Polystyrene Nanocapsules Research Articles

Polymeric nanocapsules with controllable crosslinking degree via combination of surface‐initiated atom transfer radical polymerisation and photocrosslinking techniques

The crosslinked polystyrene nanocapsules with controllable crosslinking degree have been prepared by the ultraviolet (UV)-induced photocrosslinking of the polystyrene grafted silica nanoparticles (SN-PS), which was obtained by the surface-initiated atom transfer radical polymerisation of styrene from the modified silica nanoparticle templates, after the silica templates were etched with hydrofluoric acid. The effect of the UV-irradiating time on the inner diameter of the nanocapsules, and the degree of crosslinking and the thickness of the shells was investigated. The dynamic light scattering results showed that the degree of crosslinking of the obtained nanocapsules increased with the prolongation of the UV-irradiation time, therefore the inner diameter of the nanocapsules increased. However, the percentage of grafting of the crosslinked polymer shells decreased with increasing the UV-irradiation time because of the photodecomposition of the polystyrene grafted during the UV-irradiated crosslinking process, according to the thermogravimetric analysis.

Multi-Phase Composite Nanofibers via Electrospinning of Latex Containing Nanocapsules with Core-Shell Morphology

Nanocapsules containing hexadecane (HD) as core material and polystyrene (PS) as shell, were electrospun with polyethylene oxide (PEO) as a matrix material into the fiber webs. The morphology and thermal properties of PEO fibers containing (1) both PS nanocapsules with core-shell morphology and solid PS particles, (2) only solid PS particles, and (3) without any PS particles, were compared and the effect of PEO concentration on morphology of the resultant fibers have been studied. The resultant fibers were characterized by means of Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA). Both TEM observation and DSC analyses confirmed that the PS nanocapsules were encapsulated within the PEO nanofibers. The fibers had an average diameter of 950 nm for nanocapsules containing parts, 300 nm for solid particles containing parts, and 150 nm for usual parts. The phase change temperatures and phase transition heat of the produced fibers were determined by DSC analyses. TGA was also used to confirm the preparation of multi phase fibers and to determine the amount of HD within the fibers.

Magnetic polystyrene nanocapsules with core-shell morphology obtained by emulsifier-free miniemulsion polymerization

Nanocapsules containing hexadecane and Fe3O4 magnetic nanoparticles as core materials and polystyrene as shell were produced in a new method through emulsifier-free miniemulsion polymerization using 2,2′-azobis(2-amidinopropane) dihydrochloride (V-50) as a water-soluble initiator. The effect of some parameters such as the amounts of Fe3O4 and initiator on morphology of resulting nanocapsules was studied. Transmission electron microscopy showed that the products had latex particles having a size range of about 300–1300 nanometer and both magnetic nanocapsules with core-shell morphology and solid particles. The phase transition temperature and phase transition heat of the produced capsules were determined by differential scanning calorimetric analyses. Thermal properties of the latex were compared with those of magneticparticles-free latex and with those of latex free of both magnetic particles and hexadecane. Thermogravimetric analysis was also used to confirm the encapsulation and to determine the amounts of hexadecane and Fe3O4 within the capsules.

Preparation of core-shell polymeric nanocapsules containing liquid cores via redox interfacial-initiated microemulsion polymerization

AbstractIn this work, polystyrene (PSt) nanocapsules were successfully prepared by one-stage redox Interfacial-initiated inversed micro-emulsion polymerization of styrene (St), the cumene hydroperoxide (CHPO) and tetraethylenepentamine (TEPA) as the redox initiation pairs. The water-soluble TEPA acted as the reducing component and the oil-soluble CHPO as the oxidant component of the redox initiation system. The primary radicals were produced mainly at the oil/water interface to initiate the polymerization of styrene (St). Core-shell polymeric PSt nanocapsules were obtained by one-stage polymerization via this method, which was supported by the techniques of transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The particle size and polydispersity index (PDI) of nanocapsules were determined by dynamic light scattering (DLS). The results demonstrated that interfacial-initiated inversed microemulsion polymerization to form core-shell nanocapsules containing liquid cores by one-stage is successful.

