Journal
JOURNAL OF CHROMATOGRAPHY A
Volume 1255, Issue -, Pages 259-266Publisher
ELSEVIER
DOI: 10.1016/j.chroma.2012.02.059
Keywords
Gel permeation chromatography (GPC); Multidimensional chromatography; Carbene-type polymers; pi-pi stacking
Funding
- Dutch Polymer Institute [622]
- Netherlands Organization for Scientific Research (NWO-CW VIDI) [700.55.426]
- European Research Council (ERC) [202886]
- University of Amsterdam
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Polymers, especially copolymers, are highly complex samples and, therefore, require various setups for their thorough characterization. In this work, one- and two-dimensional chromatographic approaches were applied to characterize two homopolymers and two dissimilar copolymers prepared by rhodium-mediated carbene polymerization using ethyl and benzyl diazoacetate as the monomers: poly-(EA-ran-BnA) and poly((EA)(b)-(BnA-ran-EA)(b)). Different strategies of synthesis suggested that poly(EA-ran-BnA) was an approximately 1:1 random copolymer and that poly((EA)(b)-(BnA-ran-EA)(b)) was a block-type copolymer of which the (BnA-ran-EA)(b) block is dominated by BnA. The hydrodynamic volume of the investigated polymers turned out to be comparable, i.e. size exclusion chromatography (SEC) did not separate them. Temperature-gradient interaction chromatography was not feasible and one-dimensional (solvent-)gradient-elution liquid chromatography (GELC) suffered from coelution problems. Pyrolysis-gas-chromatography (Py-GC-MS) experiments allowed determining the monomer ratio. SEC with UV and refractive-index detection indicated the presence of molecular-weight-dependent chemical heterogeneity for the poly((EA)(b)-(BnA-ran-EA)(b)) copolymer. This finding was confirmed with off-line SEC//Py-GC-MS. Only a comprehensive two-dimensional GELC x SEC setup enabled the separation of high-molecular-weight material of the less-retained homopolymer from low-molecular-weight copolymeric material. In this way it was possible to detect some high-molecular-weight homopolymeric material in one of the copolymers. (C) 2012 Elsevier B.V. All rights reserved.
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