Synthesis of high molecular weight poly(methyl methacrylate) microspheres by suspension polymerization in the presence of silver nanoparticles

To prepare high molecular weight (HMW) poly(methyl methacrylate) (PMMA)/silver microspheres, methyl methacrylate was suspension-polymerized in the presence of silver nanoparticles using a low-temperature initiator at different conditions. The rate of conversion was increased with increasing initiator concentration. In the case of adding silver nanoparticles, the rate of polymerization decreased slightly. High monomer conversion (about 95%) was obtained in spite of low polymerization temperature of 30 °C. Under controlled conditions, PMMA/silver microspheres with various viscosity-average degree of polymerization (6,000–37,000) were prepared.     

Preparation of poly (methyl methacrylate)/LDH nanocomposite by exfoliation-adsorption process

Exfoliated nanocomposite based on Mg, Al layered double hydroxide (Mg,Al-LDH) and poly(methyl methacrylate) (PMMA) has been prepared by exfoliation/adsorption process with acetone as co-solvent. The product was characterized by X-ray diffraction (XRD), thermal analysis and High Resolution Transmission Electronic Microscope (HREM). The results suggest that the brucite-like sheets of LDH disperse individually in the polymer matrix, and the thermal stability of the nanocomposite increases highly.     

Fire retardancy and biodegradability of poly(methyl methacrylate)/montmorillonite nanocomposite

The poly(methyl methacrylate) (PMMA)/montmorillonite (MMT) nanocomposite was prepared by emulsifier-free emulsion technique and its structure and properties were characterized with infra red, X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, and cone calorimetry. The highly exfoliated MMT layers with dimension 1-2 nm in thickness were randomly dispersed in the polymer matrix containing MMT lower than 5% w/v, whereas the intercalated structure was predominant with MMT content higher than 5% w/v. Consequently, the fine dispersion of the MMT and the strong interactions between PMMA and MMT created significant improvement of the thermo-stability and fire retardancy of the nanocomposite. The combustion behavior has been evaluated using oxygen consumption cone calorimetry. In addition, a scheme was proposed to describe fire retardancy of PMMA and MMT as well as the correlation between the interaction and structure in polymer/clay systems. The biodegradability of the nanocomposite fire-retardant was tested for its better commercialization.     

Reactive poly(glycidyl methacrylate) microspheres prepared by dispersion polymerization

Poly(glycidyl methacrylate) [poly(GMA)] microspheres of narrow size distribution were prepared in a simple one‐step procedure by dispersion radical polymerization. Depending on the solvent used, poly(GMA) particle size could be controlled in the range of 0.5–4 μm by changing the solubility parameter of the reaction mixture. In N,N′‐dimethylformamide (DMF)/methanol mixture, the particle size increased and the size distribution broadened with decreasing initial solubility parameter. While in the DMF/methanol solvent system, hydroxypropyl cellulose (HPC) or cellulose acetate butyrate (CAB) were taken as steric stabilizers of the dispersion polymerization, poly(vinylpyrrolidone) (PVP) was used in alcoholic media. Contrary to the DMF/methanol system, narrow particle size distributions were obtained with PVP‐stabilized polymerizations in ethanolic, methanolic, propan‐1‐olic or butan‐1‐olic medium. Both the particle size and polydispersity were reduced with increasing stabilizer concentration. If lower molecular‐weight PVP was used, larger microspheres were obtained. Poly(GMA) samples prepared in a neat alcoholic medium virtually quantitatively retained oxirane group content after the polymerization. Reactivity of the poly(GMA) microspheres was confirmed by their hydrolysis and aminolysis. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3855–3863, 2000     

Magnetic poly(glycidyl methacrylate) microspheres prepared by dispersion polymerization in the presence of electrostatically stabilized ferrofluids

