Morphology control in polystyrene/poly(methyl methacrylate) composite latex particles

The effect of the presence of different amounts of block copolymers [polystyrene-block-poly(methyl methacrylate)] on the morphology of polystyrene/poly (methyl methacrylate) composite latex particles was investigated. The block copolymers were produced in situ by controlled radical polymerization (CRP) through the addition of the second monomer to a seed prepared by miniemulsion polymerization with a certain amount of a CRP agent. With an increase in the amounts of the block copolymers, the particle morphology changed from a hemisphere morphology (for a latex without block copolymers, i.e., without the use of a CRP agent during the polymerization) to clear core–shell morphologies as a result of decreasing polymer–polymer interfacial tension © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2484–2493, 2007     

Modeling multiphase latex particle equilibrium morphology

Multiphase waterborne polymer particles provide advantages in more demanding applications and their performance depends on particle morphology. Currently, no general approach to predict the morphology of multiphase latex particles is available. In this work, a model based on Monte Carlo methods was developed for the prediction of equilibrium morphologies of multiphase waterborne systems, such as polymer‐polymer and polymer‐polymer‐inorganic hybrids. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2579–2583, 2010     

The inverse emulsion polymerization of acrylamide using polystyrene-graft-polyoxyethylene as the stabilizer

Inverse emulsion polymerization of aqueous solution of acrylamide (AM) in toluene is carried out using polystyrene-graft-polyoxyethylene (PSt-g-PEO) as an emulsifier. The kinetics of polymerization, morphology of the particle, and particle size of the inverse emulsion have been investigated. The rates of polymerization are found to be proportional to the initiator concentration, the monomer concentration, and the emulsifier concentration. The morphology of the particle shows a spherical structure. The effects of amphipathic graft copolymer structure on the average molecular weight of polyacrylamide are studied. The mechanism of the inverse emulsion polymerization using amphipathic graft copolymer as emulsifier is proposed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2719–2725, 1999     

Core–shell and gradient morphology polymer particles analyzed by X‐ray photoelectron spectroscopy: Effect of monomer feed order

The synthesis of composite latex particles possessing core–shell and gradient morphologies, respectively, using seeded starve‐fed semibatch emulsion polymerization of styrene (St) and methyl methacrylate (MMA) is presented. The focus is on the effect of the monomer feed order on the particle morphology development. The particle morphology is assessed using a novel approach which entails comparing the experimental surface composition as a function of polymerization time (particle growth) obtained by X‐ray photoelectron spectroscopy with the predicted surface composition using a mass balance mathematical model. Both types of composite latexes (core–shell and gradient) feature changes with polymerization time in the oxygen/carbon surface composition which enables one to track the morphology development. Differential scanning calorimetry is also implemented to analyze the extent of phase separation. The monomer feed order is shown to play a crucial role—under the present conditions, gradient and core–shell particles are obtained if the feed order is St/MMA (St fed first), but not if the feed order is reversed. These findings illustrate that thermodynamic factors are important, given that thermodynamically it is more favorable for MMA‐rich chains to occupy the oil–water interface to reduce the interfacial tension. Systems where St is the second stage monomer lead to mixed structures rather than the targeted core–shell or gradient morphology with St‐rich chains at the particle surface. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2513–2526     

The influence of partial emulsification on coalescence suppression and interfacial tension reduction in PP/PET blends

