Polymers Flashcards
Polymers
what is polymerisation?
a polymerisation reaction involves joining together a large number of small molecules (monomers), to form a very large molecule (polymer) ONLY
what are the two different types of poltmers?
- addition polymers and condensation polymers
What is Addition polymerisation?
Many monomers join together to form a long molecule (polymers) ONLY
How do alkenes undergo addition polymerisation?
Many alkene monomers join together to form a long-chain polymer ONLY
Are there any waste products during addition polymerisation?
there are no waste products - only the polymer is formed
what does the addition polymerisation of alkenes occur in? Wjhat is formed during this reaction?
in the presence of a catalyst and the alkene monomers link together to form saturated addition polymers
what are addition polymers also known as?
chain growth polymers
why are addition polymers also known as chain growth polymers?
because they are made by the addition of monomers to the reactive end of the growing chain
Addition polymers are formed via which mechanism?
via free radical mechanism
what are the reaction conditions for addition polymerisation?
-High pressure and free radical initiator
How can addition polymerisation also proceed through?
Cation and anion species. this type of mechanism depends on the structure and the type of catalyst used
how is poly(ethene) formed?
ethene molecules link together to form poly ethene (in the presence of a catalyst)
Addition polymers formed from alkenes are?
saturated compounds
why are addition polymers chemically unreactive/inert?
the carbon-carbon bonds are non-polar and can not be hydrolysed
why is this a useful property for the resultant polymer?
since it can not be attacked by acids, alkalis and oxidising agents
draw an equation to show the polymerisation of a SECTION of poly(ethene)?
what are polymers usually represented by?
a repeating unit
what is the repeating unit of poly(ethene)
the repeating unit of poly(ethene) has no brackets
so what is the polymerisation of poly(ethene shown as)
what does n stand for?
n - represents a large whole number
n - is the number of individual molecules (monomers) that join together to form a polymer
Different addition polymers can be made from..?
monomers in which some or all of the hydrogen atoms in ethene have been replaced
draw the structure to show how monomers can be represented by?
What can R be?
RHC=CH2
where R = H, CH2, C6H5, CL, CN, OCOCH3
Why can different polymers be used to make a range of commercial products?
because each polymer has it’s own physical properties, so different polymers can be used to make a range of commercial products
draw the addition polymerisation of phenylethene, chloroethene and methyl-2-methylpropenoate
Problems with disposal
why are poly(alkenes) are problem when it comes to disposal?
because the carbon carbon bonds in the molecule are non-polar and therefore chemically inert and cannot undergo hydrolysis so when placed in rubbish dumps they will not decay over the years (non-biodegradable)
what is a solution to this?
one solution is to use more polymers that are biodegradable so that they will decompose in landfill sites. some plastics have been designed that are completely biodegradable.
But what is the problem with biodegradable plastic?
biodegradable polymers are more expensive than traditional synthetic plastics
which type of polymers undergo hydrolysis?
poly(esters) and poly(amides) because they are biodegradable by enzyme action
Give another possible solution to disposal of polymers?
Incineration
explain what incineration does (advanatges)
incineration is the burning of polymers.
- this significantly reduces the volume of waste.
- and can also be sued to recover energy (the heat produced can be used to make steam turbines drive to produce electricity)
what are the disadvantages of incineration?
- produces grennhouse gases (carbon footprint) and other toxic gases (e.g hydrogen cyanide)
Toxic substances from flue gases can be removed but what is the downside?
but this requires very high temperature decomposition, which means a high cost process a + equipment
which process is expensive but is a better alternative to landfill and incineration?
Recycling
why is recycling good?
helps to conserve supplies of non-renewable crude oil
why is the disadvantage of recycling?
it is not straightforward and is costly to separate various types of plastics from each other.
complete separation is essential - presence of one rogue bottle will ruin an entire molten plastic batch
what are the majority of disposable polymers?
Thermoplastics
how are thermoplastics reused?
need to be melted down and reused
what does successful recycling depend on?
accumulating enough material of a particular type to re-melt
plastics used to package houshold items fall into 7 different types what are they?
type 1 - (PETE)
type 2 - (HDPE)
type 3 - (V)
type 4 -(LDPE)
type 5 - (PP)
type 6 - (PS)
type 7 - other - not suitable for recycling
what are the other problems associated with recycling?
- the energy costs associated with the plastic re-melt
- costs associated with the transport, collection and cleaning of disposed plastic
Condensation polymers
condensation polymers form two different types of polymers?
