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.     

Preparation and characterization of core–shell polystyrene–polydimethylsiloxane particles by seeded polymerization

Nanometer scale particles of seed latex were successfully prepared by polymerization induced by gamma rays. By modification of the coupling agent 3‐methacryloxylpropyltrimethoxylsilane (MPS) at the surface of polystyrene (PSt) particles, polydimethylsiloxane (PDMS) was introduced outside the PSt particles and composite latex particles with a core–shell (PSt–PDMS) structure were successfully prepared. Because of the chemical bond linkage between the core and the shell, such a structure is stable. Direct evidence of the core–shell structure was observed by transmission electron microscopy (TEM). In addition the chemical bond linkage was confirmed by Fourier‐transfer infrared (FT‐IR) spectroscopy. An indirect proof of the core–shell structure was given by water absorption ratio determination of the different samples. Copyright © 2004 Society of Chemical Industry     

Investigation of the effect of molar mass on coating properties of self-crosslinking latexes based on acrylic microgels

The effect of reducing the molar mass of the shell layer of core–shell latex particles on film-forming and final coating properties of self-crosslinking latexes was investigated. Latex particles were prepared by the semi-continuous non-seeded emulsion polymerization of methyl methacrylate, butyl acrylate and methacrylic acid as main monomers. The particle core was slightly cross-linked (using a constant amount of allyl methacrylate as a comonomer) to prevent the copolymers forming the core phase from migration into the shell phase. For interfacial cross-linking, diacetone acrylamide was copolymerized into the shell layer of latex particles to provide sites for subsequent reaction with adipic acid dihydrazide. The molar mass of copolymers forming the shell layer was systematically varied by isooctyl 3-mercaptopropionate chain transfer agent included in the synthesis of each of the shell layers and the molar mass distribution was determined using size exclusion chromatography coupled with a multi-angle light scattering detection. Fundamental properties of latexes and cast films were systematically compared. These properties included minimum film-forming temperature, pendulum hardness, adhesion, impact resistance, stress–strain properties as well as the characterization of water absorption. The results confirmed theoretical predictions and described empirically the effects of reducing the molar mass of the shell layer copolymer on final properties of coating films.     

Morphology control of hollow polymer latex particle preparation

Hollow polymer latex particles containing a hydrophilic core fully encapsulated with a hydrophobic shell were prepared by multistage polymerization followed by neutralization with a base. The diameters of the particles were monodispersed and void fractions of the prepared latex particles as high as 50% were achieved. High instantaneous monomer conversion was found to be the key point to minimize the interdiffusion of the core–shell polymer chains. The influences of the shell crosslinking agent and shell carboxyl content on the hollow morphology were also investigated. The maximum hollow diameter was observed with crosslinking agent contents of 7.5–12.5 wt %. The shell carboxyl content had an appropriate value, and an excess of it resulted in an excentric hollow structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 860–863, 2005     

Core-shell structured latex particles. III. Structure–properties relationship in toughening of polycarbonate with poly(n-butyl acrylate)/poly(benzyl methacrylate–styrene) structured latex particles

The performance of the designed structured core-shell latex particles in toughening polycarbonate (PC) matrix was examined. Izod impact testing of the PC-core-shell latex blends were used to evaluate the influence of parameters related to the core-shell latex particles on toughening polycarbonate. Among these parameters are the particle size and levels of crosslinking of the core rubber particles, composition and molecular weight of the shell polymer, and weight ratio of shell to core polymers as well as the particle morphology. In this work, core-shell structured latex particles with thinner shells of higher molecular weight polymers were found to improve the impact resistance of polycarbonate. The role of chain entanglements in increased adhesion between the discrete rubbery phase and the continuous glassy matrix and the importance of surface-to-surface interparticle distance for toughening at various temperatures are discussed. © 1995 John Wiley & Sons, Inc.     

