Differential Microemulsion Polymerization Research Articles

Understanding differential microemulsion polymerization in continuous slug flow through kinetic Monte Carlo simulation

Microreactors have been universal in polymerization and will help mitigate the residence time distribution and viscosity if conducted in a slug flow regime. The numerical simulation of this practice remains uncharted. Herein, based on our previous study, we proposed a kinetic Monte Carlo algorithm to describe the differential microemulsion polymerization in a biphasic slug flow. Propelled by an automatically spaced refreshment method and other accelerating approaches, the performance of the algorithm was boosted by over forty times. The sensitivity to the model-fitting parameters was analyzed to help understand the underlying mechanisms. After a thorough investigation on the effects of miscellaneous operating conditions regulatable in the continuous slug flow regime, the feasibility of product customization was demonstrated with case studies. Bridging the studies upon kinetics of microemulsion polymerization and interphase mass transfer in microreactors, this work should be able to provide deeper understanding of the process and guide the actual operation.

Preparation of poly(methyl methacrylate)-silica nanocomposites via DMP-assisted RAFT polymerization and NR/PMMA-RAFT-SiO2 hybrid membrane for pervaporation

Poly(methyl methacrylate)-silica (PMMA-RAFT-SiO2) nanocomposite emulsion was successfully synthesized via a combination of differential microemulsion polymerization (DMP) and reversible addition-fragmentation chain-transfer (RAFT) polymerization. The PMMA-RAFT-SiO2 emulsion with a low SiO2 loading (10 wt%) exhibited nano-sized particles (49 nm) with a core–shell structure and a high monomer conversion (88%). Natural rubber (NR) latex filled with PMMA-RAFT-SiO2 nanocomposites was cast to form hybrid membranes for pervaporation. The addition of SiO2 enhanced the physical properties of the composite membranes. The NR/PMMA-RAFT-SiO2 hybrid membrane with 4.0 wt% SiO2 content showed good mechanical properties. The hybrid membranes had hydrophilic properties and gave a high separation performance in the pervaporation of an ethanol solution (flux = 1,873–2,245 g/m2hr and pure water in permeate = 98–99%). Thus, the PMMA-RAFT-SiO2 nanocomposites had a great potential to be used as an effective filler in hybrid membranes for separation technology.

Continuous Differential Microemulsion Polymerization to Prepare Nanosized Polymer Latices in Microreactors

Microreactors are a promising platform for continuous synthesis of polymer latices when combined with emulsion polymerization. However, this application has long been haunted by fouling and clogging problems. In this work, we proposed the strategy of conducting differential microemulsion polymerization in microreactors within a biphasic slug flow and achieved rapid and stable preparation of nanosized PMMA latices (polymeric content as high as 15.7% with average particle size smaller than 20 nm). We started by exploring the temperature thresholds with thermal and redox initiation, the effect of initiator concentration, and the kinetic characteristics of microemulsion polymerization at different temperatures. Then, as for the differential microemulsion polymerization, extensive investigation was made into the effects of the volumetric flow ratio, the prepolymerization time, the initiator concentration, and the solid content of the initial microemulsion. Finally, we compared the differential microemulsion polymerization with the soap-free emulsion polymerization in the slug flow. The striking advantages in the polymerization rate, the average particle diameter, and the size distribution reflected higher density of particle nuclei, larger specific surface area of particles, and the pivotal effect of the persistent particle nucleation in the microemulsion polymerization.

Nanocomposites of high-impact polystyrene with unmodified nanosized TiO2 and polystyrene-encapsulated MPTMS-modified nanosized TiO2: mechanical, thermal and morphological properties

ABSTRACT Polymer nanocomposites of high-impact polystyrene (HIPS) with either unmodified nanosized titanium dioxide (nTiO2) or polystyrene (PS)-encapsulated MPTMS-modified nTiO2 (PS-MPTMS-nTiO2) were prepared. The PS-MPTMS-nTiO2 was synthesised via in situ differential microemulsion polymerization. The PS-MPTMS-nTiO2 exhibited a core–shell morphology with diameter of 45.3 nm. The addition of unmodified nTiO2 to the HIPS caused a reduction in the impact strength, tensile strength, and elongation at break, but an increase in the Young’s modulus. Meanwhile, the inclusion of the PS-MPTMS-nTiO2 was found to enhance the impact and tensile strength, Young’s modulus and thermal stability of the nanocomposites, while the elongation at break was deteriorated compared to that of the pure HIPS. This was due to the PS shell that hindered the agglomeration of the nTiO2 particles, leading to a better dispersion of the PS-MPTMS-nTiO2 particles in the HIPS matrix. Moreover, the Tg of HIPS in all nanocomposites was slightly affected by the nanoparticles.

