex characteristics and thermal behaviour were also investigated.     

Poly(dimethylaminoethyl methacrylate) grafted natural rubber from seeded emulsion polymerization

The grafting efficiency of dimethylaminoethylmethacrylate (DMAEMA) on to natural rubber (NR) has been studied. Grafting was by ‘topology-controlled’ emulsion polymerization, whereby polymerization is initiated by a redox couple where one component (tetraethylene pentamine) is hydrophilic and the other (cumene hydroperoxide) is hydrophobic. This should promote grafting at the interface between hydrophobic natural rubber particles and the hydrophilic DMAEMA. The effects of different amounts of monomer were examined, with NMR to obtain the percent branching, transmission electron microscopy to obtain information on morphology, gel fraction measurement and dynamic mechanical analysis to obtain information on mechanical properties. Although there will be significant amounts of ungrafted polyDMAEMA present, there is good evidence for the formation of graft copolymers of NR with core-shell morphology, and significant amounts of grafting, at high concentrations of monomer.     

Particle features of a poly(methyl methacrylate) resin prepared by a new emulsion polymerization process

A new emulsion polymerization process, in which water acted as the dispersed phase and a mixture of methyl methacrylate (MMA) and cyclohexane acted as the continuous phase, was applied to the preparation of a poly(methyl methacrylate) (PMMA) resin. The primary (latex) particles were formed in the early stage of polymerization and coagulated as the polymerization conversion increased. Scanning electron micrographs showed that the final PMMA particles were porous and composed of loosely aggregated primary particles. The porosity characterized by cold di(2‐ethylhexyl) phthalate absorption increased as the water/oil and cyclohexane/MMA mass ratios increased. The PMMA primary particles were smaller than the primary particles in the PMMA resin prepared by suspension polymerization in the presence of cyclohexane. Because of the phase composition of the reaction system, the solubility of PMMA in a mixture of cyclohexane and MMA, and the particle morphology of PMMA, a particle formation mechanism, including the formation, growth, and coagulation of primary particles in dispersed water droplets, was proposed. The primary particles formed mainly through a homogeneous nucleation mechanism and increased in size as MMA diffused from the oil phase to the water phase to the primary particles. The coagulation of the primary particles occurred because of the lower colloidal stability and the space limitations of the primary particles. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1905–1911, 2004     

Synthesis of chitosan‐modified poly(methyl methacrylate) by emulsion polymerization

Emulsion polymerization of methyl methacrylate (MMA) in the presence of chitosan was studied and a reaction mechanism was proposed. It was proved in the companion article that potassium persulfate (KPS) free radicals can degrade chitosan chains into chain free radicals. Therefore, it is possible to produce a chitosan copolymer when the monomer and the KPS initiator are added into the chitosan solution. According to the proposed mechanism, concentrations of different species such as the initiator, total free radicals, and degraded chitosan chain were calculated with the reaction time. All the results agreed with the experimental observation. The results showed that the polymerization rate varied with 0.83‐ and 0.82‐order of the total free‐radical concentration and chitosan repeating unit concentration, respectively. It was also verified that chitosan played multiple roles in the reaction system. If the monomer was added into the chitosan solution before the addition of KPS, chitosan served mainly as a surfactant. Consequently, the polymer particle number was increased with the chitosan addition and so was the polymerization rate. However, if the monomer was added into the solution where the chitosan was already degraded by KPS, the polymerization rate was decreased with the predegradation time of chitosan. In both cases, the final polymer particles consisted of the poly(methyl methacrylate) (PMMA) homopolymer and the chitosan‐PMMA copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3047–3056, 2002     

Morphological characterization of attapulgite/poly(methyl methacrylate) particles prepared by soapless emulsion polymerization

