Control SPI and UA-modified SPI slurries were freeze-dried and ground into fine powders for IR analysis. The IR spectra
were recorded by a PerkinElmer Spectrum 100 FTIR spectrome-ter (Waltham, MA) in the MID-IR range (4000–600cm−1
) with a Universal ATR (attenuated total reflectance) sampling device. Each sample was scanned 32 times at a resolution of 2cm−1