Seeded Emulsion Polymerization Research Articles

Preparation of epoxy-acrylic latex based on bisphenol F epoxy resin

ABSTRACTBisphenol F based epoxy-acrylic latex with different amount of epoxy resin was successfully prepared by semi-continuous seeded emulsion polymerization. The resulting composite latexes had a narrow size distribution of about 105 nm in diameter. The DSC result showed that the epoxy resin and polyacrylate were grafting copolymerization. The FTIR spectra showed that the epoxy group had been introduced into the epoxy acrylic latex system, and the composite latex could be crosslinked with epoxy hardener at room temperature. The crosslinked composite latex film exhibited a high Tg compared to epoxy-acrylic latexes. The surface of the films with the epoxy resin was regular, and diffused into the polyacrylate phase in the epoxy-acrylic latexes films. Since the curing reactions occurred before latex particle coalescence stage, the surfaces of the cured epoxy-acrylate latex films had a number of interface particle. Compared with the acrylic latex, the thermal stability of the epoxy-acrylate latex was increased, and the stability of the cured film increased with increasing epoxy content.

Critical rubber layer thickness of core-shell particles with a rigid core and a soft shell for toughening of epoxy resins without loss of elastic modulus and strength

Core-shell particles with a rigid silica core and a poly(butyl acrylate) (PBA) rubber shell are used to toughen epoxy resins without loss of elastic modulus and tensile strength. Both the diameter of silica core (D) and thickness of PBA shell (Ts) of silica-PBA core-shell particles are accurately controlled by sol-gel synthesis and seed emulsion polymerization process, respectively. From the results of notched Izod impact tests, a brittle-ductile transition of these epoxy/silica-PBA composites occurs when the rubber shell thickness (Ts) exceeds a critical value (Tsbd). It is found that Tsbd increases with increasing D which implies a critical rubber content (10 wt%) in the core-shell particles or a critical Ts/D ratio (0.0375), above which all composites transit from brittle to ductile failure. The composite elastic modulus decreases with increasing Ts. However, the critical thickness values of Tsm and Tss, below which composite modulus and tensile strength, respectively, are equal to or higher than the corresponding epoxy matrix values, are both larger than Tsbd. These results prove that brittle polymers can be toughened without loss of elastic modulus and tensile strength. However, the critical surface-to-surface inter-particle distance (Lc) is controlled by both properties of the core-shell particles and polymer matrix. When the rubber shell thickness Ts > Tsbd, Lc is increased when D is decreased. But when Ts < Tsbd, the brittle-to-ductile transition cannot occur, even when Lc is less than 100 nm.

Magnetorheology of Snowman-Like Anisotropic Microparticle Added Carbonyl Iron Suspension

The improvement of the magnetorheological (MR) performance of a carbonyl iron (CI)-based MR fluid was assessed by adding nonmagnetic anisotropic snowman-like polymethyl methacrylate (PMMA) particles as an additive. The snowman-like PMMA particles were synthesized by a seed emulsion polymerization method. The rheological properties of the MR fluids with and without the additives were examined by using a rotational rheometer under various applied magnetic-field strengths. Enhanced rheological properties and improved sedimentation stability of the CI/snowman-like PMMA-based MR fluid were observed compared to those of the pure CI-based MR fluid.

Fabrication and characterization of polysiloxane/polyacrylate composite latexes with balanced water vapor permeability and mechanical properties: effect of silane coupling agent

In order to improve the water vapor permeability and mechanical properties of latex films, polysiloxane/polyacrylate (PSi/PA) composite latexes were fabricated via seeded emulsion polymerization of methyl methacrylate and butyl acrylate onto PSi latex particles, and the effects of the silane coupling agent 3-methacryloyloxypropyl trimethoxysilane (MATS) on the morphologies of the latex particles and films, as well as the microphase separation degree, the water vapor permeability and the mechanical properties of the latex films were investigated. Results indicated that MATS was essential for obtaining the PSi/PA composite latex particles with PSi as core and PA as shell and made a great contribution to restrict the phase separation. The PSi/PA core/shell latex films showed similar tensile strength and elongation with pure PA film, while exhibiting promising water vapor permeability. It was found that the influences of MATS content on the water vapor permeability and mechanical properties were opposite, and on the premise of the requirements for mechanical properties, lower MATS content could provide the PSi/PA core/shell latex films with better water vapor permeability.

How Chain Intermixing Dictates the Polymorphism of PVDF in Poly(vinylidene fluoride)/Polymethylmethacrylate Binary System during Recrystallization: A Comparative Study on Core⁻Shell Particles and Latex Blend.

