Polymers Flashcards
Give an example of an addition polymer, how is it produced?
Polyethene, by repeated addition reactions of ethene monomers
Give an example of a condensation polymer, how are condensation polymers formed?
Nylon, by the linkage of two organic molecules through elimination of a small molecule (water, hydrogen chloride, methanol)
What must condensation polymers be in order to allow repeated condensation reactions?
They must be bifunctional, contain two function groups, one at the end of each molecule
Typical condensation reactions with carboxylic acids, acyl chlorides and methyl esters and alcohols give…
… an ester and water, hydrochloric acid and methanol respectively
How can condensation polymers be identified?
Because of monomers linked by ester bonds
What is a polyester?
A polymer produced by linking monomers together by ester linkages
How is terylene (PET) made? What can it be used for?
1) By repeated condensation reactions of the -COOH groups of 1,4-benzenedicarboxylic molecules and the -OH groups of ethane-1,2-diol molecules. High temperatures are required to drive the equilibrium towards the polymer
2) can be made into thin films for packaging. Can also be used for making windsurfer sails, flexible printed circuit boards and cable insulation m
What is a thermoplastic? What can they be used for?
1) A plastic that can be repeatedly heated to soften and melt it and cooled to solidify it
2) Can be extruded to form fine fibres for use in artificial fabrics, or be blow moulded into drinks bottles and other containers
Give an example of a polyamide
Nylon. Nylon-6,6 is a type of nylon, with the numbers referring to the number of carbon atoms in the dicarboxylic acid and the diamine monomers
How is a nylon-6,6 produced? Why aren’t the monomers just reacted together?
1) The dicarboxylic acid is usually converted into hexane-1,6-dioyl chloride by reaction with thionyl chloride (SOCl2). This diacyl chloride reacts with the diamine much faster because of the evolution of hydrogen chloride, the equilibrium shifts almost entirely towards the polymer product
2) The reaction between the amine group and carboxylic acid group to form an amide link is slow and the equilibrium established contains a significant amount of unreacted amine and acid
How is a polyamide produced?
The dicarboxylic acid is converted into a diacyl chloride which is then reacted with the diamine. This reaction is fast due to the production of hydrogen chloride which shifts the equilibrium almost entirely towards the polymer product
Why does the drawing out process of condensation polymers increase the strength of the fibre?
During the process linear molecules align and the fibres formed become increasingly linked with H bonds between chains. This increases the strength of the fibre
What is nylon used for? How can it be made to last longer?
1) Ropes, velcro, machinery parts and a wide range of clothing
2) By mixing it with wool and cotton (in clothing and carpets)
How can polyamides be produced by the condensation of amino acids? Give an example
1) Amino acids are bifunctional molecules that contain an amine and carboxylic acid group on the same molecule. Proteins are condensation polymers if naturally occurring amino acids
2) Heating the naturally occurring amino acid glycine generates the condensation polymer polyglycine
Why are polyesters and polyamides biodegradable?
They can be hydrolysed by reaction with either aqueous acids or bases into carboxylic acids and alcohols (esters) or amines (amides). Under the action of acid catalysts or bacterial enzymes the amides and ester links can be hydrolysed into smaller fragments
