Structural characterization of hyperbranched polyesteramides: MSn and the origin of species

Four hyperbranched synthetic polyesteramides were synthesized by the polyco ndensation of the trifunctional diisopropanolamine (D) and difunctional anh ydrides (X) of succinic acid, glutaric acid, 1,2-cyclohexane dicarboxylic a cid, and phthalic acid. The polymers were analyzed with electrospray ioniza tion Fourier transform ion cyclotron resonance mass spectrometry. The most intense oligomer series observed was XnDn+1 containing diisopropanolamine e nd groups as expected from the polycondensation conditions. A series of oli gomers XnDn+1-H2O is observed as well, which can have its origin in the pol ymerization process or alternatively could result from in-source fragmentat ion of XnDn+1. Breakdown diagrams of the protonated parent ions X3D4 and ad ditional MSn (n = 1, 2, 3) measurements gave insight in the fragmentation b ehavior of the polymers. Three main fragmentation pathways have been observ ed for all polymers of which the loss of H2O to oxazolonium ions has the lo west onset energy followed by the rearrangement of the amide and ester bond s also leading to oxazolonium ions. The loss of a second H2O to allylic or morpholine end groups has highest onset energy. MS3 experiments demonstrate d that the presence of a series of oligomers XnDn+1-H2O can be attributed t o the polymerization process. Most probably an allylic end group has formed from one of the alcohol end groups. The formation of allylic end groups pa rtly terminates the polymerization reaction and results in a change of the composition of the molecular weight distribution and decrease of the number average molecular weight. (C) 2001 Elsevier Science B.V.