Preparation of poly(β-hydroxybutyrate) and poly(lactide) hollow spheres with controlled wall thickness

Microfluidic Fabrication of Structure-Controlled Chitosan Microcapsules via Interfacial Cross-Linking of Droplet Templates

In this work, a simple and flexible method for the fabrication of chitosan microcapsules with controllable structures and functions via the interfacial cross-linking reaction of the water-in-oil (W/O) emulsion templates is developed. The interfacial cross-linking reactions of chitosan and terephthalaldehyde (TPA) in W/O emulsion templates are comprehensively studied. The interfacial cross-linking reactions of the droplet templates in both batchwise and continuous conditions are studied. A poly(dimethylsiloxane) (PDMS) droplet-capture microfluidic chip is fabricated to investigate the interfacial reaction in continuous conditions online. In this study, the size and shell thickness of the microcapsules are affected by the preparation condition, such as the template size, emulsifier concentration, TPA concentration, and cross-linking time. Moreover, the size and shell thickness changes of chitosan microcapsules prepared in continuous conditions are much faster than those prepared in batchwise conditions. By regulating the preparation parameters, the microcapsules with controllable structures are fabricated in both batchwise and continuous conditions. The drug release behaviors of the microcapsules with controllable structures are studied. Furthermore, by adding magnetic nanoparticles to the aqueous solution, magnetic-responsive microcapsules are fabricated easily. This work provides valuable guidance for the controllable fabrication of chitosan microcapsules with designed structures and functions via single emulsion templates.

Preparation of polydopamine nanocapsules in a miscible tetrahydrofuran–buffer mixture

A non-emulsion soft template method based on a miscible tetrahydrofuran–tris buffer mixture has been used to fabricate polydopamine nanocapsules.

Preparation and Characterization of Magnetic Chitosan Microcapsules

By dispersing aqueous precipitant in liquid paraffin to prepare a W/O emulsion then adding chitosan (CS) solution, CS microcapsules have been successfully prepared. It is a facile way to prepare polymer microcapsules by using aqueous precipitant or nonsolvent as template, which avoids the removal of template and would free from the necessity to cross-link the microcapsule as usual methods to directly form dense shell. The hollow feature of the obtained materials is revealed. The diameter of the microcapsules ranges from severalμm to over 100 μm. Magnetic CS microcapsules have been prepared in this way when Fe3+and Fe2+were mixed with CS to prepare a mixture starting solution. The appearance and microstructure of the composite microcapsules were studied. The results indicate that the formed Fe3O4nanoparticles are embedded in the CS matrix evenly due to strong interaction between the Fe3O4nanoparticles and the CS molecules. The Fe3O4content and the magnetic properties of the composite microcapsule were measured. The composite microcapsules were calcined in air at 700°C to prepare pure inorganic hollow microspheres. It is general to prepare hollow polymeric or composite particles by using this method.

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.

Polymerization Behavior and Polymer Properties of Eosin-Mediated Surface Modification Reactions

Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eight fold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from 5-fold lower eosin surface densities (2.8 vs. 14 eosins/µm(2)) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities.