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

Published

May 1, 2018

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

Pub Type

Journals

Download Paper

https://doi.org/10.1007/s10337-018-3512-6

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 October 10, 2025)