Solid-state ¹³ C, ¹⁵ N and ²⁹ Si NMR characterization of block copolymers with CO₂ capture properties

Natural abundance solid-state multinuclear (¹³ C, ¹⁵ N and ²⁹ Si) cross-polarization magic-angle-spinning NMR was used to study structures of three block copolymers based on polyamide and dimethylsiloxane and two polyamides, one of which including ferrocene in its structure. Assignment of most of the resonance lines in ¹³ C, ¹⁵ N and ²⁹ Si cross-polarization magic-angle-spinning NMR spectra were suggested. A comparative analysis of ¹³ C isotropic chemical shifts of polyamides with and without ferrocene has revealed a systematic shift towards higher δ -values (de-shielding) explained as the incorporation of paramagnetic ferrocene into the polyamide backbone. In addition, the ¹³ C NMR resonance lines for ferrocene-based polyamide were significantly broadened, because of paramagnetic effects from ferrocene incorporated in the structure of this polyamide polymer. Single resonance lines with chemical shifts ranging from 88.1 to 91.5 ppm were observed for ¹⁵ N sites in all of studied polyamide samples. ²⁹ Si chemical shifts were found to be around -22.4 ppm in polydimethylsiloxane samples that falls in the range of chemical shifts for alkylsiloxane compounds. The CO₂ capture performance of polyamide-dimethylsiloxane-based block copolymers was measured as a function of temperature and pressure. The data revealed that these polymeric materials have potential to uptake CO₂ (up to 9.6 cm³  g^-1 ) at ambient pressures and in the temperature interval 30-40 °C. Copyright © 2016 John Wiley & Sons, Ltd.