Synthesis of silicone–acrylate copolymer latexes and their film properties

Emulsion copolymerization of silicones (octomethyl tetracyclosiloxane, D₄ and methacryloxypropyl trimethoxy silane, MATS) and acrylics was carried out using three different polymerization processes: semicontinuous monomer emulsion addition, batch and initiator solution addition. Results showed that only the semicontinuous process led to a stable latex with monodisperse particles. Various polymerizations were carried out through this process with varying silicone/acrylic ratios and MATS content. Films were obtained from different latexes: their properties are significantly influenced by silicone and MATS contents in copolymers.     

离子型共聚单体用于高固含量无皂乳液聚合的研究——甲基丙烯酸异丁酯/甲基丙烯酸甲酯/丙烯酸丁酯无皂乳液聚合体系

该文采用自行合成的一种带亲水性磺酸离子基团及羟基的可共聚单体 3 烯丙氧基 2 羟基丙磺酸钠(AHPS)用于甲基丙烯酸异丁酯 /甲基丙烯酸甲酯 /丙烯酸丁酯 (IBMA/MMA/BA)无皂乳液聚合体系 .对乳胶粒粒径大小、乳液流体力学行为、共聚物的动态力学性质、拉伸行为及耐水性进行了研究 ,并对乳胶粒的成核机理进行了探讨 .实验结果表明 ,带亲水性离子基团可共聚单体AHPS的加入可获得 0 6μm左右的乳胶粒 ,乳液固含量可达 60 % ,表现粘度测定结果表明乳液呈Bingham流体 .三元共聚物在动态粘弹谱图上只出现单一的玻璃化转变温度峰 ,是完全的无规共聚物 ,拉伸强度明显大于常规乳液聚合方法得到的聚合物 ,耐水性也得到显著提高 .     

Morphology control in polymeric multiphase systems with block copolymers and structured latexes

Some application possibilities of block copolymers for the morphology control in polymeric multiphase systems are reviewed. The microdomain formation of block copolymers in the solid state is illustrated in the case of functionalized block copolymers and for interpolymer complexes. The preparation of “hairy latex” by emulsion polymerization in the presence of hydrophilic-hydrophobic block copolymers is shown in connection with their applications in the controlled agglomeration process of latexes and for the preparation of polymer particles having microvoids. The surface activity of block copolymers in polymeric oil-in-oil systems is illustrated for silicone oil filled polymers. These materials have a low kinetic friction coefficient and act as reservoir systems with the lubricant incorporated in the polymer matrix.     

有机硅改性丙烯酸酯共聚乳液合成方法及胶膜性能的研究

用一次投料法、单体乳液滴加法和引发剂滴加法有机硅改性丙烯酸酯共聚乳液，聚合过程、胶粒形态及乳液稳定性的观测结果表明：单体乳液滴加法是合成该类乳液的最佳方法，研究了单体乳液滴加法中有机硅含量与聚合反及胶膜性能的关系，结果表明：有机硅含量在１５％以下时，聚合反应可以顺利进行，胶膜性能不仅依赖于聚合时有机硅单体的总量，而且还依赖于有机硅单体中活性硅氧烷所占的比例。     

Block Copolymers in Emulsion and Dispersion Polymerization

Summary: This article deals with recent progress including the authors' work concerning the application of block copolymers as polymeric surfactants in heterophase polymerizations. The synthesis methods for preparing block copolymers by emulsion and dispersion techniques are outlined, with emphasis on recently developed controlled free radical polymerizations in aqueous media. Specific characteristics of amphiphilic block copolymers are described, for example, micellization and emulsifying effects. A general overview of emulsion and dispersion polymerization in an aqueous and organic medium with ionic and nonionic block copolymers is presented for the preparation of electrosteric and sterically stabilized latex particles. Typical examples of microemulsion, miniemulsion, oil‐in‐oil emulsion, and micellar polymerizations are provided. Current and potential developments of so‐called “hairy latexes”, inverse‐, multiple‐, and solid emulsions, as well as of nonaqueous polymeric dispersions are also discussed.

PS foam obtained by free radical polymerization of water‐in‐styrene, stabilized with a PS–PEO diblock copolymer.     

