Novel synthesis of polymer and copolymer nanoparticles by atomized microemulsion technique and its characterization

The present paper relates to the atomized process for the synthesis of nanoparticles of polystyrene (nPS), polyacrylonitrile (nPAN), and poly(styrene/acrylonitrile) (nP[SAN]) copolymers with different monomer ratios and with controlled particle size in the range from 10 to 100 nm. In this process, ammonium persulfate (APS) was used as thermal initiator, along with sodium dodecyl sulfate (SDS) and n‐pentanol (n‐Pt) as surfactant and cosurfactant, respectively. The effect of different parameters on particle size and morphology of polymer nanoparticles has been reported in this work. Transmission electron microscopy (TEM) study showed the changes in particle morphology of pure nPS, nPAN, and their copolymers. Structural property and interaction of PS and PAN were investigated by Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD). The effect of particle size and crystalline structure on glass transition temperature (T_g) and melting temperature (T_m) were also investigated by differential scanning calorimetry (DSC). Thermal stability of polymer nanoparticles was studied by thermo gravimetric analyzer (TGA) and it showed that the copolymer nanoparticles of nP[SAN] were more stable with minimum weight loss (W_L). Copyright © 2010 John Wiley & Sons, Ltd.     

Facile and controllable synthesis of polyoxometalate nanorods within polyelectrolyte matrix

Well dispersed polyoxometalate nanorods have been selectively and controllably synthesized within the polyelectrolyte (PE) films via a layer-by-layer (LbL) adsorption-precipitation method. The PE matrix was fabricated by LbL self-assembly technology and then the multilayer films containing polyoxometalate nanorods were constructed by repetitive adsorption of polyanions and subsequent precipitation with counter ions-tetraethylammonium bromide (TEAB). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) was used to observe the variation of size and morphology of the nanorods. The growth process and composition of the multilayer films containing nanorods were also studied.     

Microwave-assisted synthesis of anhydrous CdS nanoparticles in a water-oil microemulsion

Microwave irradiation at a frequency of 2.45 GHz and a power ranging between 22 and 30 W was used, in a water-oil microemulsion at 35+/-2 degrees C, to obtain stable, small, crystalline, anhydrous CdS nanoparticles exhibiting enhanced luminescence properties. The process of nanoparticles growth at different irradiation times was followed by UV-vis spectroscopy. It was observed that irradiated nanoparticles grew faster and their size reached a constant value. The final mean nanoparticle diameter was 2.7 nm, smaller than that observed in a non-irradiated sample, in which particle dimensions slowly increased even after 10 h. This finding was confirmed by high resolution transmission electron microscopy which also suggested that the spherical nanoparticles had a narrow size distribution and were spatially well separated. Furthermore, Fourier transform infrared spectroscopy was used to obtain information about structural changes that the microemulsion underwent when irradiated by microwaves. In particular, the evolution of the stretching and bending bands of water molecules along with the CO and SO3 stretching bands of the surfactant molecules, showed that water was selectively and almost completely extracted from the aqueous core of the reversed micelles. Changes in the surroundings of the nanoparticles surface were monitored by photoluminescence spectroscopy and variations in the emission band profiles indicated enhanced luminescence properties. The latter finding, as well as the inhibition of the nanoparticles growth process, are attributable to the progressive reduction of water content in the core of the reversed micelles.     

Controlled nucleation and growth of CdS nanoparticles in a polymer matrix

In-situ synchrotron X-ray diffraction (XRD) was used to monitor the thermal decomposition (thermolysis) of Cd thiolates precursors embedded in a polymer matrix and the nucleation of CdS nanoparticles. A thiolate precursor/polymer solid foil was heated to 300 degrees C in the X-ray diffraction setup of beamline W1.1 at Hasylab, and the diffraction curves were each recorded at 10 degrees C. At temperatures above 240 degrees C, the precursor decomposition is complete and CdS nanoparticles grow within the polymer matrix forming a nanocomposite with interesting optical properties. The nanoparticle structural properties (size and crystal structure) depend on the annealing temperature. Transmission electron microscopy (TEM) and photoluminescence (PL) analyses were used to characterize the nanoparticles. A possible mechanism driving the structural transformation of the precursor is inferred from the diffraction features arising at the different temperatures.     

