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Determining the chemical-heterogeneity-corrected molar mass averages and distribution of poly(styrene-co-t-butyl methacrylate) using SEC/MALS/UV/DRI

Published

Author(s)

Andre M. Striegel, Imad Haidar Ahmad

Abstract

Chemical heterogeneity, defined as the change (or lack thereof) across the molar mass distribution (MMD) in the monomeric ratio of a copolymer, can influence processing and end-use properties such as solubility, gas permeation, conductivity, and the energy of interfacial fracture. Given that each parent homopolymer of the copolymer monomeric components has a different specific refractive index increment (dn/dc) from the other component, chemical heterogeneity translates into n/c heterogeneity. The latter, in turn, affects the accuracy of the molar mass (M) averages and distributions of the copolymers in question. Here, employing size-exclusion chromatography coupled on-line to multi-angle static light scattering, ultraviolet absorption spectroscopy, and differential refractometry detection, the chemical heterogeneity (given as mass percent styrene) was determined for a poly(styrene-co-t-butyl methacrylate) copolymer. Also determined were the chemical-heterogeneity-corrected M averages and MMD of the copolymer. In the present case, the error in molar mass incurred by ignoring the effects of chemical heterogeneity in the M calculations is seen to reach as high as 53,000 g mol-1 at the high end of the MMD. This error could be much higher, however, in copolymers with higher M or with larger difference among component n/c values, as compared to the current analyte.
Citation
Chromatographia
Volume
81

Keywords

Chemical heterogeneity, copolymer, multi-detector size-exclusion chromatography, specific refractive index increment, molar mass, poly(styrene-co-t-butyl methacrylate)

Citation

Striegel, A. and Haidar, I. (2018), Determining the chemical-heterogeneity-corrected molar mass averages and distribution of poly(styrene-co-t-butyl methacrylate) using SEC/MALS/UV/DRI, Chromatographia, [online], https://doi.org/10.1007/s10337-018-3512-6 (Accessed April 17, 2024)
Created May 1, 2018, Updated April 25, 2019