Effect of unmodified kraft lignin concentration on the emulsion and miniemulsion copolymerization of styrene with n‐butyl acrylate and methacrylic acid to produce polymer hybrid latex

The introduction of non‐modified kraft LignoBoost® lignin (KL) to produce polymer hybrid latex has received much attention in recent years because it is derived from renewable resources. The focus of this work is to develop a polymer hybrid latex by emulsion and miniemulsion copolymerization of styrene with n‐butyl acrylate and methacrylic acid in the presence of different concentrations of KL furnished by the pulp and paper industry. The study intends to substitute a styrene in the system to understand the effect of non‐modified KL on the properties not only of the latexes, but also on the copolymers themselves. Each polymerization was carried out by shot‐process of tertbutyl hydroperoxide and sodium formaldehyde sulfoxylate as the redox system. The polymer latexes were characterized in relation to overall conversion, particle diameter, particle morphology, coagulum formation, surface tension, zeta potential, and atomic force microscopy. The polymers were evaluated through gel permeation chromatography, water absorption, and thermal properties. The results show that the addition of non‐modified KL results in inhibition of the polymerization and that KL acts as a colloid stabilizer. Small particles were generated in the initial stages of the polymerizations. The presence of the KL altered the color of the latexes; the increase in KL concentration resulted in increase in the absorption of water of the polymer films; the increase in KL concentration resulted in decrease of the molar mass of the copolymers.     

Ab Initio Emulsion Atom‐Transfer Radical Polymerization

Stable latexes of poly(meth)acrylates with predetermined molecular weights, narrow molecular‐weight distributions, and controlled architecture were prepared by true ab initio emulsion atom‐transfer radical polymerization. Water‐soluble (macro)initiators in combination with a hydrophilic catalyst, Cu/tris(2‐pyridylmethyl)amine, initiated the polymerization in the aqueous phase. The catalyst strongly interacted with the surfactant sodium dodecyl sulfate (SDS), thereby tuning the polymerization within nucleated hydrophobic polymer particles. Long‐term stable latexes were obtained, even with SDS loading below 3 wt % relative to monomer. Block and gradient copolymers were prepared in situ. The reaction volume and solid content were successfully increased to 100 mL and 40 vol %, respectively, thus suggesting facile scale‐up of this technique. The proposed setup could be integrated in existing industrial plants used for emulsion polymerization.     

Microemulsion polymerization for producing fluorinated structured materials

When perfluoropolyether microemulsions are used during polymerization of fluoropolymers, the structure of the reaction environment can be strictly controlled. In particular, the number and size of polymer particles in latexes can be set freely, yielding a number of advantages. First, as a result of radical segregation, terminations can be decreased without reducing polymerization rate: in this way high molecular weights are easily obtained also with poorly reactive monomers. Moreover, in combination with a reversible chain transfer mechanism based on iodine, particle segregation allows establishing pseudo-living polymerization conditions. In this situation formation of long branches in the polymer can be controlled by using bifunctional molecules that are able to link two different polymer chains to each other during polymerization. This is the so-called “branching and pseudo-living” technology. Finally, by co-coagulating latexes of different polymers prepared by microemulsion polymerization, very small particles and, thus, high interface areas are generated. In this way properties of different polymers, such as fluoroelastomers and fluorinated semicrystalline polymers, are matched effectively, generating new nanocomposite materials that exhibit outstanding properties. In this paper these results are reported and an overview of some novel sophisticated fluoropolymers obtained in microemulsion is given.     

High-Solids Content Waterborne Polymer-Clay Nanocomposites

Summary: Waterborne polymer clay nanocomposites (WPCN) were prepared by emulsion and miniemulsion copolymerization of butyl acrylate and methyl methacrylate with enhanced mechanical, thermal and barrier properties for coating applications. Emulsion polymerization was used to synthesize WPCN using pristine Na-MMT (sodium montmorillonite) and miniemulsion polymerization to prepare the WPCNs when the pristine clay was organically modified and hence its incorporation into the polymerization loci was not guaranteed by the conventional emulsion polymerization technique. Both techniques allowed preparing stable nanocomposite latexes of BA/MMA copolymers with partially exfoliated morphologies as demonstrated by wide X-ray difraction (WAXD) and transmission electron microscope (TEM) measurements. Furthermore, latexes with solids contents up to 45 wt% and manageable viscosities were prepared for the first time using seeded semibatch emulsion polymerization.     

