Formation of carboxyl endgroups in polymers and their detection by the dye partition test

Carboxyl groups or endgroups have been introduced into polymers by use of the following four general methods: (1) use of a carboxyl‐bearing initiator, (2) copolymerization with a carboxyl‐bearing monomer, (3) chain transfer with a molecule containing an actual or potential COOH group, and (4) transformation of a reactive group already present in the polymer. The presence of the carboxyl endgroup in the polymer has been tested for a new technique called the “dye partition test,” developed in this laboratory. It has been demonstrated that all these methods can be used successfully to incorporate COOH groups in the polymer. Of particular interest is the fact that the incorporation of solvent fragments in polymers by chain transfer can be demonstrated very simply and conveniently by this method.