Effects of Poly(Methyl Methacrylate)-Encapsulated Nanosilica on Mechanical Properties of Poly(Lactic Acid)/Ethylene Vinyl Acetate Nanocomposites

In this study, poly(lactic acid) (PLA) was melt mixed with three weight percentages (10–30wt%) of ethylene vinyl acetate copolymer (EVA) in an internal mixer, followed by a compression molding. According to a better combination of mechanical properties, the 90/10 (w/w) PLA/EVA was selected for preparing hybrid nanocomposites with three loadings (1, 3 and 5 parts per hundred of resin , phr) of poly(methyl methacrylate)-encapsulated nanosilica (PMMA-nSiO2). The nanolatex of PMMA-nSiO2 was synthesized via in situ differential microemulsion polymerization. The obtained PMMA-nSiO2 showed a core-shell morphology with nSiO2 as a core and PMMA as a shell, having an average diameter of 43.4nm. The influences of the EVA and PMMA-nSiO2 on the impact strength and the tensile properties of the PLA/EVA nanocomposites were studied and compared. It is found that the impact strength and the tensile properties of the 90/10 (w/w) PLA/EVA were improved with the appropriate amounts of the EVA and PMMA-nSiO2.

Morphology and drug release behavior of N-isopropylacrylamide/acrylic acid copolymer as stimuli-responsive nanogels

Thermo- and pH-responsive N-isopropylacrylamide (NIPAM) nanogels can be obtained by copolymerization of acrylic acid (AA) comonomer through differential microemulsion polymerization. The effects of comonomer, cross-linker, surfactant contents, and water/oil ratio were preliminarily investigated by a 24 full factorial design in order to eliminate the insignificant parameters from the polymerization analysis. The smallest poly(NIPAM-co-AA) nanogel particles were 40 ± 1 nm in diameter with 6 wt% of solid content and 98% conversion without coagulation. The comonomer amounts controlled the morphologies and LCST of the poly(NIPAM-co-AA) nanogels. The hairy microgels of poly(NIPAM-co-AA) with a 10:90 mol ratio of AA/ NIPAM had a lower critical solution temperature (LCST) of 6 °C. With an increase in the AA amount to a 17 mol ratio, the LCST increased to 27 °C, resulting in core-shell morphology. The morphology of resultant nanogels was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, and differential scanning calorimetry. Nuclear magnetic resonance spectroscopy was used to calculate the mole ratio of NIPAM and AA in resultant nanogels after dialysis. Both nanogel mole ratio and morphology effectively retained the cationic anti-cancer drug of methylene blue for several hours, an important basic requirement for a drug delivery system. Compared to core-shell microgels, a higher methylene blue release was obtained from the hairy microgels in simulated intestinal fluid.

Preparation of poly(methyl methacrylate)‐Silica nanoparticles via differential microemulsion polymerization and physical properties of NR/PMMA‐SiO2 hybrid membranes

Poly(methy methacrylate) (PMMA)‐SiO2 nanoparticles were prepared via differential microemulsion polymerization. The effects of silica loading, surfactant concentration, and initiator concentration on monomer conversion, particle size, particle size distribution, grafting efficiency, and silica encapsulation efficiency were investigated. A high monomer conversion of 99.9% and PMMA‐SiO2 nanoparticles with a size range of 30 to 50 nm were obtained at a low surfactant concentration of 5.34 wt% based on monomer. PMMA‐SiO2 nanoparticles showed spherical particles with a core‐shell morphology by TEM micrographs. A nanocomposite membrane from natural rubber (NR) and PMMA‐SiO2 emulsion was studied for mechanical and thermal properties and pervaporation of water‐ethanol mixtures. PMMA‐SiO2 nanoparticles which were uniformly dispersed in NR matrix, significantly enhanced mechanical properties and showed high water selectivity in permeate flux. Thus, the NR/PMMA‐SiO2 hybrid membranes have great potential for pervaporation process in membrane applications. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

