Improvement of the storage stability and photostability of colored latex prepared by miniemulsion polymerization

Polymer particles containing oil-soluble dyes (colored latex) were prepared by miniemulsion polymerization. The dye preservation properties of colored latex loaded with different types of dye were studied; preservation depended on the rate of dye diffusion and thus on the size of the dye molecules and the hardness of the polymer matrix in the latex particles. Hindered amine stabilizers (HAS) were used to improve the photostability of colored latex. The effect of HAS in colored latex was investigated both as an additive and as a comonomer. The photostability of latex particles containing a simple mixture of dye and HAS was improved with increasing HAS content up to 20% in particles. In the case of colored latex particles combined with HAS by a covalent bond, the optimal amount of HAS for photostability improvement was between 8 and 20%.     

Preparation of colored latex containing oil-soluble dyes with high dye content by mini-emulsion polymerization

Polymer particles containing oil-soluble dyes (colored latex particles) were prepared by mini-emulsion polymerization. Copper phthalocyanine dyes and styryl dyes were used as oil-soluble dyes. Highly hydrophobic dyes played the role of hydrophobe by themselves and enabled the full incorporation of dyes in the latex without additional hydrophobes. Two phthalocyanine dyes having similar color were blended in a mini-emulsion polymerization so that the resulting colored latex showed enough strong color depth as a colorant. Colored latexes with high dye content (more than 30 wt% for phthalocyanine dye system and 40 wt% for styryl one) and with particle size less than 100 nm were obtained.     

Synthesis and characterization of covalently colored polymer latex based on new polymerizable anthraquinone dyes

Novel polymerizable red and yellow dyes, consisting of anthraquinone chromophore, alkyl spacer, and acryloyl group, were first synthesized and then used as comonomers in the semicontinuous emulsion copolymerization of styrene, butyl acrylate, and methacrylic acid to fabricate polymer latexes. The influences of the dye monomers on the emulsion polymerization process, the latex particle size and its distribution, the molecular weight of the latex polymer, as well as the light fastness of the polymer latex films, were investigated. Results indicated that, despite of the inhibition effect of the polymerizable dyes on polymerization, stable colored polymer latexes could be prepared with high conversion of total monomers, whereas the conversion of the polymerizable dye decreased as increasing the amount of dye. The light fastness of the covalently colored polymer latex films was proved to be much better than that of the noncovalently colored polymer latex films due to the covalent bond of dye and polymer chains.     

Effect of Monomer Feeding Mode on thePreparation of Hollow Latexes with High MAA Content in the Core Latex Preparation简

In order to prepare hollow latex particles with optimum morphology based on osmotic swelling principle, three- layer core/shell latex particles with 40 wt% MAA in the core were first prepared via multistep seeded emulsion copolymerization, in which monomers were added by a semi-continuous process with monomer addition under two different forms： pure monomers＇ mixture （monomer addition）, and pre-emulsified monomers （pre-emulsion addition）. Then, the hollow latex particles with different morphologies were obtained after alkali post-treatment. Influences of the monomer feeding mode on the emulsion polymerization and the particle morphology were investigated. Results showed that the pre- emulsion addition could significantly improve the polymerization stability in each step, and greatly enhance the uniformity of shell encapsulation. The sizes of the core and core/shell latex particles obtained by the pre-emulsion addition were smaller and more uniform than those synthesized by the monomer addition, and the hollow latex particles with intact morphology were generated by alkali post-treating of the core/shell latexes prepared from the pre-emulsion addition. As the core size increased, the morphology of the post-treated particles underwent evolution from hollow to collapse. Moreover, the mechanism of the particle morphological evolution was proposed.     