Polysiloxane/polyacrylate composite latexes with balanced mechanical property and breathability: Effect of core/shell mass ratio

Polysiloxane/polyacrylate (PSi/PA) core/shell latexes are fabricated, and the particle morphology, the film structure, as well as the properties of the latex films are investigated by comparing with blend latexes, and the relationship between structure and property is proposed. Results indicate that the structure and property of the latex films heavily depend on the particle morphology. The sea–island latex films with uniform distribution of PSi phases can be formed from the PSi/PA core/shell latexes, and with the mass ratio from 1:1 to 1:4, their tensile strength and elongation at break are close to the pure PA latex film, while the elastic recovery and water vapor permeability improve notably. It is found that the phase segregation occurs in the blend latex films, and although the blend latex films provide better water vapor breathability, their mechanical properties sacrifice obviously. Therefore, the various properties must be balanced for practical applications and the core/shell latexes are competitive for meeting the balanced requirements. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45258.     

Investigation of fluorinated polyacrylate latex with core–shell structure

Fluorinated polyacrylate latices with core–shell structure were prepared by semi‐continuous emulsion polymerization, using a mixed emulsifier system composed of a reactive emulsifier and a small amount of anionic emulsifier. The conversion and chemical components of the final latices were studied by gravimetric methods and Fourier‐transform infrared (FTIR) spectrometry, respectively. The structure of the latex particles was determined by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and particle size analysis. The latex films exhibited a low surface energy and high water‐contact angles. The surface analysis from X‐ray photoelectron spectroscopy (XPS) revealed that the fluorinated components preferentially self‐organized at the film–air interface. From XPS depth profiling of the film, it was found that a gradient concentration of fluorine existed in the structure of the latex film from the film–air interface to the film–glass interface. Compared with the core–shell structure with a fluorinated core, the core–shell structure with a fluorinated shell was more effective for modifying the properties of the latex films. Copyright © 2005 Society of Chemical Industry     

Facile preparation of nylon 6 nanocomposites based on clay reinforcement and core‐shell latex toughening: Morphology,properties, and impact fracture behavior

This work is focused on a facile route to prepare a new type of nylon 6‐based nanocomposites with both high fracture toughness and high strength. A series of nylon 6‐matrix blends were prepared via melting extrusion by compounding with poly (methyl methacrylate‐co‐butadiene‐co‐styrene) (MBS) or poly(methyl methacrylate‐co‐methylphenyl siloxane‐co‐styrene) (MSIS) latices as impact modifier and diglycidyl ether of bisphenol‐A (DGEBA) as compatibilizer. Layered organic clay was also incorporated into above nylon 6 blends for the reinforcement of materials. Morphology study suggests that the MBS or MSIS latex particles could achieve a mono‐dispersion in nylon 6 matrix with the aid of DGEBA, which improves the compatibilization and an interfacial adhesion between the matrix and the shell of MBS or MSIS. High impact toughness was also obtained but with a corresponding reduction in tensile strength and stiffness. A moderate amount of organic clay as reinforcing agent could gain a desirable balance between the strength, stiffness and toughness of the materials, and tensile strength and stiffness could achieve an improvement. This suggests that the combination of organic clay and core‐shell latex particles is a useful strategy to optimize and enhance the properties of nylon 6. Morphology observation indicates that the layered organic clay was completely exfoliated within nylon 6 matrix. It is found that the core‐shell latex particles and the clay platelets were dispersed individually in nylon 6 matrix, and no clay platelets were present in MBS or MSIS latex particles. So the presence of the clay in nylon 6 matrix does not disturb the latex particles to promote high fracture toughness via particle cavitation and subsequent matrix shear yielding, and therefore, provides maximum reinforcement to the polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of monodispersed hollow polymer particles by seeded emulsion polymerization under low emulsifier conditions

In a low emulsifier system, the MMA‐BA‐MAA copolymer emulsions were prepared as seed latices and the seeded emulsion polymerization of MMA‐MAA‐DVB was consequently carried out to prepare carboxylated core particles. The hydrophobic shell was then synthesized onto the core using styrene, acrylonitrile, and divinylbenzene as comonomers. The hollow latex particles were obtained by alkalization treatment of the core‐shell latex particles. The effects of the feeding rate of monomer mixture, contents of emulsifier SDBS and crosslinking agent DVB, and ratio of the monomers during the core stage and shell stage on the morphology and volume expansion of the latex particles were investigated. The results show that the monodispersed hollow latex particles with large size can be obtained when the feeding rate is 0.1 g/min, SDBS content is 0.15 and 0.2 wt % during the core stage and shell stage, respectively, DVB contents are 1% during the preparation of shell copolymers, and the monomer ratio of the core particle to shell layer is 1 : 8. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1505–1510, 2005     

