Butyl acrylate batch emulsion polymerization in the presence of sodium lauryl sulphate and potassium persulphate

The batch emulsion polymerization of butyl acrylate in the presence of sodium lauryl sulphate as emulsifier and potassium persulphate as initiator was investigated. The effects of emulsifier concentration, initiator concentration, and monomer/water ratio on the kinetic features were studied. The kinetic data showed that at the conditions studied, the number of particles is proportional to [KPS]^0.39 and [SLS]^0.54. The number of particles did not practically vary with monomer concentration at the high range of monomer and emulsifier concentrations. At low emulsifier concentration, particle coagulation occurred in the course of reaction, which increased with monomer concentration. Particle nucleation was found to occur during Interval III of the batch process if undissociated micelles exist. It was also confirmed that the zero-one kinetics system can better fit the experimental results, compared to the pseudobulk kinetics. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3957–3972, 1999     

Particle formation and coagulation in the seeded semibatch emulsion polymerization of butyl acrylate

Particle formation and coagulation in the seeded semibatch emulsion polymerization of butyl acrylate were studied under monomer‐starved conditions. To investigate the importance of the kinetics of the water phase in the nucleation process, the monomer feed rate was used as a variable to alter the monomer concentration in the aqueous phase. The emulsifier concentration in the feed was employed to alter the particle stability. Particle formation and coagulation were discussed in terms of critical surface coverage ratios. Particle coagulation occurred if the particle surface coverage dropped below θ_cr1 = 0.25 ± 0.05. The secondary nucleation occurred above a critical surface coverage of θ_cr2 = 0.55 ± 0.05. The number of particles remained approximately constant if the particle surface coverage was within θ_cr1 = 0.25 < θ < θ_cr2 = 0.55. This surface coverage band is equivalent to the surface tension band of 42.50 ± 5.0 dyne/cm that is required to avoid particle formation and coagulation in the course of polymerization. The kinetics of the water phase was shown to play an important role during homogeneous and micellar nucleations. For any fixed emulsifier concentration in the feed and above θ_cr2, the number of secondary particles increased with monomer concentration in the aqueous phase. Moreover, the presence of micelles in the reaction vessel is not the only perquisite for micellar nucleation to occur, a sufficient amount of monomer should be present in the aqueous phase to enhance the radical capture by partially monomer‐swollen micelles. The rate of polymerization increased with the surfactant concentration in the aqueous phase. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3612–3630, 2000     

Semicontinuous seeded cationic emulsion polymerization of styrene: The effects of the concentration and type of cationic surfactant

The objective of this work was to analyze the effects of the concentration and type of cationic surfactant on the kinetic features (instantaneous and overall conversions) and colloidal characteristics [mean particle diameter, particle size distribution (PSD), and surface charge density] in the semicontinuous seeded cationic emulsion polymerization of styrene. 2,2′‐Azobis(N,N′‐dimethyleneisobutyramidine)dihydrochloride was used as an initiator. The surfactants were dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethylammonium bromide (HDTAB). So that the evolution of some polymeric and colloidal characteristics of the synthesized latices could be followed, the overall and instantaneous conversions were defined and determined gravimetrically. The PSDs and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The surface charge density was determined by conductimetric titration. The evolution of the instantaneous conversions, the total number of particles, and the PSDs of the different reactions were related to the nucleation, growth, and coagulation processes taking place in the semicontinuous seeded emulsion polymerizations. The PSDs obtained from the reactions carried out with the emulsifier DTAB, at a concentration equal to its critical micelle concentration (cmc) and at a concentration twice its cmc, presented more and smaller particles than those obtained by the addition of HDTAB to the polymerization recipe. At lower emulsifier concentrations equal to half of the cmc, the system had lower colloidal stability with DTAB. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2322–2334, 2003     

Monodisperse micron-sized crosslinked polystyrene particles. IV. Effect of network structure on polymerization procedure

Monodisperse micron-sized polystyrene particles crosslinked using urethane acrylate were produced by dispersion polymerization in ethanol solution and the effect of the crosslinked network structure on the polymerization procedure was studied. The influences of the concentrations of the initiator and urethane acrylate on the particle diameter (D _n), the particle number density (N _p), and the polymerization rate (R _p) were found to obey the approximate relationships D _n ∝ [initiator]^0.43 [urethane acrylate]^0.05, N _p ∝ [initiator]^−1.30 [urethane acrylate]^0.19, and R _p ∝ [initiator]^{0.24 ± 0.02}. The power-law dependence of D _n and N _p on the initiator concentration showed a similar trend to that of linear polystyrene reported in the literature. Especially, it was found that urethane acrylate does not have a serious effect on D _n and N _p of the particles produced. The dependence of R _p on the initiator concentration was observed to be higher than that of linear polystyrene, suggesting that there is still competition between heterogeneous polymerization and solution polymerization because of the crosslinked network structure of the primary particle. Received: 1 April 1999 Accepted in revised form: 29 June 1999     

