polymers Flashcards
(28 cards)
polymer
long chain molecules made of lots of small molecules joined together by covalent bonds
monomer
small molecules that join together to form polymers
addition polymerisation
the formation of longchain molecules from lots of small molecules joining together with no other products formed. unsaturated monomers of the same type (?) (have C=C; alkenes) react to form a polymer
condensation polymerisation
formation of longchain molecules by the condensation reactions between many monomers. two different types of molecule(?) join together and release a small molecule
(if reaction not polymerisation then modulate answer)
polyalkenes have the following characteristics
chemically inert and non biodegradable
this is because they are nonpolar so unreactive and not susceptible to attack by nucleophiles
many strong and nonpolar CC and CH bonds
examples of polyalkenes
polyethene
PVC - rigid used for guttering, window frames; plasticised used for clothing and wire insulation
polypropene
repeat unit
polymer structure
without the n and brackets
with the n AND brackets
what are the forces between polymer chains in addition polymers/polyalkenes
because they have non-polar bonds (so non biodegradable) they have VdW forces between molecules
what are the forces between polymer chains in condensation polymers
?
they have polar bonds in their chains so they could have permanent D-D interactions unless polar bonds cancel out i supporse
could have H bonding eg polyamides because H bonded to very electronegative atom of N (,O, or F). h bonding due to polarity of NH bonds within molecules. so polyamide bp > polyester bp because h bonding > dd
the __ bonds in polyalkenes means what 2 things
STRONG NONPOLAR non biodegradable; unreactive
no D-D interactions, have VdW as strongest IMF between molecules
these strong bonds aren’t just the ch bonds
the __ bonds in condensation polymers means what 2 things
POLAR bonds in their chains
so they can be attacked by nucleophiles ad broken down by hydrolysis reactions. they are biodegradable (but is slow)
have dd or h bonding as strongest imfs
their biodegradability is good because it prevents build up of waste in landfill and they can be broken down by natural processes
hydrolysis
how can polyester and polyamides be hydrolysed
type of decomposition reaction where a molecule is broken down into components by adding water. water is a reactant
polyesters and polyamides can be hydrolysed by acid and alkali. In both monomers are reformed. in the acid hydrolysis diamines are protonated and form ionic bonds. in the alkali hydrolysis the dicarboxylic acid monomers form dicarboxylate ion salts
- _Acid hydrolysis of polyesters_ involves breaking down the polymer chains using water in the presence of a strong acid, resulting in the formation of the original diol and dicarboxylic acid monomers.
- _Acid hydrolysis of polyamides_ involves breaking down the amide linkages in the polymer chain using water and a catalyst, typically an acid. This process leads to the formation of the original dicarboxylic acid and the ammonium salt of the diamine. because it’s acidic conditions the diamines that formed the polyamide will be protonated (so nh3+ instead of nh2). then the anion from the acid will form ionic bonds
- _the alkali hydrolysis of polyester_ forms diol and dicarboxylate salt with the cation from the strong base eg K+ from KOH
- _the alkali hydrolysis of polyamides_ results in the formation of the cation salt of the dicarboxylic acid, and a diamine.
where else have we seen acid or alkali hydrolysis?
hydrolysis of esters or triglycerides
ACID HYDROLYSIS
- of esters is just the backwards reaction of the eqm. ester and water react to frm c acids and alcohol
- of triglycerides forms glycerol and fatty acids
ALKALINE HYDROLYSIS
- of esters makes carboxylate salt and alcohol
- of triglycerides is saponification. forms salts of fatty acids and glycerol. forms soap because hydrophilic and hydrophobic regions. must be boiled with excess metal hydroxide
condensation polymers are…
they are formed in the reactions between…
they are organic molecules formed from c. reactions.
reactions
- dioic acids and diols (polyesters)
- dioic acids and diamines (synthetic polyamides)
- amino acids (polypeptides - biological polyamides)
what are two examples of types of c polymers
polyesters or polyamides.
polyesters have an ester linkage
polyamides are polymers with -CONH- repeating bonds; an amide linkage. includes polypeptides (biological, cellular), or aliphatic polyamides (man made) or aromatic polyamides (man made)
how can you form an ester
c acid and alcohol. also forms water
acyl chloride and alcohol. also forms HCl
so for forming polyesters you have dioic acids with diols, or diacyl chlorides with diols
why is making an ester (or polyester) using acyl chloride and alcohol better than c acid and alcohol
(the di’s for the polyester formation)
goes to completion
esterification remember requires acid catalyst and is an equilibrium.
how can you form amides
c acid and amine. also forms water
acyl chloride and amine. also forms HCl
so for making a polyamide you react a dioic acid with diamine, or diacyl chloride with diamine.
examples of polyamides
nylon. this is an aliphatic polyamide
kevlar. this is an aromatic polyamide.
about nylon 6,6
hexanedioic acid and 1,6 diaminohexane
react to form nylon polymer and H2O
6,6 is the C chain length. Different length carbon chains produce different polyamides
about kevlar
polyamide made from 1,4-benzenedicarboxylic acid and
1,4-benzenediamine.
Bullet proof vests, bc the strong h bonding due to polar bonds of N-H hold separate polymer chains in strong structure
example of polyester. monomers and useage
terylene.
monomers: made from ethanediol and 1,4-benzenedicarboxylic
acid.
t fabric is used in clothing and tire cords
general equation for c polymerisation
n A + n B → ([-A-B-]n) + (n-1) C
where ‘A’ and ‘B’ are monomers, ‘C’ is a small molecule, and ‘n’ is the number of repeating units in the polymer
shortcut for finding the repeating unit/polymer structure of given monomers
condensation
identify f groups reacting
have them react so have the middle linkage there and ready
then on either side, whatever reacts, remove and leave dangling bond