Nanocomposites of NR/SBR Blend Prepared by Latex Casting Method: Effects of Nano-TiO2 and Polystyrene-Encapsulated Nano-TiO2 on the Cure Characteristics, Physical Properties, and Morphology

Nanocomposites of 80/20 (w/w) natural rubber (NR)/styrene butadiene rubber (SBR) blend with four loadings of either nanosized titanium dioxide (nTiO2) or polystyrene-encapsulated nTiO2 (PS-nTiO2), ranging from 3 to 9 parts by weight per hundred of rubber (phr), were prepared by latex casting method. The PS-nTiO2 synthesized via in situ differential microemulsion polymerization displayed a core-shell morphology (nTiO2 core and PS shell) with an average diameter of 42 nm. The cure characteristics (scorch time, cure time, and cure rate index), mechanical properties (tensile properties, tear strength, and hardness), thermal stability, glass transition temperature, and morphology of the prepared nanocomposites were quantified and compared. The results showed that the cure characteristics of all the nanocomposites were not significantly changed compared to those of the neat NR/SBR blend. The inclusion of an appropriate amount of either nTiO2 or PS-nTiO2 into the NR/SBR blend apparently improved the tensile strength, modulus at 300% strain, tear strength, hardness, and thermal stability but deteriorated the elongation at break of the nanocomposites. Based on differential scanning calorimetry, the glass transition temperature of all the nanocomposites was similar to that of the neat NR/SBR blend. Moreover, the morphology of the PS-nTiO2-filled rubber nanocomposites fractured surface analyzed by scanning electron microscopy showed an improvement in the interfacial adhesion between the rubber phase and the nanoparticles.

Effect of Particle Size on the Synthesization of Latex Nanoparticles

The differential microemulsion polymerization method was used to prepare the latex nanoparticles at different amount of monomer. The monomer mixture consists different amount of butyl methacrylate (BMA) that was varied from 5.7 g to 9.7 g. Thin film of latex nanoparticles was prepared using the spin coating method and has been dried at 100°C for 5 minutes. The particle sizes of latex nanoparticles were characterized using Zetasizer nanoseries and the structural properties of the samples was studied using Atomic Force Microscopy (AFM). As the BMA amount increased, the particle sizes of latex nanoparticles has found to decrease from 69.66 nm to 31.16 nm and the roughness has detected to reduce from 3.78 nm to 2.63 nm. We have found that the BMA content in the polymerization has sensitively effect the particle sizes and the structural properties of the latex nanoparticles.

Synthesis of polybutadiene-silica nanoparticles via differential microemulsion polymerization and their hydrogenated nanoparticles by diimide reduction

Polybutadiene (PB)–SiO2 nanoparticles were successfully synthesized via differential microemulsion polymerization. The core-shell structured PB-SiO2 nanoparticles were designed to achieve a monodispersion with reduced nanosilica aggregation. A high monomer conversion (81.5%), grafting efficiency (78.5%) and small particle size (27 nm) with narrow size distribution was obtained under optimum reaction conditions when using an extremely low surfactant concentration, 5 wt% based on monomer. The PB-SiO2 latex could be hydrogenated by diimide reduction in the presence of hydrazine and hydrogen peroxide to provide hydrogenated polybutadiene (HPB)–SiO2. A high hydrogenation degree of 98.6% was achieved at a ratio of hydrazine to hydrogen peroxide of 0.75:1, and showed a maximum degradation temperature of 469.6 °C resulting in excellent thermal stability. A new nanocomposite of PB-SiO2 and HPB-SiO2 could be used as a novel nanofiller in natural rubber. Especially, NR/HPB-SiO2 composites had improved mechanical and thermal properties, and exhibited good resistance toward ozone exposure.