This study examines how the relative role of coalescence suppression and interfacial tension reduction influence the particle size at various levels of in situ compatibilization. The polymers studied are polyethylene terephthalate (PET) as matrix and a polypropylene (PP) as dispersed phase compatibilized by a triblock copolymer of poly(styrene–hydrogenated butadiene–styrene) (SEBS) grafted with maleic anhydride. The interfacial tension was studied by the breaking‐thread method, and it was used along with the morphology to characterize the emulsification efficacy of the copolymers. By modifying the concentration of MA grafted on the SEBS, different levels of emulsification of the blends were obtained. A comparison of 1/99 and 10/90 PP/PET blends compatibilized by SEBS‐g‐MA allows one to distinguish the relative role of interfacial tension and coalescence suppression in diminishing particle size. It is shown that varying degrees of residual coalescence remain, depending on the level of %MA in the copolymer. A detailed study of the 2%MA system below interfacial saturation was carried out to shed further light on the dependence of coalescence suppression on emulsification level and interfacial coverage. After separating out the contribution of interfacial tension on particle size reduction, it is shown that coalescence suppression for this system increases gradually with areal density of modifier at the interface right up to the region of interfacial saturation. Finally, the interfacial and morphological data were used to test the ability of the Lee and Park model to describe coalescence in polymer blends. Reasonable agreement was found between the parameter c₁, describing the coalescence in that model, and the trends related to residual coalescence from this study. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 939–951, 1999     

Preparation,morphology, and thermoresponsive properties of poly(N‐isopropylacrylamide)‐based copolymer microgels

In this research, thermoresponsive copolymer latex particles with an average diameter of about 200–500 nm were prepared via surfactant‐free emulsion polymerization. The thermoresponsive properties of these particles were designed by the addition of hydrophilic monomers [acrylic acid (AA) and sodium acrylate (SA)] to copolymerize with N‐isopropylacrylamide (NIPAAm). The effects of the comonomers and composition on the synthesis mechanism, kinetics, particle size, morphology, and thermoresponsive properties of the copolymer latex were also studied to determine the relationships between the synthesis conditions, the particle morphology, and the thermoresponsive properties. The results showed that the addition of hydrophilic AA or SA affected the mechanism and kinetics of polymerization. The lower critical solution temperature (LCST) of the latex copolymerized with AA rose to a higher temperature. However, because the strong hydrophilic and ionic properties of SA caused a core–shell structure, where NIPAAm was in the inner core and SA was in the outer shell, the LCST of the latex copolymerized with SA was still the same as that of pure poly(N‐isopropylacrylamide) latex. It was concluded that these submicrometer copolymer latex particles with different thermoresponsive properties could be applied in many fields. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 356–370, 2006     

Preparation and characterization of polymer/silica nanocomposites via double in situ miniemulsion polymerization

Polymer/SiO₂ nanocomposite microspheres were prepared by double in situ miniemulsion polymerization in the presence of methyl methacrylate, butyl acrylate, γ‐methacryloxy(propyl) trimethoxysilane, and tetraethoxysilane (TEOS). By taking full advantage of phase separation between the growing polymer particles and TEOS, inorganic/polymer microspheres were fabricated successfully in a one‐step process with the formation of SiO₂ particles and the polymerization of organic monomers taking place simultaneously. The morphology of nanocomposite microspheres and the microstructure, mechanical properties, thermal properties, and optical properties of the nanocomposite films were characterized and discussed. The results showed that hybrid microspheres had a raspberry‐like structure with silica nanoparticles on the shells of polymer. The silica particles of about 20 nm were highly dispersed within the nanocomposite films without aggregations. The transmittance of nanocomposite film was comparable to that of the copolymer film at around 70–80% from 400 to 800 nm. The mechanical properties and the fire‐retardant behavior of the polymer matrix were improved by the incorporation of silica nanoparticles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3128–3134, 2010     

Organic solvent‐free catalytic hydrogenation of diene‐based polymer nanoparticles in latex form: Part I. Preparation of nano‐substrate

