Modified emulsifier‐free emulsion polymerization of butyl methacrylate with ionic or/and nonionic comonomers

A modified emulsifier‐free emulsion polymerization of butyl methacrylate (BMA) with ionic or/and nonionic comonomers was successfully used to prepare nanosized poly(butyl methacrylate) (PBMA) latices with high polymer contents. After seeding particles were generated in an initial emulsion system, consisting of a portion of BMA, water, ionic comonomer [sodium styrenesulfonate (NaSS)] or nonionic comonomer [2‐hydroxyethyl methacrylate (HEMA)] and potassium persulfate, most of the BMA monomer or the mixture of BMA and HEMA was added dropwise to the polymerizing emulsion over a period of 6–12 h. Stable latices with high PBMA contents up to 27% were obtained. It was found that the latex particle sizes (2R_h) were largely reduced (34 nm) by the continuous addition of monomer(s) compared to those (107 nm) obtained by the batch polymerization method. The effect of comonomer concentration on the particle size, the number of PBMA particles/mL of latex (N_d), and the molar mass (M_w) of copolymer during the polymerization were discussed. The surface compositions of latex particles were analyzed by X‐ray photoelectron spectroscopy, indicating that the surface of latex particles was significantly enriched in NaSS or/and HEMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3080–3087, 2004     

Morphology of latex particles formed by poly(methyl methacrylate)-seeded emulsion polymerization of styrene

Poly(methyl methacrylate)–polystyrene composite particle latexes were prepared by poly(methyl methacrylate)-seeded emulsion polymerization of styrene employing batch, swelling-batch, and semibatch methods. The changes in particle morphology taking place during the polymerization reaction were followed by electron microscopy. Anchoring effect exerted by ionic terminal groups introduced by ionic initiator was found to be the main factor in controlling the particle morphology. The polymer particles obtained by oil-soluble hydrophobic initiators such as azobisisobutyronitrile and 4,4′-azobis-(4-cyanovaleric acid) gave the inverted core-shell morphology. Water-soluble hydrophilic initiator, K₂S₂O₈, also gave the inverted core-shell morphology. However, in this case the occurrence of the halfmoonlike, the sandwichlike, and the core-shell morphologies were also observed depending upon the polymerization conditions. The distribution of terminal ? SO groups on the surface area of polystyrene particles could be controlled by initiator concentration and polymerization temperature. Viscosity of polymerization loci dictated the movement of polymer molecules, thus causing the unevenness of particle shape and phase separation at high viscosity state. Viscosity was controlled by the styrene/poly(methyl methacrylate) ratio, the addition of a chain transfer agent or a solvent which is common to polystyrene and poly(methyl methacrylate).     

核壳型纳米SiO2/含氟聚丙烯酸酯复合乳液的合成与表征

采用原位乳液聚合法,在可聚合阴离子乳化剂/非离子乳化剂复配体系下,以γ-甲基丙烯酰氧丙基三甲氧基硅烷(KH-570)改性的纳米SiO2、甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、丙烯酸(AA)等为核相组成,以MMA、BA及甲基丙烯酸十二氟庚酯(DFMA)为壳相单体,合成纳米SiO2/含氟聚丙烯酸酯复合乳液.考察了纳...     

改性纳米SiO2/聚氨酯-含氟丙烯酸酯无皂乳液合成及其胶膜性能表征

引言水性聚氨酯相对溶剂型聚氨酯具有不燃、气味小、不污染环境等优点[1-2],从而广泛用于涂料[3]、胶黏剂[4]、油墨[5]等领域。目前,常用于软包装领域的薄膜主要是表面能很低的非极性膜,而水性聚氨酯胶黏剂具有较高的表面自由能,对非极性膜的润湿性差,因此需要降低水性聚氨酯的表面张力,达到润湿非极性膜的目的。     

Preparation and properties of soapless poly(styrene–butyl acrylate–acrylic acid)/SiO2 composite emulsion

