Philip Samuel Nisson has written:

'Derivatives of terephthalic acid ..' -- subject(s): Terephthalic acid

Ethylene glycol + Terephthalic acid

carboxylic acids

It is a colourless di-carboxylic acid. It has 2 carboxilic functional groups attached to a benzene ring.

Polyesters are co-polymers, meaning they have more than one monomer. Instead of a chain made of repeated identical units, A-A-A-A-A-A-A-....., they have alternating units, A-B-A-B-A-B-A-B-.....In theory you start with a dicarboxylic acid such as terephthalic acid with a diol such as ethylene glycol, which react by a series of condenstation reactions to form the polymer. In practice they often start with acid derivatives such as dimethyl terephthalate, which then reacts by a transesterification reaction with the glycol. The precise monomers depend on which polyester you are making, but terephthalic acid and ethylene glycol make the commonest one, poly(terephthalic ester) or PET.