Poly(butadiene‐co‐acrylonitrile) (NBR) nanoparticles were synthesized in a semibatch emulsion polymerization system using Gemini surfactant trimethylene‐1,3‐bis (dodecyldimethylammonium bromide), referred to as Gemini‐type surfactant (GS) 12‐3‐12, as the emulsifier. In this polymerization system, an enhanced decomposition rate of initiator ammonium persulfate was achieved even under the low temperature of 50 °C which is attributed to the acidic initiation environment provided using GS 12‐3‐12. The microstructure and copolymer composition of the polymer nanoparticles were characterized by Fourier‐transformed infrared and ¹H nuclear magnetic resonance spectroscopy. The effects of the surfactant concentration on the particle size, zeta potential, polymerization conversion, copolymer composition, molecular weight, and glass transition temperature (T_g) were investigated. It was found that the particle diameter can be controlled by the surfactant concentration and monomer/water ratio and particle sizes below 20 nm can be reached. The obtained latex particles exhibit a spherical morphology. A kinetic study of the copolymerization reaction was carried out, which indicated that an azeotropic composition was produced. The synthesized fine NBR nanoparticles can be employed as the nano substrate for a subsequent hydrogenation process so as to overcome the challenge involved in the field of latex hydrogenation of polymers, which can be found in a related report: Organic Solvent‐Free Catalytic Hydrogenation of Diene‐based Polymer Nanoparticles in Latex Form: Part II. Kinetic Analysis and Mechanistic Study. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

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     

RAFT‐mediated emulsion polymerization of styrene using brush copolymer as surfactant macro‐RAFT agent: Effect of the brush copolymer sequence and chemical composition

The nonionic amphiphilic brush polymers such as poly[poly(ethylene oxide) methyl ether vinylphenyl‐co‐styrene] trithiocarbonate [P(mPEGV‐co‐St)‐TTC] and poly[poly(ethylene oxide) methyl ether vinylphenyl‐b‐styrene‐b‐poly(ethylene oxide) methyl ether vinylphenyl] trithiocarbonate [P(mPEGV‐b‐St‐b‐mPEGV)‐TTC] with different monomer sequence and chemical composition are synthesized and their application as macro‐RAFT agent in the emulsion RAFT polymerization of styrene is explored. It is found that the monomer sequence in the brush polymers exerts great influence on the emulsion RAFT polymerization kinetics, and the fast polymerization with short induction period in the presence of P(mPEGV‐co‐St)‐TTC is demonstrated. Besides, the chemical composition in the brush polymer macro‐RAFT agent effect on the emulsion RAFT polymerization is investigated, and the macro‐RAFT agent with high percent of the hydrophobic PS segment leads to fast and well controlled polymerization. The growth of triblock copolymer colloids in the emulsion polymerization is checked, and it reveals that the colloidal morphology is ascribed to the hydrophobic PS block extension, and the P(mPEGV‐co‐St) block almost have no influence just on the size of the colloids. This may be the first example to study the monomer sequence and the chemical composition in the macro‐RAFT agent on emulsion RAFT polymerization, and will be useful to reveal the block copolymer particle growth. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Nanoscopic confinement effects on ethylene polymerization by intercalated silicate with metallocene catalyst

In this article we report a study of in situ polymerization of ethylene by intercalated montmorillonite (MMT) with metallocene, allowing an investigation of the nanoscopic confinement effect of olefin polymerization and of the structure of polymer prepared in situ. Ethylene polymerization by intercalated MMT with metallocene and the varied aggregation morphology of the resulting polymer during polymerization were studied by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). The polymerization kinetics and the resulting polymer before and after destruction of the silicate registry were different. The laminated structure of silicate lowered the all‐reaction rate, including the propagation, chain transfer, and termination reactions, producing polymer of a high molecular weight. Moreover, the melting point of the polymer gradually increased during the in situ polymerization, indicating that nanoscopic confinement between solid surfaces affects the crystallization behavior of polyethylene via in situ polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 38–43, 2004     

Emulsion copolymerization of butyl acrylate with cationic monomer using interfacial redox initiator system

The polymerization kinetics of butyl acrylate/[2‐(methacryloyoxy)ethyl]trimethyl ammonium chloride (BA/MAETAC) macroemulsion and miniemulsion copolymerizations was investigated with cumene hydroperoxide/tetraethylenepentamine as a redox initiator system. The postulate of an interfacial copolymerization with the two‐component redox initiator system (one hydrophobic and the other hydrophilic) was confirmed. Adding MAETAC had a complex effect on the polymerization kinetics of BA. The influence was ascribed to variations in the nucleation mechanism, which were dependent on the level of MAETAC, and the polymerization method (macroemulsion vs miniemulsion). It was proposed that at the beginning of a macroemulsion copolymerization with high MAETAC composition the micellar copolymerization occurred, which controlled the nucleation process. The hydration properties of the latex were used to characterize the copolymer composition. The composition of the copolymer from the interfacial polymerization was very heterogeneous. The copolymer composition was lower in BA when there was an increase in BA conversion or the particle size. Adding salt increased the MAETAC content and decreased the BA content in the copolymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2696–2709, 2001     