Soapless emulsion polymerization of styrene-butyl acrylate-acrylic acid was carried out using single or combined polymerizable emulsifiers, such as hydroxypropyl methacrylate sodium sulfate (HPMAS), sodium vinyl sulfate, and vinyl alkylphenol polyether sulfates (NRS-10), in the presence of colloidal nano-SiO₂ solution in order to obtain films with high degree of hardness and water-resistance. Monomer conversion, formation of coagulum, viscosity, particle size, size distribution, and surface tension of the emulsions, as well as the film properties, were determined and compared with those of an emulsion prepared with the conventional emulsifier sodium dodecyl sulfate and polyoxyethylene octylphenol ether. Emulsions prepared from a mixture of two polymerizable emulsifiers NRS-10 and HPMAS (1:1, weight ratio) have presented high monomer conversion, low coagulum, and small particle sizes. When the emulsifier level increased within a certain level, the monomer conversion increased but particles size decreased. Increased amounts of reactive emulsifiers led to low monomer conversion, large amount of coagulum and small particle sizes. With the increase of nano-SiO₂ the particle sizes and the viscosity of the emulsion also increased. The introduction of reactive emulsifiers improved the water-resistance of the resulting films, and the addition of nano-SiO₂ increased the hardness of the coatings. Under optimal conditions, the coatings made from emulsions produced from a combination of reactive emulsifiers such as NRS-10 and HPMAS (1:1, weight ratio) at 2?% level (based on monomer weight) exhibited remarkable hardness, adhesion force and water-resistance.     

Secondary nucleation of styrenated hydroxyl-functionalized latexes

In this study, secondary nucleation in emulsion polymerization of butyl acrylate (BA), styrene (St), and 2-hydroxyethyl methacrylate (HEMA), was investigated. Different molar ratios of BA and St were used. Average particle size, particle size distribution (PSD), polymerization kinetics, glass transition temperature (T_g), and surface tension were monitored and compared. All synthetic latexes were prepared through seeded semi-batch emulsion polymerization process. Three different BA to St ratios (1:1, 1:2, 2:1) were combined with eight different HEMA contents (0, 1, 3, 5, 10, 20, 30, 40 mol%) in monomer composition, respectively. In the case of high HEMA content (10–40 mol%) it is found that secondary nucleation is mainly affected by HEMA. Secondary nucleation at low HEMA content (1–5 mol%) is dependent on the BA to St monomer ratio, and consequently a reflection of z-mer hydrophobicity.     

Novel synthesis of poly(methyl methacrylate) brush encapsulated silica particles

Silica (SiO₂)‐crosslinked polystyrene (PS) particles possessing photofunctional N,N‐diethyldithiocarbamate (DC) groups on their surface were prepared by the free‐radical emulsion copolymerization of a mixture of SiO₂ (diameter = 20 nm), styrene, divinyl benzene, 4‐vinylbenzyl N,N‐diethyldithiocarbamate (VBDC), and 2‐hydroxyethyl methacrylate with a radical initiator under UV irradiation. In this copolymerization, the inimer VBDC had the formation of a hyperbranched structure by a living radical mechanism. The particle sizes of such core–shell structures [number‐average particle diameter (D_n) = 35–40 nm] were controlled by the variation of the feed amounts of the monomers and surfactant, or emulsion system. The size distributions were relatively narrow (weight‐average particle diameter/D_n ≈ 1.05). These particles had DC groups on their surface. Subsequently, poly(methyl methacrylate) brush encapsulated SiO₂ particles were synthesized by the grafting from a photoinduced atom transfer radical polymerization approach of methyl methacrylate initiated by SiO₂‐crosslinked PS particles as a macroinitiator. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(methyl methacrylate) and polyacrylonitrile dispersions stabilized by gelatin

