Two-dimensional liquid chromatography of polystyrene-polyethylene oxide block copolymers

In this study, liquid chromatography at critical conditions of polystyrene (PS) and polyethylene oxide (PEO) is used as the first dimension for the two-dimensional analysis of PS-b-PEO copolymers. Comprehensive two-dimensional liquid chromatography, with size exclusion chromatography as the second dimension, reveals information about the molar mass distributions of all separated fractions from the first dimension. Furthermore, fractions eluting at the critical conditions of one block were collected and subjected to analysis in the second dimension at the critical conditions of the other block. These fractions were analysed by FTIR to determine their chemical compositions. The combination of the above approaches and the calibration of the evaporative light scattering (ELS) detector for the first-dimensional analysis yield deep insights into the molecular heterogeneity of the block copolymer samples. The composition of the samples and the chemical composition of the real block copolymer are also calculated by combining results obtained at both critical conditions.