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In this study, sub-200 nm, crosslinked latex particles with a narrow particle size distribution were prepared by one-step emulsion polymerization in the presence of particle coagulation. The relationship between the particle shape and particle coagulation was investigated by varying the time of crosslinking network structure formation and particle coagulation. Particles with irregular shapes such as doublet, triplet, and ellipsoid were obtained using divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA) as the crosslinking agents, because the crosslinking network structure of particles was formed before the particle coagulation. In contrast, latex particles with a uniform spherical shape were also prepared using triallyl isocyanurate (TAIC) or dihydrodicyclopentadienyl acrylate (DCPA) as the crosslinking agents by delaying the time of crosslinking network structure formation. Alternatively, uniform spherical latex particles were prepared by bringing forward the particle coagulation time using cationic initiator, 2, 2′-azobis (2-methylpropionamidine) dihydrochloride (AAPH). This study presents a new idea that would further broaden the application of particle coagulation in emulsion polymerization. [ABSTRACT FROM PUBLISHER]

Particle coagulation technology is a facile approach to prepare large-scale and narrowly dispersed polymer particles. However, diverse shapes such as ellipsolid, snowman, dumbbell, and trimer among others were obtained if the cross-linker was directly added into the initial reaction mixtures due to the restriction of the highly cross-linking particle fusion process. In this study, we prepared sub-200 nm, narrowly dispersed, highly cross-linked, and spherical latex particles using particle coagulation technology by controlling the relation between the cross-linking net formation and particle coagulation. Depending on the addition time or feeding rate of the cross-linker (divinylbenzene, DVB), the particles with different sizes or shapes were obtained. The later the addition start time of DVB, the narrower the particle size distribution of the latex particles. Alternatively, the increase of the continuing feeding time could also be used to decrease the width of particle size distribution of the ultimate latex. In addition, narrowly dispersed and spherical latex particles also could be directly obtained by advancing the particle coagulation time using 2, 2′-Azobis (2-methylpropionamidine) dihydrochloride as a cationic initiator. Our study presents a new method that will further widen the fields of application of particle coagulation technology. [ABSTRACT FROM AUTHOR]

Highly uniform polymer latex particles with controlled particle size have been widely applied in many fields such as nanotechnology, drug delivery, biomedical separation, and material templates. Since the particle size plays a critical role in determining the application fields, various technologies such as two-stage swelling method and dynamic swelling method have been used to control the particle size in the polymerization process. However, these methods usually need a multi-step polymerization reaction and long reaction time. This review focuses on a method of controlling particle size, that is, particle coagulation technology. Particle coagulation technology can be used to produce large sized, monodispersed polymer particles by soap-free emulsion polymerization, macroemulsion polymerization, and dispersion polymerization. In this review article, an overview of the concept of particle coagulation is given, followed by the description of the particle coagulation process in different polymerization systems. Some representative publications about particle coagulation were also reviewed, especially the effect of reaction parameters on the particle coagulation extent and time. Finally, the relationship between the particle coagulation and particle size distribution is reviewed extensively. [ABSTRACT FROM AUTHOR]

A novel approach to synthesize narrow particle size distribution cationic latex particles based on styrene and butyl acrylate was proposed. The effect of monomer/water ratios, surfactant (cetyltrimethylammonium chloride) concentrations, and monomer compositions on the evolution of particle size, distribution, number, and morphology as a function of monomer conversion was concerned in order to confirm the optimum polymerization condition. As expected, the particle size of the ultima latex increased with monomer/water ratios and styrene contents decreased with increasing surfactant concentrations. Continuous nucleation phenomena occurred when monomer/water ratio was lesser than 30/70, resulting in a gradual increase in the number of particles in the whole polymerization process. Combined with the previous work (Colloid and Polymer Science, 2014, 292: 519–525), it was concluded that particle coagulation easily took place in cationic emulsion polymerization of styrene. Thus, the narrow particle size distribution cationic latexes with particle scale between 50 nm and 80 nm, 30 wt% solid content could be prepared in a short reaction time. [ABSTRACT FROM PUBLISHER]

This article is an extensive investigation on particle coagulation growth in emulsion polymerization proposed by our team (Colloid and Polymer Science, 2013, 291, 2385–2398). Monodispersed, large-scale, high-solid content poly (butyl acrylate) latex was obtained by varying the reaction procedures in previous studies. However, the present method, which could be used in other monomer systems such as styrene, methyl methacrylate, or the copolymerization of different monomers, has not been reported to date. In this article, the particle formation and growth behaviors of different monomer compositions were investigated in regard to the range of application and to clarify the effect of monomer characteristics on particle coagulation. Experimental results indicated that polymer characters such as hydrophilicity play an important role in particle coagulation, which was increased with increasing monomer hydrophilicity. Moreover, particle coagulation could improve reaction system stability and enhance the likelihood of obtaining a high solid content. The optimal systems for styrene, methyl methacrylate, and butyl acrylate were 40, 50, and 60 wt%, respectively, due to variation in monomer hydrophilicity. [ABSTRACT FROM PUBLISHER]