In the past few decades, Poly(vinylidene fluoride)/Polymethylmethacrylate (PVDF/PMMA) binary blend has attracted substantial attention in the scientific community due to possible intriguing mechanical, optical and ferroelectric properties that are closely related to its multiple crystal structures/phases. However, the effect of PMMA phase on the polymorphism of PVDF, especially the relationship between miscibility and polymorphism, remains an open question and is not yet fully understood. In this work, three series of particle blends with varied levels of miscibility between PVDF and PMMA were prepared via seeded emulsion polymerization: PVDF–PMMA core–shell particle (PVDF@PMMA) with high miscibility; PVDF/PMMA latex blend with modest miscibility; and PVDF@c–PMMA (crosslinked PMMA) core–shell particle with negligible miscibility. The difference in miscibility, and the corresponding morphology and polymorphism were systematically studied to correlate the PMMA/PVDF miscibility with PVDF polymorphism. It is of interest to observe that the formation of polar β/γ phase during melt crystallization could be governed in two ways: dipole–dipole interaction and fast crystallization. For PVDF@PMMA and PVDF/PMMA systems, in which fast crystallization was unlikely triggered, higher content of β/γ phase, and intense suppression of crystallization temperature and capacity were observed in PVDF@PMMA, because high miscibility favored a higher intensity of overall dipole–dipole interaction and a longer interaction time. For PVDF@c–PMMA system, after a complete coverage of PVDF seeds by PMMA shells, nearly pure β/γ phase was obtained owing to the fast homogeneous nucleation. This is the first report that high miscibility between PVDF and PMMA could favor the formation of β/γ phase.

Preparation and thermal properties of a novel core‐shell structure flame‐retardant copolymer

In order to improve the flame retardancy of polystyrene (PS), a phosphorus and nitrogen comonomer, named AC2NP2, was synthesized and then incorporated into various amounts of PS by seeded emulsion polymerization. The modified methacrylate (AC2NP2) was used as the core phase, the styrene as the shell phase, then flame‐retardant effect copolymers with core‐shell structure were prepared successfully. The particle size was ranged from 40 to 60 nm, and the structure and properties of the copolymers were characterized in detail. Notably, despite a few amounts of the AC2NP2 units in the copolymers, all the copolymers exhibited significantly enhanced thermal stability and reduced flammability as compared with pure PS. Furthermore, from differential scanning calorimetry test, it was observed that the glass transition temperature was tinily influenced with the incorporation of commoner. The incorporation of P‐N comonomer into PS backbone did not lead to negative effect on the glass transition behavior of PS.

Enhanced toughness for polyamide 6 with a core-shell structured polyacrylic modifier

Polyamide 6 (PA 6) is an important thermoplastic with excellent strength, stiffness, and good chemical resistance. The notch sensitivity and low notch impact toughness of PA 6, however, limit its application. A core-shell structured polyacrylic modifier, poly(n-butyl acrylate)/poly(methyl methacrylate-co-methacrylic acid) modifier (PBM-co-MAA), was used to toughen PA 6. To study the effect of PBM-co-MAA particles on the toughness of PA 6, various contents of poly(BA) in PBM-co-MAA latexes of 300 nm were synthesized by seed emulsion polymerization. The results showed that polymerization had an instantaneous conversion higher than 95 wt% and an overall conversion higher than 97 wt%. The PBM-co-MAA particles had a clear core–shell structure confirmed by transmission electron microscope (TEM). The mechanical properties of PA 6/PBM-co-MAA blends showed that the notch impact strength of PA 6/PBM-co-MAA blends with 85 wt% poly(BA) and 0.5 wt% MAA in PBM-co-MAA was nearly six times greater than that of pure PA 6, being consistent with the scanning electron microscope (SEM) observations on the fractured surfaces. The notch impact strengths of PA 6/PBM-co-MAA blends were also better than that of PA 6/PBM blend, which did not contain MAA functional group in the modifier. Dynamic mechanical analysis (DMA) results showed improved compatibility between PA 6 matrix and core-shell toughening modifier, which should contain a functional group in the shell layer and a suitable core rubbery content to toughen PA 6 effectively.