Methyl methacrylate was polymerized in an aqueous medium in the presence of gelatin using potassium persulfate as initiator. The dispersion mode of polymerization, when the monomer is completely miscible with water, was investigated and compared with an emulsion process, which proceeds at higher monomer concentration. Spherical and relatively uniform polymer particles were formed. Macroscopic precipitation of polymer is prevented by combination of the steric stabilization by grafted gelatin and of repulsive electrostatic interactions from the initiator residues attached to the particle surface. Static and dynamic light scattering have been used to determine the molar mass (molar mass of the whole dispersion particle, M_wD ～ 10⁸-10⁹ g mol^?1) and hydrodynamic radius (R_hD ～ 50-120 nm) of the particles. The number of particles per unit volume does not depend on overall monomer concentration, and it is higher, and therefore the particle size is smaller, than that observed for the soapless emulsion polymerization. The addition of gelatin may be thus used to modify the particle size. Acrylonitrile dispersions were prepared under similar conditions. Unlike methyl methacrylate, this monomer does not swell the polymer particles. While poly(methyl methacrylate) particles are spherical and relatively uniform, the polyacrylonitrile dispersions consist of polydisperse aggregates of tiny polymer particles.     

Comparing emulsion polymerization of methacrylate-monomers with different hydrophilicity

A comprehensive experimental study concerning the influence of various types of initiator-emulsifier systems on emulsion polymerization of methacrylate monomers (2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA) and butyl methacrylate (BMA)) reveals interesting relations between initiator and surfactant hydrophilicity on the one hand and the hydrophilicity of the monomers on the other hand. For the water-soluble HEMA stable latexes are only obtained if hydrophobic initiators such as 2,2′-azobisisobutyronitrile or dibenzoyl peroxide in combination with alkyl sulfate surfactants with carbon chain lengths greater than 10 or surface active initiators of the 2,2′-azobis(N-2′-methylpropanoyl-2-amino-alkyl-1)-sulfonate type with alkyl chain lengths greater than 8 are employed. Stable nano size range poly(2-hydroxyethyl methacrylate) (PHEMA) particles have been prepared also by batch emulsion polymerization using ionic surface active initiators (inisurfs). The results clearly show that the formation of stable latex particles requires a proper choice of the initiator-emulsifier system regarding its hydrophilic-hydrophobic balance. The PHEMA particles prepared with surface-active initiators keep their identity and spherical shape even in the dried state whereas in the case of the other initiator-emulsifier systems complete coagulation and coalescence occurs during drying.     

Surface and mechanical properties of an organic-inorganic super- hydrophobic coating using modified nano-SiO2 and mixing polyurethane emulsion as raw materials

A series of organic-inorganic super-hydrophobic coatings were prepared using nano-SiO₂ particles modified by fluorine and silicone coupling agents, and a mixing polyurethane emulsion as main raw materials. The mixing polyurethane emulsion was consisted of the polyurethane emulsion end-terminated by double bond (WPUD) and polyurethane emulsion modified by silicone (WPUS). The influence of content of modified nano-SiO₂ particles and the weight ratio of WPUS to WPUD on microstructure and hydrophobicity of the coating surface were studied. The morphologies of coating surface were examined using SEM and AFM, hydrophobicity of the coating was researched by examining static water contact angle and so on. It was found that modified nano-SiO₂ particle was an indispensable factor during the preparation of super-hydrophobic coating. The roughness and hydrophobicity of the coating surface were enhanced obviously with an increase of the content of the modified nano-SiO₂ particles. When the content of the modified nano-SiO₂ particles increased up to 1.5%, the surface of coating possessed good super-hydrophobicity, and static water contact angle reached 169.1°. It was also noticed that the weight ratio of WPUS to WPUD in the base layer has also an important influence on the hydrophobicity and mechanical property of coating surface. With an increase of the ratio of WPUS to WPUD the hydrophobicity of the coating was enhanced, the tensile strength and peel strength reduced, but the elongation at break increased. When the weight ratio of WPUS to WPUD reaches up to 9/100, the static water contact angle reaches the maximum value of 169.1°.     

