I used deuterated trifluoroacetic acid, CF3COOD,  for both 1H and 13C NMR of poly(ester-siloxanes) based on PBT and PDMS, as well as for PBT homopolymer. CF3COOD was used as a solvent and an internal standard. The results were quite good. Good luck!

Here is an article.

Article Synthesis and characterization of thermoplastic poly(ester–siloxane)s

Thanks so much, is it possible to use CF3COOH as solvent for C13 NMR? I searched and no lab provided CF3COOD as NMR solvent

Try Sigma-Aldrich link.

http://www.sigmaaldrich.com/catalog/product/aldrich/152005?lang=en®ion=BA

Oh thanks so much

We used mixtures of deuterated trifluoracetic acid and CDCl3 = 30/70 (w/w)