Polymers Flashcards
What type of polymer is nylon?
A condensation polymer
What type of polymer is nylon?
A condensation polymer
How are condensation polymers formed?
A condensation reaction links two organic molecules together with the elimination of a small molecule
Why must the monomers used for condensation polymers be bifunctional?
In order to allow repeated condensation reactions and build up a polymeric structure
What does it mean if something is a bifunctional monomer?
This means they must contain two functional groups, one at each end of the molecule.
For most synthetic polymers what does condensation occur between?
Two different monomers. One containing two carboxylic acid functional groups and the other containing two alcohol groups to make a polyester or two amine groups to make a polyamide
What do typical condensation reactions involve?
The reaction of carboxylic acids, acyl chlorides and methyl esters with alcohols to give an ester and water, hydrochloric acid and methanol
What does replacing the alcohol with an amine generate?
Amides from carboxylic acids or acyl chlorides via a condensation reaction
How are all natural condensation polymers formed?
By the elimination of water
How can condensation polymers be identified?
Because the monomers are linked by ester or amide bonds
What is the repeating unit in addition polymers?
The section of the polymer chain that is added sequentially every time a further monomer adds. It is the smallest section of the monomer that can be identified in the repeat pattern
How are polymers often written?
With the repeat unit surrounded by square brackets
What is a polyester?
A polymer produced by linking together monomers via ester linkages
What is terylene?
A polyester made by linking 1,4 -benzenedicarboxylic acid and the alcohol ethane-1,2-diol.
What is another name for terylene?
Poly(ethylene)terephthalate (PET)
How is Terylene made?
Repeated condensation reactions occur between the -COOH groups of the acid molecules and the -OH groups of the alcohol molecules. A high temperature is required to drive the equilibrium towards the polymer
Terylene is thermoplastic. What does this mean?
It can be repeatedly heated to soften and melt it and cooled to solidify it.
What can thermoplastic polymers be used for?
- it can be extruded into fine fibres for use in artificial fabrics
- it can be blow moulded into fizzy drinks bottles and other containers
- it can be used to produce thin films of PET which are used extensively for packaging
- it can be used yo make windsurfer sails, flexible printed circuit boards and cable insulation
What is the best known artificial polyamide?
Nylon
Why is Nylon -6,6 called this?
Because the two monomers it is made from (diamine and a dicarboxylic acid) contain six carbon atoms: hexane-1,6-diamine and 1,6-hexandioic acid
Why is the dicarboxylic acid usually coverted to hexane-1,6-dioyl chloride when making 6,6 nylon?
Because the reaction between an amine group and a carboxylic acid group to form an amide link is slow and the equilibrium established contains a significant proportion of unreacted amine and acid. The diacyl chloride reacts with the diamine much faster and because HCl is produced the equilibrium shifts almost entirely towards the polymer product
What does a dicarboxylic acid react with to be converted to hexane-1,6-dioyl chloride?
Thionyl chloride SOCl2
Condensation polymers such as nylon -6,6 are long chain molecules which can be drawn out at room temperature to form fibres. What happens during this process?
The linear molecules allign and become increasingly linked by hydrogen bonds between adjacent chains. This causes the strength of the fibre to increase
What is nylon used for?
- It is a substitute for silk
- used to make rope, twines, velcro, machinery parts and a wide range of clothing
- in clothing and carpets natural fibres such as cotton or wool are often mixed with nylon to make them last longer
Apart from being prepared by the condensation reaction between a carboxylic acid and amine how else can polyamides be prepared and why?
By the condensation of amino acids. This is because amino acids are bifunctional compounds that contain both an amine and a carboxylic acid in the same molecule
Why will condensation polymers biodegrade when placed in landfill sites?
Simple esters and amides can be hydrolyses by reaction with either aqueous acids or bases into carboxylic acids and alcohols or amines. Condensation polymers are linked by ester or amide linkages and so can undergo hydrolysis. Under the action of acid catalysts or bacterial enzymes the amide and ester links in polyamides and polyesters can be hydrolysed into smaller fragments
What are the three main ways of disposing polymers?
Landfill, incineration and recycling
What are the advantages and disadvantages of landfill?
Advantages:
• buried at specific contained site
• biodegradable polymers will slowly degrade
Disadvantages:
• limited land available
• gas emissions (methane)
• slow degradation of plastics (addition polymers)
• leaching of toxic compounds (if not well maintained)
What are the advantages and disadvantages of incineration?
Advantages:
• less space than landfill
• Energy released from burning can generate electricty
• prevents build up of polymers in the environment
Disadvantages:
• increase in CO2 (greenhouse gas)
• toxic gas emissions to atmosphere
• particulates
What are the advantages and disadvantages of recycling?
Advantages:
• reduction of waste going to landfill
• reuse and conservation of precious hydrocarbon resources
Disadvantages:
• collection, sorting, seperating and remoulding all require energy
• expensive
