Determining the chemical-heterogeneity-corrected molar mass averages and distribution of poly(styrene-co-t-butyl methacrylate) using SEC/MALS/UV/DRI
Andre M. Striegel, Imad Haidar Ahmad
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.
and Haidar, I.
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 June 9, 2023)