Phase separation in semicrystalline blends of poly(phenylene sulfide) and poly(ethylene terephthalate). II. Effect of poly(phenylene sulfide) homopolymer solubilization of PPS‐graft‐PET copolymer on morphology and crystallization behavior

The morphology and crystallization behavior of poly(phenylene sulfide) (PPS) and poly(ethylene terephthalate) (PET) blends compatibilized with graft copolymers were investigated. PPS‐blend‐PET compositions were prepared in which the viscosity of the PPS phase was varied to assess the morphological implications. The dispersed‐phase particle size was influenced by the combined effects of the ratio of dispersed‐phase viscosity to continuous‐phase viscosity and reduced interfacial tension due to the addition of PPS‐graft‐PET copolymers to the blends. In the absence of graft copolymer, the finest dispersion of PET in a continuous phase of PPS was achieved when the viscosity ratio between blend components was nearly equal. As expected, PET particle sizes increased as the viscosity ratio diverged from unity. When graft copolymers were added to the blends, fine dispersions of PET were achieved despite large differences in the viscosities of PPS and PET homopolymers. The interfacial activity of the PPS‐graft‐PET copolymer appeared to be related to the molecular weight ratio of the PPS homopolymer to the PPS segment of the graft copolymer (M_H/M_A). With increasing solubilization of the PPS graft copolymer segment by the PPS homopolymer, the particle size of the PET dispersed phase decreased. In crystallization studies, the presence of the PPS phase increased the crystallization temperature of PET. The magnitude of the increase in the PET crystallization temperature coincided with the viscosity ratio and extent of the PPS homopolymer solubilization in the graft copolymer. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 599–610, 2000     

Nanoencapsulation of a hydrophobic compound by a miniemulsion polymerization process

The nanoencapsulation of hydrophobic compounds by miniemulsion polymerization, a convenient one‐step encapsulation technique for nanocapsules, was investigated in terms of the thermodynamics and kinetics. The encapsulation was achieved by polymerization inducing phase separation within minidroplets dispersed in an aqueous phase. Thermodynamic factors (the level and type of surfactant, the level of the hydrophilic comonomer, and the monomer/paraffin ratio), kinetic factors (the level of the crosslinking agent or chain‐transfer agent), and nucleation modes were all found to have a great influence on the latex morphology. Specifically, for a styrene/paraffin system, there were optimum levels of sodium dodecyl sulfate (1.0 wt %), the hydrophilic comonomer (1.0 wt % methyl acrylate acid), and the chain‐transfer agent (0.2 wt % n‐dodecanethiol) for obtaining well‐defined nanocapsules of paraffin with a styrene/paraffin ratio of 1:1. When the styrene/paraffin ratio was reduced, however, it was more difficult to achieve a fully encapsulated particle morphology. Homogeneous nucleation could compete with encapsulation, and this resulted in a pure polymer particle and a half‐moon morphology. Conditions were also found under which complete encapsulation could be observed with a water‐soluble initiator (potassium persulfate), contrary to certain reports. Replacing potassium persulfate with an oil‐soluble initiator (2,2‐azobisisobutyronitrile) had little influence on the morphology under those conditions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2145–2154, 2004     

Functional copolymer/organo‐MMT nanoarchitectures. XIX. Nanofabrication and characterization of poly(MA‐alt‐1‐octadecene)‐g‐PLA layered silicate nanocomposites with nanoporous core–shell morphology