反应性复合乳液的合成、表征及其交联反应

利用种子半连续乳液聚合方法合成了核层或壳层带有环氧基以及壳层带有羧基的3种不同核/壳结构的乳胶粒子,通过物理共混带环氧基和羧基的乳胶粒子,得到了两种反应性复合乳液.利用透射电镜和激光动态光散射对乳胶粒子进行了表征,其粒径分布较窄,粒径分布的多分散系数为0.062,平均粒径约76 nm,乳胶粒子具有明显的核/壳结构.通过胶膜的凝胶率和膨胀率的测定和红外光谱分析对反应性复合乳液中乳胶粒子的扩散及交联反应进行了研究,并探讨了不同核壳结构复合乳液对涂膜机械性能的影响.研究表明,当反应性复合乳液中的环氧基和羧基分别分布在乳胶粒子的核层和壳层时,有利于聚合物分子链的充分扩散和化学交联反应的进行,从而提高涂膜的物理化学性能,当甲基丙烯酸缩水甘油酯(GMA)含量为10 wt%时,涂膜的拉伸强度达20.3 MPa.     

Synthesis and characterization of core–shell polyacrylate latex containing fluorine/silicone in the shell and the self-stratification film

A series of core–shell polyacrylate latexes with different fluorine/silicone monomer concentrations were prepared successfully by seeded emulsion polymerization. Dodecafluoroheptyl methacrylate and perfluorooctyl methacrylate with different fluorinated side chains were employed as fluorinated monomers, and γ-methacryloxypropyl triisopropoxidesilane (MAPTIPS) was used as a silicone-containing monomer as well as a self-cross-linking agent. The morphology and chemical structure of the latexes were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and differential scanning calorimetry, and the self-stratification properties of the latex film were verified by X-ray photoelectron spectroscopy and static contact angle measurement. The results showed that the fluorine/silicone-containing polyacrylate latexes presented a uniformly spherical core–shell structure, and the latex films displayed a preferential distribution of fluorinated composition near the surface, which was more remarkable with the synergism effect between the fluorine monomer and MAPTIPS. Additionally, the hydrophobicity and oleophobicity of the latex films exhibited high relevance with the fluorine/silicone monomer concentrations as well as the fluorinated side-chain structure.     

Effect of introduction mode of hydroxyl functionality on morphology and film properties of cycloaliphatic diepoxide crosslinkable core‐shell latex

Three series of core‐shell hydroxyl‐functionalized latexes were synthesized and then crosslinked with a cycloaliphatic diepoxide. The same amount of hydroxyl functional monomer was added during the core stage, shell stage, or partitioned equally between the core and the shell. The morphology of the latexes was examined with transmission electron microscopy and contact‐angle measurement. The stress‐strain behavior, viscoelastic properties, and water adsorption were evaluated for the latex films as a function of hydroxyl location. The location of hydroxyl groups within latex particles appeared to be dependent on the introduction mode of hydroxyl functional monomers. The introduction of hydroxyl groups during the shell polymerization resulted in a higher crosslinking density but a lower Tukon hardness and tensile properties. Not surprisingly, distribution of hydroxyl groups in both core and shell polymerization provided the lowest water adsorption and impact resistance as well as the highest tensile elongation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4256–4265, 2002     

Adsorption of Bovine Serum Albumin onto Polystyrene Latex Particles Bearing Saccharidic Moieties

The adsorption of bovine serum albumin (BSA) onto polystyrene latexes bearing various amounts of sugar moieties has been investigated as a function of pH and ionic strength and the results were compared to those for bare polystyrene latexes having negative surface charges. The functionalized latexes were produced by seeded copolymerization of (0.3 μm) liposaccharidic monomer onto polystyrene particles obtained by soap-free emulsion polymerization of styrene using potassium persulfate as initiator. At first, the electrophoretic mobility behavior of the various latexes was examined as a function of pH: a significant decrease was observed in the case of saccharide-containing latex particles compared to the bare particles. The adsorption of BSA onto these latexes exhibited a reduced amount of adsorbed BSA for those latex particles bearing saccharide groups. This adsorbed amount depends on the yield of saccharidic monomer incorporated onto the surfaces of the latex particles.     

