Polymers

Definitions

• Polymer: a long chain molecule made up of many small identical units.

• Monomer: the smallest repeating unit of a polymer (propene in polypropylene).

.

IUPAC Definition • A polymer is a substance composed of

molecules characterized by the multiple repetition of one or more species of atoms or groups of atoms (constitutional repeating units) linked to each other in amounts sufficient to provide a set of properties that do not vary markedly with the addition of one or a few of the constitutional repeating units.”

Common Polymers

• Polymers are common in nature. Wood, rubber, cotton, silk, proteins, enzymes, and cellulose are all examples of polymers

• A wide variety of synthetic polymers have been produced, largely from petroleum based raw materials. These include polyurethane, teflon, polyethylene, polystyrene, and nylon.

Polymer Recycling CodesCommon household polymers

Polymers• The number code indicates the polymer type

Polymers

• Types of synthetic and natural polymers.

Polymer Structure• Molecular Mass:

– Polymers are high molecular mass structures– Extremely large molecular weights are to be found in

polymers with very long chains.

• Molecular Shape: – Polymer chain molecules are usually straight chains – These chains may bend, coil and kink, leading to

extensive intertwining and entanglement of neighboring chain molecules.

– These random coils and molecular entanglements are responsible for many of the important characteristics of polymers.

The Polymer Structure Determines its Characteristics

The physical properties of a polymer, such as its strength and flexibility depend on:

Chain length - In general, the longer the chains the stronger the polymer;

Side groups - Polar side groups give stronger attraction between polymer chains, making the polymer stronger;

Branching - Straight, unbranched chains can pack together more closely than highly branched chains. These polymers are more crystalline and therefore stronger;

Cross-linking - If polymer chains are linked together extensively by covalent bonds, the polymer is harder and more difficult to melt.

•