Characterization of Unsaturated Polymers Using High‐Temperature Size Exclusion Chromatography Coupled with Ultraviolet‐Evaporative Light Scattering Dual Detection

Size exclusion chromatography (SEC) is a technique routinely used at high temperature to analyze the molar mass distribution (MMD) in polymers. The distribution of comonomer along the molar mass axis in a copolymer is a key microstructural feature that determines the macroscopic properties of the material and thus its range of possible applications. However, unsaturated polymers requiring high dissolution temperature, measurement of chemical composition distribution (CCD) along the molar mass axis, have so far been hampered by the lack of suitable detection methods. Toward this goal, the potential of ultraviolet (UV) detection for high temperature SEC of ethylene-styrene, propylene-styrene copolymers, and ethylene-propylene-diene terpolymers is investigated. The influence of experimental parameters such as analyte concentration, unsaturation content, and mobile phase on the spectroscopic response is probed. An evaporative light scattering detector (ELSD) is employed to monitor the analyte concentration, in combination with the UV detector, to quantitatively measure the distribution of unsaturation content along the MMD. A slice-by-slice UV/ELSD ratio is calculated to determine the average chemical composition of each molar mass fraction after SEC separation.