Microstructural characterization of aromatic copolyesters made by step reactions, by gradient polymer elution chromatography

Abstract

The potentials of Gradient Polymer Elution Chromatography (GPEC) in both the Reversed‐Phase (RP) and Normal‐Phase (NP) mode, for the characterization of aromatic copolyesters made by step reactions, according to their chemical microstructure, were studied. Hereto, a number of copolyesters, varying in molar mass and chemical composition (CC) were synthesized, which allowed a systematic study on the effects of those parameters in GPEC. By RP‐GPEC, highly detailed separations were obtained. Information on chemical composition differences could, however, only be obtained for the lower molar masses. From these results, qualitative evidence for differences in the chemical microstructure of two strongly resembling copolyesters was found that could not be obtained by other methods such as SEC and NMR. Nevertheless, it was found difficult to unambiguously assign observed differences in the high molar mass parts of RP‐GPEC chromatograms. Therefore, RP‐GPEC must mainly be considered as a versatile, qualitative fingerprinting tool. In contrast, NP‐GPEC provides more and quantitative information on microstructural differences. By a combination of SEC and NP‐GPEC the Molar‐Mass‐Functionality‐Type‐Distribution (MMFTD) of the (co)polyesters, and the Molar‐Mass‐Chemical‐Composition‐Distribution (MMCCD) of the fraction containing two alcoholic end groups of the copolyesters could be studied. Significant differences between strongly resembling copolyesters were found which, for the MMCCDs, can only be the cause of the relative importance of reaction kinetics in step reaction copolymers. This makes the assumption that a predictable, theoretical statistically determined CCD is formed in all cases, questionable. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 183–201, 1999

Molar mass effects in reversed-phase gradient polymer-elution chromatography of oligomers

“…(9) adequately describes the retention of an oligomeric series in a given chromatographic system, the terms a and m are correlated [23]: m = q +p'a (10) where p ' and q are constants. (9) adequately describes the retention of an oligomeric series in a given chromatographic system, the terms a and m are correlated [23]: m = q +p'a (10) where p ' and q are constants.…”

Mass spectra of copolymers which display compositional drifts or sequence constraints

“…Earlier, (in 1967) Yamadera and Murano [33] reported results on the copolymer resulting from the melt-mixing of two homopolymers and they defined the degree of randomness as the sum of two P-terms, which is essentially identical to the FOMA definition of degree of randomness. Philipsen et al [38] analyzed the microstructure of an aromatic copolyester and they detected changes in the molar ratio of the two monomers as the size of the oligomer changes, but they did not model these changes. During attempts to obtain exactly alternating copolycondensates, such as poly-(ether-sulfone-alt-ether-ketone) [12] or poly(resorcinealt-bisphenolA carbonate) [13], scrambling reactions occurred and the sequence distribution of the resulting copolymers was approximately FOMA.…”

Chapter 5 Size-exclusion chromatography

“…Gradient polymer elution chromatography (GPEC) in both reversed-phase (RP) and normal-phase (NP) modes have been applied in microstructural characterization of aromatic co-polymers [250]. It is, therefore possible to selectively separate polymers with respect to hydrodynamic volume, chemical composition, and functionality by the use of different modes of LC.…”