BACKGROUND: The synthesis of core–shell inorganic/polymer nanocomposites, in which the polymer shell determines the chemical properties and the interaction with the environment, whereas their physical properties are governed by both the size and shape of the inorganic core and the surrounding organic layer, is an area of increasing research activity. RESULTS: Core–shell and bead–string shaped attapulgite/poly(methyl methacrylate) (ATP/PMMA) nanocomposite particles were prepared by soapless emulsion polymerization in an aqueous suspension of attapulgite organically modified with cetyltrimethylammonium bromide. CONCLUSION: Transmission electron microscopy analysis results showed that the amounts of the monomer added had no influence on the morphologies of the ATP/PMMA particles. The morphologies only depended on the length/diameter ratio of the attapulgite fibrillar single crystal used. Long ATP needles formed the bead–string structure while short ATP needles formed the core–shell structure. Copyright © 2007 Society of Chemical Industry     

Iron (II) chloride catalyzed emulsion polymerization of methyl methacrylate using different initiators

The emulsifier and emulsifier-free emulsion polymerization of methyl methacrylate (MMA) using sodium bisulphite, acetaldehyde sodium bisulphite (ACSB), octyladehyde sodium bisulphite (OSB), benzaldehyde sodium bisulphite (BSB), and acetone sodium bisulphite (ASB) as different initiators, and dodecyl benzene sodium sulphonate (DBSS) as an emulsifier, were carried out at 30, 40, and 50°C. The effect of iron (II) chloride on the rate of polymerization and on the viscosity-average molecular weight was investigated. The effect of temperature, iron (II) chloride, and the type of initiator on the tacticity of the obtained polymers was investigated by means of nuclear magnetic resonance (NMR) spectroscopy. The effect of iron (II) chloride and the four carbonyl adducts (ACSB, OSB, BSB, and ASB) on the volume-average diameter and the number of polymer particles per unit volume was investigated. It was found that iron (II) chloride has a pronounced catalytic effect on the emulsion polymerization. The initiating powers of the four carbonyl adducts, ACSB, BSB, OSB, and ASB, were found to be 3.27, 0.6, 1.78, and 0.23, respectively. The rate of emulsion polymerization and viscosity-average molecular weight were found to be dependent on the emulsifier concentration, initiator type and concentration, temperature, and amount of the catalyst (FeCl₂). © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1725–1738, 1998     

Synthesis and characterization of poly(methyl methacrylate) nanoparticles by emulsifier‐free emulsion polymerization with a redox‐initiated system

In this study, the emulsifier‐free emulsion polymerization of methyl methacrylate (MMA) was initiated directly by a Cu²⁺/HSO redox system. Latex particles with negative charge due to the bonded anionic sulfite ion were successfully synthesized after 2 h of reaction at 40–60°C. Scanning electron microscopy pictures showed a uniform particle size distribution, and the average size decreased from 223 to 165 nm wit increasing reaction temperature from 40 to 60°C. The initiation step in the polymerization mechanism was proven to be a redox reaction, in which Cu²⁺ oxidized the bisulfite ion to produce an anionic sulfite radical and proton. The produced anionic sulfite radical then initiated the polymerization of MMA. Moreover, Cu²⁺ not only served as one component in the redox initiator system but also as a chain‐transfer agent that terminated growing polymer chains to produce chains with unsaturated end groups [poly(methyl methacrylate) (PMMA)? CH?CH₂]. For this system, about 17% PMMA? CH?CH₂ was produced. The tacticities of the PMMA latex prepared at 40–60°C were almost the same, about 62–64% syndiotactic, 33–35% heterotactic, and 3% isotactic. These PMMA latexes had almost the same glass‐transition temperature, 125–127°C, regardless of the reaction temperatures, and their weight‐average molecular weights were in the range between 254,000 and 315,000. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(methyl methacrylate) copolymer nanocapsules containing phase‐change material (n‐dodecanol) prepared via miniemulsion polymerization