The Influence of Leucanol on the Aggregative Stability of Synthetic Latexes

On the example of model systems (polystyrene latexes and copolymers of styrene with polar monomers, acrylonitrile and ethoxyethyl acrylate), the effect of sodium naphthyl formaldehyde sulfonate on the aggregative stability of synthetic latexes was analyzed. Upon reaching the limit conversion, these latexes during storage spontaneously transfer to a solid gel having a periodic colloidal crystal-like structure. It is shown that the gelation process obeys the Smoluchowski law for coagulation. An increase in the molecular weight of the polymer and in the size of the latex particles during the formation of the gel was recorded. The introduction of a NF dispersing agent neutralizes the gel effect, stabilizes the system, prevents gelation and leads to a slight increase in the molecular weight of the polymer and the degree of polydispersity of the polymers obtained. It has been suggested that stable macroradicals accumulating from the gel-effect stage and remaining in the system after completion of polymerization can be one of the reasons for the loss of aggregative stability of latexes, and incorporating the dispersing agent into the adsorption layer of polymer-monomer particles leads to the recombination of these radicals within the particle and the stabilization of latexes in the polymerization process.     

可乳化共聚单体AGES用于无皂乳液聚合的研究

合成了一种新型可共聚单体烯烃基甘油醚磺酸盐(AGES),不仅含有具有反应活性的烯键,而且带有起乳化作用的磺酸离子基团及羟基,可用于MMA/BA无皂乳液聚合体系。对乳胶粒大小、乳液的流体力学行为及共聚物的动态力学性能进行了研究。实验结果表明:通过AGES的引入,可获得直径为0.5μm左右的分布均匀的乳胶粒,乳液含固量高(60%),粘度低,是稳定的塑性非牛顿流体乳液,共聚物为典型的无规共聚。     

Phase separation in polystyrene latex interpenetrating polymer networks

Polystyrene/polystyrene latex interpenetrating polymer networks (IPNs) were prepared by seeded emulsion polymerzation of styrene–divinylbenzene mixtures in crosslinked monodisperse polystyrene seed latexes. The resulting latexes comprised uniform nonspherical particles, which were formed by separation of the second-stage monomer from the crosslinked seed network during swelling and polymerization. The kinetics of phase separation were investigated by examining the changes in particle morphology using optical microscopy, which revealed that the phase separation was induced by the relaxation of the polymer chains before polymerization began and was enhanced by increased conversion. The thermodynamics of phase separation were investigated by analysis of the free-energy changes during swelling and polymerization, and the phase separation was described by a nucleation-and-growth mechanism. The results of this study have been applied to the design and synthesis of a series of uniform nonspherical particles of different morphology.     

Polymerization of styrene with ionic comonomer,nonionic comonomer,or both

Nanosized polystyrene latexes with high polymer contents were obtained from an emulsifier-free process by the polymerization of styrene with ionic comonomer, nonionic comonomer, or both. After seeding particles were generated in an initial emulsion system consisting of styrene, water, an ionic comonomer [sodium styrenesulfonate (NaSS)] or nonionic comonomer [2-hydroxyethyl methacrylate (HEMA)], and potassium persulfate, most of the styrene monomer or a mixture of styrene and HEMA was added dropwise to the polymerizing emulsion over 6 h. Stable latexes with high polystyrene contents (≤25%) were obtained. The latex particle weight-average diameters were largely reduced (41 nm) by the continuous addition of monomer(s) compared with those (117 nm) obtained by the one-pot polymerization method. Latex particles varied from about 30 to 250 nm in diameters, whereas their molar masses were within 10⁴ to 10⁵ g/mol. The effect of the comonomer concentration on the number of polystyrene particles per milliliter of latex and the weight-average molar masses of the copolymers during the polymerization are discussed. The surface compositions of the latex particles were analyzed by X-ray photoelectron spectroscopy, which indicated that the surface of the latex particles was significantly enriched in NaSS, HEMA, or both. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1634–1645, 2001     

Characterization of particle surface and morphology in vinyl acetate-butyl acrylate emulsion copolymers — Influence of the copolymerization pathway

Surface characterization was investigated in vinyl acetate (VAc) butyl acrylate (BuA) copolymer latexes of various compositions and prepared with four different emulsion polymerization processes: conventionnal batch, composition-controlled batch, core-shell, emulsifier-free semi-continuous. Surface end-groups (sulfate or carboxylic) titration results were first compared and discussed according to the type of process and as a function of conversion. As previously shown [1], it was confirmed that batch latex particles present a heterogeneous structure with a rich VAc outlayer, as in core-shell particles. As expected, semi-continuous and composition-controlled batch particles exhibit surface end-group characteristics revealing a more homogeneous distribution of both monomers within the particles. These differences in particle morphology were corroborated by analyzing water-polymer interface in these latexes using the soap titration method, with the sodium dodecyl sulfate (SDS) or sodium hexadecyl sulfate (SHS) as emulsifier probes. When the BuA was batch-polymerized onto PVAc seed particles, the estimated surface composition seemed to show that probably phase rearrangement occurs in the particle during the synthesis or upon aging. It was also confirmed that SDS displays an abnormal adsorption due to complexation and solubilization in the rich-VAc shell of the particles.     

