Detailed structural analysis of diblock copolymers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The individual block length distributions of poly(α-methylstyrene)-b-poly(4-vinylpyridine) diblock copolymers have been determined by the MAC MALDI-TOFMS method of analysis of copolymers, which combines matrix assisted laser desorption/ionization time-of-flight mass spectrometry with computational data treatment. The problem of the possibility of multiple assignments of chemical composition to the mass spectral peaks is discussed in detail. A solution based on the pattern of peak clusters is proposed and verified using the statistical random coupling hypothesis test. The progress of the anionic polymerization in a series of polymers prepared by sequential addition of the second monomer to a living chain system is studied and shown in three-dimensional (3-D) plots of experimental individual blocks length distributions. The presence of unreacted homopolymer has been observed as well as bimodal and trimodal distributions for the poly(α-methylstyrene) and the poly(4-vinylpyridine) segments. A depolymerization process of the homopoly(α-methylstyrene) in the series of poly(α-methyl-styrene)-b-poly(4-vinylpyridine) diblock copolymers was detected following a temperature rise. It was confirmed that it is impossible to place a single unit of 4VP at the end of each PαMS chain.