Facile Preparation and Excellent Ultraviolet Shielding Application of Polyurethane-TiO2 Composite Microcapsules

In this work, butyl stearate, isophorone diisocyanate, and glycerol are used to prepare reticulated polyurethane microcapsules using interfacial polymerization. In addition, anatase nano-TiO₂ is added to prepare TiO₂-polyurethane phase change microcapsules during the polymerization process. Polarized light microscope, scanning electron microscope, Fourier-transform infrared spectroscopy, thermogravimetric, differential scanning calorimeter, and other methods demonstrate the successful preparation of microcapsules, and microcapsules with different TiO₂ content have differences in morphology and performance. It is worth noting that the addition of TiO₂ enhances the thermal stability and mechanical strength of the prepared composite microcapsules. In addition, TiO₂ particles allow the microcapsules to have photocatalytic properties and ultraviolet shielding properties, and the prepared TiO₂-polyurethane composite capsules show good catalytic degradation properties for methyl orange solution. Moreover, the ultraviolet absorption performance of the TiO₂-polyurethane composite microcapsule coating is tested, and the results show that the strength of ultraviolet light is weakened after passing through the coating, indicating that the composite microcapsule can enhance the UV resistance of the coating. This work shows the preparation of multifunctional microcapsules and their potential applications in photocatalysis and UV resistance.     

Solute Permeability of Certain Polymeric Films Applied on Aspirin Crystals to Form Microcapsules

A study was carried out to investigate the solute permeability of various polymer films applied on aspirin crystal to form microcapsules. The coating materials were an acrylate methacrylate (AMA), poly 3‐hydroxybutyrate‐hydroxyvalerate (Biopol^®) and poly (lactic‐glycolic) acid (PLGA). Organic solutions of the polymers were applied on the aspirin crystals (core) by a spray coating technique in a Wurster column. The microcapsule surfaces were investigated using scanning electron microscopy (SEM), while permeability studies were carried out on single microcapsules serving as micro dialysis cells. The amount of drug (m) permeating through the applied films in time (t) was analysed on the basis of Fickian diffusion. The SEM revealed numerous surface pores of size range 2.4 to 24 μm for the AMA films, while the PLGA and Biopol films, on the other hand, exhibited very few surface pores of size range 2.2 to 18 μm. However, the AMA films were more spongy than the PLGA and Biopol. The AMA films displayed a retarded release while the PLGA or Biopol films displayed a burst release, attributable to the differences in the film's porous structure. The Permeability coefficient (P) depended on the core weight of the single microcapsules, decreasing with increase in core weight. Thus, for an ensemble of the microcapsules the permeability coefficients of the films of the component microcapsules will have a distribution of P values even though the coating material is the same. This finding is important in the simulation of drug release from coated multiparticulate systems.     

Micelles‐Encapsulated Microcapsules for Sequential Loading of Hydrophobic and Water‐Soluble Drugs

Layer‐by‐layer (LbL) assembly was conducted on CaCO₃ microparticles pre‐doped with polystyrene‐block‐poly(acrylic acid) (PS‐b‐PAA) micelles, and resulted in micelles encapsulation in the microcapsules after core removal. Distribution of the micelles in the templates and capsules was characterized by transmission electron microscopy and confocal laser scanning microscopy. The micelles inside the capsules connected with each other to form a chain and network‐like structure with a higher density near the capsule walls. The hydrophobic PS cores were then able to load small uncharged hydrophobic drugs while the negatively charged PAA corona could induce spontaneous deposition of water‐soluble positively charged drugs such as doxorubicin.

     

In situ Localization of Molecules in Crosslinked Particles during Electrohydrodynamic Process: Simple Route to Produce Microcapsules and Fibers with Controlled Release

This study reports a spontaneous selective localization of molecules in crosslinked particles during electrospraying and electrospinning polymer solutions containing the particles. It provides a facile way of preparing microcapsules and fibers with controlled release. The dye molecules were phase separated from the crystalline polymer matrix during the electrohydrodynamic process and moved to the solvent‐rich crosslinked particles. The position of the particles in the microcapsules and fibers could be controlled by adjusting compatibility of the particles with the matrix polymer. The microcapsules and fibers did not show the initial burst release of the molecules and gave considerably prolonged release behavior.

     

相变微胶囊的热导率测量

提出应用3ω谐波探测技术进行脲醛树脂-石蜡相变微胶囊的等效热导率测量方法。测试了跨越相变温度区间的微胶囊等效热导率,分析了等效热导率随温度的变化关系。在其相变温度区间内,热导率存在极大值,该极值点对应的温度与其相变温度峰值一致。同样温度下,降温时的等效热导率略小于升温,这主要是由降温时相变材料的过冷引起。     

Raman imaging and photodegradation study of phthalocyanine containing microcapsules and coated particles

We present the results of using Raman molecular imaging and atomic force microscopy (AFM) investigation of the composition, stability, and photodegradation of polyelectrolyte multilayer microcapsules and coated microparticles containing copper–phthalocyanine and iron–phthalocyanine. The influence of laser light on degradation of these phthalocyanine dyes embedded in the walls of polyelectrolyte multilayer capsules and shells of microparticles was studied by both AFM and Raman molecular imaging, but only the latter technique gave information on dynamics of photodegradation. Raman peak assignment was performed according to theoretical calculations. The degradation rate of phthalocyanine dyes is estimated from Raman signal measurements and a model is proposed to account for the degradation rate. Practical applications of our approach are outlined. Copyright © 2011 John Wiley & Sons, Ltd.     

壳聚糖─海藻酸钠微囊对蛋白质控制释放的研究

采用乳化法制备了可注射用壳聚糖海藻酸钠微囊, 其粒径小于２００ μｍ ,且具有相对较窄的近似高斯分布。牛血清白蛋白作为模型药物在微囊中的包埋率可超过５０ ％ 。通过壳聚糖在海藻酸钠微囊表面的复合,牛血清白蛋白从微囊中的持续释放时间从几个小时延长到半个月以上。     

Encapsulation of a Single Metal Nanoparticle with Tunable Size in a Monodisperse Polymer Microcapsule

A versatile approach to fabricate monodisperse poly[styrene‐co‐(divinyl benzene)] (PS‐co‐DVB) microcapsules that contain a single gold nanoparticle (AuNP) has been demonstrated. Using the PS‐co‐DVB microcapsule as a microreactor, aqueous HAuCl₄ and NaBH₄ solutions are subsequently infiltrated. The size of the resulting AuNP inside of the PS‐co‐DVB microcapsules is easily tunable by controlling the repeated infiltration cycles of aqueous HAuCl₄ and NaBH₄. PS‐co‐DVB microcapsules that contain a single silver and palladium nanoparticle are also obtained by following a similar protocol.