6.2.3 Polyesters and Polyamides Flashcards
what is condensation polymerisation
the joining of monomers with the loss of a small molecules, usually water or HCl
- industrially, common starting products include carboxylic acids and derivatives
what is needed for condensation polymerisation
at least 2 different functional groups
what are polyesters
monomers joined together by ester linkages in a long chain to form a polymer
what can polyesters be made out of
- either a single monomer, containing both COOH (or acyl chloride) and OH group
- or 2 different monomers, one containing 2 COOH groups, and the other 2 OH groups
how would you show the formation of a polyester from just one monomer
- the OH from the COOH on one side of the monomer reacts with the H from the OH from the other side of a different monomer to release water
- forms the O-C=O ester linkage
- releases water
how do you form repeat units of a polymer
from either side of the monomer(s), you take away the reacted molecules, and replace them with a single bond leading into the [] brackets
what would the repeat unit of a HO-CH2-COOH monomer look like
-[-O-CH2-C=O-]-
how would you show the formation of a polyester from 2 different monomers
the COOH and OH from the two different monomers join to release H2O, leaving behind the COO ester linkage
- the repeat unit is just the 2 monomers joined, with COO in the middle, and the functional groups on either end also altered
how much water is released when forming a polymer
(2n-1) H2O always
- as each ester/amide bond releases one molecule of water
- so 2 as occur at each end of the monomers
- but subtract 1 due to the 2 monomers at the right end, which each contain 1 functional group that has not reacted
what are polyamides
monomers joined together by amide linkages in a long chain to form a polymer
how can you form polyamides
- either a single monomer containing both a COOH (or acyl chloride) and amine group
- or 2 monomers, one containing 2 COOH (or acyl chloride) groups and one containing 2 amine groups
how do polyamides form from just one monomer
- e.g. amino acids, as contain both carboxyl and amine group, and form proteins/polypeptides [linked with amide bond]
- OH from COOH reacts with H from NH2 to release H2O
- forms the amide linkage of O=C-N-H
what would a repeat unit of a polyamide made from just one type of monomer look like
-[-NH-CH2-C=O-]-
how do you form a polyamide from 2 different monomers
- one is a dicarboxylic acid, or has 2 acyl chloride groups
- one is a diamine, so has 2 amine groups
- both groups add to form amide linkage
- plus (2n-1) H2O
what is the difference in products when an acyl chloride is used instead of a carboxylic acid in the polymer
- the Cl reacts as the OH from COOH would
- forms HCl as product instead of water
- everything else is the same
what are the two methods of hydrolysing condensation polymers
- using hot aqueous alkali (NaOH)
- using hot, aqueous acid (HCl)
how are polyesters hydrolysed by hot aqueous alkali
- uses NaOH/H2O
- the O-C=O bond breaks
- the alcohol forms as normal
- but the carboxylic acid donates its H to OH- to form H2O
- forms COO- ion, which forms salt with Na+
how are polyesters hydrolysed with hot aqueous acid
- O-C=O bond breaks
- forms COOH and OH as normal
- as nothing to accept the H+ ion
how do polyamides react with hot aqueous NaOH
- the O=C-N-H bond breaks
- forms NH2 amide as normal
- but the COOH formed is able to donate H+ to form H2O with OH-
- reacts with the Na+ to form COO-Na+
how do polyamides react with hot, aqueous acid
- the O=C-N-H bond breaks
- forms COOH as normal
- the NH2 formed is able to accept the H+ and form NH3+
- if specific acid, can form ammonium salt here, e.g. NH3+Cl-
- REMEMBER: PLUS CHARGE GOES ON THE N OF NH3!!
what are the characteristics of an addition polymer
- formed from a C=C monomer
- has backbone of continuous chain of C atoms
what are the characteristics of a condensation polymer
- formed from 2 different functional groups (either on the same monomer or 2 different ones)
- contains an ester/amide linkage
how do you identify the monomer from an polymer
- identify the repeat unit present
- and work backwards from here
