Cellulose review

Supplementary to the technical use of nano celluloses reviewed in the previous sections, BC in particular has great potential as a natural biomaterial for the development of medical devices and applications in healthcare and veterinary medicine. 

Other than scattered information on the products formed from the pyrolysis of cellulose (reviewed in the previous Sections) and some isolated experiments, there is very little definitive information on the nature, sequence, and mechanism of the secondary reactions. Therefore, it should be understood that any excursion into this area is, at this time, largely based on possibilities rather than established facts. The discussion thus far presented indicates that secondary reactions. 

A review covers the preparation and properties of both MABS and MBS polymers (75). Literature is available on the grafting of methacrylates onto a wide variety of other substrates (76,77). Typical examples include the grafting of methyl methacrylate onto mbbers by a variety of methods chemical (78,79), photochemical (80), radiation (80,81), and mastication (82). Methyl methacrylate has been grafted onto such substrates as cellulose (83), poly(vinyl alcohol) (84), polyester fibers (85), polyethylene (86), poly(styrene) (87), poly(vinyl chloride) (88), and other alkyl methacrylates (89). 

Because of the importance of cellulose and the difficulty in unraveling its secrets, several societies (CeUucon, American Chemical Society, and TAPPI) are dedicated to cellulose, lignin, and related molecules, as is at least one journal that is abstracted by Chemicaly hstracts (3). The length of the proceedings of the Tenth Cellulose Conference (1638 pages) (4) indicates the vitaUty and interest in this subject, but research results are pubUshed in many other journals as well. There are also several recent books on cellulose (5—9). Reference 10 is a comprehensive review and is recommended especially for the historical review of proof of chemical stmcture, one of the milestones in organic chemistry. 

Many cellulose derivatives form Hquid crystalline phases, both in solution (lyotropic mesophases) and in the melt (thermotropic mesophases). The first report (96) showed that aqueous solutions of 30% hydroxypropylceUulose [9004-64-2] (HPC) form lyotropic mesophases that display iridescent colors characteristic of the chiral nematic (cholesteric) state. The field has grown rapidly and has been reviewed from different perspectives (97—101). 

Water RepeUency. The development of water-repellent cellulose ethers has been reviewed (55) (see Waterproofing). A typical example of a commercial etherification for waterproofing cotton is with stearamidomethylpyridinium chloride ... 

The phosphonic acid reactive dyes were appHed to cellulose under slightly acid pH rather than alkaline pH required for other ceUulosic reactive dyes. This feature made them especially attractive for one bath appHcation with disperse dyes to cotton/polyester blends. A review of these dyes appears ia Refereace 5. 

When ethanol is replaced by cellulose, sodium cellulose xanthate is obtained this dissolves in aqueous alkali to give a viscous solution (viscose) from which either viscose rayon or cellophane can be obtained by adding acid to regenerate the (reconstituted) cellulose. Trithiocarbonates (CS3 "), dithiocarbonates (COS2 "), xanthates (CS2OR ), difhiocarbamates (CS2NR2 ) and 1,2-dithiolates have an extensive coordination chemistry which has been reviewed. ... 

Since the changes in physical properties are often the impetus for grafting, it is necessary to briefly touch on this, in this section. A number of general reviews on grafting have also included some discussion on the changes in physical properties [126-129] that usually determine the field of applications. Some other reviews deal with certain properties and applications, such as sorbency [70] and ion exchange properties [130] of cellulose. 

Reactions of this type are quite popular and widely used to introduce hydrophilic and ionogenic groups into linear polymers as well as directly into polymer networks. These reactions include hydrolysis (PAAm, PAAc and their analogs from PAN, PVA from poly (vinyl acetate), oxyethylation and oxymethylation of starch and cellulose, sulfurization, and other reactions. These processes are of industrial importance, well studied and widely reviewed. 

Indeed it can be stated that the history of modern expls begins with the discoveries of nitroglycerin (NG) and nitrocellulose (or more correctly cellulose nitrate or NC) nearly 125 years ago, and their application to military and commercial usage. An excellent review of the early history of NC is given by. T.L. Davis (Ref 29, pp 244—56). The early histories of NG and EGDN (discovered in 1870) are summarized, respectively, in Vol 6, G99-R to G100-R and E259-R, and in the Naoum reference cited above... 

