AVS 63rd International Symposium & Exhibition
    Surface Science Thursday Sessions
       Session SS+AS-ThA

Paper SS+AS-ThA3
Polymer Precursors Studied by Mass Spectrometry, Ion Mobility and Computational Strategies (Invited Talk)

Thursday, November 10, 2016, 3:00 pm, Room 103C

Session: Celebrating a Life in Surface Science: A Symposium in Honor of JOHN T. YATES, JR.
Presenter: David M. Hercules, Vanderbilt University
Correspondent: Click to Email
There has been considerable interest recently in using mass spectrometry and related methods to address structures of complex systems, including block copolymers. Polyurethanes (PURs) are polymers that contain multiple “hard” and “soft” blocks that have different sequences of the same units along the chain. The ultimate goal in studying such materials would be the ability to determine the exact sequence along the chain and to correlate specific sequences with polymer performance. We have established a protocol on smaller molecules that can address this type of issue using the combination mass spectrometry, collision-induced dissociation, ion mobility spectrometry (IMS), and molecular dynamics simulations. A key component of the of the project is the synthesis of model PUR oligomers having authentic component sequences. The individual components are methylene diphenyl diisocyanate (MDI), bis-diol terminated polybutylene adipate (PBA), and 1,4-butane diol (BD), each containing 3 MDIs, 4 PBAs and 4 BDs (MW = 1910). The main collision-induced dissociation fragmentation reactions occur between the PUR and PBA carbonyl groups and BD hydrogen atoms. Additionally, a 1,3 H-shift reaction occurs between the PUR N-H group and BD oxygen. Different fragment ions are observed depending on the unit size and the sequences of the units in the chain. An important aspect of the research is to use IMS to separate compounds that have identical masses but different molecular-ion scattering cross sections. Computational strategies are important for calculation of IMS collisional scattering cross sections and to aid in the interpretation of fragmentation mechanisms. They help to identify synthetic targets that will show the largest effects of the experimental measurements.