- polyamides
- polyesters
What is condensation polymerisation?
where monomers join together to make a polymer and a waste product (only)
what is condensation polymerisation formed by?
the reaction between molecules that have 2 functional groups
what usually happens during condensation polymerisation?
monomers with the functional groups at both ends of the molecule join together and a small molecule, usually water (condensation) is eliminated at the end.
the waste product is usually water but what else could it be?
it can be other small molecules such as CH3OH or HCL
Draw a diagram to show the condensation polymerisation between 2 different bifunctional group monomers?
Monomer A + Monomer B
Draw a diagram to show the condensation polymerisation of 1 monomer with different functional groups at each end react together?
Monomer A + Monomer A
what are the two types of condensation polymers?
- polyamides
- polyesters
what bond is formed between polyamides?
amide bond linkages -O=C-N-H
what are the two methods for making polyamides?
- polyamides can be formed by reacting a diamine with a dicarboxylic acid (or a dioyl chloride)
- polyamides can also be formed by the condensation polymerisation of amino acids
Show how a polyamide is formed by reacting a diamine (1,6-diaminohexane) with a dicarboxylic acid (Hexanedioic acid)?
H2N(CH2)6NH2 + HOOC(CH2)4COOH ——-> -(-H-N-(CH2)6–H-N—-C=O–(CH2)4–C=O–)
What product is formed?
Nylon 6,6
why is it called Nylon 6,6?
Nylon 6,6 is so called because it is derived from a 6 carbon diacid and a 6 carbon diamine
what is nylon good for?
nylon has a large resistance to stress and has many uses such as textiles and carpets
Show how a polyamide is formed by reacting a Diamine (benzene-1,4-diamine) with dicarboxylic acid (Benzene 1,4-dicarboxylic acid)
H2N-⌬-NH2 + HOOC-⌬-COOH —–> -(–H-N–⌬–H-N—-C=O–⌬–C=O–)-
What is the polyamide formed?
Kevlar
what is the use of Kevlar?
Kevlar is used to make bulletproof vests (and skis). Kevlar is very strong and lightweight. it has a tough sheet-like structure due to hydrogen bonding between the polymer chains.
Show how a polyamide is formed by reacting a Diamine (benzene-1,3-diamine) with dicarboxylic acid (Benzene 1,3-dicarboxylic acid)
Nomex formed
What is the use of Nomex?
use for making flame-retardant clothing
Polyamides can be made by the condensation polymerisation of amino acids
Show the condensation polymerisation between the amino acid (6-aminohexanoic acid)
Nylon 6 formed
Show the condensation polymerisation between the amino acid (5-aminopentanoic acid)
Hydrolysis of polyamides
Why are polyamides biodegradable?
polyamides are broken down by hydrolysis and are therefore biodegradable
what is formed during the hydrolysis of polyamides?
component monomers are formed
why do polyamides undergo hydrolysis?
because they have polar carbonyl bonds so when heated with NaOH solution, the :OH- nucleophile will attack the electron deficient carbon atom
Draw the hydrolysis of Nylon 6,6
Draw out the hydrolysis of the dipeptide Val.Ala?
forms two separate amino acids Valine and alanine
Nylon rope trick
how can we make the nylon rope?
- carefully pour decanedioyl dichloride (in cyclohexane) down a glass rod into a 100ml beaker containing 1,6-diaminohexane (in water)
- do not stir the mixture
- use tweezers to pull out some of the nylon 6,10 from the interface of the two solutions
- wrap the nylon 6,10 around a glass rod and slowly rotate the glass rod to make a nylon rope
Polyesters
the bonds between the polyesters are called?
ester bond linkages
How can polyesters be made?
Polyesters can be made via a condensation polymerisation reaction involving 2 different bifunctional monomers
Recap: how are esters made?
by reacting an alcohol with a carboxylic acid
How can polyesters be made by reacting..?
a dicarboxylic acid (dibasic acid) with a diol
Show the formation of the polyester formed when ethane-1,2-diol reacts with hexanedioic acid?
Show the formation of the polyester when hexane-1,6-diol reacts with butanedioic acid?
Show the formation of the polyester when ethane-1,2-diol reacts with Benzene-1,4-dicarboxylic acid.
Terylene formed
what is formed?
Terylene
what is terylene used for?
used for carpet fibres
Hydrolysis of polyesters
How are polyesters hydrolysed?
hydrolysed just as normal single esters are hydrolysed
what are the polyesters broken down into?
they undergo hydrolysis and break down into component monomers
polyesters are..?
Biodegradable
why do polyesters undergo hydrolysis?
because they have polar carbonyl bonds so when heated with NaOH solution the OH- nucleophile will attack the electron deficient carbon atom
What are the uses of polyesters?
- used to make fibres for clothes and carpets
- polyesters are moulded on a large scale to make plastic bottles for fizzy drinks
why are they ideal for this?
because they ares strong and lightweight
FINISH
