Liquid chromatography at critical conditions (LCCC): Capabilities and limitations for polymer analysis

This paper investigates liquid chromatography at critical condition (LCCC) for polymer analysis. Based on controversial claims on the separation of cydic polymers from linear analogues in the literature, the efficiency of LCCC for separation and purity analysis is questioned. Polyisobutylene (P18) and poly(3,6-dioxa-1,8-octanedithiols) (polyDODT) were used for the study. The structure of low molecular weight cyclic and linear polyDODT was demonstrated by MALDl-Tol. NMR did not show the presence of thiol end groups in higher molecular weight PIBdisulfide and polyDODT samples, so they were considered cyclic polymers. When a low molecular weight polyDODT oligomer with only traces of cycles, as demonstrated by MALDI-Tor, was mixed with an M-n = 27 K g/mol cyclic sample, LCCC did not detect the presence of linear oligomers at 6 wt%. Based on the data presented here, it can be concluded that the LCCC method is not capable of measuring <6 wt% linear contamination so earlier claims for cydic polystyrene (PS) samples purified by LCCC having <3% linear contaminants are questioned. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study questions the efficiency of liquid chromatography at critical condition (LCCC) for polymer analysis, particularly in the separation and purity analysis of cyclic polymers from linear analogues. Experimental results showed that LCCC method is not capable of accurately measuring linear contaminants below 6 wt%.