Block Length Determination of the Block Copolymer mPEG-b-PS Using MALDI-TOF MS/MS
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Crecelius, Anna; Becer, C. Remzi; Knop, Katrin; Schubert, Ulrich S.
- Abstract:
- The molar mass determination of block copolymers,
in particular amphiphilic block copolymers, has been challenging
with chromatographic techniques. Therefore, methoxy poly-
(ethylene glycol)-b-poly(styrene) (mPEG-b-PS) was synthesized
by atom transfer radical polymerization (ATRP) and characterized
in detail not only by conventional chromatographic techniques,
such as size exclusion chromatography (SEC), but also by
matrix-assisted laser/desorption ionization tandem mass spectrometry
(MALDI-TOF MS/MS). As expected, different molar
mass values were obtained in the SEC measurements depending
on the calibration standards (either PEG or PS). In contrast,
MALDI-TOF MS/MS analysis allowed the molar mass determination
of each block, by the scission of the weakest point between
the PEG and PS block. Thus, fragments of the individual blocks
could be obtained. The PEG block showed a depolymerization
reaction, while for the PS block fragments were obtained in the
monomeric, dimeric, and trimeric regions as a result of multiple
chain scissions. The block length of PEG and PS could be calculated
from the fragments recorded in the MALDI-TOF MS/MS
spectrum. Furthermore, the assignment of the substructures of
the individual blocks acquired by MALDI-TOF MS/MS was accomplished
with the help of the fragments that were obtained from
the corresponding homopolymers.
- Year:
- 2010
- Type of Publication:
- Article
- Journal:
- Journal of Polymer Science: Part A: Polymer Chemistry
- Volume:
- 48
- Pages:
- 4375 - 4384