Silicon-29 NMR Studies of Polymethylhydrosiloxanes: Spin-Lattice Relaxation Time (T(1)) Measurements

摘要

The high structrual sensitivity of chemical shifts makes silicon-29 NMR a powerful tool for determination of the structure of oligomeric and polymeric siloxanes. Detailed information can be obtained for the characterization of the different structural units, for the determination of average chain lengths or for the degree of condensation of the siloxane framework. 29SiNMR spectra of polymethylhydrosiloxanes, MeSiO(MeHSiO)nSiMe3 from n = 3 to 8 and 35, have been determined. Both chemical shifts and spin-lattice relaxation times (T usb 1) have been measured. The stereochemistry at the adjacent chiral MeHSiO unit influences the nearest neighbor 29Si chemical shift. The effect of chain length and position of MeHSiO units on T sub 1 values for Me3SiO(MeHSiO)nSiMe3 systems are discussed.