Preparation of chitin-based fluorescent hollow particles by Pickering emulsion polymerization using functional chitin nanofibers.

This study investigated the preparation of chitin-based fluorescent hollow particles by Pickering emulsion polymerization of styrene using bifunctional chitin nanofibers (ChNFs) as stabilizer, giving CNF-based composite particles, followed by solubilizing out inner polystyrene. In addition to the introduction of anionic maleyl groups on ChNFs to improve dispersibility in aqueous ammonia, polymerizable methacryl groups were substituted on ChNFs as second functionalization to provide ability in copolymerization with styrene for stabilization of hollow structures. Consequently, after the formation of styrene-in-water Pickering emulsion using the bifunctional ChNFs as stabilizer, radical polymerization was conducted in the presence of potassium persulfate as an initiator to produce the composite particles. The hollow particles were then fabricated by solubilizing out inner polystyrene with toluene, which stably dispersed in water. Encapsulation of a fluorescent dye, pyrene, into the cavity of the hollow particles was achieved by hydrophobic interaction with polystyrene present on the inner walls, which could be released by treatment of the resulting fluorescent hollow particles with surfactant, oleyl alcohol, in water. The same Pickering emulsion polymerization system was also performed in the presence of a pyrene derivative having a polymerizable group to obtain fluorescent composite/hollow particles with pyrene moieties covalently bound to polystyrene.

Preparation of composite and hollow particles from self-assembled chitin nanofibers by Pickering emulsion polymerization.

This study investigated Pickering emulsion polymerization of styrene using self-assembled chitin nanofibers (CNFs) as stabilizers to produce CNF-based composite particles, which were further converted into hollow particles. Previously, we reported that regeneration from a chitin/1­allyl­3­methylimidazolium bromide ion gel using methanol fabricated self-assembled CNFs. Prior to the emulsion polymerization, CNFs were maleylated by reaction with maleic anhydride in the presence of perchloric acid. After styrene was added to a dispersion of the produced anionic CNFs in ammonia aq., a mixture was ultorasonicated to give an emulsion, in which styrene droplets were stably surrounded by CNFs. Radical polymerization was then conducted in the presence of potassium persulfate as an initiator to produce the composite particles. Particle sizes became smaller as the amounts of CNFs increased. The hollow particles were prepared by solubilizing out the polystyrene cores with toluene.