Bacterial cellulose chemical modifications

There is a wealth of data, both in the scientific and patent literature, on the chemical modification of plant cellulose. All of these methods are equally applicable to bacterial cellulose given that the two types of cellulose are chemically identical. However, it is the physical structure of bacterial cellulose membranes that make them a potential material for PEM fuel cells. Therefore, the aim is to modify bacterial cellulose pellicules in a manner that retains the structure of the cellulose and does not... 

Native cellulose are commonly modified by physical, chemical, enzymic, or genetic means in order to obtain specific functional properties, and to improve some of the inherent properties that limit their utility in certain application. Physical/surface modification of cellulose are performed in order to clean the fiber surface, chemically modify the surface, stop the moisture absorption process, and increase the surface roughness. " Among the various pretreatment techniques, silylation, mercerization, peroxide, benzoylation, graft copolymerization, and bacterial cellulose treatment are the best methods for surface modification of natural fibers. 

Cellulose, like the polysaccharides above, has certain drawbacks. These include poor solubility in common solvents, poor crease resistance, poor dimensional stability, lack of thermoplasticity, high hydrophilicity, and lack of antimicrobial properties. To overcome such drawbacks, the controlled physical and/or chemical modification of the cellulose structure is essential [160]. Introduction of functional groups into cellulose can alleviate these problems while maintaining the desirable intrinsic properties of cellulose. Apart from the conventional plant source, cellulose is also obtained from bacteria, termed bacterial cellulose. 

Schlufter K., Schmauder H.-P., Dorn S., Heinze X., Efficient homogeneous chemical modification of bacterial cellulose in the ionic liquid l-V-butyl-3-methylimidazolium chloride, Macromol. Rapid Comm., 27, 2006, 1670-1676. 

Another purpose of adding chemicals to the culture medium is the chemical modification of the structural and physical properties of bacterial cellulose, allowing the preparation of composites directly during biosynthesis and broadening the applications of cellulose [18], as will be discussed latter. 

While there have been many ionic liquids reported to dissolve plant cellulose, the high molecular weight bacterial cellulose has only been successfully dissolved in a handful of reports. Schlufter et al [140] used l-N-butyl-3-methylimidazolium chloride to efficiently dissolve bacterial cellulose powder at 80 C at a concentration of 6% in order to complete chemical modifications of the cellulose. 

The hydrophilic nature of cellulose fibers often results in poor compatibiHty with hydrophobic polymer matrices. Therefore, it becomes necessary to modify the surface of natural fiber for better binding between fiber and matrix. Chemicals are commonly used for the modification of cellulosic materials but large amount of solvents are also usually involved. Surface modification of biofibers using bacterial cellulose (BC) is one of the best methods for greener surface treatment of biofibers. 

Figure 7.5 Hemp fiber after bacterial cellulose modification (Reprinted from [97], Copyright 2008, with permission from American Chemical Society.)...

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