Property improvement of plasticized poly(vinyl chloride) by nano‐TiO2 and poly(methyl methacrylate)–encapsulated nano‐TiO2

To improve the physical properties of plasticized poly(vinyl chloride) (p‐PVC), the p‐PVC nanocomposites filled with four loading levels (3, 5, 7, and 9 parts per hundred of PVC resin) of either nanosized titanium dioxide (nTiO2) or poly(methyl methacrylate)–encapsulated nTiO2 (PMMA‐nTiO2) were prepared by melt mixing on a two‐roll mill, followed by compression molding. The PMMA‐nTiO2 used in this study was synthesized via in situ differential microemulsion polymerization. The resulting PMMA‐nTiO2 exhibited core‐shell morphology (nTiO2 core and PMMA shell) with an average diameter of 42.6 nm. The effects of nTiO2 and PMMA‐nTiO2 on the tensile properties, hardness, morphology, and thermal stability of the as‐prepared p‐PVC nanocomposites were then investigated and compared. The inclusion of either nTiO2 or PMMA‐nTiO2 nanoparticles increased the tensile strength, Young's modulus, hardness, and thermal stability of the nanocomposites in a dose‐dependent manner and reduced the elongation at break. However, the elongation at break was still higher than that for the neat p‐PVC. Moreover, the PMMA‐nTiO2 nanocomposites had a higher enhancement of the tensile strength, Young's modulus, hardness, and thermal stability than the nTiO2 nanocomposites at a similar loading level. Hence, the PMMA grafted on the nTiO2 surface played an important role in toughening and increasing the thermal stability of the nanocomposites owing to the improved miscibility and interfacial adhesion between the encapsulated nanofiller and PVC matrix. J. VINYL ADDIT. TECHNOL., 22:433–440, 2016. © 2015 Society of Plastics Engineers

Synthesis of styrene–butadiene copolymer nanoparticles via semi-batch differential microemulsion polymerization

Styrene–butadiene rubber (SBR) nanoparticles were prepared in a semi-batch differential microemulsion polymerization (DMP) system using sodium oleate as the emulsifier. The size of the SBR nanoparticles could be easily tailored by controlling the monomer addition speed, the reaction temperature, the composition of the monomer feed stream and the amount of a surfactant introduced to the process. The smallest particle size, which is about 8nm, was achieved at 70°C with a very low surfactant concentration (25mM) as well as a reasonable conversion (72%). Moreover, the effects of n-dodecyl mercaptan (n-DDM), which was used as the chain transfer agent, on the particle size and the reaction conversion were investigated. Larger spherical particles and higher reaction conversions were observed at a higher n-DDM concentration. n-DDM can well regulate the SBR molecular weight of a polymer and a higher n-DDM concentration resulted in a smaller molecular weight. The DMP is found to be a very effective approach that requires a minimum amount of surfactant to prepare fine-tuned polymeric nanoparticles.

Styrene-assisted grafting of maleic anhydride onto deproteinized natural rubber

Grafting of maleic anhydride (MA) onto deproteinized natural rubber (DPNR) was carried out using a differential microemulsion polymerization technique. To improve the grafting efficiency (G.E) and reduce the gel content in the grafts, deproteinizing the NR latex was conducted before the grafting reaction and styrene (ST) comonomer was used to increase the G.E. The effects of initiator and monomer concentration, reaction temperature, reaction time, monomer addition rate, and ST/MA ratio on G.E and gel content were investigated. Kinetics of grafting reaction in either the presence or absence of ST was investigated. The results showed that introduction of copolymerizing styrene could significantly improve both the G.E and the grafting content. The G.E increased with increasing ST/MA ratio. The optimal grafting condition was initiator and MA concentrations of 7wt% and 9wt% of dried rubber content, ST/MA mole ratio of 4:1, and MA addition rate of 0.6ml/min at 60°C for 4h. The addition of styrene to the grafting process enhances the graft copolymerization rate of MA grafting onto DPNR.

