Polymers Flashcards
How can condensation polymers be formed
By the reactions between :
- Dicarboxylic acids and diols
- Dicarboxylic acids and diamines
- Amino acids
What are the two types of polymerisation
Addition and Condensation
How is an addition polymer formed
When unsaturated monomers react to form a polymer
Why are poly(alkenes) chemically inert and non-biodegradable
Due to the strong C-C and C-H bonds and the non-polar nature of the bonds and therefore are non-biodegradable.
They cannot be attacked by nucleophiles and cannot be hydrolysed
Dicarboxylic acid + diol =
Poly(ester) + water
Diacyl dichloride + diol =
Polyester + HCl
Dicarboxylic acid + diamine
Poly(amide) + Water
Diacyl dichloride + diamine =
Poly(amide) + HCl
Why might it be preferred to use an acyl chloride rather than the carboxylic acid to make the ester or amide
The more reactive acyl chloride goes to completion and does not need a catalyst, but if you were to use the carboxylic acid you would need an acid catalyst and would only give and equilibrium mixture so lower yield.
Dangers of using acyl chlorides in making esters and amides
Produces hazardous HCl fumes
What is the polyester terylene made from
ethane-1,2-diol and benzene-1,4-dicarboxylic acid
Uses of the polyester terylene
Clothing and tire cords
What is the linkage between the repeating units of terylene
Ester link of -C(O)=O
What is the polyamide Nylon 6,6 made from
Hexanedioic acid and Hexane-1,6-diamine
What is formed if different length carbon chains are used
Different polyamides are formed
Uses of Nylon 6,6
Clothing
Uses of Kevlar
Bullet proof vests
Why are polyesters not suitable for use under strongly acidic/alkaline conditions
The ester group is hydrolysed by the acid/alkali
How are polyesters and polyamides broken down
By hydrolysis
Why are polyesters and polyamides not hazardous/harmful to the environment
The ester group can be hydrolysed due to the presence of polar bonds and therefore are attacked by nucleophiles and so polyesters and polyamides are biodegradable
Why is it not possible to quote an exact value for the molar mass of a polymer but only an average one
It is made up of molecules of different chain lengths
Why do polyesters like terylene not have a sharp melting point
It is made up of molecules of different chain lengths. A mixture does not have a sharp melting point but melts over a range of temperatures
What are the forces between polymer chains in polyesters
There are permanent dipole forces between the polar carbonyl groups, C=O, on adjacent carbon chains in addition to the Van der Waals forces between the chains
What are the forces between polymer chains in polyamides and proteins
There is hydrogen bonding between the oxygen in the polar carbonyl groups, C=O, and the H in the N-H groups in the different chains. There is also Van der Waals forces.
What is the difference in melting points between polyesters and polyamides
Polyamides have higher melting points as there is hydrogen bonding in polyamides which is stronger than the permanent dipole forces in polyesters therefore more energy is needed to overcome the stronger intermolecular forces in polyamides.
What are the different types of disposal of polymers
Landfill Sites
Incineration
Recycling
Advantages of landfill sites
Most common method
Disadvantages of landfill sites
Many are reaching capacity
Most polymers (polyalkenes) are non-biodegradable so take many years to break down
Unsightly
Advantages of incineration
Rubbish is burnt and energy produced is used to generate electricity
Volume of rubbish greatly reduced
Disadvantages of incineration
Some toxins and greenhouse gases are emitted
Advantages of recycling
Saves raw materials such as crude oil
Disadvantages of recycling
Polymers need collecting and sorting which is costly
Polymers can only be recycled into the same type so needs careful separation
Advantages of using biodegradable polyesters/amides
They do not occupy landfill sites and do not accumulate in the environment
What is produced in the base hydrolysis of a polyester, when using hot aqueous NaOH
Sodium salt of the dicarboxylic acid + diol
What is produced in the acid hydrolysis of a polyester, using hot dilute HCl
Dicarboxylic acid + diol
What is made when two amino acid molecules join together by condensation polymerisation
Dipeptide
What is the linkage between two amino acids
Peptide link/amide link -C(=O)-NH-
What is produces in the base hydrolysis of polyamides
Sodium salt of the dicarboxylic acid + diamine
What is produced in the acid hydrolysis of polyamides
Dicarboxylic acid + ammonium salt of the diamine
How do you name aliphatic dicarboxylic acids
-dioic acid
How do you name aromatic dicarboxylic acids
-dicarboxylic acid