Fine magnetite nanoparticles, both electrostatically stabilized and nonstabilized, were synthesized in situ by precipitation of Fe(II) and Fe(III) salts in alkaline medium. Magnetic poly(glycidyl methacrylate) (PGMA) microspheres with core‐shell structure, where Fe₃O₄ is the magnetic core and PGMA is the shell, were obtained by dispersion polymerization initiated with 2,2′‐azobisisobutyronitrile (AIBN), 4,4′‐azobis(4‐cyanovaleric acid) (ACVA), or ammonium persulfate (APS) in ethanol containing poly(vinylpyrrolidone) or ethylcellulose stabilizer in the presence of iron oxide ferrofluid. The average microsphere size ranged from 100 nm to 2 μm. The effects of the nature of ferrofluid, polymerization temperature, monomer, initiator, and stabilizer concentration on the PGMA particle size and polydispersity were studied. The particles contained 2–24 wt % of iron. AIBN produced larger microspheres than APS or ACVA. Polymers encapsulating electrostatically stabilized iron oxide particles contained lower amounts of oxirane groups compared with those obtained with untreated ferrofluid. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5827–5837, 2004     

Fabrication of poly(methyl methacrylate) microfluidic chips by redox-initiated polymerization

In this report, a method based on the redox-initiated polymerization of methyl methacrylate (MMA) has been developed for the rapid fabrication of poly(methyl methacrylate) (PMMA) microfluidic chips. MMA containing 2-2'-azo-bis-isobutyronitrile was allowed to prepolymerize in a water bath to form a viscous prepolymer solution that was subsequently mixed with MMA containing a redox-initiation couple of benzoyl peroxide/N,N-dimethylaniline. The dense molding solution was sandwiched between a silicon template and a piece of 1-mm-thick PMMA plate. The polymerization could complete within 50 min under ambient temperature. The images of raised microfluidic structures on the silicon template were precisely replicated into the synthesized PMMA substrate during the redox-initiated polymerization of the molding solution. The chips were subsequently assembled by the thermal bonding of the channel plates and the covers. The new fabrication approach obviates the need for special equipment and significantly simplifies the process of fabricating PMMA microdevices. The attractive performance of the novel PMMA microchips has been demonstrated in connection with contactless conductivity detection for the separation and detection of ionic species.     

Poly(vinyl acetate)/poly(vinyl alcohol)/montmorillonite nanocomposite microspheres prepared by suspension polymerization and saponification

Poly(vinyl acetate) (PVAc)–poly(vinyl alcohol)–montmorillonite (MMT) nanocomposite microspheres were prepared through suspension polymerization followed by the heterogeneous saponification. The effects of MMT on the polymerization rate and the saponification rate of PVAc were studied. It was found that the rate of polymerization decreased when MMT content was increased. However, the saponification rate of PVAc significantly increased in the presence of nanoclay particles. The XRD measurement illustrated that the clay particles are intercalated in the polymer matrix.     

Synthesis of nano-ZnO/poly(methyl methacrylate) composite microsphere through emulsion polymerization and its UV-shielding property

Nano-ZnO/poly(methyl methacrylate)(PMMA) composite latex microspheres were synthesized by in-site emulsion polymerization. The interfacial compatibility between nano-ZnO particles and PMMA were improved by treating the surface of nano-ZnO particles hydrophobically using methacryloxypropyltrimethoxysilane (MPTMS). TEM indicated that nano-ZnO particles present in nanosphere and have been encapsulated in the PMMA phase. FT-IR confirmed that MPTMS reacted with the nano-ZnO particle and copolymerized with MMA. It was clearly found from SEM that ZnO nanoparticles can be homogeneously dispersed in the PVC matrix. The absorbance spectrum of the nanocomposite polymer suggested that increasing the amount of nano-ZnO in composite particles could enhance the UV-shielding properties of the polymers. The nano-ZnO/PMMA composite particle could eliminate aggregation of ZnO nanoparticle and improve its compatibility with organic polymer. This means that the composite particles can be widely applied in lots of fields.     