Preparation of styrene butadiene copolymer–silica nanocomposites via differential microemulsion polymerization and NR/SBR–SiO2 membranes for pervaporation of water–ethanol mixtures

• SBR–SiO 2 nanoparticles were prepared via differential microemulsion polymerization. • Modified-SiO 2 was completely encapsulated with SiO 2 as core and SBR as shell. • A high conversion and small particle size were obtained at a low SDS concentration . • NR/SBR–SiO 2 composites could be used as a novel membrane for pervaporation. • NR/SBR–SiO 2 membranes had high mechanical properties and water selectivity. Styrene butadiene copolymer (SBR)–SiO 2 nanoparticles with core–shell morphology were prepared via differential microemulsion polymerization. The effects of silica loading, monomer to water ratio, surfactant concentration and initiator concentration on monomer conversion, particle size, particle size distribution, grafting efficiency and silica encapsulation efficiency were investigated. A high monomer conversion of 86.6% and SBR–SiO 2 nanoparticles with a size range of 20–50 nm, with a narrow size distribution and high grafting efficiency of 75.5% were obtained at a low surfactant concentration of 3 wt.% based on monomer. The obtained SBR–SiO 2 nanoparticles exhibited spherical morphology with SiO 2 as the core and SBR as the shell as confirmed by TEM micrographs. Well-dispersed SBR–SiO 2 nanoparticles were successfully synthesized by differential microemulsion polymerization at a low surfactant concentration under optimum condition. A nanocomposite membrane prepared from natural rubber (NR) and a SBR–SiO 2 emulsion was tested for its mechanical properties and the pervaporation of water–ethanol mixtures. The flux and selectivity of NR/SBR–SiO 2 nanocomposite membranes were reported as a function of SBR–SiO 2 loading and water concentration. The NR/SBR–SiO 2 membranes can be used to separate water from mixtures of water/ethanol with high water selectivity.

Microfluidic assembly of uniform fluorescent microbeads from quantum‐dot‐loaded fluorine‐containing microemulsion

AbstractWe report a facile strategy for fabricating fluorescent quantum dot (QD)‐loaded microbeads by means of microfluidic technology. First, a functional fluorine‐containing microemulsion was synthesized with poly[(2‐(N‐ethylperfluorobutanesulfonamido)ethyl acrylate)‐co‐(methyl methacrylate)‐co‐(butyl acrylate)] (poly(FBMA‐co‐MMA‐co‐BA)) as the core and glycidyl methacrylate (GMA) as the shell via differential microemulsion polymerization. Then, CdTe QDs capped with N‐acetyl‐l‐cysteine (NAC) were assembled into the poly(FBMA‐co‐MMA‐co‐BA‐co‐GMA) microemulsion particles through the reaction of the epoxy group on the shell of the microemulsion and the carboxyl group of the NAC ligand capped on the QDs. Finally, fluorescent microbeads were fabricated using the CdTe QD‐loaded fluorine‐containing microemulsion as the discontinuous phase and methylsilicone oil as the continuous phase by means of a simple microfluidic device. By changing flow rate of methylsilicone oil and hybrid microemulsion system, fluorescent microbeads with adjustable sizes ranging from 290 to 420 µm were achieved. The morphology and fluorescent properties of the microbeads were thoroughly investigated using optical microscopy and fluorescence microscopy. Results showed that the fluorescent microbeads exhibited uniform size distribution and excellent fluorescence performance. © 2014 Society of Chemical Industry

Effects of Silica, Poly(methyl methacrylate) and Poly(methyl methacrylate)-Grafted-Silica Nanoparticles on the Physical Properties of Plasticized-Poly(vinyl chloride)

Nanocomposites of plasticized-poly(vinyl chloride) (PVC) filled with different contents (3-9 parts by weight per hundred of PVC resin) of nanosilica (nSiO2), nanosized poly(methyl methacrylate) (nPMMA) and PMMA-grafted-nanosilica (PMMA-nSiO2) were investigated in this study. nPMMA and PMMA-nSiO2 were synthesized via differential microemulsion polymerization. The addition of either an appropriate type or amount of nanofiller into the plasticized-PVC improved the tensile strength, Young's modulus, tear strength, and thermal stability of the obtained nanocomposites, whereas the elongation at break decreased with increasing amounts of the nanofillers. Scanning electron micrographs of all the nanocomposites showed typical dimple fracture topologies similar to the neat plasticized-PVC.

