Studying Binary Solvent Mixtures as Mobile Phase for Thermal Gradient Interactive Chromatography (TGIC) of Poly(ethylene- stat -1-octene)

Thermal gradient interactive chromatography (TGIC) is an emerging analytical tool to determine the chemical composition distribution of polyolefins. TGIC separates polyolefins based on their interaction with graphitic carbon at different temperatures in an isocratic mobile phase. In the case of copolymers of ethylene and 1-olefins, TGIC offers a larger commoner range of separation than crystallization based techniques. However, currently TGIC shows approximately only half of the resolution compared to crystallization based techniques for an ethylene content higher than 92 mol % when 1,2-dichlorobenzene (ODCB) and 1,2,4-trichlorobenzene (TCB) are used as the mobile phase. We conducted a systematic study exploring the potential of using different binary solvent mixtures as the mobile phase to increase the resolution in TGIC of poly(ethylene-stat-1-octene). Apart from the well-established chlorinated aromatic solvents like ODCB and TCB, for the first time, binary solvent mixtures containing alkanes and aliphatic alcohols have been evaluated as components of the mobile phase using an evaporative light scattering detector. As an outcome, optimized binary solvent mixtures could be identified that enabled an improvement in resolution. This was exemplarily verified by separating a model blend of two poly(ethylene-stat-octene) samples with varying 1-octene content.