Production of poly(methyl methacrylate) particles by dispersion polymerization with mercaptopropyl terminated poly(dimethylsiloxane) stabilizer in supercritical carbon dioxide

Poly(methyl methacrylate) (PMMA) particles were produced by dispersion polymerization of methyl methacrylate in the presence of mercaptopropyl terminated poly(dimethylsiloxane) (MP-PDMS) in supercritical carbon dioxide at about 30 MPa for 24 h at 65 °C. The particle diameter could be controlled in a size range of submicron to micron by varying MP-PDMS concentration. The MP-PDMS worked as not only a chain transfer agent but also a colloidal stabilizer, which was named tran stab.Part CCLI of the series Studies on suspension and emulsion     

Preparation and characterization of poly(methyl methacrylate)/titanium oxide composite particles

Before polymerization, the introduction of double bonds onto the surface of the TiO₂ particles was achieved by the treatment of the TiO₂ particles with the silane-coupling agent. Via in-situ emulsion polymerization, the poly(methyl methacrylate) (PMMA)/titanium oxide (TiO₂) composite particles were prepared by graft polymerization of MMA from the surface of the modified TiO₂ particles. The structure of the obtained PMMA/TiO₂ composite particles was characterized using fourier transform infrared spectra (FT-IR), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC) and size excluding chromatography (SEC). The morphology of the obtained PMMA/TiO₂ composite particles was observed by transmission electron microscope (TEM). The results of FT-IR and TGA measurements show that PMMA is successfully grafted from the surface of the TiO₂ particles and that the percentage of grafting and the grafting efficiency can reach 208.3% and 96.6%, respectively. At the same time, the TGA and DSC measurements indicate an enhancement of thermal stability. TEM images demonstrate a better dispersion of the TiO₂ particles in the composite latex. In addition, UV-visible absorption measurements show that the PMMA/TiO₂ composite particles can absorb over 95% UV light at 210–400 nm wavelength.     

Suspension Polymerization of Methyl Methacrylate Stabilized Solely by Palygorskite Nano Fibers简

A kind of fibrous clay, palygorskite(PAL), was used as the sole stabilizer in suspension polymerization without the using of any other stabilizer usually used, especially polymeric stabilizers. In order to improve the compatibility with the organic monomer, PAL nano fibers were organically modified with silane coupling agent methacryloxypropyltrimethoxysilane(MPS). Transmission electron microscopy(TEM) and Fourier-transform infrared(FTIR) spectroscopy results show that the hydrolyzed MPS was attached onto PAL surface through Si―O―Si bonds formation without morphology change of PAL. At a loading amount of PAL to monomer as low as 0.36 wt%, effective stabilization could be achieved. After suspension polymerization, spherical poly(methyl methacrylate)(PMMA) particles were obtained. Scanning electron microscopy(SEM) analysis on both the outer surface and the inner cracked surface of the spherical PMMA particles indicates that the PAL particles reside on the surface of the PMMA spheres. The densely stacked PAL together with attached silane coupling agent stabilized the droplets throughout the suspension polymerization.     

Magnetic poly(glycidyl methacrylate)-based microspheres prepared by suspension polymerization in the presence of modified La0.75Sr0.25MnO3 nanoparticles

With the aim of preparing new magnetic poly(glycidyl methacrylate) (PGMA) microspheres suitable for magnetic separation, La_0.75Sr_0.25MnO₃ nanoparticles were selected as a core material. In order to improve their compatibility with PGMA, the surface of the nanoparticles was treated with penta(methylethylene glycol) phosphate methacrylate (PMGPMA) as a stabilizer. Subsequently, the nanoparticles were encapsulated by the suspension polymerization of glycidyl methacrylate (GMA) resulting in a relatively homogeneous distribution of La_0.75Sr_0.25MnO₃ nanoparticle aggregates inside the polymer microspheres. Microspheres in the size range of a hundred micrometers with a broad particle size distribution were obtained. PMGPMA can be considered to be an efficient compatibilizer between La_0.75Sr_0.25MnO₃ nanoparticles and PGMA. Both PMGPMA-coated La_0.75Sr_0.25MnO₃ nanoparticles and magnetic PGMA microspheres were characterized in terms of morphology, particle size, composition and magnetic properties by the appropriate methods, such as X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), light microscopy and SQUID magnetometry.     

