MALDI-ToF-MS mass spectra of copolymers contain a lot of information on both chain length distribution (CLD) and chemical composition distribution (CCD). In this paper an approach for extracting detailed information from a MALDI-ToF-MS mass spectrum is presented that enables the study of microstructure for copolymers. More specifically, this paper is dealing with a polystyrene-block-polyisoprene copolymer, in which the growth of the second block is followed with MALDI-ToF-MS as a function of conversion. The technique is compared to 1H NMR for the evaluation of average chemical compositions, revealing that ionization efficiencies do not influence the obtained mass spectra. It is shown that MALDI-ToF-MS can extract detailed information on the chain length distributions (CLDs) for both polystyrene and polyisoprene blocks. Using random coupling statistics, it is shown that the proposed analysis yields results with a high accuracy.

The first step in the transformation of poly(butadienyl)lithium into a macromolecular atom transfer radical polymerization initiator or reversible addition-fragmentation chain transfer agent is the modification of the anionic chain end into a suitable leaving/reinitiating group. We have investigated three different modification reactions to obtain a styrenic end group at the chain end of poly(butadienyl)lithium. In all cases, we have looked at the influence of a Lewis base on the progress of the reaction. The first modification reaction with a-methylstyrene leads to partial functionalization and oligomerization. The second reaction with 1,2-diphenylethylenes, particularly trans-stilbene, results in monoaddition to the poly(butadienyl)lithium chain ends. Quantitative functionalization is not obtained, possibly because of a hydrogen abstraction reaction, which causes termination. In the third modification reaction, a small polystyrene block is successfully added to the chain ends, as shown by a detailed matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of the block copolymers. Nearly quantitative block copolymer formation is achieved, with an average styrene block size of four monomer units and a polydispersity index of 1.19 for the polystyrene block. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2536-2545, 2005