Chemical components and properties of core–shell acrylate latex containing fluorine in the shell and their films

Core–shell acrylate latices containing fluorine in the shell were prepared by semicontinuous emulsion polymerization. The chemical components of the latices were determined by Fourier transform infrared, ion‐selective electrode analysis, and differential scanning calorimetry. The average size and morphology of the latex particles were characterized by photocorrelation spectroscopy and transmission electron microscopy, respectively. The latex particles were mainly composed of a non‐fluorine core and a fluorinated shell. The dynamic water contact angles of the latex films from the Wilhelmy method indicated that the latex films containing fluorine in the shell could be wetted by water only with difficulty. The amount of the fluoromonomer played an important role in the modification on the water contact angles, water absorption, and thermal stability of the latex films. In comparison with a random structure, the core–shell structure was more effective for improving the thermal properties of the latex films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 107–114, 2006     

Preparation and characterization of core‐shell nanoparticles containing poly(chlorotrifluoroethylene‐co‐ethylvinylether) as core

Core shell latex particles with a glassy core and a low T_g polymeric shell are usually preferred. More so, the glassy core happens to be a fluoropolymer with a shell polymer that helps in processability. We describe here the preparation and characterization of core shell nanoparticles consisting of poly(chlorotrifluoroethylene‐co‐ethylvinylether) as core encapsulated in poly(styrene‐acrylate) copolymer shell using seeded emulsion polymerization method under kinetically controlled monomer starved conditions. Properties of the emulsion using surfactants (fluoro/conventional) and surfactant free conditions were investigated. Average size (100 nm), spherical shape and core–shell morphology of the latex particles was confirmed by dynamic light scattering and transmission electron microscopy. Absence of C? F and C? Cl peaks in X‐ray photoelectron spectroscopy proves that cores are completely covered. Polymerization in the presence of fluorocarbon surfactant was found to give optimum features like narrow size distribution, good shell deposition and no traces of agglomeration. Films of core shell latex particles exhibited improved transparency and enhanced water contact angles thus making them suitable for applications in various fields including coatings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphological prediction and its application to the synthesis of polyacrylate/polysiloxane core/shell latex particles

A theoretical analysis and a morphological prediction of polyacrylate (PA)/polysiloxane (PSi) latex particles with core/shell morphologies were first conducted based on interfacial tensions and relative volumes of the two polymers in the latex system. The results indicated that the normal core/shell morphology particles (PSi/PA), with hydrophobic polysiloxane as the core and with hydrophilic polyacrylate as the shell, can be easily formed. Although the inverted core/shell morphology particles (PA/PSi) with polyacrylate as the core could not be formed in most cases, even if the fraction volume of polysiloxane was larger than 0.872, which is the smallest value of forming a PA/PSi particle, the PSi/PA particles were unavoidably formed simultaneously with PA/PSi particle formation. The synthesis of PA/PSi particles containing equal amounts of polyacrylate and polysiloxane was then carried out using seeded emulsion polymerization. Before the cyclosiloxane cationic polymerization, 3‐methacryloyloxypropyl trimethoxysilane (MATS) was introduced into the polyacrylate seed latex to form an intermediate layer and chemical bonds between the core and the shell polymers. The characterization by transmission electron microscopy (TEM) demonstrated that the perfect PA/PSi core/shell particle is successfully synthesized when both the core and the shell polymers are crosslinked. The experiments showed that both the hardness and water adsorption ratio characteristics of latex films of the PA/PSi particles are in good agreement with those of the polysiloxane film. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2251–2258, 2001     

Preparation and properties of core [poly(styrene‐n‐butyl acrylate)]–shell [poly(styrene–methyl methacrylate–vinyl triethoxide silane)] structured latex particles with self‐crosslinking characteristics

Structured latex particles with a slightly crosslinked poly(styrene‐n‐butyl acrylate) (PSB) core and a poly(styrene–methacrylate–vinyl triethoxide silane) (PSMV) shell were prepared by seed emulsion polymerization, and the latex particle structures were investigated with Fourier transform infrared, thermogravimetric analysis, differential scanning calorimetry, transmission electron microscopy, and dynamic light scattering. The films that were formed from the structured core (PSB)–shell (PSMV) particles under ambient conditions had good water repellency and good tensile strength in comparison with films from structured core (PSB)–shell [poly(styrene–methyl methyacrylate)] latex particles; this was attributed to the self‐crosslinking of CH₂?CH? Si(OCH₂CH₃)₃ in the outer shell structure. The relationship between the particle structure and the film properties was also investigated in this work. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1824–1830, 2006     

