Lambda 365 uv vis spectrometer

UV-Vis spectra were measured on a PerkinElmer Lambda 365 UV-Vis spectrometer using a 1 cm path length quartz cuvette. FT-IR spectra were recorded on a Nicolet iS50 FT-IR spectrometer (Nicolet, Waltham, MA, USA) using KBr pellets. ¹H NMR spectra were performed on a Bruker AVANCE AV 400 NMR spectrometer (Bruker, Basel, Switzerland). Thermogravimetric analysis (TGA) was performed on a TA Q600 (TA Instruments, New Castle, DE, USA) at a scan rate of 10 °C·min⁻¹ under nitrogen atmosphere. Gel permeation chromatography (GPC) measurements were performed on a Waters 1525 system equipped with a HT4 styragel column (40 °C) and Waters 2414 detectors (35 °C). THF was used as an eluent with an elution rate of 1.0 mL·min⁻¹. The molecular weights were calibrated with polystyrene standards. Steady-state fluorescence emission spectra were recorded on a HORIBA Jobin Yvon FluoroMax 4 spectrometer (Horiba Jobin Yvon Inc., Edison, NJ, USA) equipped with TZL-1006D low constant temperature water baths. Cloud point (T_cp), defined as the temperature for the change half of transmittance, was determined by measuring the transmittance of 0.5% aqueous solution sample at 600 nm with the heating rate of 0.5 °C·min⁻¹ (Lambda 750s UV-Vis-NIR spectrometer equipped with a PTP-1+1 Peltier heated pool rack).

For stability analysis, the turbidity of CMPs solution was monitored using a Lambda 365 UV/VIS spectrometer (PerkinElmer, USA) according to the method described by Schulte^{38 (link)} with slight modification. Briefly, 1.5 mL CMPs dispersion was added to a semi-micro cuvette (Eppendorf AG, Germany) and BisTris buffer was used as reference. The turbidity was measured at a wavelength of 600 nm, slit width of 1 nm and absorbance was recorded for 900 s. Immediately after measurement, 40 µl SDS solution (520 mM in water) was added to CMP dispersion resulting in a 13.5 mM final concentration of SDS. The cuvette was then gently moved up and down 3 times to properly mix the SDS, placed back in the spectrometer, and measured again. All samples were measured in duplicate.

For investigating the chemical stability of CMPs, the turbidity of CMP dispersions before and after the addition of sodium dodecyl sulfate (SDS) was measured at λ = 600 nm with a Lambda365 UV-VIS spectrometer from PerkinElmer, Boston, MA, USA. Two milliliters of CMPs in Bis-Tris buffer dispersion were filled into UV-Vis semi-micro cuvettes (Eppendorf AG, Hamburg, Germany) with a path length of 10 mm. For the reference sample, pure BisTris buffer solution without CMPs was used in identical cuvettes. At a wavelength of λ = 600 nm, and a gap width of 1 nm the turbidity was recorded over t = 600 s at T = RT. The turbidity was recorded once every second. After the turbidity of CMP dispersion without SDS was measured, the cuvette was taken out of the UV-Vis spectrometer and 36.6 µL of 520 mM SDS solution was added to the CMP dispersion inside the cuvette, resulting in an overall SDS concentration of 9.34 mM. The cuvette was subsequently turned upside down 2 times to ensure sufficient mixing before it was reinserted into the UV-Vis spectrometer and the measurement was started. Turbidity measurements were undertaken for CMPs that were cross-linked for t = 1 h, 4 h and 24 h and compared to CMPs without cross-linking treatment.