Polymers Flashcards
What is a condensation reaction?
When two molecules react together and a small molecule, often water of HCl, is eliminated.
What is a condensation polymer?
Long chain molecules formed from lots of small molecules (monomers) joining together by a condensation reaction. Often made from two different monomers each with two functional groups.
Describe how polyesters are made
Two monomers are diol and dicarboxylic acid (functional groups at end of chains) Has the linkage -COO- repeated over and over again. In reaction the H from an alcohol group and the OH from a carboxylic acid group both leave to form water. For n total monomers, n-1 water molecules are eliminated.
What is Terylene?
Polyester made from benzene-1,4-dicarboxylic acid and ethane-1,2-diol.
Describe how polyamides are made
Two monomers are diaminoalkane and dicarboxylic acid. Has linkage -CONH- repeated over and over again. In reaction an H from amino group and and OH from carboxylic acid group both leave to form water. For n monomers, n-1 molecules of water are formed.
Nylon-6,6
Industrially made using 1,6-diaminohexane and hexane-1,6-dicarboxylic acid and produces water. In laboratory, reaction faster if uses a diacid chloride rather than dicarboxylic acid but this produces HCl. Many different nylons can be made from different monomers.
Kevlar
Made from benzene-1,4-diamine and benzene-1,4-dicarboxylic acid. Strength is due to rigid chains and ability of flat aromatic rings to pack together held by strong intermolecular forces.
Describe how polypeptides are made
They are polyamides. Made from either a single amino acid monomer or many different ones. Each amino acid has both an amine group and a carboxylic acid group. In reaction an H from the amine group and a OH from the carboxylic acid group leave to form a water molecule. There is a repeated linkage of -CONH- which between amino acids is called a peptide link.
How to identify monomers from a polymer
Start with the repeating unit. Break the linkage between the monomers (C-O for polyester and C-N for polyamide). Add back the components of water for each ester or amide link. This is the same process for when condensation polymers are hydrolysed.
Why aren’t addition polymers biodegradable?
They are basically long chain alkane molecules. Alkanes are unreactive because they have only strong, non-polar C-H and C-C bond. There is nothing natural that will break them down.
How are addition polymers disposed of?
Put in landfill sites along with other rubbish. Incinerated possibly to produce energy. Some are melted down and remoulded.
Problems with disposal of addition polymers
Fill up landfill sites used for other rubbish so take up space. Burning poly(alkenes) can produce poisonous carbon monoxide through incomplete combustion or would make CO2 adding to the problem of CO2 in the atmosphere. Other addition polymers may release toxic products on burning, eg polystyrene producing toxic styrene vapour.
Why could condensation polymers be biodegradable?
They can be broken down by hydrolysis so are potentially biodegradable by the reverse of the polymerisation reaction by which they were formed. The reactant added is just water. Reaction is very slow under everyday conditions.
