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

The individual block length distributions of poly(alpha-methylstyrene)-b-po ly(4-vinylpyridine) diblock copolymers have been determined by the MAC MALD I-TOFMS method of analysis of copolymers, which combines matrix assisted la ser desorption/ionization time-of-flight mass spectrometry with computation al data treatment. The problem of the possibility of multiple assignments o f chemical composition to the mass spectral peaks is discussed in detail. A solution based on the pattern of peak clusters is proposed and verified us ing the statistical random coupling hypothesis test. The progress of the an ionic polymerization in a series of polymers prepared by sequential additio n of the second monomer to a living chain system is studied and shown in th ree-dimensional (3-D) plots of experimental individual blocks length distri butions. The presence of unreacted homopolymer has been observed as well as binodal and trimodal distributions for the poly(alpha-methylstyrene) and t he poly(4-vinylpyridine) segments. A depolymerization process of the homopo ly(alpha-methylstyrene) in the series of poly(alpha-methyl-styrene)-b-poly( 4-vinylpyridine) diblock copolymers was detected following a temperature ri se. It was confirmed that it is impossible to place a single unit of 4VP at the end of each P alpha MS chain. Copyright (C) 1999 John Wiley & Sons, Lt d.