Modular synthesis of functional polymer nanoparticles from a versatile platform based on poly(pentafluorophenylmethacrylate)

Control of functionalities in polymer nanoparticles (PNPs) is important for their application. Thus, there is an interest for well‐defined nanoparticle platforms to which desired functions could readily, and in modular fashion, be imparted. Herein, we report an amine‐reactive PNP platform for the modular synthesis of functional PNPs from poly(pentafluorophenylmethacrylate) (poly(PFPMA)) through a simple substitution/nanoprecipitation/photo‐crosslinking strategy. Substitution of amine containing coumarin into poly(PFPMA) allows for the achievement of structural stability of nanoprecipitated particles through photo‐crosslinking after nanoprecipitation, making it possible to carry out subsequent chemical transformations in organic solvents if needed. We demonstrate that various small molecules and an amine‐terminated polymer could be used to modify the crosslinked PNPs to endow them with various functions including fluorescence and responsiveness to temperature changes. The functional PNPs were characterized with variable temperature dynamic light scattering (DLS), UV–vis, and photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1895–1901     

Synthesis and stabilization of cadmium and thallium metal nanoparticles in a polymer matrix

In situ synthesis of fine thallium and cadmium particles has been carried out by gamma-irradiation at room temperature in a preorganized polyacrylamide gel. It appears that Cd and Tl ions are chelated by the polymer matrix through physical entrapment as well as by weak chemical complexation. The metallic nanoparticles of Cd or Tl are well dispersed in the polymer matrix. The nanoparticles are stable in air and transfer electrons to methyl viologen (paraquat; 1,1'-dimethyl-4,4'-dipyridinium dichloride; MV(2+)(Cl(-))(2)). The radical, MV(+.), formed upon electron transfer, also gets trapped in the polymer matrix and shows high stability even in the presence of air.     

Semi-interpenetrating polymer networks synthesis by photocrosslinking of acrylic monomers in a polymer matrix

Semi-interpenetrating polymer networks have been obtained by UV-radiation curing of acrylate monomers dispersed in a polymer matrix, using an arylketone as photoinitiator. The polymerization kinetics was studied quantitatively by infrared spectroscopy for the various polymers examined: polyurethane, poly(vinyl chloride), poly(methyl methacrylate). The fastest reaction occurs in PVC films, where UV-curing develops extensively within a fraction of a second, leading to an insoluble and highly resistant material. The functionality of the acrylic monomer has a strong influence on the formulation reactivity, as well as on the mechanical and chemical properties of the final product. In PMMA, the polymerization was shown to continue to proceed efficiently for a few seconds after the UV exposure, even in the presence of air, due to both the high concentration of initiating radicals generated by the intense irradiation and the slow termination processes in solid media. © 1993 John Wiley & Sons, Inc.     

Formation of silver bromide precipitate of nanoparticles in a single microemulsion utilizing the surfactant counterion

Silver bromide precipitate of nanoparticles was prepared by addition of silver nitrate aqueous solution to a single microemulsion system consisting of dioctyldimethylammonium bromide, n-decanol, and water in isooctane. The silver ion reacted readily with the surfactant counterion, bromide, to form the precipitate of nanoparticles, which was stabilized in the water pools. The use of the surfactant counterion as a reactant is a new approach to nanoparticle preparation in microemulsions. It is characterized by high reactivity and less dependency on the intermicellar exchange of solubilizate. The effects of the surfactant and the cosurfactant concentrations, the amount of silver nitrate, and the water to surfactant mole ratio, R, were evaluated. Increasing the surfactant concentration at fixed R and amount of silver nitrate enhanced the role of intermicellar nucleation and resulted in the formation of larger particles, while increasing the amount of silver nitrate at fixed values of all the other variables enhanced the direct nucleation and resulted in the formation of smaller particles. Particle aggregation and flocculation took place when the concentration of n-decanol or the value of R was increased. Particle aggregation and flocculation were attributed to the decrease in the interaction between the surfactant protective layer and the nanoparticles in the water pools.     

Nanostructured polymer composite nanoparticles synthesized in a single step via simultaneous ROMP and ATRP under microemulsion conditions

Ring‐Opening Metathesis Polymerization (ROMP) and Atom‐Transfer Radical Polymerization (ATRP) were carried out simultaneously under microemulsion conditions with 1st generation Grubbs catalyst playing a double role: ROMP initiator and ATRP controlling agent. Starting from two distinct microemulsions—one containing the monomers and the other the catalyst—well‐defined composite nanoparticles with z‐average hydrodynamic diameter smaller than 50 nm were prepared. Depending on the monomers droplet composition, homopolymers blends or graft‐copolymers were synthesized in a one‐pot, one‐step, one‐catalyst approach. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4014–4027, 2009     

Synthesis and adsorption properties of gold nanoparticles within pores of surface‐functional porous polymer microspheres

Mesoporous polymer microspheres with gold (Au) nanoparticles inside their pores were prepared considering their surface functionality and porosity. The Au/polymer composite microspheres prepared were characterized by transmission electron microscope (TEM), X‐ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) techniques. The results showed that the adsorption of Au nanoparticles could be increased by imparting the pore structure and surface‐functional groups into the supporting polymer microspheres (in this study, poly (ethylene glycol dimethacrylate‐co‐acrylonitrile) and poly (EGDMA‐co‐AN) system). Above all, from this study, it was established that the porosity of the polymer microspheres is the most important factor that determines the distribution and adsorption amount of face‐centered cubic (fcc) Au nanoparticles in the final products. Our study showed that the continuous adsorption of Au nanoparticles with the aid of the large surface area and surface interaction sites formed more favorably the Au/polymer composite microspheres. The BET measurements of Au/poly(EGDMA‐co‐AN) composite microspheres reveals that the adsorption of Au nanoparticles into the pores kept the pore structure intact and made it more porous. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5627–5635, 2004     