Unseeded semibatch emulsion polymerization of butyl acrylate: Bimodal particle size distribution

Unseeded semibatch emulsion polymerization of butyl acrylate (BA) using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator was carried out at the conditions where secondary nucleation was probable. This was achieved by using no emulsifier in the initial reactor charge. The effects of changes in monomer emulsion feed rate, initiator concentration and distribution, emulsifier concentration in the feed, and temperature on the evolution of particle size averages and distribution were investigated. Bimodal particle size distributions (PSD) were obtained for most of the latexes. Inhibition effects were found to be important in the development of PSD. Primary particle formation occurred through micellar nucleation, whereas secondary nucleation probably occurred through homogenous nucleation. The polydispersity index (PDI) of the latexes increased with the decreasing monomer emulsion feed rate. The application of a larger amount of initiator to the reactor charge or using a higher temperature, reduced the formation of secondary particles and resulted in a formation of an unimodal PSD. The overall steady‐state rate of polymerization was found to approach the rate of monomer addition (R_p ≈ R_a ), if the emulsifier concentration in the aqueous phase was appreciable. This is different from the correlation 1/R_p = 1/K + 1/R_a obtained for the BA semibatch process with neat monomer feed. This suggests that different rate expressions can be used for BA semibatch emulsion polymerization at different conditions. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 528–545, 2000     

Stability of the polymerizable surfactant stabilized latex particles during semibatch emulsion polymerization

The effect of the polymerizable surfactant, sodium dodecyl allyl sulfosuccinate (JS-2), on the stability of polybutyl acrylate latex particles during semibatch emulsion polymerization was investigated in this work. Experimental data show that the ionic strength is the most important parameter in determining the latex stability during the reaction. Both the amount of coagulum produced by intensive coagulation and percentage of the particle volume change (ΔV) caused by limited flocculation increase with increasing electrolyte concentration. The parameter Δ V increases significantly when the concentration of JS-2 in the initial reactor charge ([JS-2]_i) increases. The amount of coagulum increases rapidly when the agitation speed is increased from 400 to 800 rpm. Experiments of coagulation kinetics were carried out to study the stability of latex products toward added salts. The experimental data show that the chemical stability of the latex product increases with increasing pH. Furthermore, the critical coagulation concentration and diffuse potential increase with increasing [JS-2]_i. It is postulated that the increasing electrostatic attraction force between two approaching particles due to the increased [JS-2] _i can increase the apparent magnitude of Hamaker constant.     

The preparation of sterically stabilized polymer dispersions

The emulsion polymerizations of styrene (St) and butyl acrylate (BA) stabilized by nonionic polyoxyethylene type emulsifiers did not show the long stationary rate interval. This was discussed in terms of two opposing effects: 1) the decreased monomer concentration at the reaction loci due to the depletion of monomer droplets or depressed monomer droplet degradation and 2) the increased number of polymer particles with increasing conversion. The continuous particle nucleation is attributed to the continuous release of emulsifier from the emulsifier saturated monomer droplets and/or the presence of monomer swollen micelles (microdroplets). The limited particle flocculation operative at lower emulsifier concentrations increases the nonstationary-state polymerization. The particle agglomeration is accompanied by the increased reaction order x (N_p vs. [E]^x) above 0.6. The increased uniformity of monomer emulsion stabilized by Tween 20 by homogenization of monomer emulsion increased the final conversion and the polymerization rate as well. The polymerization rate vs. conversion curve of the homogenized emulsion characterized with broader stationary rate interval reminds the four rate intervals system typical for miniemulsion. The accumulation of polymer and nonionic emulsifier within the monomer phase preserves the monomer droplets up to high conversion. The decreased monomer droplet degradation rises the monomer-starved condition or the depressed transport of both monomer and emulsifier to the reaction loci.     