Synthesis of polystyrene nanocapsules by redox interface‐initiated inversed microemulsion polymerization for drug release

AbstractPolystyrene nanocapsules with a diameter of 140 nm and a water‐soluble sodium salicylate core were prepared by redox interface‐initiated emulsion polymerization (RIEP) in an inversed microemulsion with cumene hydroperoxide/iron(II) sulfate as the redox initiation couple. The morphology of the nanocapsules was characterized by transmission electron microscopy and field emission scanning electron microscopy. Dynamic light scattering was used to determine the nanocapsule size and polydispersity (0.14–0.20). The release of sodium salicylate from the nanocapsules was monitored by ultraviolet–visible spectroscopy. All of the results indicate that the fabrication of core–shell nanocapsules with the water‐soluble active chemical as the core via RIEP was successful. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Facile Preparation of Crosslinked Polymeric Nanocapsules via Combination of Surface-Initiated Atom Transfer Radical Polymerization and Ultraviolet Irradiated Crosslinking Techniques

A facile approach for the preparation of crosslinked polymeric nanocapsules was developed by the combination of the surface-initiated atom transfer radical polymerization and ultraviolet irradiation crosslinking techniques. The well-defined polystyrene grafted silica nanoparticles were prepared via the SI-ATRP of styrene from functionalized silica nanoparticles. Then the grafted polystyrene chains were crosslinked with ultraviolet irradiation. The cross-linked polystyrene nanocapsules with diameter of 20–50 nm were achieved after the etching of the silica nanoparticle templates with hydrofluoric acid. The strategy developed was confirmed with Fourier transform infrared, thermogravimetric analysis, and transmission electron microscopy.

Crystallization and Melting Transitions of Hexadecane Droplets in Polystyrene Nanocapsules

Shifts to lower transition temperatures are observed for the freezing and melting of submicron-sized hexadecane droplets encapsulated within thin polystyrene shells. Supercooling of approximately 14 K is observed in the first-time cooling scans for the oil. We attribute this lowering predominantly to nucleation of the phase change originating from the oil/polymer/water interface. We obtain a rough estimate of the interfacial tension between the hexadecane oil droplet and the polystyrene of 14 mN/m assuming the Gibbs-Thomson relationship. Melting points for the hexadecane are 1-2 K below the bulk transition temperatures. This effect is connected with the surface/volume ratio of the capsules. Both the supercooling and the melting point depression approach the bulk-phase transition temperature when the sample is taken through multiple cool/heat cycles. The heating and cooling rates affects the number of cycles required before bulk-like behavior is observed. The thickness of the capsule wall is also observed to be critical to how many cooling cycles are required. Two hypotheses to explain this behavior are presented.

Preparation of Hollow Polystyrene Nanocapsules via a Miniemulsion Polymerization Process

Hollow polystyrene nanocapsules with sizes of ~100 nm have been prepared via a miniemulsion polymerization process by applying the encapsulation of a nonsolvent (i.e., isooctane). Divinylbenzene has been added to styrene as a cross-linking comonomer in order to improve a structural stability of the hollow polymer capsules. Morphology variation of nanocapsules with concentrations of divinylbenzene and also isooctane has been studied using transmission electron microscopy analysis. Kinetic study on the miniemulsion polymerization of styrene in the presence of divinylbenzene and isooctane has been carried out using fractional conversion data determined by the gravimetric analysis.

Encapsulation of Luminescent Quantum Nanodots in Polystyrene Nanocapsules by Microemulsion Polymerization

This paper reported on the one-step synthesis of polystyrene-quantum dots (PS@QD)nanoparticles using microemulsion polymerization method. The synthesized QD and PS@QD nanoparticles were characterized by UV, fluorescence spectroscopy, transmission electron microscopy (TEM) and fluorescence microscopy. The PS@QD is highly luminescent, which have the potential to be used as fluorescent probes in biological staining and diagnostics.

Preparation and optical properties of polystyrene nanocapsules containing photochromophores

Polymeric nanocapsules were prepared by the convenient one-step miniemulsion polymerization. Aqueous miniemulsion was obtained by mixing monomer, photochromophore, and initiator, and then adding the solution to an aqueous solution of surfactant and water, followed by ultrasonification. As the monomer was polymerized at 60 °C, polymeric nanocapsule particles were obtained. The morphology of the prepared nanocapsules was studied by transmission electron microscopy and showed core/shell structure with average diameter of 50–150 nm. Different types of photochromophores and initiators were applied to prepare nanocapsules and their effects on the morphology of the capsules were investigated. Thin films on glass substrates were prepared by spin coating, using a diarylethene containing nanocapsule solution. The color of the thin film was changed immediately to red upon irradiation with a UV light, which was bleached completely to an original state with the light of 500–650 nm.