What is a polymer?

Dr. Robert D. Craig, Ph.D

Chemistry for Nursing

“The Amide Link”

AMIDES MENU 

Background . . .• An introduction to amides including their physical properties.

Preparation of amides . . .• Their preparation from carboxylic acids, acyl chlorides and acid anhydrides.

The hydrolysis of amides . . .• The hydrolysis of amides using acids or alkalis (including the test for an amide).

Other reactions of amides . . .• The lack of base character in amides, the dehydration of amides to make nitriles, and

the Hofmann degradation of amides to make primary amines with one less carbon atom.

Polyamides . . .• A summary of the chemistry of simple polyamides like nylon and Kevlar, including

• their formation, structure, hydrolysis and uses.

What is a polymer?

• A polymer is a large molecule (macromolecule) composed of repeating structural units typically connected by covalent chemical bonds.

• While polymers in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties.

•

What is a polymer?

• Because of the extraordinary range of properties accessible in polymeric materials, they play an essential and ubiquitous role in everyday life, ranging from familiar synthetic plastics and elastomers to natural biopolymers such as DNA and proteins that are essential for life.

Plastics

• Polyethylene:

DNA

Examples of polymers

• A simple example is polyethylene, whose repeating unit is based on ethylene (IUPAC name ethene) monomer. Most commonly, as in this example, the continuously linked backbone of a polymer used for the preparation of plastics consists mainly of carbon atoms.

• .

Examples of polymers

• . The backbone of DNA is in fact based on a phosphodiester bond, and repeating units of polysaccharides (e.g. cellulose) are joined together by glycosidic bonds via oxygen atoms.

Examples of Polymers

• Styrofoam is a trademark of Dow Chemical Company for closed-cell extruded polystyrene foam currently made for thermal insulation and craft applications.

• In 1941, researchers in Dow's Chemical Physics Lab found a way to make foamed polystyrene

Styrofoam

• .

polystyrene

• The chemical makeup of polystyrene is a long chain hydrocarbon with every other carbon connected to a phenyl group (the name given to the aromatic ring benzene, when bonded to complex carbon substituents).

• Polystyrene's chemical formula is (C8H8)n; it contains the chemical elements carbon and hydrogen. Because it is an aromatic hydrocarbon,

Kevlar

Kevlar has many applications!• Kevlar has many applications, ranging from bicycle tires

and racing sails to body armor because of its high tensile strength-to-weight ratio—famously: "...5 times stronger than steel on an equal weight basis..."When used as a woven material, it is suitable for mooring lines and other underwater applications .

An artificial limb (prosthesis)

• An artificial limb is a type of prosthesis that replaces a missing extremity, such as arms or legs. Artificial limbs may be needed for a variety of reasons where a body part is either missing from the body or is too damaged to be repairedv

Who might be interested in artifical limbs? The Military

• .

What are polyamides?

Polyamides are polymers where the repeating units are held together by amide links.

An amide group has the formula - CONH2. An amide link has this structure:

Nylon

• In nylon, the repeating units contain chains of carbon atoms. (That is different from Kevlar, where the repeating units contain benzene rings .) There are various different types of nylon depending on the nature of those chains.

Nylon-6,6

• Nylon-6,6 is made from two monomers each of which contain 6 carbon atoms - hence its name.

• One of the monomers is a 6 carbon acid with a -COOH group at each end - hexanedioic acid.

Nylon-6,6

• The other monomer is a 6 carbon chain with an amino group, -NH2, at each end. This is 1,6-diaminohexane (also known as hexane-1,6-diamine).

condensation polymerisation.

• When these two compounds polymerise, the amine and acid groups combine, each time with the loss of a molecule of water. This is known as condensation polymerisation.

• Condensation polymerisation is the formation of a polymer involving the loss of a small molecule. In this case, the molecule is water, but in other cases different small molecules might be lost.

condensation polymerisation.

• The diagram shows the loss of water between two of the monomers

condensation polymerisation

condensation polymerisatio

• This keeps on happening, and so you get a chain which looks like this:

Kevlar

Kevlar is similar in structure to nylon-6,6 except that instead of the amide links joining chains of carbon atoms together, they join benzene rings.

• The two monomers are benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene

structure of Kevlar• If you line these up and remove water

between the -COOH and -NH2 groups in the same way as we did with nylon-6,6, you get the structure of Kevlar:

POLYAMIDES

Begin structures, formation, hydrolysis and uses of the polyamides, nylon and Kevlar.

 

What are polyamides?

Polyamides are polymers where the repeating units are held together by amide links.

An amide group has the formula - CONH2. An amide link has this structure:

What are polyamides?Polyamides are polymers where the repeating units are held together by amide links.An amide group has the formula - CONH2. An amide link has this structure:

National Institute of Standards and Technology (NIST)

• Over the past couple of decades, atomic force microscopy (AFM) has emerged as a powerful tool for imaging surfaces at astonishing resolutions—fractions of a nanometer in some cases. But suppose you're more concerned with what lies below the surface? Researchers at the National Institute of Standards and Technology (NIST) have shown that under the right circumstances, surface science instruments such as the AFM can deliver valuable data about sub-surface

conditions.

electric force microscopy can be used to detail structures well below the surface. Left, AFM height image showing the surface of a

polyimide/carbon nanotube composite. Right, EFM image revealing the curved lines of subsurface nanotubes.

Credit: NIST

Institute for soldier nanotechnolgy

• The Institute for Soldier Nanotechnologies (ISN) at MIT is an interdepartmental research center founded in 2002 by a $50 million, five-year contract with the U.S. Army Research Office. Now in its second five-year contract, the mission of the ISN is straightforward: develop and exploit nanotechnology to dramatically improve the survivability of Soldiers.

• The ultimate goal is to help the Army create a 21st century battlesuit that combines high-tech capabilities with light weight and comfort. Imagine a bullet-resistant jumpsuit, no thicker than ordinary spandex, that monitors health, eases injuries, communicates automatically, and reacts instantly to chemical and biological agents.  It’s a long-range

AT MIT . . . . . . .5 nanotechnology labs