Structure and properties of poly(methyl methacrylate) particles prepared by a modified microemulsion polymerization

Nanoscale poly(methyl methacrylate) (PMMA) particles were prepared by modified microemulsion polymerization. Different from particles made by traditional microemulsion polymerization, the particles prepared by modified microemulsion polymerization were multichain systems. PMMA samples, whether prepared by the traditional procedure or the modified procedure, had glass-transition temperatures (T_g's) greater than 120 °C and were rich in syndiotactic content (55–61% rr). After the samples were dissolved in CHCl₃, there were decreases in the T_g values for the polymers prepared by the traditional procedure and those prepared by the modified process. However, a more evident T_g decrease was observed in the former than in the latter; still, for both, T_g was greater than 120 °C. Polarizing optical microscopy and wide-angle X-ray diffraction indicated that some ordered regions formed in the particles prepared by modified microemulsion polymerization. The addition of a chain-transfer agent resulted in a decrease in both the syndiotacticity and T_g through decreasing polymer molecular weight. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 733–741, 2004     

The influence of β-FeOOH nanorods on the thermal stability of poly(methyl methacrylate)

Colloidal dispersions consisting of β-FeOOH nanorods with three different aspect ratios (4, 75 and 120) were synthesized using thermal hydrolysis of FeCl₃ solutions. After surface modification with oleic acid, the β-FeOOH nanorods were incorporated in poly(methyl methacrylate). Transmission electron microscopy and X-ray diffraction were applied for structural characterization of the β-FeOOH nanorods. The influence of inorganic phase on the thermal properties of PMMA matrix was studied using thermogravimetry and differential scanning calorimetry. Improvement of the thermal stability and increase of the glass transition temperature were found with the increase of content of inorganic phase and the increase of aspect ratio.     

Synthesis and electrorheological response of nano-sized laponite stabilized poly(methyl methacrylate) spheres

Poly(methyl methacrylate) (PMMA) nanospheres were fabricated via surfactant-free Pickering emulsion polymerization, in which hydrophilic laponite clay was used to stabilize the emulsions of methyl methacrylate dispersed in distilled water. These synthesized PMMA nanoparticles, of which the surface is compactly wrapped by laponite clay, are observed, as confirmed by scanning electron microscopy and transmission electron microscope images. Fourier-transform infrared spectra and thermogravimetry analysis confirm the chemical composition, thermal property, and mass percent of the laponite located on the surface of PMMA particles. Finally, laponite-wrapped nano-sized PMMA spheres were adopted as an electrorheological material. By using an optical microscope, the chain-like structure was observed when an external electric field was applied. In addition, the ER performance was also examined via a rotational rheometer equipped with a high voltage generator.     

Control of particle size in dispersion polymerization of methyl methacrylate

Poly(methyl methacrylate) (PMMA) particles ranging in diameter from 2 to 10 μm were prepared by dispersion polymerization. The effects of various polymerization parameters on the size and monodispersity were systematically investigated. The particle size was found to increase with increasing polymerization temperature, concentration and decomposition rate of the initiator, and solvency of the dispersion medium. It also increased with increasing concentration and molecular weight of the polymeric stabilizer, poly(vinyl pyrrolidone) (PVP). As the monomer concentration was increased from 5 to 20 wt %, a minimum was found in the particle size at a monomer concentration of 10 wt %. A costabilizer was found to be necessary for preparing monodisperse particles at stabilizer concentrations below 2 wt %. A recycling experiment showed that the consumption of PVP was quite small in each cycle and the residual materials in this system could be reused readily. © 1993 John Wiley & Sons, Inc.     

