Influence of Microstructure on the Elution Behavior of Gradient Copolymers in Different Modes of Liquid Interaction Chromatography

Abstract

We studied the influence of microstructure on the chromatographic behavior of gradient copolymers with different gradient strengths and block copolymer with completely segregated blocks by using gradient liquid adsorption chromatography (gLAC) and liquid chromatography at critical conditions (LCCC) for one of the copolymer constituents. The copolymers consist of repeating units of poly(propylene oxide) and poly(propylene phthalate) and have comparable average chemical composition and molar mass, and a narrow molar mass distribution to avoid as much as possible the influence of these parameters on the elution behavior of the copolymers. On both reversed stationary phases, the elution volume of gradient copolymers increases with the increasing strength of the gradient. The results indicate that for both modes of liquid interaction chromatography, it is important to consider the effect of microstructure on the elution behavior of the gradient copolymers in addition to the copolymer chemical composition and molar mass in the case of gLAC and the length of the chromatographically visible copolymer constituent in the case of LCCC.

Oxygenated Boron Species Generated In Situ by Protonolysis Enables Precision Synthesis of Alternating Polyesters

“…Copolymerization of PA and a large excess of PO at RTcatalyzed t BuP 1 -Et 3 B was previously shown to produce esterether gradient or block copolymers owing to the dual polymerizability of PO. 61,87 It needs to be noted that formation oxygenated boron species in this case cannot be completely ruled. However, it is obvious that protonolysis of Et 3 B is much less profound so that catalytic activity for the self-propagation of epoxides is largely maintained therein.…”