Question

Identify and write the difference between the monomer and the polymer present in cellulose
and in our hair.

Answer 1

A polymer is a chemical composed of many repeat units. These repeat units can be composed of one monomer, two or more monomers or blocks of smaller polymers. While there is a blurry line between the molecular weight different of polymers and oligimers, polymers are normally defined as molecules that have a molecular weight over 5,000 g/mol. While this simple term is easily understood, the number of different types of monomers and chemistries used to connect the monomers is truly staggering.

A monomer is the small reactive molecule, which are chemically bonded to other monomers to form a polymer. The reactive group can be one that reacts when exposed to radical generating materials (chain growth polymeri­zation), or one that reacts when two different type of reactants are added in the proper ratio with the proper catalyst and temperature (condensation polymeri­zation). Polymers are high molecular weight species that are made up of many repeat units. One major difference between polymers and small molecules (monomers) are the characte­ristics that polymers exhibit. Polymers normally have higher viscosities, higher boiling points and can show improved mechanical strength over small molecules (monomers).

Answer 2

Answer:

Cellulose is one of many polymers found in nature. Wood, paper, and cotton all contain cellulose. Cellulose is an excellent fiber. Wood, cotton, and hemp rope are all made of fibrous cellulose. Cellulose is made of repeat units of the monomer glucose. This is the same glucose which your body metabolizes in order to live, but you can't digest it in the form of cellulose. Because cellulose is built out of a sugar monomer, it is called a polysaccharide.

Now take a look at glucose in 3-D! Or click on the model on the right above.

Cellulose has an important place in the story of polymers because it was used to make some of the first synthetic polymers, like cellulose nitrate, cellulose acetate, and rayon. Click here to find out more.

Clean hair

Another cellulose derivative is hydroxyethylcellulose. It differs from plain ol' regular cellulose in that some or all of the hydroxyl groups (shown in red) of the glucose repeat unit have been replaced with hydroxyethyl ether groups (shown in blue).

These hydroxyethyl groups get in the way when the polymer tries to crystallize. Because it can't crystallize, hydroxyethylcellulose is soluble in water. In addition to being a great laxative, it's used to thicken shampoos as well. It also make the soap in the shampoo less foamy, and it helps the shampoo clean better by forming colloids around dirt particles.

Normally, particles of dirt are insoluble in water. But a chain of hydroxyethylcellulose (shown in blue) can wrap itself around a dirt particle (shown in red). This mass can be thought of as a snack cake, with the polymer chain as the cake and the dirt as the creamy filling. This snack cake is soluble in water, so by wrapping around the dirt like this, the hydroxyethylcellulose tricks the water into accepting the dirt. In this way, the dirt gets washed away instead of being deposited back onto your hair.

Visit another polysaccharide

A polysaccharide that's very similar to cellulose is starch. To find out just how starch and cellulose are different, click here.

Other polymers that are used as fibers include:

Polyethylene

Polypropylene

Nylon

Polyester

Kevlar® and Nomex®

Polyacrylonitrile

Polyurethanes