Critical retention behavior of homopolymers

The isocratic retention behavior of a homopolymer at a specific temp. and varying solvent compns. can be divided into three modes: exclusion mode, transition mode (crit. conditions) and adsorption mode. Under crit. conditions (a specific non-solvent/solvent compn. at a specific temp.) the retention of a homopolymer is independent of the molar mass. The crit. conditions depend upon the temp., the type of polymer and the type of non-solvent/solvent mixt. A difference in the crit. conditions between polystyrene stds. and polybutadiene stds. was found. No significant influence of different types of column packing on the crit. solvent compn. was noticed. The exact mechanism of the retention of a polymer under crit. condition is not clear yet. In order to det. the crit. conditions, a new method has been developed. The method can be easily performed on existing equipment. The method contains a different setup of the data acquired by isocratic HPLC than methods described in literature. Therefore, less expts. need to be performed to det. the crit. conditions compared to the current method. The newly developed method is more efficient than the methods described in the literatur