Article
Extended Data Fig. 5 | Spectroscopic data. a, b,^1 H–^29 Si (a) and^1 H–^13 C (b)
cross-polarization magic-angle spinning NMR spectra of a 3D-printed silica
aerogel. The spectra have the typical peaks for hydrophobized silica
aerogel^43 ,^44. The^1 H–^29 Si spectrum has peaks Q^4 , Q^3 and Q^2 from silica particles,
corresponding to silicon atoms coordinated by 4, 3 and 2 bridging oxygen
atoms and 0, 1 and 2 non-bridging oxygen atoms, respectively, and a peak from
trimethylsilyl (TMS) groups grafted onto the silica surfaces. The^1 H–^13 C
spectrum has an intense peak from grafted TMS groups (63.0% of total spectral
intensity) and two strong peaks from ethoxy groups grafted onto the silica
surfaces (Et, CH 2 and Et, CH 3 with 34.5% of total spectral intensity), from the
TEOS precursor of the matrix aerogel and/or from alcoholysis during solvent
exchanges. An additional five weak peaks (P1–P5), corresponding to either
pentanol adsorbed on the surface or petanoxy groups grafted onto the silica,
together account for approximately 2.5% of the total spectral intensity. The
peaks labelled ‘ssb’ correspond to spinning sidebands. No other peaks were
detected. c, FTIR spectra of the silica aerogel particles (SAPs; red), the PPGNH
(blue) and the printed object (dashed black).