Surface immobilisation of fluorinated polystyrene‐acrylate latex nanoparticles with core–shell structure by crosslinking

Fluorinated polystyrene‐acrylate (PSA) latex nanoparticles with core–shell structure were synthesised by two‐stage seeded emulsion polymerisation method in the presence of reactive emulsifier DNS‐86. Diallyl phthalate (DAP) and Vinyltriethoxysilicone (VTES) were used as crosslinking agent to immobilise the fluorinated copolymer on the surface of the latex film. Fourier transform infrared spectroscopy (FTIR) spectra show that fluorine and siloxane monomers were effectively involved in the emulsion copolymerisation. Transmission electron microscope (TEM) observation shows that the prepared emulsion particles had a core–shell structure with fluorinated copolymer in the shell. X‐ray photoelectron spectroscopy (XPS) analysis reveals that fluorine atom has the tendency of migrating to the film–air interface and the incorporation of VTES helps the migration of fluorine atom towards the film–air interface. Water contact angle (WCA) test proved that DAP and VTES as crosslinking agent can immobilise the fluorinated copolymer on the surface of the latex films. © 2011 Canadian Society for Chemical Engineering     

Synthesis and characteristics of poly(methacrylic acid–co–N-isopropylacrylamide)/Nano ZnO thermosensitive composite hollow latex particles

In this work, the poly(methacrylic acid–co–N-isopropylacrylamide)/Nano ZnO thermosensitive composite hollow latex particles was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate-co- methacrylic acid) (poly(MMA–MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second process was to polymerize MAA, N-isopropylacrylamide (NIPAAm) and N,N′-Methylenebisacrylamide (MBA) in the presence of poly(MMA–MAA) latex particles to form the linear poly(MMA–MAA)/crosslinking poly(MAA-NIPAAm) core–shell latex particles, and then the core–shell latex particles were heated in the presence of ammonia solution to form the poly(MAA-NIPAAm) thermosensitive hollow latex particles. In the third process, the poly(MAA-NIPAAm) hollow latex particles reacted with ZnO nanoparticles to form the poly(MAA-NIPAAm)/ZnO thermosensitive composite hollow latex particles on which the ZnO nanoparticles were adsorbed. Besides, a novel process was used to synthesize the poly(MAA-NIPAAm)/ZnO composite latex particles in which the ZnO nanoparticles were encapsulated. The effects of various variables on the morphology of poly(MAA-NIPAAm)/ZnO composite hollow latex particle were studied.     

Synthesis and characteristics of poly(methyl methacrylate-methacrylic acid-3,3-(trimethoxysilyl) propyl methacrylate) hollow latex particles and their application to drug carriers

In this study, the hollow latex particle was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate-co-methacrylic acid) (poly(MMA-MAA)) copolymer latex particles by the method of soapless emulsion polymerization. Following the first process, the second process was to polymerize MMA, MAA, 3,3-(trimethoxysilyl) propyl methacrylate (MPS), and ethylene glycol dimethacrylate in the presence of poly(MMA-MAA) latex particles to form the linear poly(MMA-MAA)/crosslinking poly(MMA-MAA-MPS) core–shell latex particles. In the third process, the core–shell latex particles were heated in the presence of ammonia to form the poly(MMA-MAA-MPS) hollow latex particles. A sufficient heating time and high-heating temperature were necessary for the ammonia to dissolve the linear poly(MMA-MAA) core to form a perfect hollow structure. The crosslinking poly(MMA-MAA-MPS) shell was a barrier for the ammonia to diffuse into the latex particles so that the latex particle with the high-crosslinking shell showed an imperfect hollow structure. Besides, the hollow poly(MMA-MAA-MPS) latex particles reacted with ZnO nanoparticles, which were synthesized by a traditional sol-gel method, to form the polymer/inorganic poly(MMA-MAA-MPS)/ZnO composite hollow latex particles. With the increase of crosslinking degree would increase the amount of ZnO bonding. Moreover, the poly(MMA-MAA-MPS) hollow latex particles were used as carriers to load with the model drug, caffeine. The release of caffeine from poly(MMA-MAA-MPS) hollow latex particles was investigated.     