Synthesis and characterization of new polysiloxane bearing vinylic function and its application for the preparation of poly (silicone-co-acrylate)/montmorillonite nanocomposite emulsion

A new silicone containing acrylic monomer, methacryloxyethyl polymethylhydrosiloxane ether (MEPMHSE), based on polymethylhydrosiloxane (PMHS) and 2-hydroxyethyl methacrylate (HEMA) has been synthesized for formulation of nanocomposite emulsion. Then Poly (silicone-co-acrylate)/montmorillonite (PSAM)/nanocomposite emulsion were prepared by in situ intercalative emulsion polymerization of methyl methacrylate (MMA), butyl acrylate (BA), methacrylic acid (MAA) and MEPMHSE, in the presence of organic modified montmorillonite (OMMT) with different OMMT contents (0, 0.5, 1.0, 1.5 and 2 wt%) and auxiliary agents in the presence of potassium persulphate (KPS) as initiator. Alkylphenol ethersulphate and Arkupal N-300 were used as anionic and non-ionic emulsifiers, respectively. The resulting monomer was characterized by Fourier transformer infrared spectroscopy (FTIR), proton (¹H NMR), and carbon (¹³C NMR) nuclear magnetic resonance spectroscopes. The OMMT was characterized by FTIR and X-ray diffraction (XRD). The nanocomposite emulsions were characterized by using Fourier transform infrared spectroscopy (FTIR), laser light scattering and surface tension. Thermal properties of the copolymers were studied by using thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) and then the effects of OMMT percent on the water absorption ratio and drying speed were examined. Results showed that OMMT could improve the properties of emulsion, in other words, the properties of nanocomposite emulsion were better when compared with those of the silicone–acrylate emulsion. The property of nanocomposite emulsion containing 1 wt% OMMT was the best one, and the following advantages were obtained: smaller particle size, faster drying speed, smaller surface tension, and improved resistant water by the incorporation of OMMT.     

Interfacial phenomena controlling particle morphology of composite latexes

A thermodynamic analysis and a mathematical model were derived to describe the free energy changes corresponding to various possible morphologies in composite latex particles. Seeded batch emulsion polymerization was carried out at 70°C using as seed monodisperse polystyrene latex particles having different surface polarity. The surface polarity was estimated by contact angle measurement at the latex “film”/water interface for octane as the probe liquid. Methyl methacrylate and ethyl methacrylate were polymerized in a second stage seeded emulsion polymerization using polystyrene particles as seed in the presence of a nonionic stabilizer, nonyphenol polyethylene oxide (Igepal Co-990). Two types of initiators, potassium persulfate (K₂S₂O₈) and azobisiobutyronitrile (AIBN), were used to change the interfacial tension between the second stage polymer (in monomer) and water interface. The values of the interfacial tension of polymer solutions in the second stage monomer vs. the aqueous phase, measured by drop-weight–volume method under conditions similar to those prevailing during the polymerization, correlated well with the determined particle surface polarity and the observed TEM particle morphology. The results showed that, rather than the polymer bulk hydrophilicity, the surface particle polarity is the controlling parameter in deciding which phase is inside or outside in the composite particle. The variation of the polymer phase interfacial tension with polymer concentration was also estimated. Based on experimentally measured interfacial tensions, composite particle configurations were predicted. The predicted morphologies showed good agreement with the observed particle morphologies of the composite latexes.     

Dispersion polymerization of 2-hydroxyethyl methacrylate stabilized by a hydrophilic/CO2-philic poly(ethylene oxide)-b-poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) (PEO-b-PFDA) diblock copolymer in supercritical carbon dioxide

Dispersion polymerization of 2-hydroxyethyl methacrylate (HEMA) has been successfully performed in supercritical carbon dioxide at P=370 bar and T=65 °C with azobis(isobutyronitrile) as initiator and a hydrophilic/CO₂-philic poly(ethylene oxide)-b-poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) (PEO-b-PFDA) block copolymer as steric stabilizer. The PEO-b-PFDA (2K/21K) block copolymer was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Spherical particles of poly(HEMA) were obtained in the range of 200-400 nm diameter size with a narrow particle size distribution (D_w/D_n<1.1). The effect of the stabilizer concentration on the dispersion polymerization was investigated from 20 w/w% down to 3.5 w/w% versus HEMA. Precipitation polymerization in the absence of stabilizer lead to the formation of large aggregates of partially coalesced particles whereas discrete spherical particles of poly(HEMA) were obtained by dispersion polymerization even at low concentration of PEO-b-PFDA (3.5 w/w% versus HEMA).     

