Recent advances in the resolving power of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) enable the detailed characterization of linear homopolymers, and in particular provide invaluable data for the determination of their end-group functionalities. With the growing importance of macromolecular coupling reactions in building complex polymer architectures, the ability to accurately monitor end-group transformations is becoming increasingly important for synthetic polymer chemists. This tutorial demonstrates the application of MALDI-TOF MS in determining both end-group functionalities and their transformations for linear homopolymers. Examples of both polycaprolactone and polystyrene are examined, and the strengths and weaknesses of various approaches to data analysis are given.

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The propensity of various insulins and their analogs to oligomerize was investigated by mass spectrometric methods including measurement of the relative abundances of oligomers in the gas phase and the kinetics of H/D amide exchange. The kinetics of deuterium uptake show a good fit when the exchanging amides are placed in three kinetic groups: fast, intermediate, and slow. r-Human insulin, of the insulins investigated, has fewer amides that exchange at intermediate rates and more that exchange at slow rates, in accord with its higher extent of association in solution. We adapted PLIMSTEX (protein ligand interactions by mass spectrometry, titration, and H/D exchange) to determine protein/ligand affinities in solution, to determine self-association equilibrium constants for proteins, and to apply them to various insulin analogs. We term this adaptation SIMSTEX (self-association interactions using mass spectrometry, self-titration and H/D exchange); it gives affinity constants that compare well with the literature results. The results from SIMSTEX show that some mutants (e.g., GlnB13) have an increased tendency to self-associate, possibly slowing down their action in vivo. Other mutants (e.g., lispro and AspB9) have lower propensities for self-association, thus providing potentially faster-acting analogs for use in controlling diabetes. (J Am Soc Mass Spectrom 2006, 17, 1526 -1534

The transport properties of water in neat poly(aryl‐ether‐ether‐ketone) (PEEK) coupons (2 to 6 mm thick) were investigated by gravimetric and mass spectrometric methods. The solubility of water increases from 0.44 wt.% at 35°C to 0.55 wt.% at 95°C; the temperature coefficient is 8 kJ/mol (1.9 kcal/mol). The diffusion processes for sorption, desorption, and resorption at 35°, 50°, 65°, 80°, and 95°C are, within experimental error, the same. The activation energy for diffusion is 42.7 kJ/mol (10.2 kcal/mol). The diffusion process is classical Case I Fickian in the temperature region investigated.

The absorption and subsequent desorption of benzene, toluene, carbon disulfide, and chloroform in amorphous and 27% crystalline poly (aryl‐ether‐ether‐ketone) (PEEK) were determined. At 35°C, the equilibrium weight gain (solubility) of benzene, toluene, chloroform, and CS2 are 23.5, 19.8, 51.2, and 21.2 wt%, respectively. The initial weight gain is linear with root‐time and pseudodiffusion constants for absorption into amorphous PEEK ranging from 0.35 to 9.85 x 10‐12m2/s were calculated. The desorption processes are two‐step and are controlled by the Tg of the penetrant‐resin mixture. The rate of diffussion into the crystalline material is extremely slow; crystalline PEEK reaches saturation (12.5 wt%) after immersion in CS2 (35°C) for several hundred hours but, even after 1300 h immersion, the other fluids do not reach saturation.