6.2.3 Polyesters and Polyamides

the joining of monomers with the loss of a small molecules, usually water or HCl • industrially, common starting products include carboxylic acids and derivatives

at least 2 different functional groups

monomers joined together by ester linkages in a long chain to form a polymer

• 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

• 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

from either side of the monomer(s), you take away the reacted molecules, and replace them with a single bond leading into the [] brackets

-[-O-CH2-C=O-]-

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

(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

monomers joined together by amide linkages in a long chain to form a polymer

• 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

• 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

-[-NH-CH2-C=O-]-

• 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

• the Cl reacts as the OH from COOH would • forms HCl as product instead of water • everything else is the same

• using hot aqueous alkali (NaOH) • using hot, aqueous acid (HCl)

• 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+

• O-C=O bond breaks • forms COOH and OH as normal • as nothing to accept the H+ ion

• 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+

• 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!!

• formed from a C=C monomer • has backbone of continuous chain of C atoms

• formed from 2 different functional groups (either on the same monomer or 2 different ones) • contains an ester/amide linkage

• identify the repeat unit present • and work backwards from here