Pe 2400 chn elemental analyzer

Melting points were measured with a Stuart apparatus (Bibby Scientific Limited, Staffordshire, United Kingdom) and were uncorrected. The NMR spectra were recorded by Varian Gemini-300BB 300 MHz FT-NMR spectrometers (Varian Inc., Palo Alto, CA, USA). ¹H and ¹³C spectra were run at 300 and 75 MHz, respectively, in deuterated dimethyl sulfoxide (DMSO-d₆). Chemical shifts (δ_H) are reported relative to TMS as internal standard. All coupling constant (J) values are given in hertz. Chemical shifts (δ_C) are reported relative to DMSO-d₆ as internal standards. The abbreviations used are as follows: s, singlet; d, doublet; m, multiplet. Microanalyses were carried out using Perkin Elmer PE 2400 CHN Elemental Analyzer (Akron, OH, USA) and the results were within ±0.4%. Analytical thin layer chromatography (TLC) on silica gel plates containing UV indicator was employed routinely to follow the course of reactions and to check the purity of products. All reagents and solvents were purified and dried by standard techniques.

IBD hydrogel-modified silica beads were probed by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and zeta potential. The compositions of modified silica beads were determined by elemental analysis (PE2400 CHN elemental analyzer, PerkinElmer, Waltham, MA, USA), and attenuated total reflection FTIR spectra (FTIR-4700; Jasco, Tokyo, Japan) were recorded to confirm bead modification with each IBD hydrogel. Field-emission scanning electron microscopy (S4700, Hitachi High Technologies, Tokyo, Japan) was used to observe the surface morphology of IB5D5 hydrogel-modified silica beads. The zeta potentials of IB5D0, IB5D1, and IB5D5 hydrogel-modified silica beads were measured by laser Doppler velocimetry using a capillary cell (Zetasizer nanoZS, Malvern Instruments, Malvern, UK) to probe the electrostatic properties due to the presence of DMAPAAm. Detailed procedures for elemental analysis and zeta potential were described in Electronic Supplementary Material (ESM).