Carbon dioxide switchable polymer surfactant copolymerized with 2‐(dimethylamino)ethyl methacrylate and butyl methacrylate as a heavy‐oil emulsifier

A CO₂‐switchable polymer surfactant was synthesized with 2‐(dimethylamino)ethyl methacrylate and butyl methacrylate. The conductivity, ζ potential, and particle size change illustrated the switchability of the surfactant, and this change could be repeated. Its surface tension decreased sharply when the sample was bubbled with CO₂; this indicated the enhancement of the surface activity. In the heavy‐oil emulsion with a surfactant concentration of 8 g/L, the viscosity almost reached the highest stability. When CO₂ overflowed the emulsion, it became unstable when the temperature beyond 40°C. The emulsion had a nice resistance to inorganic salt, which was maintained stably even when the concentration of NaCl was as high as 90,000 ppm. The emulsion could later be broken by the removal of CO₂. Its hydration rate was over 22 times faster than that in the presence of CO₂. The amount of residual oil in water was only about 53.84 ppm; this showed a good demulsification ability. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41307.     

Effect of Long-Chain Acrylate on the Properties of Polyacrylate/Nano-SiO2 Composite Leather Finishing Agent

Polyacrylate/nano-SiO₂ composite leather finishing agent was prepared via emulsion polymerization with butyl acrylate, methyl methacrylate, lauryl methacrylate as the main raw materials. The effects of different polymerization processes, lauryl methacrylate on the properties of composite were studied. The results show pre-emulsified emulsion polymerizations obtain a lower gel rate and higher conversion rate. Adding lauryl methacrylate can improve the water resistance, physical and mechanical properties of the composite film. Leather finished with P(Butyl acrylate/Methyl methacrylate/Lauryl methacrylate)/nano-SiO₂ composite latex show lower water-vapor permeability, lower water uptake and better resistence to the external force than that of the leather finished with P(Butyl acrylate/Methyl methacrylate)/nano-SiO₂ composite latex.     

Kinetics of emulsifier–free emulsion polymerization of methyl methacrylate

The influences of polymerization temperature, initiator and monomer concentrations, ionic strength of the aqueous phase, as well as ethylene glycol dimethacrylate (EGDM) co-monomer, on the kinetics of the emulsifier-free emulsion polymerization of methyl methacrylate (MMA) and on the properties of the resulting poly(methyl methacrylate) (PMMA) lattices were studied. The polymerizations were carried out using potassium persulfate (KPS) as the initiator. Monodisperse PMMA lattices with particle diameters varying between 0.14–0.37 μm and polymer molecular weights of the order 0.4 × 10⁶ to 1.2 × 10⁶ g/mol were prepared. The initial rate of polymerization increases with increasing temperature, KPS-MMA mole ratio, EGDM content, or with decreasing ionic strength of the aqueous phase. It was shown that the bead size can be limited by reducing the monomer concentration or by using the cross-linking agent EGDM. The ionic strength of the aqueous phase has a dominant effect on final particle diameter and polymer molecular weight. The uniformity of the latex particles increases as the temperature increases or as the initiator concentration decreases. The experimental results can be reasonably interpreted by the homogeneous nucleation mechanism of the emulsifier-free emulsion polymerization of MMA. © 1996 John Wiley & Sons, Inc.     

