Poly(ethylene glycol) of 2050 Da, poly(propylene glycol) of 2000 Da, poly(ε-caprolactone)-diol of 2000 Da, hexamethylene diisocyanate (HMDI) 99%, dibutyltin dilaurate 95% were purchased from Sigma Aldrich and used as received without further purification. Anhydrous toluene and anhydrous diethyl ether are sourced from TEDIA. Toluene was further dried and stored over pre-activated 4 Å molecular sieves.
Gel permeation chromatography (GPC) was conducted on a Viscotek TDAmax which consists of three components – the GPCmax integrated solvent and sample delivery module, the TDA 302 Triple Detector Array, and the OmniSEC software. The TDA 302 array incorporates refractive index (RI) and light scattering detectors as well as a viscometer. 2 columns (2 × PLgel 10 μm mixed-B (500 to 10 000 000)) were applied in sequence for separation. THF was used as the eluent at 1.0 ml min−1 with column and detector temperature at 40 °C. Polystyrene standard (Mw 21 960, dn/dc = 0.185, IV = 0.1471, PDI = 1.02) was used for the multi-detector calibration to calibrate the detector constants. Samples' concentration was input to determine their dn/dc and Mw. 1H nuclear magnetic resonance (NMR) spectra were recorded using a JEOL 500 MHz NMR spectrometer (Tokyo, Japan) at room temperature.
Gel permeation chromatography (GPC) was conducted on a Viscotek TDAmax which consists of three components – the GPCmax integrated solvent and sample delivery module, the TDA 302 Triple Detector Array, and the OmniSEC software. The TDA 302 array incorporates refractive index (RI) and light scattering detectors as well as a viscometer. 2 columns (2 × PLgel 10 μm mixed-B (500 to 10 000 000)) were applied in sequence for separation. THF was used as the eluent at 1.0 ml min−1 with column and detector temperature at 40 °C. Polystyrene standard (Mw 21 960, dn/dc = 0.185, IV = 0.1471, PDI = 1.02) was used for the multi-detector calibration to calibrate the detector constants. Samples' concentration was input to determine their dn/dc and Mw. 1H nuclear magnetic resonance (NMR) spectra were recorded using a JEOL 500 MHz NMR spectrometer (Tokyo, Japan) at room temperature.