We are working on a project to characterize the structure of
silsesquioxanes,
which are the resins of Si containing polymers with very complicated
(ladder or cage) structure. Although 1D NMR (29Si, 13C and 1H) has been
used extensively to identify the functionalities, we think the 2D
(especially
13C-29Si or O17-Si29 correlation experiments) would provide us
some unprecedented information on the connectivities, as well as unit
structure, therefore giving us better understanding of the materials.
To build up the knowledge, we started with some model compounds. Here
is the one with known (Me)3SiO(Me)2SiO(Me)2SiO(Me)2SiOSiVi(Me)2
structure. As you can imagine, there are five well separated resonances in
Si29 spectra. We also acquired an nice O-17 NMR spectrum (natural abundance)
within a couple of hours, three peaks with the ratio 2:1:1 for four oxygens,
but we don’t know which is which, especially for the later two.
I am wondering if someone out there could help to run an O-17 - Si29 2D
correlation NMR, since we don’t have that capability in house. If it is
successful, we are looking forward to launching a collaboration project
with you to work on much more complicated model or even resin compounds.
Any other suggestions on how to tackle this kind of problems are highly
appreciated.
I know you may read this message after the July 4th break. Hope you have
had a wonderful time off. For those who read it before the July 4th, Have
a great Holiday!
Regards,
Sanlin Hu
Dow Corning Corporation
NMR Lab, Analytical Sciences
(517) 496-8526 (o)