Velocity Sedimentation and Intrinsic Viscosity Analysis of Polystyrene Standards with a Wide Range of Molar Masses

Abstract

Analytical ultracentrifugation is one of the key methods among the molecular hydrodynamic methods of polymer science, biophysics, and colloid science. The aim of this work is to demonstrate the possibilities of a modern instrument, the Beckman XLI Analytical Ultracentrifuge, coupled with the now available software for the molecular characterization of synthetic polymers. For this purpose the classical system polystyrene in methyl ethylketone was investigated. The samples of low polydispersity index were studied in a 1 000‐fold interval of molar mass values. The exhaustive analysis of such hydrodynamic values as velocity sedimentation coefficient, frictional ratio, concentration Gralen coefficient, and intrinsic viscosity, was done. The values of partial specific volume, refractive index increment, and hydrodynamic invariants were also determined and discussed. The estimation of the statistical segment length (or persistent length) of polystyrene chains was made taking into account the intrachain excluded volume and draining effects (Gray–Bloomfield–Hearst theory). The obtained experimental data and results of its analysis allow the conclusion that the method of velocity sedimentation, coupled with the numerical solution of the Lamm equation, represents a powerful absolute characterization method for molar mass determination of flexible polymers of low polydispersity in relatively poor solvent.magnified image

Hydrodynamic Analysis Resolves the Pharmaceutically-Relevant Absolute Molar Mass and Solution Properties of Synthetic Poly(ethylene glycol)s Created by Varying Initiation Sites

“…In the self-sufficient analysis presented here, ( f/f sph ) 0 is used as a hydrodynamic parameter to estimate translational diffusion coefficients, D 0 (eq 7), respectively, directly and the absolute molar mass M s,f (eq 10). As being shown here for the studied macromolecules as well as demonstrated before for other macromolecules, 16,17,38 the estimated values of frictional ratios (consequently diffusion coefficients, eq 7) by numerical solution of the Lamm eq (eq 3) are adequate which, in turn, qualifies sedimentation velocity as a practical absolute method. This situation can be inferred by the discussed values of the hydrodynamic invariants (eq 9) that bring into consideration values of intrinsic viscosities, [η], and intrinsic sedimentation coefficients, [s].…”

“…However, though analytical ultracentrifugation is well-known and a classical, indispensable tool in biochemistry and biophysics, its application for studying synthetic macromolecules is still rather limited until now. − With respect to macromolecular characterization science, the information extracted from sedimentation velocity experiments in the ultracentrifuge can be combined with orthogonal hydrodynamic methods used in classical macromolecular science, e.g., viscometry and diffusion measurements. , This combined approach applied for homologous series including that of existent and potentially up-and-coming pharma-polymers will provide most reliable and comprehensive information on the macromolecular characteristics, void of the necessity or existence of a notoriously needed reference standard.…”

Characterization of mixed solutions of hyperbranched and linear polystyrenes by a combination of size‐exclusion chromatography and analytical ultracentrifugation

“…The result clearly shows that the values of molar mass are consistent with each other for five fractions, confirming that AUC can separate and characterize the molar masses of linear polystyrene at the same time. In addition, the sedimentation coefficient of linear polystyrene scales with the molar mass obtained by AUC with a scaling index of 0.46 (data not shown), which is slightly smaller than the value 0.48 reported by McCormick and Pavlov et al in different solvents, indicating that the linear polystyrene adopts a random coil conformation in THF …”

Hydrodynamic and Molecular Study of Poly{4‐[4‐(hexyloxy)phenyl]ethynylphenyl methacrylate} in Dilute Solutions and Conformational Peculiarities of Brush‐Like Macromolecules

“…The two approaches using differentiation led to virtually identical values of the velocity sedimentation coefficient and, moreover, virtually coincided with the values obtained by the Sedfit program (Figure 2). It was shown in previous investigations that the Sedfit program allows the determination of both the velocity sedimentation coefficient and the frictional ratio for a variety of linear polymer–solvent systems 53–56…”