Negative mode MS/MS to read digital information encoded in sequence-defined oligo(urethane)s: A mechanistic study

[Display omitted] •Small polyurethanes (PUs) were studied to anticipate MS/MS behavior of long chains.•Three mechanisms were evidenced for O(CO)NH bond cleavage in deprotonated PUs.•Main issue with long chains was not related to CID but to negative mode ESI yield.•A new design of PU end-groups allowed this sensitivity issue to be addressed. MS/MS sequencing is an unrivaled technique to decipher binary information chemically encoded in the backbone of sequence-controlled synthetic polymers constructed with two co-monomers of different mass, arbitrarily designated as the 0- and 1-bit of the ASCII alphabet. Efficiency of this “reading” step relies however on the simplicity of MS/MS patterns, which depends on both polymer chemistry and chain length. In this context, polyurethanes (PUs) were very promising candidates as dissociation of small deprotonated oligomers (n