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5 Clothing and Shelters: Polymeric Material
atom and, accordingly, a positive charge on the carbon atom. The bond C–Cl is thus
said to be polar, and the monochloro methane molecule as a whole is polar. These
partial electric charges on this molecule make their interaction stronger.
Diamond is the hardest solid; diamond is talked about in Chap. 15. To summarize
the reasons for it to be a solid, diamond is made of carbon atoms that are strongly
bound (by covalent bonding) and make up a three-dimensional structure. In other
words, in diamond the interparticle (atom) interaction is very strong. It has a very
high melting temperature and boiling temperature; 3,550 or so and 4,827°C,
respectively.
Let us talk about another type of compound. Glucose is made of 6 carbon atoms,
12 hydrogen atoms, and 6 oxygen atoms (C
6
H
12
O
6
) and is solid at room temperature.
This is a typical example of carbohydrate which means “hydrated carbon,” as the
chemical formula C
6
(H
2
O)
6
indicates. In terms of (molar) mass (which roughly rep-
resents the number of electrons), glucose is similar to a hydrocarbon of 12 carbon
atoms (dodocane = C
12
H
26
), which is liquid at room temperature. Well, this means
that the intermolecular interaction in glucose is much stronger than that in dode-
cane. It turns out that glucose has five OH groups in it. As we mentioned in the
chapter on water (Chap. 1), the OH groups interact with each other relatively
strongly through hydrogen bonds. Hence, glucose has a relatively high melting tem-
perature of 146°C for the size. What would happen if we make a compound that is
made by combining two glucose-like molecules? Such a compound is sugar
(sucrose), though one of the two C
6
carbohydrate units is not glucose. Its melting
temperature is yet higher, 186°C, understandably.
However, glucose and sugar are soluble in water unlike the hydrocarbons (oil)
mentioned above. Well, if the material is soluble in water, it would not be suitable
for clothes or shelter, would it? It turns out that if you combine a large number of
glucose in a certain linear fashion, you obtain “cellulose.” Cellulose can be regarded
as a polymer of glucose. Such a polymer made of glucose or similar compounds is
called in general “polysaccharide” (polymer of sugars). The plant cell walls are
made of cellulose and lignin. A special plant, cotton plant, produces cotton, i.e.,
cellulose in chemical terms. (By the way, glucose and similar compounds are the
initial products of “photosynthesis” conducted in green leaves. This is talked about
in another chapter).
Well, if glucose and sugar are soluble in water, would not “cotton” (cellulose) be
also soluble in water because its constituent, glucose, is soluble? It would be so,
because it has a lot of “OH” groups that can interact with water. The fact of the mat-
ter is that, however, cellulose (cotton) is not soluble in water. Why? We come to that
later. But the fact that cellulose would interact with water, i.e., it has an affinity
toward water, is suggested by the observation that paper towel, which is made of
cellulose, sucks up water.
Starch is another polymer of glucose, like cellulose. But you know that starch is
quite different from cellulose. Plant starch typically consists of two components:
water-soluble amylose and water-insoluble amylopectin. Amylose is a linear poly-
mer of glucose, but its connection is different from that in cellulose. The structure
of amylopectin is different from that of amylose. We discuss these issues later.