Effect of Solvent Type on High‐Temperature Thermal Gradient Interaction Chromatography of Polyethylene and Ethylene–1‐Octene Copolymers

Abstract

The effects of the solvent type and operation conditions on the high‐temperature thermal gradient interaction chromatography (HT‐TGIC) of ethylene homopolymers, ethylene–1‐octene copolymers, and their blends are investigated. While the HT‐TGIC profiles of single polymers measured with 1,2,4‐trichlorobenzene (TCB) and chloronaphthalene (CN) are similar, they are always narrower when o‐dichlorobenzene (ODCB) is used, particularly for samples with lower 1‐octene fractions. Significant differences between the experimental and the calculated profiles of binary blends are observed with all three solvents, but better peak separation is seen when the ODCB is used. Having higher fractions of a 1‐octene‐poor component in the blend causes a more significant distortion of the shape expected for the peak from the component with the higher 1‐octene fraction. The effect of the molecular weight on HT‐TGIC profiles is also studied using samples with the same comonomer content and different molecular weights. Samples with low molecular weight have broader distributions and significant lower‐temperature tails, particularly when TCB is used. Chain crystallization after adsorption effects may also play a minor role for low‐comonomer samples. Finally, HT‐TGIC profiles are compared with their equivalent crystallization elution fractionation (CEF) profiles. The HT‐TGIC curves are broader than the equivalent CEF profiles, but these differences decrease as the comonomer content increases.

Joint Effect of Poly(ethyhlene‐co‐1‐octene) Chain Length and 1‐Octene Fraction on High‐Temperature Thermal Gradient Interaction Chromatography

“…When binary blends of ethylene/1‐olefin copolymers are analyzed by HT‐TGIC, sometimes copolymers of different compositions affect each other's HT‐TGIC profiles, a phenomenon that has been attributed to co‐adsorption and/or co‐desorption of these species. In a previous publication from our group, we showed that copolymer microstructure, analytical conditions, and type of the mobile phase influence these phenomenon. We also defined a co‐desorption index (CDI) to quantify these effects where (d w /d T ) exp and (d w /d T ) pred are the normalized heights of the experimental and calculated HT‐TGIC profiles of the blend at each data point, respectively.…”

“…Monrabal et al [22] reported that the HT-TGIC peak position did not depend on molecular weight for polyethylene with M n higher than 25 000 g mol −1 . Alghyamah and Soares [23][24][25] used a set ethylene/1-octene copolymers with comonomer contents up to 3.5 mol% to study the effect of solvent type, sample injection volume, and adsorption/desorption temperature range on HT-TGIC chromatograms of individual samples and their blends. They showed that o-dichlorobenzene increased elution peak temperatures and had slightly better resolution than 1,2,4-trichlorobenze.…”

Quantifying the Effect of Polyethylene Molecular Weight, Comonomer Fraction, and Comonomer Type on High-Temperature Thermal Gradient Interaction Chromatography

“…Chang et al were the first to use TGIC to fractionate polymers according to molecular weight as an alternative to gel permeation chromatography. 26 Al-Khazaal et al 27 and Alghyamah et al 28 investigated several parameters affecting HT-TGIC fractionation of polyolefins, such as polymer molecular weight and α-olefin fraction, heating rate, cooling rate, elution flow rate, support particle size, column length, solvent type, and type of packing material. These previous HT-TGIC investigations concentrated on polyethylenes with number average molecular weights, M n , higher than 25 000.…”

Molecular Dynamics Simulation of Ethylene/Hexene Copolymer Adsorption onto Graphene: New Insight into Thermal Gradient Interaction Chromatography

“…Increasing heating rate leads to higher elution temperature (the temperature of the column will rise faster between the moment the polymer is desorbed and the moment it reaches the detector). Decreasing the elution rate results in higher elution temperature and broaden the TGIC profile probably due to an increased residence time in the column …”

“…Decreasing the elution rate results in higher elution temperature and broaden the TGIC profile probably due to an increased residence time in the column. [34][35][36] One of the key features of the TGIC profile is the broadening of the peaks at high α-olefins content. A similar feature was observed with TREF and it was attributed to the Stockmayer bivariate distribution of the copolymer chemical composition.…”