Preparation of poly(methyl methacrylate) microcapsules by in situ polymerization on the surface of calcium carbonate particles

Poly(methyl methacrylate) (PMMA) microcapsules were prepared by the in situ polymerization of methyl methacrylate (MMA) and N,N′-methylenebisacrylamide on the surface of calcium carbonate (CaCO₃) particles, followed by the dissolution of the CaCO₃ core in ethylenediaminetetraacetic acid solution. The microcapsules were characterized using fluorescence microscopy, atomic force microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. The average sizes of the CaCO₃ particles and PMMA capsules were 3.8 ± 0.6 and 4.0 ± 0.6 μm, respectively. A copolymer consisting of MMA and rhodamine B-bearing MMA was also used to prepare microcapsules for fluorescent microscopy observations. Fluorescein isothiocyanate-labeled bovine serum albumin was enclosed in the PMMA microcapsules and its release properties were studied.     

Polyaniline microsphere encapsulated by poly(methyl methacrylate) and investigation of its electrorheological properties

Microspheres consisting of a poly(methyl methacrylate) (PMMA) shell wrapping the conductive polyaniline (PANI) particle as a core were prepared by an in-situ suspension polymerization method and then adopted as an electrorheological (ER) material. The polymerization reaction and encapsulation were confirmed by Fourier transform infrared spectrum analysis. The rod-like PANI particles were synthesized via an emulsion polymerization protocol and observed by transmission electron microscopy. In addition, a spherical shape of encapsulated PANI/PMMA (core/shell) microspheres was observed by scanning electron microscopy. The thermal stability of PANI/PMMA particles was examined by use of thermogravimetric analysis. The PANI/PMMA particle-based suspension in silicone oil exhibited typical ER behavior. The conductivity of PANI/PMMA particles was much lower than that of the rod-like PANI.     

Synthesis of core/shell structure of glycidyl–functionalized poly(methyl methacrylate) latex nanoparticles via differential microemulsion polymerization

The differential microemulsion polymerization technique was used to synthesize the nanoparticles of glycidyl-functionalized poly(methyl methacrylate) or PMMA via a two-step process, by which the amount of sodium dodecyl sulfate (SDS) surfactant required was 1/217 of the monomer amount by weight and the surfactant/water ratio could be as low as 1/600. These surfactant levels are extremely low in comparison with those used in a conventional microemulsion polymerization system. The glycidyl-functionalized PMMA nanoparticles are composed of nanosized cores of high molecular weight PMMA and nano-thin shells of the random copolymer poly[(methyl methacrylate)-ran-(glycidyl methacrylate)]. The particle sizes were about 50 nm. The ratios of the glycidyl methacrylate in the glycidyl-functionalized PMMA were achieved at about 5–26 wt.%, depending on the reaction conditions. The molecular weight of glycidyl-functionalized PMMA was in the range of about 1 × 10⁶ to 3 × 10⁶ g mol⁻¹. The solid content of glycidyl-functionalized PMMA increased when the amount of added glycidyl methacrylate was increased. The glycidyl-functionalized polymer on the surface of nano-seed PMMA nanoparticles was a random copolymer which was confirmed by ¹H-NMR spectroscopy. The amounts of functionalization were investigated by the titration of the glycidyl functional group. The structure of the glycidyl-functionalized PMMA nanoparticles was investigated by means of TEM. The glycidyl-functionalized PMMA has two regions of T_g which are at around 90 °C and 125 °C, respectively, of which the first one was attributed to the poly[(methyl methacrylate)-ran-(glycidyl methacrylate)] and the second one was due to the PMMA. A core/shell structure of the glycidyl-functionalized PMMA latex nanoparticles was observed.