Direction of temperature gradient and retention mechanism in normal-phase temperature gradient interaction chromatography for poly(methyl methacrylate) fractionation

Temperature gradient interaction chromatography (TGIC) is a powerful technique for molecular characterization of polymers, in which the interaction strength is controlled by varying the column temperature. In the present paper, the direction of temperature gradient for normal-phase mode TGIC in poly(methyl methacrylate) (PMMA) fractionation was studied by using System I (column: cyano-modified silica // eluent: 1,4-dioxane/n-hexane) and System II (bare silica // 1,4-dioxane/CH2Cl2), respectively. It was found that PMMA samples were separated by positive and negative temperature gradients using the respective systems. The results were also discussed theoretically.