Synthesis and surface properties of a novel fluorine modified acrylate colloid

AbstractThe novel modified acrylate colloid was synthesized by semi‐continuous seeded emulsion polymerization which was initiated with potassium persulfate (KPS), and octylphenol polyoxyethylene ether (OP‐10) and sodium dodecyl benzene sulfonate (SDBS) were used as surfactants. Butyl acrylate (BA) and methyl methacrylate (MMA) were used as the main monomers and hexafluorobutyl methacrylate (HFMA, C8H8F6O2), and benzyl methacrylate (BZMA, C11H12O2) were used as functional monomers. Factors such as the amount of initiator, mass ratio of SDBD to OP‐10 and monomers, which have an influence on particle size and morphology of the resultant colloid, are studied. Chemical composition of the modified acrylate colloid was evaluated by Fourier transform infrared spectrometry (FTIR). The thermal performances were characterized by differential scanning calorimetry (DSC) and thermogravimetry (TG). Furthermore, surface hydrophobicity of the latex film was examined by measurement of water absorption and water contact angle. Results indicate that the modified acrylate colloid has highest monomer conversion rate and lowest coagulation percentage when the mass fraction of emulsifier was 4% and mass ratio of SDBS to OP‐10 was 1:2, mass fraction of initiator was 0.3%, mass percent of HFMA was 6%, and the amount of BZMA was 2%. Benzene ring‐containing monomer is effectively participated in the reaction and has improved the thermal performance and surface properties of copolymer colloid. The resultant colloid has excellent hydrophobicity and low surface energy. Solid content of the resultant colloid was about 30% (wt %).

Micromorphology, phase behavior, and properties of environmental, multi-cross-linked polyurethane/polyacrylate microemulsions based on in situ surfactant-free polymerization

The aqueous environmental polyurethane/polyacrylate (PUA) microemulsions were obtained through in situ surfactant-free emulsion polymerization exempt of any organic solvents. Hydroxyethyl acrylate (HEA) and pentaerythritol triacrylate (PETA) of different functionalities were adopted as cross-linker to connect polyurethane (PU) and polyacrylate (PA) to obtain PUAH and branched multi-cross-linking PUAP, respectively. It is interesting to note that PUA microemulsion was unstable if no connection was built between PU and PA when in situ surfactant-free emulsion polymerization was adopted, which is different from conventional seed emulsion polymerization. The particle size decreased from 75.27 to 51.24 nm and dispersibility index (DPI) decreased from 0.394 to 0.122 with the increase of vinyl content, and DPI was further decreased with the incorporation of PETA with three vinyl groups at the same vinyl content. Effects of HEA and PETA on the physicochemical properties of PUA films including micromorphology, gel content, surface composition, phase behavior, thermal stability, and water resistance were investigated. TEM and XPS analysis demonstrated that the micromorphology transferred from multi-morphology to single core-shell morphology with PA as the core and PU as the shell and then changed to uniform morphology with homogeneous distribution of PU and PA inside PUAP. High cross-linking density, together with uniform distribution of PU and PA inside PUA system, is beneficial to improve the PUA performance. In addition, the as-prepared microemulsions can be utilized as the surface sizing agent for cellulose fiber paper to greatly increase the physical strength and water resistance.

PLLA/PMMA blend in polymer nanoparticles: influence of processing methods

The preparation and synthesis of PLLA/PMMA blend nanoparticles by miniemulsion/solvent evaporation, miniemulsion polymerization, and seeded emulsion polymerization strategies is herein presented. We evaluate the effect of nanoparticle preparation technique and blend ratio over nanoparticle morphology and blend miscibility, and our results indicate that the nanoparticle processing method can greatly influence the final morphology characteristics of blend nanoparticles. By miniemulsion/solvent evaporation, miscible blend and homogeneous nanoparticles were obtained, and an increase in PMMA content led to a concomitant increase of nanoparticle size. Miniemulsion polymerization, on the other hand, resulted in an immiscible blend with a core-shell-like morphology nanoparticles. Under the conditions used, seeded emulsion polymerization led to the formation of secondary smaller particles of pure PMMA in addition to miscible PLLA/PMMA blend nanoparticles. PLLA/PMMA nanoparticles were further used to encapsulate a hydrophobic drug with high entrapment efficiency, showing to be a promising hydrophobic compound carrier.

New insights into the impact toughness of ASA (acrylonitrile-styrene-acrylate) with controllable core–shell structure synthesized by three-stage seeded emulsion polymerization

ABSTRACTAcrylonitrile-styrene-acrylate (ASA) with controllable core–shell structure was prepared through three-stage seeded emulsion polymerization. A series of characterizations had been performed to study the effect of different core–shell ratios on the properties of ASA. The most interesting was that the impact strength of ASA exhibited a “wave” variation instead of a linear variation with the increasing loading content of poly(butyl acrylate) (PBA) core. Moreover, the threshold of impact strength appeared at 49.725 wt% PBA content, nearly 33 kJ/m2. To explain this unusual variation, an impact schematic was proposed.

