Cellulose, Chemical Uses Of
Cellulose is the major component of the cell walls in plants strengthens the roots, leaves, and stems, making them rigid. It is a polysaccharide, a long molecule composed of oxygen, hydrogen, and sugar, which is very similar to sugars and starches. The hydroxide groups in cellulose are isotactic--that is, they are placed on alternating sides of the main chain. These pendant groups bind with others on long cellulose molecules to form microfibrils.
Henri Braconnet (1780-1855), a French chemist, verified the existence of cellulose in 1819. Braconnet was a leading scientist in the field of animal and plant chemistry; he was apprenticed to an apothecary in 1793 and became a pharmacist in 1795 in Strasbourg, Germany. He discovered cellulose in mushrooms and called it fungine, then began experimenting on the effects of sulfuric acid on wood. Braconnet eventually succeeded in creating a nitrated cellulose, which he called xyloidine, by adding wood or potato starch to nitric acid.
The next major development for cellulose came in 1834 when Anselme Payen, a French chemist, isolated cellu from wood. Four years later, Théophile Jules Pelouze (1807-1867), another French chemist, also developed nitrocellulose. This discovery was just one achievement in a long and significant career in chemistry which began when Pelouze encountered Joseph-Louis Gay-Lussac (1775-1850) on an omnibus. He impressed Gay-Lussac enough that the famous scientist made Pelouze his laboratory assistant. Pelouze became a professor at Lille in 1830 and then moved on to teach at France's major scientific academy, the École Polytechnique. He conducted many successful experiments in collaboration with Gay-Lussac as well as on his own and eventually established a private laboratory school for chemistry in Paris; there he trained students and allowed foreign chemists to conduct private research.
In 1845 the German chemist Christian Schönbein developed guncotton by accident. He was experimenting with nitric and sulfuric acids in his kitchen and spilled them. After he used his wife's cotton apron to clean up the mess and hung it up to dry over the oven, it burst into flames. Schönbein realized that the nitric acids had bonded with the cotton fibers to form nitrocellulose, which he marketed as guncotton. Guncotton flourished briefly as a smokeless gunpowder, but it was highly unstable. Schönbein eventually developed a gel he called collodion, made from guncotton mixed with ether, which helped render the substance much more stable than was guncotton alone. Alexander Parkes developed the first plastic, made from cellulose, in 1855. He dissolved pyroxylin (a nitrated cellulose) in alcohol and camphor containing ether to produce a moldable solid. Parkes was not successful in marketing his invention. Fifteen years later John Wesley Hyatt, in an attempt to win a contest held to discover a substitute for ivory, improved on Parkes's technique and developed celluloid. Hyatt did not win the prize but was successful in marketing celluloid as a material for rattles, collars, photographic film, and dental plates. It was, however, highly flammable, which limited its utility in range of ways. During the same year the rayon industry began. The term rayon refers to any fiber developed from cellulose. George Audemars, a Swiss chemist, was granted the first patent for synthetic fibers in 1855. Sir Joseph Swan, an English chemist, produced fibers from nitrocellulose in 1880.
Hilaire Chardonnet was the man who accelerated the production of nitrocellulose fibers. He developed a process in which the highly flammable nitrocellulose could be denitrated using an acid sulfide solutions. Previous attempts to denitrate fibers had left them weak and unable to compete with the strength of natural fibers. Chardonnet's technique left the cellulose xanthate fibers with strength comparable to silk. In fact rayon, as the fibers were called, was sometimes called artificial silk. Another production techniques for rayon was introduced by Hermann Pauly in 1897. The process yields rayon known as Pauly silk, Bemberg rayon, or cuprammonium rayon. The process yields a finer thread but is not widely used.
The most common process for the production of viscose rayon was developed by Charles F. Cross and Edward J. Bevan, both of England, in 1894. They also received a patent for the production of cellulose acetate. The cellulose for acetate rayon comes from cotton, rather than wood pulp as in viscose rayon.
It is interesting that with all of the uses developed for cellulose, the method of cellulose production in plants was not discovered until the late 1930s. Wanda Farr, an accomplish biologist and microscopist, made the discovery. She established that in each cell of every cellulose-containing plant there are plastids in the protoplasm that produce cellulose. Even then, scientists did not understand the exact mechanism of cellulose production. Then, in 1997 researchers finally discovered a gene in the plant Arabidopsis that is responsible for the synthesis of cellulose. Although there is much yet to be learned about polysaccharide synthesis in plants, this breakthrough discovery is anticipated to lead to in an understanding of how plants generate their cell walls.
Cellulose is widely used today in photographic film, fibers, tapes and many other products. The largest applications for cellulose polymers are in the production of inks and paint systems. One increasingly important use of cellulose is in low fat non-dairy foods that closely resemble real dairy products. For example, cellulose derivatives are being used in low fat frozen desserts, processed cheese and sour cream. NutraSweet Kelco Co of San Diego, CA, is one unveiled developers of cellulose food products.
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