Senterra spectrometer

The morphology of samples was characterized by SEM (JEOL JSM-2100, JSM-7800F, Japan), TEM (JEOL JEM-2100, Japan) and optical microscope (Keyence VHX-5000, Japan). The Raman spectra were recorded on a Bruker Senterra spectrometer (Germany). The SAXS patterns were recorded on an Antonparr Saxes M2 scattering system (Austria). The unit-cell parameters were calculated from the equation of a₀ = 2d₁₀₀/√3. The XPS measurement was conducted on a Thermo Fisher ESCALAB 250Xi spectrometer (USA) using Al Kα radiation (15 kV, 10.8 mA). The thermogravimetric analysis (TGA, Netzsch STA 449 F3) was performed from 40 to 900 °C with a heating rate of 10 °C min⁻¹ under air atmosphere. The nitrogen adsorption/desorption isotherms were measured on a QuantaChrome Quadrasorb SI analyzer (USA) after vacuum degassing at 120 °C for 6 h. The specific surface areas and the pore volumes were calculated using the Brunauer–Emmett–Teller (BET) method. The pore size distributions were obtained from the adsorption branches of the isotherms using Barrett–Joyner–Halenda (BJH) model. The microporous specific surface areas and pore volumes were analyzed using t-plot method. The elemental analysis (C, N and H) of samples was carried out using an Elementar Vario EL III analyzer (Germany).

The Raman spectra were measured using a Bruker Senterra spectrometer operated in backscattering mode at ambient conditions. The utilized wavelength of 532 nm was obtained from a frequency-doubled Nd:YAG laser. A 50× objective and a thermoelectrically cooled CCD detector (−65 °C) were used. The spectral resolution of the system is 2–3 cm⁻¹.

Raman spectroscopy measurements were obtained from a composition comprising 30 ​nL SAP, 60 ​nL PEGMA, 10 ​nL DMAEMA, and 30 nLl PEGDMA (5 ​mol%) with a Bruker Senterra spectrometer (Bruker Optics, Germany). For focusing of the excitation laser and collimation of backscattered light an Olympus MPLAN 20 ​× ​objective (NA 0.4) was used, resulting in a spot diameter of 5 μm on the sample surface. The excitation laser (λ ​= ​532 ​nm) was operated at 10 ​mW output power. Each spectrum was integrated over 60 ​s with three coadditions (3 ​× ​20 ​s). The total number of measurement spots per hydrogel micropad was 144, arranged in a 12 ​× ​12 matrix (Fig. S4).

The Raman spectra were obtained using a Bruker SENTERRA spectrometer, solid state laser excitation operating at a wavelength of 785 nm and a CCD detector. The measurements were made with resolution of 3–5 cm⁻¹, aperture of 25 × 1000 μm and over a spectral range of 1780 to 390 cm⁻¹. The laser power at the exit of the laser was 50 mW and 10 accumulations were made with an acquisition time of 50 s each. These parameters were previously adjusted to obtain the best signal-to-noise ratio without altering the physical and chemical integrity of the samples. The spectra obtained were treated with OPUS 7.0 and Origin 8 software from Bruker and a baseline correction was applied.
SEM measurements were performed in a scanning electron microscope combined with an Energy dispersive X-ray spectroscopy (EDS) Hitachi model TM 3000 compact instrument, with a smoothing magnification of 15x up to 30,000x (digital zoom: 2x and 4x), which allows topographic images to be obtained with a large depth of focus. No sample preparation was required for the analyses, and each one of the samples were fixed in a specific metallic sampler from the SEM equipment.