Raspberry-like patchy particles achieved by decorating carboxylated polystyrene cores with snowman-like poly(vinylidene fluoride)/poly(4-vinylpyridiene) Janus particles

Nonspherical poly(vinylidene fluoride)/poly(4-vinyl pyridine) (PVDF/P4VP) composite particles were prepared via a facile one-step soap-free seeded emulsion polymerization. A moderate amount of ammonia solution was introduced into the polymerization system to make the composite latex particles uniform and stable, possibly due to the prevention of P4VP nucleation in the aqueous phase. Depending upon the stirring speed, the composite particles exhibited either the dumbbell-like shape (at a low speed) or the snowman-like shape (at a high speed). The size of the P4VP bulges in the composite particles could be easily adjusted by controlling the feed ratio of 4VP/PVDF. Utilizing the strong interactions between pyridine and carboxylic acid units, self-assembly of snowman-like PVDF/P4VP composite particles with carboxylated PS particles induced the formation of raspberry-like colloidal particle clusters (RCPCs) with PVDF bulges protruding outward. This study provides an alternative way to prepare hierarchical RCPCs.

Asymmetrical Morphology and Performance of Composite Colloidal Particles Controlled via Hydrophilic Comonomer Addition Time in the Presence of Polyvinylidene Fluoride Latex

Anisotropic composite latex particles with heteromorphous bowl-like and popcorn-like shapes were fabricated by a general approach: seeded emulsion polymerization. The morphologies of polyvinylidene fluoride@poly(styrene-co-butyl acrylate-co-3-trimethoxysilyl propyl methacrylate) composite particles [PVDF@P(St-co-BA-co-MPS)] could be efficiently controlled by varying the feeding time of hydrophilic MPS. The deformation mechanism of bowl-like particles was largely attributed to the diverse rigidities of the P(St-co-BA-co-MPS) phase from the inhomogeneous cross-linking density formed through changes in the MPS feeding time. During the polymerization, the PVDF crystallization behaviors demonstrated an obvious transformation from unconfined to confined crystallization. Additionally, the chemical properties and morphologies of the particles’ surface greatly impacted the hydrophilic–hydrophobic character of the particle films. After the capping of the hydrophilic functional groups of the surface, the contact ang...

One-pot synthesis of non-spherical hollow latex polymeric particles via seeded emulsion polymerization

Non-spherical (ns) hollow latex (HL) particle with a void on one side of a polymer particle surrounded by a double-layered shell was fabricated via the one-pot seeded emulsion polymerization (SEP). Start from the ns seed formed by swelling styrene (St) or methyl methacrylate (MMA) mixed with azobisisobutyronitrile into a crosslinked spherical poly(styrene/divinyl benzene/acrylic acid) P(St/DVB/AA) particle and then polymerized. The ns seed particle having two lobes of crosslinked P(St/DVB/AA) and polystyrene (PS) protrusion obtained was then swelled with MMA/DVB/AA monomers (MMA:DVB = 1:2). After polymerization, the obtained ns HL particle with a single void on the PS side was generated without the seed removal. The key success factors are the locus of polymerization at the seed surface and the fast/efficient phase separation between PS seed and shell polymers. The double-layered shell composing of PS inner shell and P(DVB/MMA/AA) outer shell prevented the collapse of hollow structure. The ns HL particles (0.79 μm in diameter and 1.04 μm in over length) as a white pigment in the coating had a hiding power better than ns solid particles (ASTM D2803-96a, 2003).

Fluoro‐silicone Modified Polyacrylate Latex Emulsified with Green Surfactants

AbstractFluoro‐silicone modified polyacrylate latex was successfully prepared by semi‐continuous seeded emulsion polymerization in the presence of a green mixed emulsifier consisting of cashew phenol polyoxyethylene ether sulfonate (BCE‐10B) anionic surfactant and alkyl polyglycoside (APG) nonionic surfactant, in which the mixed monomers were initiated with potassium persulfate (KPS). The structure and properties were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and contact angle (CA), respectively. Results show that the optimal conditions of synthesizing the novel emulsion are as follows: the total concentration of mixed emulsifiers is 5.0%; the optimum mass ratio of APG to BCE‐10B is 2:1; the amount of initiator is 0.6%; the composition of main monomers of MMA:BA = 1:1; and the concentrations of HFMA and VTES are 4.0 and 6%, respectively. In this case, the resultant emulsion showed good thermal stability and hydrophobicity.