反相微乳液中憎水性纳米金的原位还原法合成

利用十八胺(C18NH2)/正丁醇/正庚烷/HAuCl4(aq)W/O型微乳液体系,在常温的碱促进条件下由正丁醇原位还原氯金酸合成了具有高度单分散的憎水性金纳米粒子。由C18NH2稳定的金纳米颗粒运用紫外可见光谱(UV-vis)、透射电镜(TEM)和X射线衍射(XRD)等分别进行了表征和分析,并探讨了微乳液体系各组分对形成金纳米粒子形貌、尺寸和单分散性的影响。结果显示,随十八胺/氯金酸摩尔比的增加,金粒子的尺寸逐渐减小而单分散性逐渐提高。在正丁醇原位慢还原氯金酸的过程中,实验所选W/O型微乳液模板和表面活性剂十八胺分子对憎水性金纳米粒子的形貌和尺寸仍具有良好的控制作用。     

Radiation-induced synthesis of gold nanoparticles within lamellar phases. Formation of aligned colloidal gold by radiolysis

A sheared lamellar phase has been used as a nanoreactor for the synthesis of gold nanoparticles by radiolysis and by a photochemical approach. A gold salt solution (KAuCl4, 10(-2) M) is introduced into the aqueous compartments between the lipid-based bilayers. Gold nanoparticles grow within the lamellar phase as shown by TEM analysis and X-ray diffraction, limiting the particle size. Homodisperse, 2.4- and 5.9-nm-sized, spherical nanoparticles are produced by gamma irradiation and UV irradiation, respectively. When produced by radiolysis, they are perfectly aligned along the lamellae. Their UV-vis spectra display a maximum at 565 nm suggesting that nanoparticles are coupled by dipole-dipole interactions within the lamellar phase.     

Coupling of photoactive transition metal complexes to a functional polymer matrix**

Conductive polymers represent a promising alternative to semiconducting oxide electrodes typically used in dye-sensitized cathodes as they more easily allow a tuning of the physicochemical properties. This can then also be very beneficial for using them in light-driven catalysis. In this computational study, we address the coupling of Ru-based photosensitizers to a polymer matrix by combining two different first-principles electronic structure approaches. We use a periodic density functional theory code to properly account for the delocalized nature of the electronic states in the polymer. These ground state investigations are complemented by time-dependent density functional theory simulations to assess the Franck-Condon photophysics of the present photoactive hybrid material based on a molecular model system. Our results are consistent with recent experimental observations and allow to elucidate the light-driven redox chemical processes – eventually leading to charge separation – in the present functional hybrid systems with potential application as photocathode materials.     

Formation of the bimodal ensemble of silver nanoparticles in polymer solutions

Silver nanoparticles synthesized in polymer solutions are studied by spectroscopy (in near ultraviolet, visible, and infrared spectral regions) and high-resolution transmission electron microscopy. It is established that the ensemble with bimodal particle size distribution is formed from initially polydisperse nanoparticle ensemble in methylhydroxy ethyl cellulose solution. In contrast to the classical scheme of the ripening of colloidal dispersions, the number of small particles increases with time in the studied system; moreover, particles with a size of about 2 nm turned out to be stable. The large particles grow with time and their concentration drops.Translated from Kolloidnyi Zhurnal, Vol. 67, No. 1, 2005, pp. 87–93. Original Russian Text Copyright © 2005 by Serebryakova, Uryupina, Roldughin.     

Aerosol-assisted synthesis of mesoporous titania nanoparticles with high surface area and controllable phase composition

Mesoporous titania nanoparticles (denoted as MTN) with high surface area (e.g., 252 m² g⁻¹) were prepared using tetrapropyl orthotitanate (TPOT) as a titania precursor and 10–20 nm or 20–30 nm silica colloids as templates. Co-assembly of TPOT and silica colloids in an aerosol-assisted process and immediate calcination at 450 °C resulted in anatase/silica composite nanoparticles. Subsequent removal of the silica colloids from the composite by NaOH solution created mesopores in the TiO₂ nanoparticles with pore size corresponding to that of silica colloids. Effects of silica colloids’ contents on MTN porosity and crystallites’ growth at a higher calcination temperature (e.g., 1000 °C) were investigated. Silica colloids suppressed the growth of TiO₂ crystallites during calcination at a higher calcination temperature and controllable contents of the silica colloids in precursor solution resulted in various atomic ratios of anatase to rutile in the calcinated materials. The mesostructure and crystalline structure of these titania materials were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), differential thermal analysis (DTA)-thermo-gravimetric analysis (TGA), and N₂ sorption.