Novel bioengineering functional copolymer‐g‐biopolymer‐based layered silicate nanocomposites were fabricated by catalytic interlamellar bulk graft copolymerization of L‐lactic acid (LA) monomer onto alternating copolymer of maleic anhydride (MA) with 1‐octadecene as a reactive matrix polymer in the presence of preintercalated LA…organo‐MMT clay (reactive ODA‐MMT and non‐reactive DMDA‐MMT) complexes as nanofillers and tin(oct)₂ as a catalyst under vacuum at 80°C. To characterize the functional copolymer layered silicate nanocomposites and understand the mechanism of in situ processing, interfacial interactions and nanostructure formation in these nanosystems, we have utilized a combination of variuous methods such as FT‐IR spectroscopy, X‐ray diffraction (XRD), dynamic mechanical (DMA), thermal (DSC and TGA‐DTG), SEM and TEM morphology. It was found that in situ graft copolymerization occurred through the following steps: (i) esterification of anhydride units of copolymer with LA; (ii) intercalation of LA between silicate galleries; (iii) intercalation of matrix copolymer into silicate layers through in situ amidization of anhydride units with octadecyl amine intercalant; and (iv) interlamellar graft copolymerization via in situ intercalating/exfoliating processing. The main properties and observed micro‐ and nanoporous surface and internal core–shell morphology of the nanocomposites significantly depend on the origin of MMT clays and type of in situ processing (ion exchanging, amidization reaction, strong H‐bonding and self‐organized hydrophobic/hydrophilic interfacial interactions). This developed approach can be applied to a wide range of anhydride‐containing copolymers such as random, alternating and graft copolymers of MA to synthesize new generation of polymer‐g‐biopolymer silicate layered nanocomposites and nanofibers for nanoengineering and nanomedicine applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Structural effects of dopants and polymerization methodologies on the solid‐state ordering and morphology of polyaniline

The solid‐state three‐dimensional ordering of polyaniline–dopant complexes was investigated with four structurally different sulfonic acid dopants. The doped materials were produced in three different ways: polyaniline emeraldine base doped with sulfonic acid (aqueous route), in situ polymerization at the organic–water solvent interface (interfacial route), and in situ polymerization in organic and aqueous solvent mixtures (bilayer route). p‐Toluenesulfonic acid (PTSA), 5‐sulfosalicilic acid (SSA), camphorsulfonic acid (CSA), and dodecylbenzene sulfonic acid (DBSA) were employed as dopants. The conductivity of the aqueous‐route samples showed 10 and 100 times higher conductivity than the interfacial and bilayer routes, respectively. WXRD studies suggested that the crystallinity of the doped samples was dependent on both the structure of the dopants and the polymerization techniques. DBSA increases the polyaniline interplanar distance and produced highly crystalline materials via the aqueous and bilayer routes but failed with the interfacial route because of poor solubility in water. CSA, PTSA, and SSA produced highly crystalline samples by the interfacial route but failed with the aqueous (except for CSA) and bilayer routes. SEM analysis revealed that the doped materials of the interfacial route had excellent continuous morphology and uniform submicrometer‐size particle distributions in comparison with those of the aqueous and bilayer routes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1321–1331, 2005     

The relative role of coalescence and interfacial tension in controlling dispersed phase size reduction during the compatibilization of polyethylene terephthalate/polypropylene blends

The breaking thread and the sessile drop methods have been used to evaluate the interfacial tension between a polypropylene (PP) and a polyethylene-terephthalate (PET). An excellent correlation was found between the two. The breaking thread technique was then used to evaluate the interfacial tension of these blends at various levels of a styrene-ethylene butylene-styrene grafted with maleic anhydride (SEBS-g-MA) compatibilizer. In order to evaluate the relative roles of coalescence and interfacial tension in controlling dispersed phase size reduction during compatibilization, the morphology of PP/PET 1/99 and 10/90 blends compatibilized by a SEBS-g-MA were studied and compared. The samples were prepared in a Brabender mixer. For the 10/90 blend, the addition of the compatibilizer leads to a typical emulsification curve, and a decrease in dispersed phase size of 3.4 times is observed. For the 1/99 blend, a 1.7 times reduction in particle size is observed. In the latter case, this decrease can only be attributed to the decrease of the interfacial tension. It is evident from these results that the drop in particle size for the 10/90 PP/PET blend after compatibilization is almost equally due to diminished coalescence and interfacial tension reduction. These results were corroborated with the interfacial tension data in the presence of the copolymer. A direct relationship between the drop in dispersed phase size for the 1/99 PP/PET blend and the interfacial tension reduction was found for this predominantly shear mixing device. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2271–2280, 1997     

