Mingyao Zhang

Initiator Systems Effect on Particle Coagulation and Particle Size Distribution in One-Step Emulsion Polymerization of Styrene

Particle coagulation is a facile approach to produce large-scale polymer latex particles. This approach has been widely used in academic and industrial research owing to its higher polymerization rate and one-step polymerization process. Our work was motivated to control the extent (or time) of particle coagulation. Depending on reaction parameters, particle coagulation is also able to produce narrowly dispersed latex particles. In this study, a series of experiments were performed to investigate the role of the initiator system in determining particle coagulation and particle size distribution. Under the optimal initiation conditions, such as cationic initiator systems or higher reaction temperature, the time of particle coagulation would be advanced to particle nucleation period, leading to the narrowly dispersed polymer latex particles. By using a combination of the Smoluchowski equation and the electrostatic stability theory, the relationship between the particle size distribution and particle coagulation was established: the earlier the particle coagulation, the narrower the particle size distribution, while the larger the extent of particle coagulation, the larger the average particle size. Combined with the results of previous studies, a systematic method controlling the particle size distribution in the presence of particle coagulation was developed.

Sulfonated nanocrystal cellulose/sulfophenylated poly(ether ether ketone ketone) composites for proton exchange membranes

Nanocomposites were prepared with sulfonated nanocrystal cellulose (sNCC) and sulfophenylated poly(ether ether ketone ketone) (Ph-SPEEKK) for studying proton exchange membranes. The properties, including proton conductivity, mechanical properties, water uptake and swelling ratio were thoroughly investigated. The proton conductivity of the sNCC/Ph-SPEEKK composite membrane was much higher than that of pure Ph-SPEEKK in the range of 30–90 °C when the sNCC ratio was less than 10%. The presence of the hydroxyl and sulfonic acid groups on the sNCC was supposed to benefit the network formation via hydrogen bonds for the proton conduction. In addition, the mechanical properties of the composite membranes were much improved compared with those of the pure Ph-SPEEKK membrane. And the swelling ratio of the composite membranes was acceptable for the application. It was proved that the incorporation of sNCC into the sulfonated polymer matrix as a component to enhance the performance of the proton exchange membrane is one of the promising preparation strategies.

Crosslinking network structure effects on particle coagulation in the emulsion polymerization of styrene in methanol solution

This work is an extension of previous research results reported by our team (Colloid Polym Sci 292:519–525; 1347–1353), where how to control particle size distribution by adjusting particle coagulation has been investigated. There is limitation in previous studies, that is, the particles taking part in coagulation only possess a linear structure. However, the crosslinking network structure is necessary to many fields, such as rubber and plastic modifier. Thus, it is very significant to investigate the effect of the crosslinking network structure on particle coagulation for understanding the nature of particle coagulation and controlling particle size distribution. In this manuscript, dihydrodicyclopentadienyl acrylate (DCPA) is chosen as a crosslinker to copolymerize with styrene to promote particle structure shift from the linear to the crosslinking network structure and to investigate further the coagulation behavior of the particles with the crosslinking network structure. Experimental results are explained by the collision frequency of particles and stability dependence of the particle structure.

Preparation of monodisperse, sub-micrometer polymer particles by one-step emulsion polymerization under particle coagulation

The particle coagulation technology in emulsion polymerization is a novel and facile approach to prepare large-scale, narrowly dispersed latex particles. However, the formation of narrowly dispersed latex particles under particle coagulation at a high zeta potential is surprising. To elucidate this observation, a detailed investigation on the relationship between particle coagulation and particle size distribution was carried out. Unlike the conventional emulsion polymerization, a rapid decrease in the particle number and an increase in the particle size were clearly observed during the polymerization. The results confirm the occurrence of particle coagulation. The width of zeta potential and particle size distribution also decreased with particle coagulation, resulting in large-size, narrowly dispersed latex particles. These phenomena were explained by the competitive growth mechanism.

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.

Exothermal Behavior and Particle Scale Evolution in High Solid Content One-Step Batch Emulsion Polymerization

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.

Facile synthesis of large sized and monodispersed polymer particles using particle coagulation mechanism: an overview

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.

In situ charge neutralization on governing particle coagulation nucleation and size distribution in macroemulsion polymerization

Fabricating monodispersed polymer latex particles with ∼300 nm size at high monomer concentrations by batch macroemulsion polymerization remains significantly challenging because of latex stability. In this study, we developed a novel approach based on in situ charge neutralization to prepare 40 wt% solid content latex containing monodispersed sub-300 nm latex particles. The cationic initiator 2,2′-azobis(2-methylpropionamidine)dihydrochloride (AIBA) was used to induce in situ charge neutralization in the particle nucleation period and shield the negative charges of surfactant sodium dodecyl sulfate molecules to further reduce the electrostatic repulsion between primary particles, resulting in primary particle coagulation nucleation. The primary particle coagulation promoted particle number decreased to ∼1016 L−1, and the average particle size increased to ∼100 nm at a very low monomer conversion (<0.12). With increasing AIBA concentrations from 0.6 and 0.8 to 1.0 wt% (the molar ratio of AIBA/SDS is 0.64, 0.85 and 1.06, respective), the average particle size of the latex ultimately attained from 170.6 and 221.7 to 288.0 nm, respectively. Moreover, the addition of an electrolyte and copolymerization composition also governed the particle coagulation extent and affected the particle size distribution of the ultimate latex particles. To the best of our knowledge, this is the simplest, most efficient, and inexpensive approach to prepare large sized, monodispersed latex particles.

The performance and morphology of PMMA/SAN/ABS blends

Abstract Acrylonitrile-butadiene-styrene (ABS) graft copolymers were synthesized via seeded emulsion polymerization techniques by grafting styrene (St) and acrylonitrile (AN) on polybutadiene (PB) particles. Poly (methyl methacrylate) (PMMA)/styrene-acrylonitrile (SAN)/ABS blends were prepared by melt blending ABS graft copolymers with PMMA and SAN resins. The properties, morphology and grafted chains behaviors of PMMA/SAN/ABS blends were investigated. The results showed that with the increase of the ratio of PMMA/SAN, the toughness of PMMA/SAN/ABS blends slightly decreased, the transmittance first increased and then decreased, and tensile strength was not dependent on the ratio of PMMA/SAN. The evolution of impact strength of the blends was similar with the tendency of grafted degree (GD) with the increase of cumene hydroperoxide (CHP) and tert-dodecyl mercaptan (TDDM). From transmission electron microscopy (TEM), it was found that ABS graft copolymers were uniformly dispersed in PMMA/SAN matrix.

Synthesis of Sub-100 nm and Narrow Particle Size Distribution Cationic Latex by One-Step Emulsion Polymerization

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. GRAPHICAL ABSTRACT