STUDY ON THE POLYMERIZATION KINETICS AND STABILITY OF P(UA)/MMA MICROEMULSION*

 Urethane acrylate anionomer (APUA) as a kind of new type polymerizable emulsifier was synthesized using 2,4-toluene diisocyanate (TDI), polypropylene glycol (PPG), 2-hydroxyethyl methacrylate (HEMA) and dimethylolpropionic acid (DMPA). The critical micelle concentration (CMC) of APUA was measured by the methods of conductance and surface tension. The comparative studies between polymerizable emulsifier AUPA and conventional emulsifier sodium dodecyl sulfate (SDS) were carried out in the emulsion polymerization of methyl methacrylate (MMA). Polymerization kinetics,stability, size and morphology of the latex particles were investigated. It was found that in APUA both water soluble initiator potassium persulfate (KPS) and oil soluble initiator 2,2'-azobisisobutyronitrile (AIBN) can start the reaction of MMA, and the polymerization rate and yield were very high. On using AIBN as an initiator, the conversion-time behavior of MMA with APUA as emulsifier was different to that of SDS as emulsifier, signifying a different nucleation mechanism of the polymer latex particle. The average size of the two kinds of particles is about 50 nm. The particle size decreases with increasing emulsifier concentration. On using KPS as the initiator, APUA as emulsifier, cross-linking hydrogel of PMMA would be formed, but SDS was used as emulsifier and the hydrogel of PMMA was not present.     

Analysis of particle formation under monomer-starved conditions in emulsion polymerization reactors

An important characteristic of monomer-starved nucleation in semibatch reactors is that the rate of growth of particles is controlled by the rate of monomer addition. The reduced rate of growth of particles prolongs the nucleation interval by slowing down the rate of emulsifier micelle depletion and forms a larger number of particles (N_p). Model calculations show how N_p varies with the formulation parameters as the monomer-flooded nucleation shifts into monomer-starved one. Particle formation in the intermediate conversion of interval III of the styrene batch emulsion polymerization also showed an enhancement because of a low rate of growth of newly formed particles. However, at a higher conversion, the rate of particle formation decreased significantly. Modeling results show that the reduction in the rate of particle formation at high conversions could not be simply explained by existing theories which rely on the decrease in monomer concentration in the aqueous phase as a means to explain the decrease in the rate of radical capture.     

Kinetic study of the nitroxide‐mediated controlled free‐radical polymerization of n‐butyl acrylate in aqueous miniemulsions

The controlled free‐radical homopolymerization of n‐butyl acrylate was studied in aqueous miniemulsions at 112 and 125 °C with a low molar mass alkoxyamine unimolecular initiator and an acyclic β‐phosphonylated nitroxide mediator, N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl) nitroxide, also called SG1. The polymerizations led to stable latices with 20 wt % solids and were obtained with neither coagulation during synthesis nor destabilization over time. However, in contrast to latices obtained via classical free‐radical polymerization, the average particle size of the final latices was large, with broad particle size distributions. The initial [SG1]₀/[alkoxyamine]₀ molar ratio was shown to control the rate of polymerization. The fraction of SG1 released upon macroradical self‐termination was small with respect to the initial alkoxyamine concentration, indicating a very low fraction of dead chains. Average molar masses were controlled by the initial concentration of alkoxyamine and increased linearly with monomer conversion. The molar mass distribution was narrow, depending on the initial concentration of free nitroxide in the system. The initiator efficiency was lower than 1 at 112 °C but was very significantly improved when either a macroinitiator was used at 112 °C or the polymerization temperature was raised to 125 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4410–4420, 2002     

Preparation of poly(n‐butyl acrylate)‐b‐polystyrene particles by emulsifier‐free,organotellurium‐mediated living radical emulsion polymerization (emulsion TERP)

We have successfully demonstrated the preparation of poly(n‐butyl acrylate)‐b‐polystyrene particles without any coagulation by two‐step emulsifier‐free, organotellurium‐mediated living radical emulsion polymerization (emulsion TERP) using poly(methacrylic acid) (PMAA)–methyltellanyl (TeMe) (PMAA₃₀‐TeMe) (degree of polymerization of PMAA, 30) and 4,4′‐azobis(4‐cyanovaleric acid) (V‐501). The final particle size was ～30 nm and second particle nucleation was not observed throughout the polymerization. M_n increased linearly in both steps with conversion and blocking efficiency was ～75%. PDI was improved by increasing radical entry frequency into each polymer particle due to an increase of the polymerization temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Microemulsion polymerization of butyl acrylate. IV. Effect of emulsifier concentration

The oil/water microemulsion polymerizations of butyl acrylate initiated by a water (ammonium peroxodisulfate, APS) or oil (dibenzoyl peroxide, DBP) soluble radical initiator at different emulsifier concentrations were investigated. The rate of polymerization vs. conversion curve shows two intervals. The rate of polymerization is found to decrease with the emulsifier concentration. This finding was discussed in terms of the decrease of both radical and monomer concentration, the chain transfer to emulsifier, desorption of chaintransferred radicals, and the contribution of solution polymerization. The polymerization is faster with APS. In the APS system the rate per particle or the number of radicals per particle increases exponentially with increasing particle size. The particle size and number increase during the whole polymerization. This behavior was discussed in terms of the nucleation of monomer-containing micelles and agglomeration of primary particles during the whole polymerization. © 1995 John Wiley & Sons, Inc.     