Poly(methyl methacrylate) copolymer nanocapsules containing the phase‐change material n‐dodecanol, which could be used for energy storage, were prepared with different comonomers via miniemulsion polymerization. The thermal properties, morphology, and composition of nanocapsules were characterized with differential scanning calorimetry, thermogravimetric analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy. The results show that the thermal properties and morphology of the nanocapsules were influenced greatly by the type and amount of comonomers. Under the same dosage of 4 wt %, the nanocapsules prepared with the comonomer acrylamine and which had a moderate hydrophilicity showed the highest phase‐change latent heat of 109.3 J/g; the acrylamine that had a moderate hydrophilicity and the highest encapsulation efficiency of 91.3%. The size of the nanocapsules ranged from 50 to 100 nm with a uniform spherical shape and apparent core–shell structure. We also found that when the amount of the soft comonomer butyl acrylate was increased, the phase‐change latent heat of the nanocapsules first decreased slightly, then increased to the maximum value with deformed spherical and conglutinated morphology, and finally decreased continuously. The thermal stability of the nanocapsules became weaker with higher contents of core material. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42334.     

Ultrasonically initiated free radical‐catalyzed emulsion polymerization of methyl methacrylate (i)

The emulsion polymerization of methyl methacrylate initiated by ultrasound has been studied at ambient temperature using sodium lauryl sulfate as the surfactant. The investigation includes the: (1) nature and source of the free radical for the initiation process; (2) effects of different types of cavitation; and (3) dependence of the polymerization rate, polymer particle number generated, and the polymer molecular weight on acoustic intensity, argon gas flow rate, surfactant concentration, and initial monomer concentration. It was found that the polymerization could be initiated by ultrasound in the emulsion systems containing methyl methacrylate, water, and sodium lauryl sulfate at ambient temperature in the absence of a conventional initiator. The source of the free radical for the initiation process was found to come from the degradation of the sodium lauryl sulfate, presumably in the aqueous phase. The weight average molecular weight of the poly(methyl methacrylate) obtained varied from 2,500,000 to 3,500,000 g mol⁻¹, and the conversion for polymerization was up to 70%. Deviations from the Smith–Ewart kinetics were observed. The polymerization rate was found to be proportional to the acoustic intensity to the 0.98 power; to the argon gas flow rate to the 0.086 power; to the surfactant concentration to the 0.08 power, with the 0.035M–0.139M surfactant concentration range; and to the surfactant concentration to the 0.58 power, with the 0.139M–0.243M surfactant concentration range. The polymerization rate was found to increase with increasing initial monomer concentration up to a point where it became independent of initial monomer concentration. The polymer particle number generated per milliliter of water was found to be proportional to the acoustic intensity to the 1.23 power; to the argon gas flow rate to the 0.16 power; to the surfactant concentration to the 0.3 power, with the 0.035M–0.139M surfactant concentration range; and to the surfactant concentration to the 1.87 power, with the 0.139M–0.243M surfactant concentration range. The polymer weight average molecular weight was found to be proportional to the acoustic intensity to the 0.21 power, and to the argon gas flow rate to the 0.02 power. It was found to be inversely proportional to the surfactant concentration to the 0.12 and 0.34 power, with the 0.035M–0.139M and the 0.139M–0.243M surfactant concentration ranges, respectively. The polymer yield and polymerization rate were found to be much larger than those obtained from an ultrasonically initiated bulk polymerization method. The polymerization rates obtained at ambient temperature were found to be similar to or higher than those obtained from the conventional higher temperature thermal emulsion polymerization method. This investigation demonstrated the capability of ultrasound to both initiate and accelerate polymerization in the emulsion system, and to do this at a lower temperature that could offer substantial energy savings. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 797–825, 1999     

Lamotrigine‐loaded polyacrylate nanoparticles synthesized through emulsion polymerization

A series of copolymeric nanoparticles of the partially water‐soluble monomer ethyl methacrylate and the water‐soluble monomer 2‐hydroxyl ethyl methacrylate were synthesized from emulsions containing sodium dodecyl sulfate via free‐radical polymerization. Lamotrigine, as a model drug, was loaded in nanoparticles during in situ polymerization. A stable and transparent poly(ethyl methacrylate‐co‐hydroxyl ethyl methacrylate) nanolatex was produced for all compositions and characterized for particle size by dynamic light scattering and transmission electron microscopy. Particles were found to be smaller than 50 nm in size. Structural characterization of copolymers was done by infrared spectrometry, gel permeation chromatography, and NMR spectroscopy. Drug encapsulation efficiency was determined by ultraviolet (UV)–visible spectrometry and was found to be 26–62% for copolymers with different compositions. UV data suggest molecular‐level dispersion of the drug in the nanoparticles. In vitro drug‐release studies showed the controlled release of lamotrigine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Ultrasound‐assisted emulsion polymerization of methyl methacrylate and styrene

