Poly(methyl methacrylate) nanoparticles prepared through microwave emulsion polymerization

The emulsifier‐free emulsion polymerization of methyl methacrylate (MMA) was conducted with microwave irradiation. Superfine and monodisperse poly(methyl methacrylate) (PMMA) microspheres were obtained. Microwave irradiation notably promoted the polymerization reaction. This phenomenon was ascribed to the acceleration of the initiator [potassium persulfate (KPS)] decomposition by microwave irradiation. The experimental results revealed that the apparent activation energy of KPS decomposition decreased from 128.3 to 106.0 kJ/mol with microwave irradiation. The average particle size of the prepared PMMA latex was mainly controlled with the MMA concentration; it increased linearly from 103 to 215 nm when the MMA concentration increased from 0 to 0.3 mol/L and then remained almost constant at MMA concentrations of 0.3–1.0 mol/L. The KPS concentration had no effect on the average particle size, but the particle size dispersity was significantly reduced by a high KPS concentration. With a mixed polymerization phase (water/acetone = 1:3 v/v) or a redox initiation system, PMMA nanoparticles were obtained with an average particle size of 45 or 67 nm, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2815–2820, 2004     

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     

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     

Emulsification in batch emulsion polymerization

Dispersion of liquid–liquid systems is often applied in industrial processes such as extraction, suspension, and emulsion polymerization. The influence of emulsification of the monomer in the aqueous phase on the course and outcome of the batch emulsion polymerization of styrene has been studied. A visual criterion was applied for determining the lowest impeller speed for sufficient emulsification (N*). It appeared that in polymerization experiments under the same conditions, N* was the critical value above which no further increase in polymerization rate was observed. Using a turbine impeller instead of a pitched blade impeller as well as using a larger impeller diameter provides better emulsification at constant power input. The results indicate that scale‐up with constant impeller tip speed is most appropriate in case of a turbine impeller. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3225–3241, 1999     

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     

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.     

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     

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     

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     

Single‐ and two‐step procedures of AGET emulsion ATRP of methyl methacrylate in a well‐mixed batch reactor

This study investigates the atom transfer radical emulsion polymerization of methyl methacrylate in a 2 L well‐mixed stirred batch reactor using activators generated by electron transfer as the initiation technique. The polymerization was carried out with ethyl‐2‐bromoisobutyrate as the initiator, copper bromide with 4,4′‐di‐5‐nonyl‐2,2′‐bipyridine as the catalyst system, Brij 98 as the surfactant, and ascorbic acid as the reducing agent. The reaction was carried out at constant temperature in the range of 50 to 70 °C under a blanket of nitrogen to minimize the presence of air in the system. Polymerizations were carried out according to single‐step and two‐step procedures. The coagulation was found to be a major problem, especially at high monomer conversion. However, adding more surfactant and lowering the reaction temperature weakened the effect of the coagulation but at the expense of the low monomer conversion. Measurement of molecular weight distribution and ? using gel permeation show that the two‐step techniques produced polymers with living features of atom transfer radical emulsion polymerization much better than those in the single‐step procedure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45308.     

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.     

Influence of compositions and polymerization processes on morphologies,molar mass distributions,and phase structures of n‐Butyl acrylate–methyl methacrylate copolymers

The target of the research is to examine influence of a polymerization process and monomer ratio on structures and compositions of phases in an emulsion copolymerization of n‐butyl acrylate (BA) and methyl methacrylate (MMA). Emulsion copolymerizations are performed using three different BA/MMA weight ratios (60%/40%, 50%/50%, and 40%/60%) and two different processes, statistical batch and seeded emulsion polymerizations. Phase structures, monomer compositions, and morphological stabilities of copolymers are investigated by differential scanning calorimetry, ¹H‐NMR, and scanning electron microscopy. Gel permeation chromatography is used to follow the changes in the molar mass distribution during syntheses. The gel content and backbiting level of end products are measured by extraction and ¹³C‐NMR, respectively. Copolymerizations give products with a bimodal molar mass distribution and three or two separate phases having different BA/MMA compositions. The morphological stability of particles decreases with the increasing BA fraction in the feed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41467.     

