Polymers - Topic 9 Flashcards
Polymer:
a substance of high average relative molecular mass made up of small repeating units (monomers)
Polymerisation:
- the joining up of many small molecules (called monomers) to form extremely long chains (called polymers)
- the repeat unit has the same atoms as the monomer because no other molecule is formed in the reaction
General equation for polymerisation:
n M → —————M-M-M-M-M-M——————-
What is the addition polymer formed called?
polythene
Change in structure from alkene to poly(alkene):
all atoms coming off carbon must be vertical to C
How can other addition polymers be made?
by combing together other monomer molecules containing C=C to include ply(propene), poly(chloroethene), (PVC) and poly(tetrafluoroethene)
Properties of poly(ethene):
- flexible
- cheap
- electrical insulator
- inert/unreactive
- waterproof/weatherproof
- light
Uses of poly(ethene):
- plastic bags and bottles
- coating on electrical wires
Properties of poly(propene):
- flexible
- strong
Uses of poly(propene):
- buckets
- crates
Properties of poly(chloroethene)/PVC:
- tough
- cheap
- long lasting/durable
- good insulator
- waterproof/weatherproof
- inert/unreactive
Uses of poly(chloroethene)/PVC:
- window frames
- gutters
- water pipes
- insulation for electrical wires
Properties of PTFE:
- slippery
- non stick
- tough
- high mp/high resistance
- inert/unreactive
Uses of PTFE:
non-stick coating on pans
Problems with polymers:
- availability of starting materials
- persistence in landfill sites, due to non-biodegradability
- don’t break down in the environment via natural processes
- end up with a build-up of non-disposable plastics
- fill up/new landfill sites needed
- harmful to animal habitats
- toxic gases produced during disposal by combustion/burning
- HCl acid/gas produced from burning of PVC
- CO2 released contributing to global warming
- CO released
- toxic ash/solids formed
- requirement to sort polymers so that they can be melted and reformed into a new product
Advantages of recycling polymers:
- don’t need to make as many new polymers - saves crude oil, conserving finite resources
- reusing waste materials is better for the environment than burning them (as won’t release toxic emissions) or putting them in landfills (as they are non-biodegradable)
- more economically viable instead of making more polymers
Disadvantages of recycling polymers:
- difficult and expensive to first separate the different polymers - need to be sorted into types which is time-consuming
- transport to collection area/recycling point uses fuel
- slow process
- degrading - each time you recycle a plastic you degrade some of its qualities
- collection point may cause litter/eyesore
What is DNA and what is it made from/of?
DNA is a polymer made from 4 different monomers called nucleotides
What is starch and is it made up of?
starch is a polymer based on sugars
What are proteins and what are they made up of?
proteins are polymers based on amino acids
Why are polyesters condensation polymers?
- In condensation polymerisation, a small molecule is formed as a by-product each time a bond is formed between two monomers
- Alcohol and carboxylic acid functional groups react, losing a small molecule – water
- This is an ester – therefore a polyester is a lot of these monomers (esters)
Condensation polymers:
- polymers formed from condensation reactions between monomers
- a small molecules (often water) is produced as well as the polymer
What must each monomer unit have to make condensation polymers?
- each monomer unit must have 2 functional groups that can react with the other monomer
- in the process of reaction a 2nd molecule e.g. water, is eliminated
2 main types of condensation polymers:
- polyesters
- polyamides
How are esters formed?
- esters formed on reaction between carboxylic acids and alcohols with the loss of a water molecule - esterification
- in a condensation reaction the 2 molecules join a produced a larger molecule whilst eliminating a small molecule
- during esterification this small molecule is water
Properties of esters:
- characteristic smells - often used in perfumes
- insoluble in water
Ester link:
the functional group -COO
How is a polyester formed when a monomer molecule containing 2 carboxylic acid groups is reacted with a monomer molecule containing 2 alcohol groups?
- the dicarboxylic acid loses the OH group off of each COOH group
- the di-alcohol loses the H off of each OH group
- the remaining molecules join together to make a polyester (the alcohol group combines with a carboxylic acid group) and an ester link is formed
- a water molecule is eliminated
- so basically if a dicarboxylic acid reacts with a diol, a polymer called a polyester is formed and water is released
How is a molecule of water formed each time an ester link is formed?
the OH and H groups combine to make H2O
What type of polymer is DNA?
condensation polymer
Peptide bond formation:
Protein/polypeptide:
How is polymer formed from an alkene?
- double carbon bond is broken
- many monomers link together to form a long chain
Do polymers of alkenes decolorise bromine water?
no - polymers do not decolorise bromine water