Stability of Polymer–Monomer Particles of Synthetic Latexes

The presence of “living” macroradicals in the volume of a polymer–monomer particle may be one of the factors responsible for the loss of the aggregative stability of latexes. If the adsorption protection of a polymer–monomer particle is insufficient, high content of “living” macroradicals leads to gelation in the latex in the course of storage. Correlation between the latex life time, hydration of nonionic surfactant molecules in the adsorption layer of a polymer–monomer particle, and extent of the action of the macroradicals was determined. Naphthalenesulfonic dispersing agents enhance the stability of latex systems in the step of polymerization and distillation of the monomers owing to a decrease in the critical micelle concentration of the emulsifier, to extension of the micellar period of the polymerization, to an increase in the degree of saturation of polymer–monomer particles, and to an increase in the probability of macroradical recombination in the volume of a polymer–monomer particle. With an increase in the degree of polycondensation of naphthalene-containing dispersing agents, their surface activity increases, whereas the ability to support the aggregative stability of latexes decreases.     

Uniform nonspherical latex particles as model interpenetrating polymer networks

Polystyrene/polystyrene latex interpenetrating polymer networks (IPNs) were prepared by seeded emulsion polymerization of styrene–divinylbenzene mixtures in crosslinked monodisperse polystyrene particles. The resulting latexes comprised uniform nonspherical particles, e.g., ellipsodal and egg-like singlets, symmetry and asymmetric doublets, and ice cream cone-like and popcorn-like multiplets. The nonspherical particles, which were formed by separation of the second-stage monomer from the crosslinked seed network during swelling and polymerization, are excellent models for studying phase separation in IPN's. The degree of phase separation increased with increasing degree of crosslinking of the seed particles, monomer/polymer swelling ratio, polymerization temperature, and seed particle size, and with decreasing divinylbenzene concentration in the swelling monomer. The results were consistent with a thermodynamic analysis based on the elastic-retractile force of the polymer network, the monomer/polymer mixing force, and interfacial tension force.     

Preparation of poly(vinyl chloride) latexes by polymerization of stabilized monomer droplets

Poly(vinyl chloride) latexes have been prepared by polymerization in micron and submicron sized monomer droplets. Monomer emulsions with excellent long time stability were obtained by diffusional swelling of vinyl chloride monomer into preformed, stable polydisperse pre-emulsions of water-insoluble oils or monodisperse, oligomer styrene seed particles. It was found that the size and size distribution of the final latex particles were determined by those of the parent monomer emulsions. Except for the secondary particles formed during polymerization, the size and size distributions of the latex particles were found to be com-parable to those of the monomer emulsions employed, indicating a complete nucleation of the parent emulsion droplets. The extent of secondary particle formation was found to be very dependent upon the emulsifier concentration as well as on the type and amount of initiator used. © 1995 John Wiley & Sons, Inc.     

Polystyrene (1)/poly(butyl acrylate/amide type functional monomer) (2) two-stage emulsion polymers. Synthesis and thermomechanical properties of latex films

Polystyrene (PS) (1)/Poly (n-butyl acrylate (BA)/amide type functional monomer) (2) structured latex particles were prepared through emulsion polymerization varying the hydrophilicity of the functional monomer employed. The second-stage polymerization kinetics, the size and morphology of latex particles, and the location of the functional groups in the final latexes were studied, in order to relate them to the thermomechanical properties of films cast from these latexes. It has been shown that, as expected, increasing the hydrophobicity leads to a better homogeneity in the copolymer formed during the second-stage polymerization, while the more hydrophilic functional monomer partly homopolymerizes in a separate phase. However, the functionalization by all the monomers used in this work, prevents the PS seed particles to form a continuous skeleton (percolated network). Further heat treatments at 140°C do not lead to the formation of a continuous PS phase as for pure BA/pure PS two-stage particles. In addition, some thermally induced crosslinking effects are discussed in relation with the functional monomer location within the particles. © 1995 John Wiley & Sons, Inc.     

