Chemical Composition Fractionation of Olefin Plastomers/Elastomers by Solvent and Thermal Gradient Interaction Chromatography

Abstract

Olefin plastomers/elastomers are typically copolymers with high comonomer contents and low crystallinities. Therefore, the fractionation of these materials with crystallization-based methods is not feasible. On the other hand, solvent and temperature gradient interaction chromatography (SGIC and TGIC, respectively) are suitable techniques for the separation of olefin copolymers with regard to their chemical composition. In this study, the application ranges of both techniques are investigated and compared for ethylene-propylene (EP) copolymers. A linear dependency of ethylene content versus elution volume is obtained with SGIC in practically the whole ethylene range. In the case of TGIC, a linear dependency is obtained within certain ethylene content limits. The accessible ethylene content separation range for TGIC is 50-100 mol% ethylene, and a broader 26-100 mol% ethylene range is accessible for SGIC, the latter being the technique of choice in the analysis of EP rubbers.

Recent Advances in Separation-Based Techniques for Synthetic Polymer Characterization

“…Thus increasing the column length can improve resolution for solvent gradient separations. At the same analysis time, HTLC was reported to provide a better resolution than HT-TGIC. , …”

“…The enhanced resolution for stereoisomers and small molecules on porous graphitic carbon packed columns has been utilized to analyze polypropylene stereoisomers, oxidized waxes, tacticity in poly-1-octenes and high molecular weight fractions in Jet and diesel fuels . Standard HTLC routines have been adapted to analyze poly­(ethylene-co-propylene) elastomers, carboxylic acid–functionalized PE, poly­(ethylene-co–vinyl acetate) copolymers, heterogeneity in chain walking PE and to investigate changes in the microstructure of heterophasic poly­(ethylene-co-propylene)­s with increasing ethylene content, before and after visbreaking . In furthering work toward understanding the separation mechanism in HTLC, experimental separations of poly­(ethylene-co-octene) copolymers were compared with theoretical predictions .…”

“…The separation mechanism is based on the adsorption of polymer chains onto the stationary phase, where both enthalpy and entropy contribute to the adsorption according to molecular dynamics simulation with poly-(ethylene-co-hexene) copolymers. 110 Combined with other analytical techniques, HT-TGIC has been used to provide a comprehensive understanding of molecular structures of polymers, such as polymers made by chain walking catalysis, 29 CCD of elastomeric materials, 97 poly(ethylene-co-octene) copolymers, 96,121 and oxidized waxes in adhesive applications. 94,95 The elution temperatures of HT-TGIC profiles are ∼10 to 50 °C higher than crystallization-based techniques (such as CEF and TREF), depending on comonomer content.…”

“…At the same analysis time, HTLC was reported to provide a better resolution than HT-TGIC. 121,96 Solvent Gradient Interaction Chromatography (SGIC) also Known as High Temperature Liquid Chromatography (HTLC). When the separation is controlled by varying the mobile phase composition in a gradient while keeping the temperature constant, the LAC method is termed as HTLC or SGIC.…”

In Silico Tracking of Individual Species Accelerating Progress in Macromolecular Engineering and Design

“…A natural question that arises is whether the detailed tracking of the composition of individual chains is practically feasible. In the experimental field there has been a tremendous progress in the last decades, with in particular a strong improvement for multidimensional chromatography and the possibility to perform (on‐line) electrospray ionization mass spectrometry so that end‐group patterns can be mapped . In many cases, the experimental compositional information is although relative, for example, with respect to a polymer standard of a different chemical nature than the studied ( co )polymer or versus a related macroscopic property such as hydrophilicity or crystallinity .…”