In this article, we report on the effect of using ultrasound during emulsion polymerization. This work differs somewhat from that previously reported in that ultrasound is used in conjunction with conventional initiators. The aim is to observe the changes in the nature of polymerization and the synthesized polymer. In this work, reaction conditions and compositions typical of conventional emulsion polymerization are used. Azo‐bisisobutyronitrile and potassium per sulfate are the initiators used. The initial indication is that the rate of polymerization and the final conversion are higher when ultrasound is introduced into the polymerization system. This effect is more pronounced at lower temperatures (50°C) and low initiator concentrations (0.01%). At higher temperatures (70°C) the polymerization rate is seemingly unaffected by the use of ultrasound. The final product in all the experiments is a latex. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 101–104, 2000     

Impact of impeller type on methyl methacrylate emulsion polymerization in a batch reactor

The emulsion polymerization of methyl methacrylate (MMA) was carried out in a lab‐scale reactor, which was equipped with a top‐entry agitator, four wall baffles, a U‐shaped cooling coil, and a temperature controller. Potassium per sulfate and sodium dodecyl sulfate as were used as the initiator and the surfactant, respectively. The experimental investigation demonstrated the impact of the impeller type (45° six pitched‐blade turbine and Rushton impeller), number of impellers (single and double impellers), and impeller speed (100–350 rpm) on the monomer conversion, polymer particles size, molecular weight, and glass transition temperature. The results revealed that the effect of the impeller speed on the characteristics of the polymer attained using the pitched‐blade turbine was more prominent than that for the Rushton turbine. It was also found that the impact of the impeller speed on the polymer characteristics was much more pronounced for the double pitched‐blade turbines rather than for the double Rushton turbines. However, more uniform size distribution was achieved with the Rushton turbine. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40496.     

Poly(methyl acrylate-co-methyl methacrylate)/montmorillonite nanocomposites fabricated by soap-free emulsion polymerization

The exfoliated poly(methyl acrylate-co-methyl methacrylate)/montmorillonite (MMT) nanocomposite latex solutions fabricated by soap-free emulsion polymerization were able to cast into a film. The films were transparent and ductile unless more than 5 wt% of MMT was incorporated. With the MMT content higher than 5 wt%, the inflammable residuals of nanocomposites after combustion could preserve their original film profile acting like an inflammable scaffold. Moreover, as 20 wt% MMT was incorporated, the yield strength of the films was increased up to 20 times and Young’s modulus up to 2,000 times. However, the water vapor permeability coefficient of the films was only decreased down to its half value. This unexpected behavior of permeability was associated with the decrease of T _g as the content of MMT was increased, owing to the large difference of the reactivity ratios between methyl acrylate and methyl methacrylate monomers and their differential absorption to the MMT during copolymerization.     

微波辐射无皂乳液聚合制备单分散热敏性微球

在微波辐射条件下苯乙烯(St)和N-异丙基丙烯酰胺进行无皂乳液聚合,结果表明所制备的微球粒径小于150nm且为单分散。利用透射电子显微镜(TEM)观察微球形态及粒径。通过动态激光光散射粒度仪(PCS)考察微球的热敏性,微球粒径随温度发生变化。     

