Tskgel α 4000

SEC was performed out on an HLC-8120 system (Tosoh, Tokyo, Japan) equipped with a combination of TSKgel AW-4000 and AW-2500 columns (150 mm × 6 mm ID) (Tosoh), eluted with dimethylsulfoxide (DMSO) containing 10 mM LiBr at a flow rate of 0.15 mL/min at 65 °C. The polydispersity index (M_w/M_n) was calculated from a calibration curve of standard PEGs (Agilent Technologies, Wilmington, DE, USA). For SEC with fluorescence detection, the measurements were performed on a Gulliver system (Jasco, Tokyo, Japan) consisting of a DG-2080–53 degasser (Jasco), a PU-980 pump (Jasco), an AU-950 autosampler (Jasco), a CO-965 column oven (Jasco), an FP-920 fluorescence detector (excitation wavelength: 488 nm, emission wavelength: 515 nm) (Jasco), an RI-2031 Plus refractive index detector (Jasco), and a combination of TSKgel α-4000 and TSKgel α-2500 columns (300 mm × 7.8 mm ID) (Tosoh). The solutions (50 μL) were injected into the SEC system, and the system was eluted with a mixture of water and DMSO (volume ratio 50:50) at a flow rate of 0.3 mL/min at 40 °C. ¹H NMR spectra were recorded on a Bruker Avance III 500 MHz spectrometer (Bruker BioSpin, Rheinstetten, Germany). FTIR spectra were recorded on a Spectrum 100 FTIR spectrometer (Perkin Elmer, Wellesley, MA, USA). The sample powder was mixed with KBr and pellets were prepared for FTIR measurements.

¹H nuclear magnetic resonance (NMR) spectra were recorded using a Bruker Avance III 400 MHz spectrometer (Bruker BioSpin, Rheinstetten, Germany) in dimethyl sulfoxide (DMSO)-d₆ and D₂O at 25 °C. The chemical shifts in ¹H NMR spectra were referenced to DMSO (2.5 ppm in DMSO-d₆) and HDO (4.65 ppm in D₂O). Size exclusion chromatography (SEC) was performed using a Prominence-i LC-2030 Plus system (Shimadzu, Kyoto, Japan) equipped with an RID-20A refractive index detector and a combination of TSKgel α-4000 and α-2500 columns (300 mm length, 7.8 mm internal diameter; Tosoh, Tokyo, Japan). Sample solutions were injected into the system and eluted with DMSO containing 10 mM LiBr at a flow rate of 0.35 mL/min at 60 °C. The UV–vis absorption of the solutions was measured using a V-550 UV–vis spectrophotometer (Jasco, Tokyo, Japan). Fourier-transform infrared (FT-IR) spectra were recorded using a Spectrum 100 FTIR spectrometer (Perkin Elmer, Wellesley, MA, USA) equipped with a HgCdTe (MCT) detector. The sample powders were ground with KBr to prepare the pellets for analysis.

¹H nuclear magnetic resonance (NMR) spectra were recorded using a Bruker Avance III 400 MHz spectrometer (Bruker BioSpin, Rheinstetten, Germany) in DMSO-d₆ and D₂O at 25°C. Chemical shifts in ¹H NMR spectra were referenced using DMSO (2.5 ppm in DMSO-d₆) and HDO (4.65 ppm in D₂O). Size exclusion chromatography (SEC) was performed using a Prominence-i LC-2030 Plus system (Shimadzu, Kyoto, Japan) equipped with an RID-20A refractive index detector and a combination of TSKgel α-4000 and α-2500 columns (300 mm length, 7.8 mm internal diameter; Tosoh, Tokyo, Japan). Sample solutions were injected into the system and eluted with DMSO containing 10 mM LiBr at a flow rate of 0.35 mL/min at 60°C. Fourier-transform infrared (FT-IR) spectra were recorded using a Spectrum 100 FTIR spectrometer (Perkin Elmer, Wellesley, MA, USA) equipped with an HgCdTe (MCT) detector. The sample powders were ground with KBr for preparing pellets for the analysis.