Interaction Chromatography of Random Copolymers with Tunable Monomer Sequence Distributions

We demonstrate that high performance liquid chromatography (HPLC) in the interaction chromatography (IC) mode is capable of distinguishing among various comonomer sequences in random copolymers (RCPs). A series of poly(styrene-co-4-bromostyrene) (PBr$_{x}$S), where x is the mole fraction of 4-BrS, RCPs have been prepared by brominating parent monodisperse polystyrene (PS). The distribution of S and 4-BrS segments in PBr$_{x}$S was adjusted by varying the solvent quality for PS before the bromination reaction. We utilize both normal and reversed phase IC techniques to demonstrate that the adsorption-based retention of PBr$_{x}$S RCPs is affected not only by their chemical composition, but also by the comonomer distribution in the RCP. Both IC techniques are mutually complementary; they provide information on the interplay between the macromolecular collapse and segment blockiness affected by the adsorption-based retention times in HPLC.