Silicon-29 NMR

Reversible Dynamic Behavior of Condensation‐Cured Silicone Elastomers Caused by a Catalyst

“…Solid‐state 29 Si‐NMR evidences higher integration of a signal at −67 ppm in E_2.5 ( Figure b) compared to E_0.5 (Figure 3a). As this signal corresponds to R‐ Si (O) 3 building units, [ 20 ] it can be correlated to the concentration of cross‐linking points. Increased cross‐link concentration could be explained by a faster curing reaction of E_2.5.…”

“…Samples were aged for 14 days before the experiment. d) 29 Si solid‐state NMR of elastomer E_S14 (SSBs (−28 and −72 ppm), remaining  Si OH (−13 ppm),  Si (CH 2 ) 3  (−22 ppm), and R‐ Si (O) 3 building units (−67 ppm) [ 20 ] ).…”

“…The elastomers were aged for 14 days to ensure a full cure [9] before the sol fractions were collected. [20] ). prior to the gelation point) was reached for the reaction mixture, and it was then spread into a thin film on a polyester carrier with a coating knife with a nominal coating height of 200 μm (resulting in dry film thickness ≈100 μm).…”

Interchange Reactions in Condensation Polymers and Their Analysis by NMR Spectroscopy

“…Although they are not completely resolved, a rough estimate of the block lengths according to Eq. (25) gives an average length of about four Nylon 6 and four Nylon 6,6 units. In the copolymer produced from an equimolar monomer blend subjected to polycondensation for 8 h at 260°C (Figure14B), the average length of each block type is of about 2.0.…”

“…The advantage of not polluting the sample is offset by an ineffective use of spectrometer time, which can be somewhat alleviated by using shorter pulses (40") and shorter recovery times (20 s). (iii) Using population transfer pulse programs [25].…”