Search

Polymers, macromolecules in nature and bio-polymers like proteins and antibodies are present in our every-day life and play an important role in our economy. They are obviously present as plastic products (e.g., containers, clothing, car tires) or components, e.g., as expedients in pharmaceutical formulations, additives in food and feed, stabilizers in cosmetics, used in construction materials, ceramics and are key in microchip production. Size-exclusion chromatography is the most important characterization technique for macromolecules. This review covers applications, instrumental setup, step-by-step guides for performing experiments and covers theoretical background as well as troubleshooting and tips and tricks.

A convenient method that enables determination of molecular weight distributions of diblock copolymers with conventional size exclusion chromatography (SEC) without referring to any kind of calibration curve or molar mass-sensitive detecting devices is described. It is based on the well-established procedure to calculate the number-average molecular weight of copolymers from their chemical composition and the molar mass of the first block segment (precursor), applied on an ensemble of monodisperse copolymer fractions. The chemical composition of SEC fractions is calculated from their UV and RI detector traces, and the number-average molecular weight of the precursor, which is to be known from independent measurements, is taken as the molar mass of the first block segment. The molecular weight distributions and averages obtained by this method for selected copolymer samples were found to be in reasonably good agreement with the ones determined by NMR and SEC with on-line viscosity or multiangle laser light scattering detection.

Introduction Blockcopolymers such as SBS (styrene-butadiene-styrene) are an important product class and a typical example of complex polymers. In addition to the molar mass distribution, a chemical composition distribution may [...]

The accurate characterization of molar-mass distributions of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) by size-exclusion chromatography (SEC) is addressed. Two methods are employed: direct aqueous-phase SEC on P(M)AA and THF-based SEC after esterification of P(M)AA to the associated methyl esters, P(M)MA. P(M)AA calibration standards, P(M)AA samples prepared by pulsed-laser polymerization (PLP), and PAA samples prepared by reversible addition-fragmentation chain transfer (RAFT) are characterized in a joint initiative of seven laboratories, with satisfactory agreement achieved between the institutions. Both SEC methods provide reliable results for PMAA. In the case of PAA, close agreement between the two SEC methods is only observed for samples prepared by RAFT polymerization with weight-average molar mass between 80 000 and 145 000 g mol−1 and for standards with peak molar masses below 20 000 g mol−1. For standards with higher molar masses and for PLP-prepared PAA, the values from THF-based SEC are as much as 40% below the molar masses determined by aqueous-phase SEC. This discrepancy may be due to branching or degradation of branched PAA during methylation. While both SEC methods can be recommended for PMAA, aqueous-phase SEC should be used for molar-mass analysis of PAA unless the sample is not branched. [ABSTRACT FROM AUTHOR]