Semibatch Emulsion Polymerization of Butyl Acrylate: Effect of Functional Monomers

Abstract

The concentration of sodium lauryl sulfate (SLS) in the initial reactor charge is the most important parameter in determining the latex particle size during semibatch emulsion polymerization of butyl acrylate in the presence of acrylic acid (AA), methacrylic acid, or hydroxyethyl methacrylate. The final latex particle size decreases with increasing concentration of SLS, NP-40, or functional monomer. The carboxylic monomer AA is the most efficient functional monomer to nucleate and then stabilize the latex particles. The plot of log N _f vs log SLS shows a slope of 0.4–0.8, which is more consistent with Feeney's analysis based on the coagulative nucleation mechanism. Experimental data also show that the particle size first decreases to a minimum and then increases with an increase in the concentration of the neutralizing agent NaHCO₃. The optimal concentration NaHCO₃ for achieving the smallest latex particle size occurs at a point close to 0.15–0.29%. Experimental data of the particle size distribution and molecular weight distribution show that the aqueous phase reaction can play a very important role during the particle nucleation period.     

氧化-还原低温引发苯乙烯/丙烯酸丁酯细乳液聚合粒度分布和成核机理的研究

用氧化还原引发剂(NH₄)₂S₂O₈/NaHSO₃研究了苯乙烯(St)/丙烯酸丁酯(BA)低温下的细乳液共聚合,细乳液单体液滴在亚微米级(100～400nm).测定了聚合过程中粒子大小及分布的变化,发现细乳液聚合随引发剂、乳化剂和共乳化剂浓度的增加,乳胶粒子尺寸变小,分布变宽,并且比相同条件下传统乳液聚合的粒子大.计算了聚合过程中粒子数变化规律及乳化剂覆盖率,讨论了细乳液与传统乳液中引发剂、乳化剂对反应过程的影响及成核机理的差异.     

K2S2O8/Na2SO3引发St/BA微乳液共聚合的研究

以十二烷基硫酸钠／十二烷基苯磺酸钠(SDS／SDBS)为乳化剂，过硫酸钾／亚硫酸钠(K2S2O3／Ni2SO3)为引发剂进行苯乙烯／丙烯酸丁酯(SL／BA)微孔液共聚合反应。研究了引发剂浓度[I]OR、单体总浓度[M]、乳化剂含量[E]和聚合温度T对微孔液共聚合最大反应速率Rmax和共聚物粘均分子量^-Mη的影响，测定了共聚单体的竞聚率，结果得到：Rmax∝[I]^0.98OR[M]^0.81[E]^-0．34e^-4712／T，^-Mη∝[I]^-0.27OR[M]^0.48[E]^-0.68e^2304/T；rSt=0.598，rBA=0.0206。     

On kinetics of microemulsion copolymerization of butyl acrylate and acrylonitrile

The oil-in-water microemulsion copolymerizations of butyl acrylate and acrylonitrile initiated by water (ammonium peroxodisulfate, AP)—and oil (dibenzoyl peroxide, DBP)—soluble radical initiators were investigated. Copolymerizations show two distinct nonstationary rate regions. The maximum rate of polymerization is found to be proportional to the 0.48th and 0.65th power of the AP and DBP concentration, respectively. The rate per particle is found to be proportional to the 0.05th and 0.2nd power of the AP and DBP concentration, respectively. The rate of polymerization decreases with increasing the acrylonitrile concentration. The number of particle increases with increasing conversion up to 50–70%. The number-average molecular weight increases with conversion up to ca. 20% and then decreases. The number-average molecular weights were found to decrease with increasing the concentration of both initiator and acrylonitrile. The experimental results were discussed in terms of the water-phase polymerization, the chain-transfer and radical desorption events, the particle nucleation during the whole polymerization, and recruiting monomer and emulsifier from the free monomer-swollen emulsifier micelles. © 1996 John Wiley & Sons, Inc.     

