ABSTRACT
This chapter reviews the preparation of polysaccharide-based composite materials using ionic liquids. A first topic deals with the fabrication of cellulose-polymeric ionic liquid composite materials by in situ polymerization method. Imidazolium-type ionic liquids having polymerizable groups have been used on the basis of concept on their properties that show a good affinity with cellulose, which suitably lead to well-compatibilization. Followings are the typical procedures for yielding the desired composites. Cellulose was first dissolved in ionic liquid solvents, followed by adding polymerizable ionic liquids or simply swollen with polymerizable ionic liquids. The systems were then heated in the presence of a radical initiator for the progress of in situ polymerization to give cellulose-polymeric ionic liquid composite materials. Compatibility or miscibility between cellulose and polymeric ionic liquids in the composites were evaluated by proper analytical measurements such as powder X-ray diffraction, thermal gravimetric analysis, and scanning electron microscopy. The mechanical properties were evaluated by tensile testing. As a second topic, the preparation of chitin nanofiber-synthetic polymer composite materials through the gelation of chitin with an ionic liquid was described. The author found that an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), dissolved chitin in concentrations up to ~4.8 wt% and mixtures of the higher amounts of chitin with AMIMBr gave ion gels. The chitin nanofibers were formed in the dispersion, which was produced by regeneration technique from the ion gel using methanol, followed by sonication. Moreover, filtration of the chitin nanofiber dispersion was carried out to give a chitin nanofiber film. The chitin nanofiber-synthetic polymer composite films were prepared by co-regeneration method and surface-initiated graft polymerization approach. By the former method, chitin nanofiber-poly (vinyl alcohol) composite film was obtained and the latter approach gave chitin nanofiber-poly(l-lactide-co-ɛ-caprolactone) composite film. The resulting composites can be expected as new bio-based functional materials to be used in different practical applications.
