3. Polymers Flashcards
what are the two ways of making polymers
addition polymerisation
condensation polymerisation
what are polymers
long chain molecules formed when lots of small molecules named monomers join together
how do alkenes form addition polymers
the double bonds open up and molecules join together to make long chains
e.g. of addition polymerisation
n C2H4 ->
-(-C2H4-)- n
(n is the number of repeating units)
(the bit in the bracket is the repeating unit)
- what are condensation polymers usually formed from
2. how is the polymer chain created
- two types of monomer
each monomer has at least 2 functional groups - functional group of one monomer reacts with group on other type of monomer to form a link
- in condensation polymerisation each time a link is formed what is lost
- a small molecule (usually water)
2 examples of condensation polymers
polyesters
polyamides
in polyesters what link is formed between the monomers
an ester link -COO-
in polyamides what link is formed between the monomers
an amide link -CONH-
condensation polymers are formed as what is removed
water
how can condensation polymerisation be reversed
by hydrolysis (water molecules added back and links broken)
why are condensation polymers hydrolysed with an acid or base
hydrolysis just with water is too slow
polyamides hydrolyse more easily with an acid or a base?
with an acid
- polyesters hydrolyse more easily with an acid or a base?
2. what is formed
- base
2. a metal salt of the carboxylic acid
reactions between dicarboxylic acids and diamines make
polyamides
Carboxyl -COOH groups react with amino -NH2 groups to form
Amide -CONH- links
what is lost each time an amide link is formed
a water molecule (it is a condensation reaction)
reactions between dicarbocylic acids and diols make
polyesters
carboxyl groups -COOH react with hydroxyl groups -OH to form
ester links -COO-
why does the fact that dicarboxylic acids and diamines have functional groups at each end mean long chains can form
both ends can react
1.if one of the COOH in a dicarboxylic acid is changed to 2. an acyl chloride gorup it can also react to form
instead of water ____ is eliminated in the condensation reaction
- polyesters and polyamides
2. hydrochloric acid is eliminated.
