Analysis of Diblock Copolymers of Poly(α-methylstyrene)-block-polystyrene by Mass Spectrometry

Abstract

The individual block length distributions of a series of diblock copolymers, polystyrene-b-poly(α-methylstyrene), were determined by the MAC MALDI/TOF MS method of analysis of copolymers which combines matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with computational data treatment. The robustness of the calculation technique was evaluated. The presence of unreacted homopolymer was observed as well bimodal and trimodal distributions for the poly(α-methylstyrene) segments. A new method to verify the random coupling hypothesis has been proposed. The hypothesis was verified to hold within the experimental error of the technique for all the correct assignments of polymers studied. The experimental distributions have been compared with the Poisson, Schulz−Zimm, Tung, and logarithmic-normal models, modified to account for the change of variables. The equations of the Tung model, which was found to have the best predictive capability for the PαMS blocks, were transformed into the analytical form. Overall, the Schulz−Zimm model remains the most flexible of all models.

Microstructural and conformational studies of polyether copolymers

“…The MALDI-ToF spectra from these copolymers (data not shown) are dominated by peaks from singly charged ions, even for the oligomers of highest molecular weights. The overlapping distributions of peaks from oligomers with different initiating (␣) end groups (i.e., from the tridecanol and pentadecanol mixtures of alcohols used as the initiator for the copolymers) mean that deconvolution of the data would be required for three-dimensional intensity plots to be produced, as previously shown for other copolymers (also from MALDI-ToF data) [27][28][29][30].…”

Determination of block size in poly(ethylene oxide)‐b‐polystyrene block copolymers by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

“…In this context, selection of proper experimental conditions for MALDI analysis of copolymers can become a tedious task. Although successful MALDI analysis has been reported for various copolymers,27, 35–44 the case of amphiphilic block copolymers such as PEO‐ b ‐PS, in which hydrophobicity of the two blocks is very different, remains a challenge. Indeed, despite many efforts to optimize experimental conditions from typical PEO or PS sample preparations, no MS signal could be obtained from such copolymers.…”

PEO‐b‐PCL Block Copolymers: Synthesis, Detailed Characterization, and Selected Micellar Drug Encapsulation Behavior

“…Only a few examples are known from the literature (see, e.g., refs. [21,25,26] ) where MALDI could be applied for the analysis of copolymers, since the interpretation of copolymer MALDI spectra can be very difficult as a result of the presence of two distributions, namely a molecular weight and a chemical composition distribution. Nevertheless, we were able to investigate the synthesized block copolymers by MALDI-TOF MS utilizing a recently developed multiple layer spotting technique [20] in combination with a homemade program written in Visual Basic 6.0 [21] to result in a full copolymer characterization for polymer P1 as well as a good understanding of the other block copolymers.…”