Fig. 2: Characterization of isolated polymer stabilized ACC.

The sample was isolated from a titration experiment using 0.1 g/L PAsp at pH 9.8 by quenching the solution in ethanol (see Methods section). a ¹³C direct excitation (DE) and ¹H–¹³C cross-polarization (CP) spectra of 10% ¹³C-carbonate ACC stabilized by PAsp (PAsp_disACC) at a spinning frequency of 10 kHz. The spectra are scaled at the C_α-peak of PAsp. b TGA (red) and DSC (blue) analysis. The exothermic decomposition of the bicarbonate species is highlighted in grey. c ATR-FTIR spectra of polymer-stabilized ACC sample, showing significant amounts of polymer incorporation. Pure ACC and PAsp calcium salt (PAsp_Ca) are shown as references (detailed FTIR spectra are shown in Supplementary Fig. 6). d Normalized QMID for TGA-MS measurement on the PAsp_ACC sample using ¹³C enriched carbonates in the titrations. Due to the natural abundance of carbonate distribution in the polymer, released gases from polymer (¹²CO₂; m/z = 44, black) and from mineral (¹³CO₂; m/z = 45, red) can be distinguished, showing significant amounts of mineral decomposition below 300 °C (highlighted in grey). e TGA-IR analysis of the ¹³C carbonate enriched PAsp_ACC sample confirms the strong ¹³CO₂ release from (bi)carbonate species at around 300 °C.