Hydroxypropyl cellulose (HPC)-stabilized dispersion polymerization of styrene in polar solvents: Effect of reaction parameters

Dispersion polymerization of styrene in polar solvents in the presence of hydroxypropyl cellulose (HPC) produces latex particles from ca. 1 to 26 μm depending on reaction parameters. Increasing the initiator concentration or temperature decreases the molecular weight, but increases the particle size and breadth of the size distribution. The decrease in molecular weight with increasing R_i, caused by larger initiator concentration or higher temperature, is expected based of fundamental kinetic relationships. The inverse correlation between size and rate of initiation is rationalized by polarity (stabilizing ability) of the grafted HPC-polystyrene formed in situ. High polar HPC-g-PS, which contains shorter graft polystyrene chain, stabilizes particles less effectively and this leads to larger particles. The primary influence of initial styrene concentration is a solvent effect: larger particles are obtained at high styrene concentration due to high solubility of polystyrene during the initial part of the reaction. The influence of the molecular weight of HPC is to change the polarity of the HPC-g-PS stabilizer. Comparison of particle growth of three critical polymerization systems suggests that the favorable continuous-phase solubility parameter for dispersion polymerization of styrene is around 11.6 (cal/mL)^1/2. Too high or too low polarity generates particles with broad size distribution because large particles are formed during the initial stage and nucleation continues as the polymerization proceeds. © 1992 John Wiley & Sons, Inc.     

Dispersion copolymerization of styrene and butyl acrylate in polar solvents

Monodisperse copolymer particles from 1.1 to 2.6 μm in diameter were obtained by unseeded batch dispersion copolymerization of styrene and butyl acrylate in an ethanol–water medium. A two-level factorial design using bottle polymerizations was initially carried out including the following variables: stabilizer concentration, initiator concentration, polarity of the dispersion medium, initial monomer concentration, and temperature. Once the region of experimental conditions in which monodisperse latexes can be prepared was identified, further effort was devoted to analyze the effect of other variables. It was found that the temperature at which nucleation occurs and the evolution of the temperature after the onset of nucleation were critical to obtain monodisperse particles. The particle size increased with increasing initial monomer concentration and ethanol–water weight ratio, and decreasing stabilizer concentration. A minimum quantity of emulsifier was necessary to avoid coalescence of particles and to obtain monodisperse particles. © 1996 John Wiley & Sons, Inc.     

Particle Nucleation and Growth in the Emulsion Polymerization of Styrene: Effect of Monomer/Water Ratio and Electrolyte Concentration

This work is an extension of previous research results reported by our team (Colloid and Polymer Science 2013, 291: 2385-2398), where large scale and high solid content latexes of poly(n-butyl acrylate) were obtained with the particle coagulation method induced by the electrolyte. However, how to prepare controlled particle size distribution polymer latex has not been studied. Thus, in this study, the effect of the monomer/water ratios and electrolyte concentrations on particle formation and growth methods were studied by following the tracks of the evolutions of particle size, number and distribution as a function of reaction time or conversion. Experimental results showed that the length of time that particle nucleation occurred increased with increasing monomer charged for the systems without electrolyte. A point worthy of attention here is that homogeneous nucleation may occur at high monomer concentrations (30/70, 40/60). However, electrolyte added could be made the nucleation mechanism shift from micellar/homogeneous nucleation to micelle /coagulation nucleation. As a result, the final particle size distribution can be controlled by adding an appropriate electrolyte to regulate the nucleation mechanism. Spherical and uniformly sized particles could be obtained when electrolyte concentration is between 0.2 wt% and 0.4 wt% for water at the high monomer/water ratio (40/60). The effects of electrolyte concentration on nucleation mechanism mainly were expressed by decreasing the solubility of the monomer and interparticle potential, and then preventing homogeneous nucleation and enhancing particle coagulation.     

Synthesis of saccharidic polymer colloids via free radical mini‐emulsion polymerization

Polymer colloids based on 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D ‐glucofuranose (3‐MDG) and butyl acrylate (BA) were prepared via free radical mini‐emulsion polymerization. The kinetic and colloidal features of the copolymerization were investigated. The final particle size (D) of the sugar latexes is inversely proportional to the concentration of the anionic emulsifier (sodium dodecyl sulphate, SDS) and the non‐ionic one (alkyl polyglucoside, APG). It was also found that D is independent of the concentration of either the water‐soluble initiator (potassium persulfate, KPS), or the oil‐soluble initiator (2,2′‐azobisisobutyronitrile, AIBN). The rate of mini‐emulsion polymerization is lower in comparison with the conventional emulsion polymerization under the same conditions. The polymerization rate (R_p) and the total number of particles (N_p) are proportional to the 0.72th and 0.93th power of the SDS, and to the 1.40th and 2.22th of the APG concentration. Following reaction orders, 0.79/0.06 were obtained for R_p/N_p versus the concentration of KPS, and 0.22/?0.01 for AIBN, respectively. Copyright © 2004 John Wiley & Sons, Ltd.