Synthesis of polyisoprene–montmorillonite nanocomposites via differential microemulsion polymerization and application of PIP–Mt in natural rubber

Polyisoprene–montmorillonite (PIP–Mt) nanocomposites with an average particle size of 30±7.2nm and narrow size distribution (20–50nm) were successfully synthesized via differential microemulsion polymerization. X-ray diffractometry analysis revealed that PIP was intercalated in the Mt layers expanding the d spacing of the Mt layer from 3.1nm to 3.8nm. The SDS (surfactant) concentration, isoprene monomer (IP) to water ratio and Mt loading were all found to affect the IP conversion level, and the solid content and particle size of the obtained PIP–Mt nanocomposites. An IP conversion level of 81% and a solid content of 20% were achieved at 0.25wt.% 2,2-azoisobutyronitrile (AIBN), 10wt.% Mt, 10wt.% SDS and an IP:H2O ratio of 0.24:1. These PIP–Mt nanocomposites could be used as an effective nano-filler in natural rubber (NR) latex for the preparation of NR/PIP–Mt composites, improving the mechanical properties compared to the unfilled NR. NR filled with PIP–Mt at 2wt.% showed a 1.6 and 1.1 fold higher tensile strength and a modulus of elasticity at 300% elongation, respectively. Furthermore, NR/PIP–Mt composites at 2wt.% Mt loading improved the thermal aging compared to unfilled NR, with an 87.6%, 96.2% and 84.0% retention of the tensile strength, elongation at break and modulus of elasticity, respectively compared to 52.5%, 88.9% and 58.8% for the unfilled NR.

Preparation and Characterization of Crosslinked Latex Nanoparticles by Differential Microemulsion Polymerization

The differential microemulsion polymerization was used to synthesize crosslinked latex nanoparticles. In this paper, 1, 3-butylene glycol dimethacrylate (1, 3-BGDMA) was used as a crosslinking agent respectively 0-6 weight% of monomer total. The polymerization was carried out using butyl methacrylate (BMA), butyl acrylate (BA) and methacrylic acid (MAA) as the monomer mixture. The thin film of latex nanoparticles were prepared by using spin coating method and have been dried at 100°C for 5 minutes. The amount of the crosslinking agent added in the polymerization was optimized and we found that the particle sizes fall in the range of 30-60 nm. Field Emission Scanning Electrons Microscope (FESEM) was demonstrated that the spherical image of uncrosslinked latex change to a wooden-like image when the crosslinking agent added in the polymerization.

Synthesis of poly(butyl acrylate)‐poly(methyl methacrylate) core–shell nanomaterials of anti‐crease‐whitening properties

ABSTRACTCore–shell nanomaterials of poly(butyl acrylate)‐poly(methyl methacrylate) were synthesized using a differential microemulsion polymerization method for being used as polyacrylate‐based optical materials, which meet the requirement of anti‐crease‐whitening and proper mechanical strength. The effects of reaction temperature and surfactant amount on the particle sizes, as well as the effect of reaction temperature on the conversion and solid content were investigated to reveal the dependence of the application properties on the reaction conditions. The spherical morphology of core–shell nanoparticles was also studied via transmission electron microscopy. The resulting polymers with a core–shell monomer ratio of butyl acrylate/methyl methacrylate at 32/10 (vol/vol) demonstrated the optimal balanced properties in the anti‐crease‐whitening and mechanical property, confirmed by the visible light transmittance measurement and the dynamic analysis of the viscoelastic properties of the synthesized core–shell nanomaterials. The smaller the particle size, the better the transparency of the resulting polymer films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2014,131, 39991.

Modification of deproteinized natural rubber via grafting polymerization with maleic anhydride

Modification of natural rubber (NR) via grafting polymerization with maleic anhydride (MA) has received wide attention as it could improve the hydrophilicity of NR and extend its application to a wider application field. However, the grafting efficiency of MA onto NR in either the molten state or solution state is low and is accompanied with undesired high gel content in the grafts. In this work a novel technical route was developed in that a deproteinization operation was conducted before carrying out the grafting process and a differential microemulsion polymerization technique was applied for the grafting reaction. The effects of initiator and monomer concentration, reaction temperature, and reaction time on the grafting efficiency and gel fraction were investigated, and a comparison of the reaction performance was conducted for deproteinized NR (DPNR) and NR. The results indicated that the deproteinization operation could significantly improve the grafting efficiency and reduce the gel content, and a 29% yield of MA grafted onto the rubber backbone could be achieved at a condition of a DPNR:MA:initiator ratio of 85:9:6 (wt%) at 60°C for 8h.