Dispersion polymerization of methyl methacrylate: Mechanism of particle formation

The mechanism for the formation of micron-size polymer particles in the dispersion polymerization of methyl methacrylate was investigated by applying dynamic light scattering to monitor the evolution of the average particle size in the early stages of the polymerization. In addition, the contributions of physically adsorbed stabilizer and graft copolymer were evaluated by measuring the bound, unbound (adsorbed), and free stabilizer, and by determining the amount of added stabilizer required in seeded dispersion polymerizations. Twenty nanometer particles (termed nuclei) were the smallest particles detected and are considered to be formed by aggregation of growing polymer chains precipitating from solution as they exceed their critical chain length. Aggregation of these nuclei with themselves and their aggregates continues until mature and stable particles are formed. This occurs when sufficient stabilizer occupies the particle surface which includes both the polymeric stabilizer [poly(vinylpyrrolidone)] and its graft copolymer which is created in situ. The effects of process variables are discussed based on this mechanistic picture of the dispersion polymerization process. © 1994 John Wiley & Sons, Inc.     

Synthesis of graft copolymers with “V‐shaped” and “Y‐shaped” side chains via controlled radical and anionic polymerizations

A combination of nitroxide‐mediated radical polymerization and living anionic polymerization was used to synthesize a series of well‐defined graft (co)polymers with “V‐shaped” and “Y‐shaped” branches. The polymer main chain is a copolymer of styrene and p‐chloromethylstyrene (PS‐co‐PCMS) prepared via nitroxide‐mediated radical polymerization. The V‐shaped branches were prepared through coupling reaction of polystyrene macromonomer, carrying 1,1‐diphenylethylene terminus, with polystyryllithium or polyisoprenyllithium. The Y‐shaped branches were prepared throughfurther polymerization initiated by the V‐shaped anions. The obtained branches, carrying a living anion at the middle (V‐shaped) or at the end of the third segment (Y‐shaped), were coupled in situ with pendent benzyl chloride of PS‐co‐PCMS to form the target graft (co)polymers. The purified graft (co)polymers were analyzed by size exclusion chromatography equipped with a multiangle light scattering detector and a viscometer. The result shows that the viscosities and radii of gyration of the branched polymers are remarkably smaller than those of linear polystyrene. In addition, V‐shaped product adopts a more compact conformation in dilute solution than the Y‐shaped analogy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4013–4025, 2007     

Miniemulsion polymerization of styrene with a block copolymer surfactant

A series of miniemulsion systems based on styrene/azobisisobutyronitrile in the presence of poly(methyl methacrylate‐b‐2‐(dimethylamino)ethyl methacrylate) as a surfactant and hexadecane (HD) as a cosurfactant were developed. For comparison, a series of pseudoconventional emulsions also were carried out with the same procedure used for the aforementioned series but without the cosurfactant (HD). Both the droplet size and shelf life were also measured. Experimental results indicate that it is possible to slow the effect of Ostwald ripening and thereby produce a stable miniemulsion with the block copolymer as the surfactant and HD as the cosurfactant. In addition, the extent to which varying the surfactant concentration and copolymer composition could affect both the polymer particle size during the polymerization and the polymerization rate was examined. Variation in the polymer particle sizes during polymerization indicates that droplet and aqueous (micellar or both homogeneous) nucleation occurs in the miniemulsion polymerization. With the same concentration of the surfactant used in the miniemulsion polymerization, the polymerization rates of systems with M₁₂B₃₆ are faster than those of systems with M₁₂B₁₂. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1818–1827, 2000