Polymers And Life Flashcards
The Polyester Story?
1940s - chemist Rex Winfield knew that another scientist, Wallace Carothers, had tried to produce polyesters.
Carothers had produced the award-winning nylon in 1935, but Winfield felt that Carothers had not used the acid most likely to give the desired properties for a polyester.
Whinfield used 1,4-benzenedicarboxylic acid and reacted it with ethene-1,2-diol. The structure of the polyester was formed. PET is the original polyester.
What Is PET?
Polyethylene Terephthalate,
It is produced firstly as small granules. These are melted and then pushed through small holes. The resulting filaments are spun to produce fibres.
These fibres are Terylene or Dacron - used in maki n clothes, filling duvets and for making X-ray sheets.
ThIs fibre has good heat insulation.
PET is also used for packaging.
Curing?
Curing is a polymerisation process where granules of polyester are heated to 240°C.
The polymer is then stretched and moulded which causes the molecules to be orientated in three dimensions.
The plastic has great strength and is impermeable to gases. PET is used for bottles of carbonated drinks for this reason.
The versatility of the polymer is due to the fact that molecules within the polymer can be aligned in one, two, or three dimensions. With each dimension comes different properties.
Reactions Of Carboxylic Acids?
Carboxylic acids are strong enough to react with strong bases to FORM SALTS.
Carboxylic acids also react with carbonates to form water and carbon dioxide.
The formula for this is:
CO3 2- (aq) + 2H+ (aq) —> CO2 (g) + H2O(l)
This is an acid-base reaction, where the carbonate ion, CO3 2- is the base.
Reactions Of Phenols?
Phenols are strong enough acids to react with strong bases. They do this to form SALTS, like Carboxylic acids.
Phenols do not have a great enough concentration of H+(aq) ions to react in with carbonates.
Reactions Of Alcohols?
Alcohols are not strong enough acids to react with strong bases.
Therefore, the do not form salts like carboxylic acids and phenols.
H3O+ Ion?
Is often written as H+ (aq).
Reaction Of Ethanoic Acid With Calcium Carbonate?
CaCO3 + 2CH3COOH —> Ca(CH3COO)2 + CO2 + H2O
The salt formed is called Calcium Ethanoate.
What Happens When Carboxylic Acids React With Carbonates?
The solution will fizz because of the production of carbon dioxide.
What Happens When Phenols/Alcohols React With Carbonates?
The solution will not fizz because there is not a high enough concentration of H+ (aq) ions to react with carbonates.
This means CO2 is not produced and, therefore, the solution doesn’t fizz.
What Forms Salts When Reacted With Metals?
Carboxylic acids, phenols and alcohols all react with metals to form salts.
This reaction is redox rather than acid-base, for example:
Mg + 2CH3COOH —> Mg(CH3COO)2 + H2
(This is magnesium and ethanoic acid).
Condensation Polymerisation?
The process of making polymers in which monomer units are linked together by amide groups.
Diamines and dicarboxcylic acids that contain reactive functional groups in two places in their molecules allowed them to link together to form a chain.
Condensation reaction occurs at the OH + H of the molecules and produces water.
These polymers are called polyamides because -COOH + -NH2 = -CONH2 and it’s a chain of amides (poly).
Protein Structure?
Primary structure - the order of the amino acid residues.
Secondary structure - the folding of parts of the chain into an an alpha helix or the formation of a beta sheet.
Tertiary structure - the folding of the secondary structure. Extra bonds form between different parts of the polypeptide chain. Gives the protein a 3 dimensional shape.
Why Does A Shape Of Tertiary Structure Matter?
The shape of the tertiary structure varies with the function of the protein.
Structural proteins such as muscles and hair are fibrous (thin and long) and consist only of helices.
Proteins that control metabolism (e.g. enzymes and hormones) are globular and have both sheets and helices.
An example of a protein with both sheets and helices is insulin.
Uses For Proteins?
Proteins are natural polymers with a relative molecular masses (up to around 100,000).
Proteins can be fibrous (F) or globular (G).
- they are components of membranes (F),
- they help to hold cells together (F),
- they make up hair, nails, and feathers (F),
- they allow muscles to contract by sliding over one another when the muscle relaxes/contracts in muscle fibres (F),
- they are enzymes (highly specific catalysts which control rates of reactions) (G),
- they are some hormones such as insulin (G),
- they store substances and transport substances around the body (e.g. haemoglobin) (G).
