title: Separating effective high density polyethylene segments from olefin block copolymers using high temperature liquid chromatography with a preloaded discrete adsorption promoting solvent barrier.
abstract: Recent advances in catalyst technology have enabled the synthesis of olefin block copolymers (OBC). One type is a "hard-soft" OBC with a high density polyethylene (HDPE) block and a relatively low density polyethylene (VLDPE) block targeted as thermoplastic elastomers. Presently, one of the major challenges is to fractionate HDPE segments from the other components in an experimental OBC sample (block copolymers and VLDPE segments). Interactive high temperature liquid chromatography (HTLC) is ineffective for OBC separation as the HDPE segments and block copolymer chains experience nearly identical enthalpic interactions with the stationary phase and co-elute. In this work we have overcome this challenge by using liquid chromatography under the limiting conditions of desorption (LC LCD). A solvent plug (discrete barrier) is introduced in front of the sample which specifically promotes the adsorption of HDPE segments on the stationary phase (porous graphitic carbon). Under selected thermodynamic conditions, VLDPE segments and block copolymer chains crossed the barrier while HDPE segments followed the pore-included barrier solvent and thus enabled separation. The barrier solvent composition was optimized and the chemical composition of fractionated polymer chains was investigated as a function of barrier solvent strength using an online Fourier-transform infrared (FTIR) detector. Our study revealed that both the HDPE segments as well as asymmetric block copolymer chains (HDPE block length≫VLDPE block length) are retained in the separation and the barrier strength can be tailored to retain a particular composition. At the optimum barrier solvent composition, this method can be applied to separate effective HDPE segments from the other components, which has been demonstrated using an experimental OBC sample.
authors: Materials Science and Engineering, The Dow Chemical Company, Midland, MI 48674, United States. Electronic address: tchatterjee@dow.com.
authors: Tirtha
authors: T
authors: Chatterjee
authors: Analytical Sciences, The Dow Chemical Company, Midland, MI 48667, United States.
authors: Mark A
authors: MA
authors: Rickard
authors: Analytical Sciences, The Dow Chemical Company, Midland, MI 48667, United States.
authors: Eric
authors: E
authors: Pearce
authors: Analytical Sciences, The Dow Chemical Company, Midland, MI 48667, United States.
authors: Todd O
authors: TO
authors: Pangburn
authors: Analytical Sciences, The Dow Chemical Company, Midland, MI 48667, United States.
authors: Yongfu
authors: Y
authors: Li
authors: Analytical Sciences, The Dow Chemical Company, Midland, MI 48667, United States.
authors: John W
authors: JW
authors: Lyons
authors: Performance Plastics Characterization, The Dow Chemical Company, 2301 Brazosport Blvd., Freeport, TX 77541, United States.
authors: Rongjuan
authors: R
authors: Cong
authors: Performance Plastics Characterization, The Dow Chemical Company, 2301 Brazosport Blvd., Freeport, TX 77541, United States.
authors: A Willem
authors: AW
authors: deGroot
authors: Analytical Sciences, The Dow Chemical Company, Midland, MI 48667, United States. Electronic address: dmeunier@dow.com.
authors: David M
authors: DM
authors: Meunier
mesh_terms: D000327:Adsorption; D000475:Alkenes / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D020959:Polyethylene / Q000737:chemistry* / Q000302:isolation & purification; D011108:Polymers / Q000737:chemistry* / Q000302:isolation & purification; D016062:Porosity; D012997:Solvents / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D000475:Alkenes; D011108:Polymers; D012997:Solvents; D020959:Polyethylene
keywords: Adsorption; HTLC; LC-FTIR; Olefin block copolymers (OBC)