Gas-Phase Structure of Supermolecular Assemblies and POSS Clusters

This is a project in collaboration with Prof. Michael Bowers at UCSB (current ACS award winner in Physical Chemistry!) and funded by the Air Force Office of Scientific Research (AFOSR).  See the Bowers group website at http://bowers.chem.ucsb.edu.

 

We are currently collaborating with Prof. Peter Stang and his group at the University of Colorado. The motivation for this collaboration  is the characterization of coordination-based supramolecular assemblies for which x-ray structures are not known in general.  Ion mobility mass spectrometry is able to achieve this goal  Rectanglar and triangular structures have been thoroughly studied and the results published . Two supramolecular structures are much larger in cross-section and currently being studied.  We hope to obtain structural information consistent with their known x-ray structures and, since they are rigid molecules,  use them for calibrating our theoretical calculations for large molecules.

 

Another goal of this current research effort is to continue interfacing the ongoing synthetic program at Edwards AFB on polyhedral oligomeric silsesquioxane (POSS) with the structural characterization capabilities of the Bowers group at UCSB.   I recently completed a National Research Council Senior Associateship with the Bowers group doing ion mobility mass spectrometry, data analysis and computer modeling of POSS structures and am continuing the work on an active AFOSR grant.  

The POSS family of molecules have recently become of great interest due to their inherent thermal stability and their ability to improve the thermal, physical and chemical properties of host polymer systems.  Mass spectrometric-based methods have been recently developed to both identify and structurally characterize POSS and POSS containing materials.  These methods use ion mobility to experimentally obtain molecular shapes and extensive molecular mechanics/molecular dynamics calculations to generate detailed structural information consistent with experiment.  Initial studies on well characterized POSS cages yielded structures virtually identical with X-ray structures.  The Bowers group is currently collaborating with synthetic groups at both Edwards AFB and at the Institute of Polymer Studies, University of Massachussetts, and can give rapid feedback on synthetic outcomes using only nanomoles of material.  This allows the development of rational synthetic strategies tailored to efficiently generate new POSS based materials.  Examples of ongoing and new projects I am involved with include building block development, and POSS-polymer adduction.

E. R. Brocker, S. E. Anderson, B. H. Northrop, P. J. Stang, and M. T. Bowers, "Structures of Metallosupramolecular Coordination Assemblies Can Be Obtained by Ion Mobility Spectrometry-Mass Spectrometry,"J. Am. Chem. Soc.,  132, 13486, (2010).

S. E. Anderson, A. Somogyi, T. S. Haddad, E. B. Coughlin, G. Gadodia, D. F. Marten, J. Ray, and M.  T. Bowers, "ESI and MALDI Mass Spectrometry of Large POSS Oligomers," Int. J. Mass Spectrom. 2010, 292, 38,  (2010).

S. E. Anderson, D. J. Bodzin, T. S. Haddad, J. A. Boatz, J. M. Mabry, C. Mitchell, and M. T. Bowers,  “Structural Investigation of Encapsulated Fluoride in Polyhedral Oligomeric Silsesquioxane Cages Using Ion Mobility Mass Spectrometry and Molecular Mechanics,” Chem. Mater., 20, 4299, (2008).

S. E.  Anderson, C. Mitchell, T. S. Haddad, J. J. Schwab, A. Vij, and M. T. Bowers, “Structural Characterization of POSS Siloxane Dimer and Trimer,”  Chem. Mater., 18, 1490, (2006). 

S. E.  Anderson, E. S. Baker, T. S. Haddad, C. Mitchell, and M. T. Bowers, “Structure of Hybrid Polyhedral Oligomeric Silsesquioxane Polymethacrylate  Oligomers Using Ion Mobility Mass Spectrometry and Molecular Mechanics,” Chem Mater., 17, 2537 (2005). 

E. S. Baker, J. Gidden, S. E.  Anderson , T. S. Haddad, and M. T. Bowers, “Structural Characterization of Sodiated Polyhedral Oligomeric Silsequioxanes (POSS) Isomers with Mixed Styryl/Epoxystyryl Capping Agents,” Nano Lett., 4, 779 (2004).    

E. S. Baker, J. Gidden, D. P. Fee, P.R. Kemper, S. E. Anderson, and M.T. Bowers, “3-dimensional structural characterization of cationized polyhedral oligomeric silsesquioxanes (POSS) with Styryl and phenylethyl capping agents,” Int. J. Mass Spectrom, 227, 205 (2003).

J. Gidden, P.R. Kemper, E. Shammel, D. Fee, S. E. Anderson, and M.T. Bowers, “Application of ion mobility to the gas-phase conformational analysis of polyhedral oligomeric silsesquioxanes (POSS),"  Int. J. Mass Spectrom, 222, 63 (2003). 

(website to download PDF files  requires on-line access to journals) or click on 2010b.pdf, 2010.pdf, 2008.pdf, 2006.pdf, 2005.pdf, 2004.pdf, 2003a.pdf, 2003b.pdf  for the above references or click on  1997_1.pdf, 1999_1.pdf, 1999_2.pdf, 1999_3.pdf, 2000_1.pdf, 2000_2.pdf, 2002_1.pdf, 2004_1.pdf, 2004_2.pdf, and 2004_3.pdf  for additional general polymer papers published by the Bowers group.

Stratospheric Ozone Measurements

We were involved in developing simple inexpensive instrumentation for the measurement of stratospheric ozone since 1993. The goal has been to set up a worldwide network which can monitor ozone accurately. Trends in the Santa Barbara region have been monitored for more than three years. We have been able to develop calibration procedures which ensure accurate ozone measurements. This work has been in collaboration with the inventor of the Microtops ozone spectrometers, Forrest Mims, and with Marian Morys at Solar Light Company in Philadelphia, PA.

Several Westmont students have just contributed to a publication on this subject:

M. Morys, F.  Mims  III, S. Hagerup, S. E.  Anderson, A.  Baker, J.  Kia,  and T.  Walkup, "Design, Calibration, and Performance of MICROTOPS II Handheld Ozone Monitor and Sun Photometer,"  J. Geophys. Res., 106, 14573 (2001).

(click to download manuscript PDF file)