Abstract
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.
Highlights
Hollow polymeric microcapsules have characteristics such as low density, high speci c surface area, surface permeability, and economical, which make them promising applications in chemistry, biotechnology, and materials science [1,2,3]. e preparation of polymeric microcapsules has o en involved self-assembly of amphiphilic block copolymers [4, 5], sacri cial core-template method [2, 6,7,8,9,10], and emulsion polymerization [11, 12]
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. e hollow feature of the obtained materials is revealed. e diameter of the microcapsules ranges from several μμm to over 100 μμm
Magnetic CS microcapsules have been prepared in this way when Fe3+ and Fe2+ were mixed with CS to prepare a mixture starting solution. e appearance and microstructure of the composite microcapsules were studied. e results indicate that the formed Fe3O4 nanoparticles are embedded in the CS matrix evenly due to strong interaction between the Fe3O4 nanoparticles and the CS molecules. e Fe3O4 content and the magnetic properties of the composite microcapsule were measured. e composite microcapsules were calcined in air at 700○C to prepare pure inorganic hollow microspheres
Summary
Hollow polymeric microcapsules have characteristics such as low density, high speci c surface area, surface permeability, and economical, which make them promising applications in chemistry, biotechnology, and materials science [1,2,3]. e preparation of polymeric microcapsules has o en involved self-assembly of amphiphilic block copolymers [4, 5], sacri cial core-template method [2, 6,7,8,9,10], and emulsion polymerization [11, 12]. Especially sacri cial template method, have been developed to prepare the chitosan hollow microspheres or microcapsules. Cross-linked N-methylated chitosan hollow microspheres have been prepared by using templates of cyclohexane droplets [18]. Li et al [19] prepared uniform-sized hollow chitosan microspheres by sacri cial template method. Stimuli-responsive multilayer chitosan hollow microspheres were fabricated by sacri cial template method combined with a sequential layer-by-layer electrostatic assembly technique [20]. The preparation of hollow chitosan microsphere by the sacri cial template method is tedious and the process of removal of templates may ruin the shells. E aqueous template avoids the removal of template as usual methods for preparation microcapsules, and the aqueous precipitant or nonsolvent would free from the necessity of cross-linking of the microcapsule to directly form dense shell. It is expected to develop a new method of fabrication of polymer microcapsules by using aqueous nonsolvent as template
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