Preparation of Covalently‐colored Polymer Latex via Batch Emulsion Polymerization

Covalently‐colored polymer latex was synthesized via batch emulsion copolymerization of styrene, butyl acrylate and methacrylic acid in the presence of red polymerizable dye monomer consisting of anthraquinone chromophore, alkyl spacer and acryloyl group, and the influences of the initiator, surfactant and polymerizable dye on the polymerization and the latex properties were investigated. Results showed that the initiator amount was a determinative factor for the monomer conversion, and a high conversion of the polymerizable dye could be achieved when the ammonium persulfate amount was equal to or more than 1 wt% to the total monomers. Most of the chromophores were covalently bonded to the polymer chains if the polymerizable dye was used in the range of 0–1.5 wt%. The light fastness of the resulting latex film was much better than that of the noncovalently‐colored polymer film.     

Polystyrene(1)/poly(butyl acrylate-methacrylic acid)(2) core-shell emulsion polymers. Part I. Synthesis and colloidal characterization

Polystyrene (PS) (1)/Poly(n-butyl acrylate (BA)-methacrylic acid (MAA)) (2) structured particle latexes were prepared by emulsion polymerization using monodisperse polystyrene latex seed (118 nm) and different BA/MAA ratios. Three main aspects have been investigated: i) the polymerization kinetics; ii) the particle morphology as a function of reaction time; iii) the distribution of MAA units between the water phase and the polymer particles.The amount of MAA in the shell copolymer was found to be the main factor controlling the particle shape and morphology. The shape of the structured particles was, generally, non-spherical, and the shape irregularities increased as a particles was, generally, non-spherical, and the shape irregularities increased as a function of reaction time. At the beginning of the second stage reaction, new small particles were observed, which coalesced onto the PS seed as the polymerization proceeded. The distribution of the MAA groups in the latex particles and the serum was analyzed by alkali/back-acid titration, using ionic exchanged latexes. No MAA groups were detected in the latex serum. Due to the lowTg of the BA-MAA copolymers, alkali conductimetric titrations accounted for all the MAA groups on and within the polymer particles. Therefore, for these systems, this method is not only limited to a thin surface layer, as it is often assumed.     

Morphology control of magnetic latex particles prepared from oil in water ferrofluid emulsion

The use of magnetic latex particles as solid support in biomedical applications is favourable when homogeneous and well-defined core–shell polymer particles are used. Accordingly, this paper concerns with the synthesis of magnetic poly(styrene–divinylbenzene) latex particles using emulsion polymerization of styrene (St) and divinylbenzene (DVB) monomers in the presence of preformed oil in water organic ferrofluid emulsion droplets as seed. The key parameters which affect on formation and morphology of the prepared magnetic latexes were investigated, including type of magnetic emulsion, St/DVB monomers ratio, DVB amount, type of initiator and surfactant nature. In this study, two different magnetic emulsions were used, low and high octane content magnetic emulsions. The magnetic emulsions were stabilized using different types of surfactants including AP, Triton X 405 and SDS. In addition, four different initiators, including AIBN, V50, ACPA and KPS were examined. The morphology of the prepared magnetic latexes was investigated using transmission electron microscopy. In addition, particle size and size distribution, magnetic content and magnetic properties of the prepared magnetic latexes were also examined, using various techniques, e.g. dynamic light scattering, thermal gravimetric analysis and vibrating sample magnetometer, respectively. The results showed that the morphology type (Janus like, moon like and/or core–shell) of the prepared magnetic latex particles could be controlled depending mainly on the used formulation. In fact, the use of styrene monomer leads to anisotropic morphology. Whereas, the progressive use of DVB in presence of KPS intiator leads to a well-defined magnetic core and polymer shell structure.

超声无皂乳液聚合制备BA/St/AM三元共聚物乳胶粒及其聚合机理研究

将超声技术引入到无皂乳液聚合方法中,在不加入任何引发剂和乳化剂的情况下,制备了丙烯酸丁酯(BA)/苯乙烯(St)/丙烯酰胺(AM)三元共聚纳米乳胶粒.研究了不同超声时间对单体转化率、乳胶粒粒径以及乳液粘度的影响.同时还探讨了超声无皂乳液聚合机理,认为AM在聚合过程中起到了引发和稳定的作用.TEM照片表明,乳胶粒直径大约在80nm左右,FTIR及DSC分析表明产物为三元共聚物,而不是共混物.     

Preaparation of cationic latexes of poly(styrene-CO-butyl acrylate) and their properties evolution in latex dilution

Cationic latexes were prepared through emulsion copolymerization of styrene(St) and butyl acrylate(BA) with a cationic surfactant,cetyl trimethyl ammonium bromide(CTAB).Latex properties,including particle size,size distribution,ζpotential,surface tension and monomer conversion,were determined for latexes prepared with different CTAB amounts. Evolution of these properties during emulsion polymerization was followed in order to understand the mechanism of the particles formation.Results showed that both particle size andζpotential were function of polymerization time and latex solids.Parallel emulsion polymerizations with cationic,anionic charged initiator and charge-free initiators were also carried out,the latex properties were determined at different polymerization time.All these results were attentively interpreted based on the mechanisms of emulsion polymerization,surfactant adsorption and latex particle stabilization.     

MORPHOLOGY EVOLUTION OF POLY（St-co-BuA）/SILICA NANOCOMPOSITE PARTICLES SYNTHESIZED BY EMULSION POLYMERIZATION

Poly（St-co-BuA）/silica nanocomposite latexes were synthesized via conventional emulsion polymerization in the presence of 3-（trimethoxysilyl）propyl methacrylate modified colloidal nano-silica. The effects of surface property, particle size and content of colloidal nano-silica as well as the concentrations of monomer and surfactant on the morphology of nanocomposite latex particles were investigated by transmission electron microscope （TEM） and scanning electron microscope （SEM） in detail. Various interesting morphologies such as grape-like, Chinese gooseberry-like, pomegranate-like and normal core-shell structures were observed. Droplet nucleation mechanism competing with micelle nucleation mechanism was proposed to explain the morphological evolution of the nanocomposite particles.     

A Facile One‐Step Method to Prepare Three‐Dimensional Ordered Latex Particles

Three‐dimensional ordered latex particles were prepared in presence of polymerizable anionic emulsifier—sodium undec‐10‐enoate (UDNa) in emulsion polymerization. Only under a certain monomer/emulsifier ratio can we get such a result. Three‐dimensional ordered latex particles cannot be acquired with the use of conventional emulsifiers such as sodium dodecyl sulfate (SDS), etc. The double bond of polymerizable emulsifier can copolymerize with the main monomer and become covalently bound to integrate with the main polymer chains which result in stable latexes. TEM and SEM images show that whether it is diluted or not the latexes can always keep in the three‐dimensional regularly order.     

Surface functionalization of styrene/butyl acrylate latex with a water‐soluble monosaccharide monomer. Synthesis and morphology of the polymer particles

New polymer latexes bearing saccharide moieties on the particle surface were synthesized by using a water‐soluble sugar monomer, such as 1‐deoxy‐1‐methacryl‐amido‐D ‐glucitol, (MAG). All the latexes were prepared by a two‐stage emulsion polymerization technique. In the first step, the core was prepared with butyl acrylate (BA) and styrene (St). In the second step, the seed latex was polymerized with ethyl acrylate (EA) and MAG. The influence of a bifunctional monomer such as allyl methacrylate (ALMA), introduced at various concentrations, on the final latexes morphologies and properties was investigated. It was found that the latex particles exhibit a core‐shell structure. The mass balance of MAG showed that the main part of the sugar moiety is on the shell layer. The molecular properties, such as structure, composition, and molecular weight, were determined by elemental analysis, ¹H‐ and ¹³C‐NMR spectroscopy. Colloidal (particle size and their distributions), thermal, and rheological properties were also studied. Copyright © 2003 John Wiley & Sons, Ltd.