This investigation is an extension of the previous study (Colloid Polym Sci. 291: 2385–2398), where the latex of poly(butyl acrylate) with large particle scale (300–600 nm) and high solid content was obtained via batch emulsion polymerization technology according to particle coagulation mechanism induced by electrolyte. However, some technological parameters such as the variation in the maximum reaction temperature and the time at which this maximum occurs with the initial temperature and electrolyte concentrations were not been discussed in that article. These variations play important roles in determining the design of reactor and industry production. Thus, in this study, the evolution of reaction temperature, particle scale, and number as functions of reaction time are of concern in order to confirm the effect of particle coagulation on polymerization process and finally the latex properties. Experimental results indicated that the maximum value of the polymerization system decreased with decreasing the initial reaction temperature, and with increasing electrolyte concentration. The addition of electrolyte not only reduced the maximum value of reaction temperature ranging from 92.4°C to 71°C, but also made the particle scale increase to ∼650 nm from 315 nm, and the viscosity of latexes decrease to 40.2 mPa · s from 200.1 mPa · s. [ABSTRACT FROM AUTHOR]

The poly(methyl methacrylate-co-styrene) was prepared by batch emulsion polymerization to clarify the effect of characteristics of polymer on particle coagulation. Experimental results showed that the size of final latex particle increased with increasing methyl methacrylate in initial recipe, ranged from 84 to 193 nm, which was attributed to the particle coagulation. With the methyl methacrylate increased, the hydrophilicity of polymeric particle improved, thus led to the surfactant molecules packed loosely on the polymer surface, further, enhanced particle coagulation occurred. On the contrary, the surfactant molecules adsorbed on tightly the polymeric particle surface (methyl methacrylate content low) surface led to the electrostatic repulsion energy of polymer particle improved, and polymer particle stability was also improved. Thus, combined with the results previously reported by us (Colloid Polym Sci 291: 2385-2398, 2013 and Colloid Polym Sci 292: 519-525, 2014), the particle coagulation depended not only on the aqueous phase such as electrolyte concentration and methanol content, but also on the nature of polymer such as hydrophilicity. [ABSTRACT FROM AUTHOR]

Macroemulsion polymerization is the most widely used approach for the fabrication of the monodisperse polymer particles. During the polymerization process, particle nucleation plays a critical role in determining particle size distribution of the ultimate particles. In general, the repulsion between ionic oligomeric radicals and micelles enhances particle nucleation, resulting in smaller particle sizes. In this study, methacryloxyethyltrimethyl ammoniumchloride (MATMAC) and 2′azobis (2methylpropionamidine) dihydrochloride (AIBA) were used as the cationic species to shield the negative charges of sodium dodecyl sulfate micelle, inducing in situ charge neutralization in the nucleation period, and further decreasing the particle number, enlarging the particle size of the ultimate latex particles. The ultimate particle size of MATMAC or AIBA system reached ～ 200 nm, which is the 2 times bigger than that without any cationic species. Moreover, a narrow particle size distribution was obtained for these systems. The in situ charge neutralization between the cationic species and surfactant molecules enhanced the oligomeric radical capture rate of micelles, further narrowing the particle nucleation time and inducing primary particle coagulation. [ABSTRACT FROM AUTHOR]

A novel approach to prepare sub-200 nm, narrowly dispersed polystyrene latex particles is proposed for the emulsion polymerization of a ca. 40 wt% solid-content solution. The presented method exploits the cationic comonomer methacryloxyethyltrimethyl ammonium chloride (MATMAC) or the initiator 2,2′-Azobis (2-methylpropionamidine) dihydrochloride (AIBA) to generate cationic oligomeric radicals shielded the negatively charged surfactant molecules adsorbed on the particles surface, further induced particle coagulation by in situ charge neutralization. By adjusting the types and amounts of the comonomer, the extent of the in situ charge neutralization is controlled. In consequence, the extent of the particle coagulation is controlled, resulting in the production of large-size latex particles. The particle coagulation induced by in situ charge neutralization occurs at the particle nucleation stage, which extends the times of particle completive growth and reversible coagulation, and therefore, narrowed the width of the particle size distribution of the ultimate latex particles. The resulting colloidal latexes containing 40 wt% solid content are very stable by presenting the absolute value of zeta potentials larger than 40 mV. This approach is likely to be used for large-scale industrial productions of narrowly dispersed polymer particles. [ABSTRACT FROM AUTHOR]

This study is an extension of the previous research results reported by our group (Colloid and Surf. A: Physicochem. Eng. Aspects 452 (2014) 159–164), where a novel approach to prepare large-scale polymer particles with a narrow distribution was reported. However, many important problems such as the visual evidence of particle coagulation, the relationship between particle distribution and particle coagulation, and the reasons of particle coagulation were not addressed in this article. In this manuscript, the polyisoprene latex particles were added to the polymerization systems as the indicator to follow the process of particle coagulation, and the reasons of particle coagulation are also discussed. The experimental results show that the final latex particles possessed a special structure similar to multicores and single-shell structure for the system containing polyisoprene particles and could be considered as a direct evidence of the particle coagulation. In addition, the competitive growth kinetics and reversible particle coagulation were used to analyze the reasons of a narrow particle size distribution of the final latex particles. In the combination with the Derjaguin–Landau–Verwey–Overbeek theory, the effect of the aqueous phase composition and initiator types on the particle coagulation were explained in the view of interaction energy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Particle scale and polydispersity were controlled via adjusting aqueous phase composition. [•] Particle coagulation was considered as the dominant particle growth method. [•] The relationship between particle coagulation and aqueous phase composition were investigated. [Copyright &y& Elsevier]