Addition and Condensation Polymers | Chemistry for Grade 11 (IGCSE) PDF Download

Addition Polymers

• Addition polymers result from the bonding together of numerous monomers and are exclusive to monomers featuring C=C bonds.
• Within each C=C bond, one of the bonds is broken, forming a connection with the adjacent monomer, leading to the formation of a polymer characterized by single bonds exclusively.
• Many polymers can be synthesized through the addition of alkene monomers, while others originate from alkene monomers featuring diverse atoms attached, like chlorine or a hydroxyl group.
• To name the polymer, the monomer's name is enclosed in brackets, with "poly-" prefixed to it. For instance, using propene as the alkene monomer results in the polymer being named poly(propene).
• Poly(ethene) is created through the addition polymerization of ethene monomers.

Deducing the Polymer from the Monomer

• Polymer molecules are significantly larger compared to most other molecules.
• Repeat units are utilized when representing the formula of a polymer.
• To depict a repeat unit, convert the double bond in the monomer to a single bond in the repeat unit.
• Include a bond at each end of the repeat unit, with the bonds extending outside the brackets (known as extension or continuation bonds).
• Use a small subscript 'n' at the bottom right to indicate a large number of repeat units.
• Add the remaining groups in the same sequence as they encircled the double bond in the monomer.

Deducing the Monomer from the Polymer

• Identify the repeating unit in the polymer.
• Convert the single bond in the repeat unit to a double bond in the monomer.
• Eliminate the bond from each end of the repeat unit.

Condensation Polymers

• Condensation polymers are created by linking two distinct monomers together with the elimination of a small molecule, typically water.
• This process contrasts with addition polymers, where polymer molecules form exclusively.
• During condensation polymerization, one water molecule is produced for each polymer linkage.
• Monomers involved in condensation polymers possess two functional groups each, located at opposite ends.
• These functional groups react with one another, forming extended chains of alternating monomers that constitute the polymer.
• Reversing the reaction by hydrolysis (adding water) under acidic conditions breaks the peptide link, yielding the original monomers.

Forming Nylon

• Nylon, a polyamide, is synthesized from dicarboxylic acid monomers, which contain a carboxylic group (-COOH) at both ends, and diamines, which feature an amino group (-NH₂) at each end.
• The -COOH groups of one monomer react with the -NH₂ groups of another monomer.
• This reaction results in the formation of an amide linkage, accompanied by the removal of a water molecule for each bond.
  
• The arrangement of nylon can be illustrated by depicting the polymer with rectangular shapes to symbolize the carbon chains.
  

Forming Polyesters

• PET, or polyethylene terephthalate, is a type of polyester.
• It is derived from dicarboxylic acid monomers and diols.
• Each -COOH group in the monomers reacts with an -OH group from another monomer.
• This reaction forms an ester linkage and releases a water molecule.
• Condensation polymerization, responsible for PET formation, produces one water molecule for each ester linkage.
• PET is commonly used in synthetic fibers and is marketed under the brand name terylene.
  
• The structure of PET, along with other polyesters, can be depicted by illustrating the polymer using boxes to symbolize the carbon chains.
• This method can be applied universally to represent the structures of various polyesters.