2D-LC characterization of comb-shaped polymers using isotope effect.

A rigorous molecular characterization of comb-shaped polystyrene (PS) was carried out taking advantage of its molecular structure, a normal hydrogenous backbone, and deuterated side chains. Normal phase LC (NPLC) can separate the comb PS species well according to their molecular weight. Nonetheless, it cannot distinguish the backbone from the side chains and the differently structured polymers having a similar molecular weight, e.g, a single backbone comb and a coupled backbone comb with fewer side chains. In contrast to NPLC, the hydrogenous polymer is retained longer than the deuterated counterpart in reversed phase LC (RPLC). When the isotope sensitivity of RPLC is taken advantage of, the comb PS is cross fractionated by NPLC and RPLC, and a two-dimensional mapping with respect to the backbone chain length and the number of branches is fully established.