Identification of Poly(p-phenylene terephthalamide) Branching and Metathesis Products

摘要

This presentation will focus on the identification of the structural distributions within poly(p-phenylene terephthalamide) (PPD-T) (Kevlar~(~R)) fibers. The limits of MALDI-TOF MS, using the E-G ethod, in aramid anlaysis will first be discussed. Comparisons will be made between low molecular mass poly(p-phenylene terephthalamide) (PPD-T), synthesized using various molar ratios of reactants, and high molecular mass Kevlar~(~R) fibers. Observed end groups were predominantly in agreement with the monomer ratios used during synthesis. However, small quantities of cyclic and imine branched species, which were also found in the oligomeric portion of model PPD-T oligomers and commercially produced Kevlar~(~R). Also, "unexpected" mass peaks were observed in the MALDI spectra which could only be explained through the existence of aramid metathesis reactions. However, the degree of branching was difficult to predict and more definitive information was necessary to put forth the existence of aramid metathesis reactions. Following this, examples will be shown which exploit the use of the evaporation-grinding MALDI sample preparation method with ion mobility (IM) separations and TOF/TOF CID fragmentation to overcome some of these problems. In these examples, MALDI-IM/MS will be used to provide clear separation of linear and branched species, and distinction between the branched meta-para-aramid (MP-amide) trendline and the branched Kevlar~(~R) (para-para-aramid) trendline. The MALDI-TOF/TOF CID fragmentation studies identified a weak link at the carbonyl-phenyl bond which will be incorporated into fragmentation mechanisms that explain the CID spectra. Both the linear and branched fragmentation spectra displayed many similar fragment peaks. However, end-group and main-chain modifications introduce "fingerprint" fragment peaks that identify "additional" end groups and branch point location.