Novel Maleate Surfmer for Stabilization High-solid Content of Methyl Methacrylate/Butyl Acrylate Copolymer Emulsion System

ABSTRACTA novel polymerizable surfactant (surfmer) based on nonyl phenol ethoxylate backbone and maleic anhydride was synthesized. The chemical structure of the surfmer was characterized by 13C, 1H nuclear magnetic resonance, and surface tension analyses. The surfmer was used in emulsion system of methyl methacrylate/butyl acrylate copolymer at different concentrations to explore its stabilization efficiency using seed emulsion polymerization technique. The result of thermogravimetric analysis showed that the incorporation of the surfmer retarded the decomposing of the polymer chain. The stability of the emulsion was enhanced by adding the surfmer, but the glass transition of the film was decreased dramatically.

Shape-Tunable Synthesis of Sub-Micrometer Lens-Shaped Particles via Seeded Emulsion Polymerization

Shape-Tunable Synthesis of Sub-Micrometer Lens-Shaped Particles via Seeded Emulsion Polymerization

St-MMA-BuA terpolymerization in emulsion: II. The kinetic azeotropy and the problem of homogeneity in composition

An analysis of the kinetic azeotropy of the terpolymer from styrene(St)-methyl methacrylate(MMA)-butyl acrylate(BuA) in emulsion polymerization is effectuated. The objective is to determine the conditions for obtaining terpolymers uniform in composition. In this regard, a composition near to the unitary azeotrope is used in batch, semicontinuous and seeded emulsion polymerization processes. As expected, the monomer partition between the different phases modifies the terpolymer composition, in particular at the beginning of the semicontinuous processes. It is also observed that the unitary azeotrope in batch and semicontinuous emulsion polymerization is conserved in a large range of conversion due to the constancy of monomer concentration and radicals in the particle. In this way, a terpolymer with almost an accumulated constant composition is obtained in the seeded process. A thermodynamic analysis of the kinetic azeotropy is also made. The correspondence between the azeotropes of the binary copolymers and the values of the Flory interaction parameters of the monomers χιj is correlated. It is found that the lesser repulsion of the St-MMA pair respect to that of St-BuA provoked that the composition of the terpolymer tends to the copolymer azeotrope of St-MMA.

Preparation and characterization of trilayer core–shell polysilsesquioxane–fluoroacrylate copolymer composite emulsion particles

ABSTRACTPolysilsesquioxane–fluoroacrylate copolymer [poly(methyl methacrylate)–butyl acrylate–dodecafluoroheptyl methacrylate)] (FPSQ) composite latex particles with a trilayer core–shell morphology were manufactured by seeded emulsion polymerization, where PSQ latex particles bearing reactive methacryloxypropyl moieties were first produced by the hydrolysis‐condensation of (3‐methacryloxypropyl)trimethoxysilane, and then they were utilized as seeds, with methyl methacrylate, butyl acrylate, and dodecafluoroheptyl methacrylate as the inner and outer shell monomers. Fourier‐transform infrared spectra and 1H‐NMR confirm the structure of the FPSQs. Transmission electron microscopy and scanning electron microscopy demonstrate that the obtained composite emulsion particles emerge with the trilayer core–shell pattern. Due to the anchoring of PSQ nanoparticles, the thermal stabilities of the FPSQ films are strengthened, and the resistance to heat is gradually improved along with the increase of the fluoroacrylate dose in the polymer matrix composite. X‐ray photoelectron spectroscopy, atomic force microscopy (AFM), and hydrophobicity investigations indicate that the fluorinated chain segments tend to concentrate at the film–air two‐phase interface. In addition, the AFM result denotes that importing more fluorine into the FPSQ hybrid material will engender greater phase separation and enrichment of the fluoroalkyl segments and a rougher morphology. Thus, the water contact angle of the FPSQ film can ultimately reach 121.4°. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44845.

Synthesis of SiOH-functionalized composite particles with buckled surface by seeded emulsion polymerization

We demonstrate the synthesis of SiOH-functionalized composite particles with buckled surface via a seeded emulsion polymerization method, their evolution into bicompartmental particles and their application in superhydrophobic coatings. By using polystyrene spheres swelled with non-polymerizable solvent as seeds, emulsion polymerization of 3-(trimethoxysily) propyl methacrylate and styrene leads to the formation of deflated ball- or dried plum-shaped composite particles. The change of solvent amount causes the variation of the morphologies of the obtained particles. With these composite particles as seeds for further emulsion polymerization, bicompartmental particles with unique morphologies are fabricated. On account of the silanol groups generated by hydrolysis of 3-methacryloxy propyl trimethoxysilane (MPS) on their surface, these particles are easily functionalized with organosilane for various applications and also could be applied in the synthesis of more complex organic–inorganic hybrid materials. The modification of the particles with fluorinated silane and their application in the fabrication of superhydrophobic surfaces are demonstrated.