The CP/MAS NMR spectra are an important source of information regarding the structure of cellulose and its polymorphos. A number of groups have investigated these spectra 11 15) and also reviews on the subject have been published 16 17>. For an orientation in the field Table 1 shows the most important features of the solid-state NMR spectra of cellulose I, II and IV and in Fig. 3 the numeration of the carbon atoms of the cellulose basic unit is given. It is evident that the polymorphs... 

Five articles on polysaccharide helices solved prior to 1979 have appeared in the volumes published between 1967 and 1982.2-6 The first was a review on X-ray fiber diffraction and its application to cellulose, chitin, amylose, and related structures, and the rest were bibliographic accounts. Since then, X-ray structures of several new polysaccharides composed of simple to complex repeating units have been successfully determined, thanks to technological advances in fiber-diffraction techniques, the availability of fast and powerful computers, and the development of sophisticated software. Also, some old models have been either re-... 

Due to the lack of a commercial supply, as well as their usually low molecular weight and poor solubility, xylans have found little industrial utility and interest in their modification has been rather low in comparison to commercially available polysaccharides such as cellulose or starch. With the aim of improving the functional properties of xylans and/or imparting new functionalities to them, various chemical modifications have been investigated during the past decade. Most of them were presented in recent reviews [3,399]. 

Several review articles are available on the synthesis, physico-chemical properties, and bio degradability of natural-based polymers, and their composites [6-9]. The same aspects have been the subjects of recent books [10-12]. In the following account, we concentrate on organic esters of cellulose. 

The main focus of this account is to review some aspects of the chemistry of cellulose esters. Emphasis is placed on the esterification reaction, carried out under the homogenous reaction conditions (HRC) scheme. Unconventional methods for the synthesis of cellulose derivatives, e.g., esters and ethers... 

The discussion is organized in the following order First the advantages of HRC scheme, relative to the industrial (i.e., heterogenous) process are briefly commented on second, the relevance of celMose activation and the physical state of its solution to optimization of esterification are discussed. Finally, the use of recently introduced solvent systems and synthetic schemes, designed in order to obtain new, potentially useful cellulose esters with controlled, reproducible properties is reviewed. A comment on the conformity of these methods with the concepts of green chemistry is also included. 

Ramesh, R., Bhattacharya, S.K. and Gopalan, K. 1986 Stable isotope systematics in tree cellulose as palaeoenvironmental indicators—a review. Journal of the Geological Society of India 27 154-167. 

Silicone rubber Warrick et al. [29] reviewed the reinforcement of sUicone elastomers with various types of discontinuous fibers, some of which were generated in situ by graft polymerization. Polyester, cellulose and carbon fibers were also used to reinforce sUicone mbber [30,31]. 

The exceptional ability of PCL to form blends with many other polymers has stimulated a large amount of research. The subject has been reviewed a number of times (7,8). To date, the potential of such blends for drug delivery has been largely unexploited. The permeability of blends of PCL with cellulose propionate, cellulose... 

Brown, W Stilbs, P Lindstrom, T, Self-Diffusion of Small Molecules in Cellulose Gels using FT-Pulsed Field Gradient NMR, Journal of Applied Polymer Science 29, 823,1984. Brownstein, KR Tarr, CE, Importance of Classical Diffusion in NMR Studies of Water in Biological Cells, Physical Review A 19, 2446, 1979. 

C. Oligo- and Poly-nucleotides.—The stepwise enzymatic synthesis of internucleotide bonds has been reviewed. A number of polynucleotides containing modified bases have been synthesised " in the past year from nucleoside triphosphates with the aid of a polymerase enzyme, and the enzymatic synthesis of oligodeoxyribonucleotides using terminal deoxynucleotidyl transferase has been studied. Primer-independent polynucleotide phosphorylase from Micrococcus luteus has been attached to cellulose after the latter has been activated with cyanogen bromide. The preparation of insolubilized enzyme has enabled large quantities of synthetic polynucleotides to be made. The soluble enzyme has been used to prepare various modified polycytidylic acids. ... 

The use of n-butylamino-derivatives of cyclophosphazenes in flame-proofing cellulose-based fabrics has been described in a patent application. The topic of fiame retardants is also covered in a recent review, where phosphazenes are important because of their relatively high phosphorus and nitrogen contents. 

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