Analía Bellizzi – Chemistry Classes

Ronald Reagan Senior High School

Polymers

Define polymers as…
● Large molecules built up from small units (monomers)
Understand that different polymers have different units and/or different
linkages
● Each polymer is made from a certain monomer or monomers, therefore
different polymers have different units and/or different linkages (depending on
how the monomer(s) join up to form the polymer)
● monomers can be different lengths or can have different groups attached
● can have a C-C linkage, ester linkage or amide linkage

Polymerisation 

Polymer   

A large molecule produced when small molecules join together. These small molecules are called monomers.

There are two types of polymers: natural and synthetic

  • Natural Polymers:

The ones we find in nature: cellulose, starch, proteins nails, hair, bones, muscles, etc.

  • Synthetic Polymers:

The ones that are man-made. Nylon, polystyrene (Styrofoam), polyesters, polyamides, PVC etc.

It is the process of producing a polymer. There are two types of polymerisation

  • Addition Polymerisation:

All the atoms in the monomer are used to form the polymer

  Example:

  Many molecules of Ethene       ==>                            Polyethene 

  • Condensation Polymerisation:

  All monomers join up forming a small molecules that are released in the process. Most of the time the molecule is water or a hydrogen halide. (Hydrogen chloride for example)

Many molecules of            Aminoacid          ===>      protein + water

Addition Polymers

Facts:  

  • during polymerisation, an alkene undergoes an addition reaction with itself.
  • All the atoms in the original alkenes are used to form the polymer
  • Long hydrocarbon chains are formed

The equation shows the original monomer and the repeating unit in the polymer

Condensation Polymers

Before speaking about condensation polymerization, you should recognize the main functional organic groups used in polymerization

These functional groups can be in both sides of the molecule or combined, as follows: 

Note: the green boxes between the functional groups are generic branches. We do not concentrate in this. We only look at the reaction within the functional groups and how the polymerization takes place.

In the condensation Polimerisation, different monomers get together and one of the following molecules will be produced (H2O or HCl)

  We will study only 4 types of condensation polymers:

  • Proteins or polypeptides
  • Starch or Polysaccharides
  • Terylene or Polyesters
  • Nylon or Polyamides 

The monomers for the condensation polymers we will study are as follows:

Proteins

  • When 2 aminoacids combine, they form a dipeptide.
  • If three aminoacids combine, we have a tripeptide.
  • With more than 30 aminoacids, we have a special polypeptides. We call them proteins.
  • chains can be lined up with each other
  • the C=O and N-H bonds are polar due to a difference in electronegativity
  • hydrogen bonding exists between chains. Many are soluble in water.

water is formed between the OH of the acid and the H of the amino group. (that is why we call them condensation polymers)