Chitin bionanocomposites

Although chitin can be processed in the form of films, it has been largely used as reinforcement to bionanocomposites. Chitin nanowhiskers have been used to prepare a variety of bionanocomposites with matrices such as natural rubber, PLA, PCL, PVA, silk fibroin, and chitosan [185-194], as will be discussed throughout the text below. 

In another study Feng et al. [86] presented the stmcture and properties of new thermoforming bionanocomposites based on chitin whiskers-graft-polycaprolac-tone. The synthesized material was characterized by FTIR, SEM, TEM and XRD. The surface and mechanical properties were also determined and discussed. Ha-riraksapitak et al. [87] prepared a neat hyaluronan-gelatin scaffolds and chitin-whisker-reinforced hyaluronan-gelatin scaffolds. The obtained cylindrical scaffolds obtained were about 10 mm in diameter and 2 mm in height, whereas the disc-shaped scaffolds were about 1 mm in thickness these were later cut into a desired shape and size for the mechanical property assessment. 

Preparations of Si02-chitin/carbon nanotubes (CNTs) bionanocomposites have also been reported by many researchers [90]. The use of nanomaterials such as CNTs to fabricate matrices for biosensors is one of the most exciting approaches because nanomaterials have a unique structure and high surface to volume ratio [90]. The surfaces of nanomaterials can also be tailored in the molecular scale in order to achieve various desirable properties [91]. The diverse properties of nanocomposite materials such as unique structure and good chemical stability enable them to provide a wide range of applications in sensor technology [92]. 

Fig. 3.17 Reaction scheme for the preparation of Si02-chitin/CNTs bionanocomposites [90]...

Zia et al. [115] presented that nanostructure and morphological pattern of chitin/bentonite clay based polyurethane bionanocomposites. The clay dispersion within chitin was characterized by both XRD and optical microscopy (OM), which is the most frequently, used and approachable methods to study the structure of nanocomposites. There are one acetamide (-NHCOCH3) group at C-2 position and two (two hydroxy (-OH)) groups at C-3 (C3-OH) and C-6 (C6-OH) positions on chitin chains which can serve as the coordination and reaction sites [95], The crystalline structure of chitin has been reported by many researchers [96],... 

Feng, L., Zhou, Z., Dufresne, L., Huang, J., Wei, M., An, L.J. Structure and Properties of New Thermoforming Bionanocomposites Based on Chitin Whisker-Graft-Polycaprolactone. 

In recent years, there has been a quest to find alternatives for metallic composites in bone repair. Bionanocomposites that can mimic the structure of bone are of great importance. Biopolymer composites containing collagen, chitosan, and chitin have the desired mechanical and biological... 

This chapter focuses on the use of nanotechnology in the development of cellulose and chitin nanoctystals and their novel biomedical applications. It consists of four main sections. The first section is a brief introduction. The second section focuses on cellulose nanocrystals (CNCs) and their preparation procedure, physical properties, and surface modifications. Cationic modification of CNCs is also presented to produce positively charged CNCs. Various bioapplications of CNCs in bionanocomposites, drug delivery, and biosensors are discussed as well. The third section focuses on chitin nanoctystals (CHNCs). Except for a short introduction on chitin and its structure, the methods of isolation and characterization of chitin are discussed and the surface modifications and properties of CHNCs are summarized. The applications of CHNCs as reinforcing fillers in nanocomposites and several biomedical applications are discussed. The fourth section is a summary and perspective highlighting the future directions on the application of these natural nanoctystals in various key industries related to biomedicine. 

Saralegi A, Fernandes SCM, Alonso-Varona A, Palomares T, Foster EJ, Weder C, et al. Shape-memory bionanocomposites based on chitin nanocrystals and thermoplastic polyurethane with a highly crystalline soft segment. Biomacromolecules December 2013 14(12) 4475-82. 

In another study, chitin nanofibers were prepared by using deep eutectic solvents (DESs), including mixtures of choline halide (chloride/bromide)-urea and choline chloride-thiourea. The produced chitin nanofibers were utilized for manufacturing calcium alginate bionanocomposite gel beads to improve elasticity and retard drug release [21]. 

Feng Liangdong, Zhou Ziyan, Dufresne Alain, Huang Jin, Wei Ming, and An Lijia. Structure and properties of new thermoforming bionanocomposites based on chitin whisker-graft-polycaprolactone. J. Appl. Polym. Sci. 112 no. 5 (2009) 2830-2837. 

Chitosan has also been used as a matrix for bionanocomposites with a variety of nanoreinforcements such as chitin, days, and cellulose nanofibrils [189, 196-200]. 

Mathew et al. [196] developed cross-Hnked bionanocomposites using chitosan reinforced with chitin nanocrystals and gluteraldehyde as the cross-linker. These composites were characterized by FTIR, XRD, and atomic force microscopy (AFM). The authors found that cross-hnking and chitin whiskers content were both found to impact the water uptake mechanism. Cross-hnking provided dimensional stabihty in addic medium and significantly decreased the equihbrium water uptake. Moreover, incorporation of chitin nanocrystals provided increased permeation selectivity to chitosan in neutral and addic medium. 

PCL, is an important APES with many potential applications in biomedical and environmental fields [144]. This polymer was the first one to be studied in bionanocomposite when in the early 1990s, GianneUs group from Cornell University (Ithaca, NY, USA) started to work on the elaboration of PCL-based nanocomposites by intercalative polymerization [295]. Since then, a vast number of bionanocomposites have been prepared [87]. Several groups used intercalation, master batches, and in situ polymerization of PCL with clays to produce a variety of nanocomposites as can be seen in Table 11.2. Not only clays, but also various types of nanoreinforcements such as cellulose [296] and StNs [297, 298], chitin [299] nanowhiskers, carbon nanotubes [300, 301], and silica nanoparticles [302] have been used to prepare bionanocomposites with PCL. 

StNs and chitin nanowhiskers have also been reported to produce PCL bionanocomposites with improved properties [296,298, 315]. For example, Habibi and Dufresne [316] prepared cellulose and StNs obtained from the acid hydrolysis of ramie fibers and waxy maize starch granules, respectively, which were subjected to... 

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