Morphological characterization of the core–shell latex particle by transmission electron microscopy and image analysis

To describe the morphology of the core–shell latex particle of methyl methacrylate–butadiene–styrene graft copolymer (MBS) quantitatively, we propose four parameters, that is, the diameter of the core, the shell thickness (TH), the roundness of the core, and the eccentricity (E); we calculated these parameters with geometrical parameters determined by the analysis of transmission electron microscope images. The mean values and distributions of the four parameters based on a certain amount of particles were used for quantitative characterization of MBS latex samples. With increasing monomer‐to‐polymer ratios of the graft polymerization, both the MBS TH and the numbers of homopolymer particles increased, and the core–shell morphology tended to be irregular. For the MBS latices derived from poly(styrene–butadiene) latex with a wide distribution of particle sizes, the core–shell structures of the larger particles were different from those of smaller ones to a certain extent, and both the TH and the E decreased with increasing core size. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 855–861, 2003     

Synthesis and characterization of poly(methyl methacrylate–butyl acrylate–acrylic acid)/polyaniline core–shell nanoparticles in miniemulsion media

Conductive polymer particles, polyaniline (PANI)‐coated poly(methyl methacrylate–butyl acrylate–acrylic acid) [P(MMA–BA–AA)] nanoparticles, were prepared. The P(MMA–BA–AA)/PANI core–shell complex particles were synthesized with a two‐step miniemulsion polymerization method with P(MMA–BA–AA) as the core and PANI as the shell. The first step was to prepare the P(MMA–BA–AA) latex particles as the core via miniemulsion polymerization and then to prepare the P(MMA–BA–AA)/PANI core–shell particles. The aniline monomer was added to the mixture of water and core nanoparticles. The aniline monomer could be attracted near the outer surface of the core particles. The polymerization of aniline was started under the action of ammonium persulfate (APS). The final product was the desired core–shell nanoparticles. The morphology of the P(MMA–BA–AA) and P(MMA–BA–AA)/PANI particles was characterized with transmission electron microscopy. The core–shell structure of the P(MMA–BA–AA)/PANI composites was further determined by Fourier transform spectroscopy and ultraviolet–visible measurements. The conductive flakes made from the core–shell latexes were prepared, and the electrical conductivities of the flakes were studied. The highest conductivity of the P(MMA–BA–AA)/PANI pellets was 2.05 S/cm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and structure control of hollow polymer particles: Influence of seeded emulsion polymerization and alkalization treatment process

Hollow polymer latex particles containing a hydrophilic core were prepared by seeded emulsion polymerization with MAA/BA/MMA/St as comonomers, followed by stepwise alkalization treatment with ammonia. The size and morphology of composite latex particles was determined by TEM. The effects of the seeded emulsion polymerization conditions and alkalization treatment on the size and hollow structure of latex were investigated. The results showed that the optimum content of crosslinking agent in the shell polymers was about 0.5–1.0 wt %, emulsifier was about 0.8–1.1 wt %, and the core/shell weight ratio was 1/7. To obtain uniform hollow latex particles with large size, the starved feeding technique should be adopted in seeded emulsion polymerization, and the neutralization temperature should equal to the T_g of the shell polymer. Then, the obtained polymer particles under this condition had an excellent hollow structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

表面含磺酸基的核-壳型乳胶粒子的制备与表征

为了合成表面含磺酸基的双亲型核-壳聚合物,本文采用两步乳液聚合法,第1步合成PS种子乳液;第2步用氧化还原引发体系在PS种子乳胶粒外包覆1层交联的聚苯乙烯磺酸酯,得到表面含磺酸酯的核-壳型聚苯乙烯(CPS)乳胶粒子。通过调节壳层单体的加入量,可以控制外壳层聚合物的质量分数(相对核层)在10%~30%之间。将外壳层的磺酸酯基水解转化成磺酸基得目标产物。用透射电子显微镜(TEM)、红外光谱(IR)、差热分析(DSC)和热失重分析(TGA)、X射线光电能谱(XPS)等方法对制备的乳胶粒子进行了测试和表征。