title: Chromatographic examination of the chemical composition and sequence distribution of copolymers from ethyl and benzyl diazoacetate.
abstract: 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×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.
authors.affiliation: Institute of Analytical Chemistry, Johannes Kepler University, 4040 Linz, Austria. evareingruber@hotmail.com
authors.forename: Eva M
authors.initials: EM
authors.lastname: Reingruber
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Chojnacka
authors.forename: Erica
authors.initials: E
authors.lastname: Jellema
authors.forename: Bas
authors.initials: B
authors.lastname: de Bruin
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Buchberger
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Schoenmakers
mesh_terms: D002850:Chromatography, Gel / Q000379:methods*; D003979:Diazonium Compounds / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D008697:Methane / Q000031:analogs & derivatives / Q000737:chemistry; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry*
chemical_list: D003979:Diazonium Compounds; D011108:Polymers; C030011:carbene; C032111:diazoacetic ester; D008697:Methane