Methacryloylamidoglutamic acid functionalized poly(2-hydroxyethyl methacrylate) beads for UO22+ removal

A novel approach was developed to obtaining high uranium adsorption capacity utilizing 2-methacryloylamidoglutamic acid (MAGA) as a metal-complexing ligand. MAGA was synthesized by using methacryloyl chloride and glutamic acid. Spherical beads with an average size of 150–200 μm were obtained by suspension polymerization of MAGA and 2-hydroxyethyl methacrylate (HEMA) conducted in an aqueous dispersion medium. Poly(2-hydroxyethyl methacrylate–methacryloylamidoglutamic acid) [p(HEMA–MAGA)] beads have a specific surface area of 56.7 m²/g. p(HEMA–MAGA) beads were characterized by swelling studies, FTIR and elemental analysis. The p(HEMA–MAGA) beads with a swelling ratio of 63%, and containing 3.5 mmol MAGA/g were used in the removal of UO₂²⁺ from aqueous solutions. Adsorption equilibrium was achieved in about 120 min. The adsorption of uranium(VI) ions onto pHEMA was negligible (1.4 mg/g). The MAGA incorporation significantly increased the uranium adsorption capacity (204.8 mg/g). Adsorption capacity of MAGA incorporated beads increased significantly with pH and then reached the maximum at pH 6.0. Consecutive adsorption and elution operations showed the feasibility of repeated use for p(HEMA–MAGA) chelating beads.     

Adsorption of trypsin onto poly(2-hydroxyethyl methacrylate)/polystyrene composite microspheres and its enzymatic activity

Poly(2-hydroxyethyl methacrylate)/polystyrene (PHEMA/PS) composite microspheres were produced by emulsifier-free seeded emulsion polymerization for styrene in the presence of PHEMA seed particles. Effects of the surface characteristics of the PHEMA/PS composite microspheres on the adsorption immobilization of trypsin and on its enzymatic activity were discussed. Above 5 mol% of HEMA content, trypsin molecules adsorbed had high activity, 65–100% of the activity of free trypsin. The excellence of the composite microspheres as a carrier for trypsin seems to be closely related with the surface heterogeneity consisting of both hydrophilic and hydrophobic parts.     

Monodisperse polymer beads as packing material for high-performance liquid chromatography. Synthesis and properties of monidisperse polystyrene and poly(methacrylate) latex seeds

The effects of initiator concentration, ionic strength of polymerization medium, polymerization temperature, and monomer/water phase ratio on particle size, particle size distribution and molecular weight of the resulting polymers prepared by an emulsifier-free emulsion polymerization of styrene, methyl methacrylate and glycidyl methacrylate have been studied. Optimal conditions for preparation of uniformly sized polystyrene particles larger than 1 μm have been found. An attempt to synthesize monodisperse particles of similar size from methacrylate monomers and crosslinked particles has failed. It is shown that the swelling ability of “non-activated” latex particles does not exceed 70 fold increase in the volume and strongly depends on the size of the original particles.     

Role of fluorocarbon surfactant in the preparation of polytetrafluoroethylene‐modified polyacrylate emulsion

Role of fluorocarbon surfactant in the preparation of polytetrafluoroethylene‐modified polyacrylate emulsion is investigated. The fluorocarbon surfactant has an efficient preemulsification to polytetrafluoroethylene (PTFE) powder. It enables PTFE powder to be introduced into the copolymer of n‐butyl acrylate, n‐methyl methacrylate, n‐styrene, and α‐methacrylic acid. Thereby, stable PTFE‐modified polyacrylate emulsion can be formed. The effects of fluorocarbon surfactant on the surface tension, particle size and particle size distribution of the emulsion, as well as the relation between fluorocarbon surfactant and the amount of PTFE powder are fully investigated. The particle size and the surface tension of emulsion strongly depend on the fluorocarbon surfactant concentration in the reaction system. The particle size distribution becomes narrower and the stability of the emulsion is improved with the increasing of the fluorocarbon surfactant concentration. According to the experiments, a possible mechanism of fluorocarbon surfactant in polymerization is proposed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007