Hydrolysis of polyamides and polyesters

POLYMERS

• Polyesters and polyamides are a type of polymer called a condensation polymer
• This means that when they are formed many monomers join together while a small molecule, water, is released
• Just as these polymers can be formed, they can also be broken down with acid or alkaline hydrolysis

• Polyamides can be identified by their characteristic O=C-N-H bond
• Polyamides will hydrolyse with an acid much more readily than they will with a base

POLYAMIDE + H2O + HCl ------- > DICARBOXYLIC ACID + DIAMMONIUM SALT

• In this reaction the acid acts as both a catalyst and a reagent
• Although technically hydrolysis is the breakdown of the polymer using water, this reaction is so slow that it can be almost disregarded

• Polyamides can also be hydrolysed using alkaline hydrolysis
• Polyamides are much more resistant to this type of hydrolysis

POLYAMIDE + NaOH --------- > DIAMINE + DICARBOXYLATE SALT

• Here, the base only acts as a reagent and not a catalyst

• Polyesters can also be hydrolysed by acid and alkaline hydrolysis
• Although, in a way, polyesters are the opposite of polyamides because they are hydrolysed much more readily by alkaline hydrolysis than acid hydrolysis

POLYESTER + H2O ------------ > DICARBOXYLIC ACID + DIOL

• Unlike with polyamides, the acid is simply a catalyst and does not take part in the overall reaction

• Polyesters hydrolyse more readily with alkaline hydrolysis 

POLYESTER + NaOH -------- > DICARBOXYLATE SALT + DIOL

• Again, the base is just a reagent, not a catalyst