Factorial experimental design approach in semicontinuous emulsion polymerization of methyl methacrylate to study the effect of process variables

This article describes the effect of various process variables in the semicontinuous emulsion polymerization of methyl methacrylate. A series of poly(methyl methacrylate) (PMMA) emulsions were prepared using ammonium persulphate as initiator in absence and presence of Dowfax 2AI as surfactant. The effect of process variables such as initiator concentration, monomer concentration (solid content), surfactant concentration, reaction temperature, monomer feeding time, and holding time were systematically studied on monomer conversion, particle size, gel content, and molecular weight using a two‐level fractional factorial experimental method. Analysis of fractional factorial design revealed that surfactant concentration, monomer concentration, initiator concentration, and monomer feeding time affect all the properties. However, the surfactant concentration and the interaction effect of initiator and monomer feeding time are the key variables influencing the properties of PMMA latex. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

甲基丙烯酸甲酯与丙烯酸正丁酯乳液聚合的研究

以甲基丙烯酸甲酯与丙烯酸正丁酯为主要原料,过硫酸铵为引发剂,OP-10、十二烷基硫酸钠(K12)为乳化剂,用乳液聚合法合成了聚丙烯酸酯类共聚乳液,考察了聚合条件对乳液聚合的影响。实验结果表明,在单体、引发剂、水用量一定时,合适的反应条件为乳化剂(OP-10∶K12=1∶1)2%,单体滴加时间以60~90min,80℃反应2h左右。     

Continuous emulsion polymerization of styrene in a single Couette–Taylor vortex flow reactor

The effect of the geometrical and operational parameters on the mixing characteristics of a Couette–Taylor vortex flow reactor (CTVFR) were investigated and were correlated with the same parameters by using the tank‐in‐series model. Continuous emulsion polymerization of styrene was conducted at 50°C in a CTVFR to clarify the effects on kinetic behavior and reactor performance of operational parameters such as rotational speed of inner cylinder (Taylor number), reactor mean residence time, and emulsifier and initiator concentrations in the feed streams. It was found that steady‐state monomer conversion and particle number could be freely varied only by varying the Taylor number. In order to explain the observed kinetic behavior of this polymerization system, a mathematical model was developed by combining the empirical correlation of the mixing characteristics of a CTVFR and a previously proposed kinetic model for the continuous emulsion polymerization of styrene in continuous stirred tank reactors connected in series (CSTRs). On the basis of these experimental results, it was concluded that a CTVFR is suitable for the first reactor (prereactor) of a continuous emulsion polymerization reactor system. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1931–1942, 2001     

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     

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     

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.     

Study of different types of monomer emulsion feedings to semibatch emulsion polymerization reactors

Semibatch emulsion polymerization processes with a monomer emulsion feed are of great importance in both academia and industry. Monomer emulsion feeds can be applied to semibatch reactors using either a stream of an emulsified monomer or two streams of a neat monomer feed and an aqueous solution of an emulsifier. The effect of the feeding policy on the rate of polymerization and on the secondary particle formation was studied for a seeded semibatch emulsion polymerization of styrene. When a single-stream monomer emulsion feed is applied to a semibatch process, the monomer-swollen micelles formed in the feed might become the locus of initiation upon entering the reaction vessel. Under the conditions of this study, the application of monomer emulsion feed in either one stream or two streams did not result in secondary particle formation. The incoming monomer-swollen micelles were disintegrated to supply emulsifier molecules for the stability of growing particles, before they can capture radicals and become polymer particles. The rate of polymerization was found to be independent of the way that the monomer emulsion feed is added. In the absence of nitrogen, the rate of polymerization decreased more appreciably for the monomer emulsion feed, due to the oxygen dissolved in the emulsified monomer. The number of particles, however, was not affected by the purging policy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2472–2477, 2001