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.     

室温自交联丙烯酸酯乳液的制备与表征

使用3种含不饱和双键硅氧烷,乙烯基三(β-甲氧基乙氧基)硅烷(A172)、乙烯基三乙氧基硅烷(VTES)和γ-甲基丙烯酰氧丙基三甲氧基硅烷(A174)为功能单体,采用半连续乳液聚合法制备了室温自交联丙烯酸酯乳液,探讨了硅氧烷功能单体在不同pH条件下水解情况以及其种类和用量对乳液及乳胶膜性能的影响.结果表明,pH在7～9之间时硅氧烷功能单体水解最慢;A172在pH为8.4时5h内就水解完全;增加VTES和A174的用量均能提高乳胶膜的交联度、力学性能和耐水性.控制聚合过程的pH值以抑制硅氧烷功能单体的水解并调节乳液成膜时的pH值以加速硅氧烷功能单体的水解从而增强胶膜的交联程度,发现酸性或碱性条件下得到乳胶膜比中性条件下胶膜的力学和耐水性能均有不同程度的提高,并且在酸性条件下胶膜的性能提高最多.对比使用A174和VTES制备的胶膜,发现这种方法对含有A174胶膜的效果不明显,而含VTES胶膜的性能提高最为显著.     

Surface‐initiated nitroxide‐mediated polymerization of sodium 4‐styrene sulfonate from latex particles

In this study, we report the use of a double‐headed dialkoxyamine trithiocarbonate ( I ) capable of acting as chain transfer agent via reversible addition‐fragmentation chain transfer polymerization or as initiator via nitroxide‐mediated polymerization. It is worth mentioning that I was revealed as an effective dual chain transfer agent in the synthesis of multiblock copolymers via bulk and emulsion processes. In this article, we report the employing of I in dispersed systems to obtain amphiphilic multiblock copolymers and latexes. In this case, a water soluble macroagent of PAA previously synthetized was used in disperse media using a mixture of methanol/water (70:30, w/w). Stable latexes were obtained via polymerization‐induced self‐assembly and surface‐initiated polymerization of SSNa from alkoxyamine‐functionalized latex PAA‐b‐PS‐b‐PAA was also obtained © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 437–444     

Unusual Kinetics in Aqueous Heterophase Polymerizations

The heterogeneous nature of aqueous heterophase polymerizations is the base for an easy route to unique block copolymers, for the development of new and more effective polymerization strategies, and the abilities to unique studies of radical polymerization kinetics. Thermo-sensitive double hydrophilic block copolymers and micro- or nano-gel particles of poly(N-isopropyl acrylamide) as thermo-responsible block and charged or uncharged hydrophilic polymers can easily be prepared if the polymerization of N-isopropyl acrylamide is started with the corresponding polymeric radicals. The application of extremely fast microwave heating allows the development of highly effective pulsed thermal polymerization strategies and the production of polymers with desired molecular weight distributions over wide ranges. 2,2′-azobisisobutyronitrile simultaneously initiates the polymerization in both the monomer and the aqueous phase and leads, even under surfactant-free conditions, to stable latex particles.     

Nonaqueous Emulsions – A Versatile Tool for New Types of Functional Nanoparticles

Summary : The preparation of functional polymer latex particles is usually carried out in aqueous heterogeneous systems, i.e. for example in emulsion or mini-emulsion polymerization. Due to the presence of water, moisture sensitive reactions like step growth polymerizations or metal catalyzed reactions can not be accomplished without side reactions and / or decomposition. In order to avoid these side reactions, different nonaqueous emulsion systems have been developed. According to the desired polymerization procedure, these systems consist of a nonpolar organic phase surrounded by a perfluorinated solvent or of a polar organic phase which is dispersed in a nonpolar organic solvent. Both emulsions are stabilized by amphipolar block copolymers and result in long time stable particle dispersions. The resulting dispersions yield particles with narrow size distributions and – depending on the reaction conditions – diameters down to tens of nanometers. This technique allows the formation of particles consisting of numerous different classes of polymers, e.g. polyurethanes, polyesters, polyolefins etc. and the formation of more complex morphologies such as core shell structures.     

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.