The Characterization of Copolymers and Blends by Quintuple-Detector Size-Exclusion Chromatography

Published

June 14, 2012

Author(s)

Andre M. Striegel, Steven Rowland

Abstract

The properties imparted, oftentimes synergistically, by the different components of copolymers and blends account for the widespread use of these in a variety of industrial products. Most often, however, processing and end-use of these materials (especially copolymers) is optimized empirically, due to a lack of understanding of the physicochemical phase-space occupied by the macromolecules. Here, this shortcoming is addressed via a quintuple-detector size-exclusion chromatography (SEC) method consisting of multi-angle static light scattering (MALS), quasielastic light scattering (QELS), differential viscometry (VISC), ultraviolet absorption spectroscopy (UV), and differential refractometry (DRI) coupled on-line to the separation method. Applying the SEC/MALS/QELS/VISC/UV/DRI method to the study of a poly(acrylamide-co-N,N-dimethyl acrylamide) copolymer in which both monomer functionalities absorb in the same region of the UV spectrum, we demonstrate how to determine the chemical heterogeneity, molar mass averages and distribution, and solution conformation of the copolymer. Additionally, through the various mutually-independent conformational and architectural metrics provided by combining the five detectors, including the fractal dimension (derived from two different detector combinations), two different dimensionless size parameters, the chemical heterogeneity, and the persistence length, it is shown that the monomeric arrangement is most likely alternating at lower molar masses, thus causing the copolymer to adopt a more extended conformation in solution in this molar mass (M) regime. At high M, however, the copolymer is shown to be and to behave more like a random coil homopolymer, after passing through a 250 kg/mol-broad region of intermediate chain flexibility. Thus, the combination of five detectors provides a unique means by which to determine absolute properties of the copolymer, solution-specific physical behavior, and the underlying c

Citation

Analytical Chemistry

Pub Type

Journals

Citation

Striegel, A. and Rowland, S. (2012), The Characterization of Copolymers and Blends by Quintuple-Detector Size-Exclusion Chromatography, Analytical Chemistry (Accessed April 19, 2024)