水性聚氨酯/聚甲基丙烯酸甲酯杂化乳液的合成

用异佛尔酮二异氰酸酯(IPDI)、聚丙二醇(PPG)和二羟甲丙酸(DMPA)合成了水性聚氨酯分散体(WPU),讨论了PPG摩尔质量,NCO/OH及PPG/DMPA比例对WPU乳液和涂膜性能的影响。以WPU为种子与甲基丙烯酸甲酯进行乳液聚合制备杂化乳液,研究了不同PU/PMMA物质的量比例对杂化乳液及涂膜性能的影响,并采用TEM对WPU及杂化乳液粒子进行了表征。结果表明,在以PPG1000为原料,NCO与OH物质的量比为1.4∶1,PPG与DMPA物质的量比为1∶0.8条件下制备的WPU杂化乳液,随着PMMA比例增加,杂化乳液的稳定性和成膜性变差,聚合物膜断裂伸长率降低,但铅笔硬度、耐水性及耐乙醇性均得到了改善。     

Poly(methyl methacrylate) multihollow particles by water in oil in water emulsion polymerization

Multihollow‐structured poly(methyl methacrylate) (PMMA) particles were produced employing the water in oil in water (W/O/W) emulsion polymerization technique where sorbitan monooleate was used as a primary surfactant and sodium laurylsulfate and Glucopen, a polypeptide derivative, were used as secondary surfactants. Vinyl acetate was copolymerized to improve the wettability of the particles. The agitation speed and concentration of the urethane acrylate employed as a reactive viscosity enhancer played a crucial role in determining the morphology and average size of the PMMA multihollow particles. In high agitation speed the multihollow particles displayed a small size and narrow size distribution resulting from efficient droplet breakup. Especially when the urethane acrylate was incorporated, PMMA multihollow particles with a smooth and clear surface were achieved. This was believed to be because the urethane acrylate increased the viscosity of the monomer mixture and helped to form the stable W/O/W emulsion droplets that restricted droplet coalescence during polymerization. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 38–44, 2000     

Concentrated emulsion polymerization of methyl methacrylate/butyl acrylate initiated by a redox system

Stable concentrated emulsions of methyl methacrylate/butyl acrylate were prepared with sodium dodecyl sulfate and cetyl alcohol as the compound surfactant and poly(vinyl alcohol) as the major reinforcer of the liquid film. With a redox system based on benzoyl peroxide/N,N′‐dimethyl phenylamine introduced into the concentrated emulsions, polymer particles with different shapes and sizes were obtained by initiation of the polymerization at low temperatures. We investigated the kinetic behaviors of concentrated emulsion polymerization and drew linear regression diagrams of its time–conversion curves in a constant rate phase (conversions ranged from 20 to 70%), and the experimental results show that the variation of the concentrations of the compound surfactant and initiator, the categories of reinforcers of the liquid film, the temperatures, and so on were responsible for the polymerization stability and the polymerization rate. Finally, the kinetics equation and activation energy of the initiator were obtained. The particle size and distribution of particle diameters of latex particles were determined by photon correlation spectroscopy. The determination results reveal that concentrations of the compound surfactant, polymerization temperatures, and so on affected the shape and size of the polymer particles greatly. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1695–1701, 2005     

Soapfree emulsion polymerization of methyl methacrylate in the presence of CaSO3

In the soapfree emulsion polymerization of a methyl methacrylate-K₂S₂O₈-CaSO₃-H₂O system, the polymerization rate, average molecular weight of polymer, particle size and particle concentration would vary with the concentration of CaSO₃. It was shown that when the concentration of CaSO₃ was well below the saturation concentration (3 × 10^?4mol/litre H₂O), the polymerization rate was higher than that of the system not containing CaSO₃. On the other hand, when the concentration of CaSO₃ was above the saturation concentration, the polymerization rate at the latter stage was lower than that of the system not containing CaSO₃ within our experimental conditions. The molecular weight of polymer was measured by Gel Permeation Chromatography (GPC). It decreased initially and then increased due to the gel effect over the entire course of polymerization. The size of the polymer particles was measured by both photo correlation spectroscopy (PCS) and transmission electron microscopy (TEM), The reaction mechanism was studied according to the above observation. The mechanical property of poly(methyl methacrylate)-CaSO₃ composite obtained from soapfree emulsion polymerization was tested and compared with that obtained from mechanical blending.