Gpc system

The ¹H NMR spectra were collected using a Varian MR400 spectrometer in deuterated chloroform solution with trimethylsilane (TMS) as reference. Gel permeation chromatography (GPC) spectra were collected on a Shimadzu GPC system with THF as the solvent. The samples used for NMR and GPC measurements were fabricated on quartz and encapsulated with a cover glass similar to the OPV device. The package lids were removed after light soaking under 1 sun illumination. Laser desorption/ionization time-of-flight mass spectra were collected using a Bruker AutoFlex Speed MALDI-TOF instrument from the aged thin-film sample under nitrogen laser pulse illumination.

The molecular weight and homogeneity of the polysaccharide fractions were determined by size exclusion chromatography (HPSEC) with light scattering (ELSD) detection according to the procedure reported by Cheong et al. (2015) [77 (link)], with modifications. The GPC system (Shimadzu) is equipped with two HPLC pumps (Shimadzu), the GPC TSKgel SuperMultipore PW-H column, 6.0 ID × 150 mm, (TOSOH Bioscience), Guard SuperMP PW-H 4.6 mm ID × 35 mm (TOSOH Bioscience), column oven (Shimadzu) and evaporator lamp–scattering detector (ELSD LTII). Deionized water was used as the mobile phase. Column and detector temperatures were 40 °C and 50 °C, respectively, and the flow rate and injection volume were 0.4 mL/min and 20 µL, respectively. The β-glucan standards (40 kDa, 123 kDa, 183 kDa, 245 kDa, 359 kDa, Megazyme, Ireland and 500 kDa, Boc Sciences, New York USA) and α-glucan standards (401 kDa, 277 kDa, 196 kDa, 124 kDa, 43.5 kDa, 21.4 kDa, 9.9 kDa, 4.4 kDa, PSS Polymer Standards Service Gmbh) were used to plot a calibration curve. A calibration curve was plotted as the correlation between the retention time and the molecular weight (Mp) of the standards.

PBLA was synthesized via ring-opening polymerization of BLA-NCA initiated by the primary amino group of n-butylamine as reported previously [14]. Briefly, BLA-NCA (1.35 g, 5.42 mmol) was mixed with n-butylamine (4.87 μL, 49.3 μmol) as an initiator in the solution containing a mixture of distilled CH₂Cl₂ and distilled DMF. This solution was continuously stirred at 35 °C for 3 days. The completion of polymerization was confirmed based on the disappearance of peaks in the infrared (IR) spectrum corresponding to the carboxylic anhydride group of NCA in an IR Report-100 instrument (JASCO Corporation, Tokyo, Japan). The reaction mixture was poured into a large amount of diethyl ether to precipitate PBLA, and was followed by vacuum-drying. The molecular weight distribution (M_w/M_n) of PBLA was analyzed by size exclusion chromatography (SEC) (GPC system, Shimadzu Corporation, Kyoto, Japan) using a TSKgel column (SuperAW4000). NMP with 50 mM LiBr was used as an eluent (Figure S1(a)). The degree of polymerization (DP) of PBLA was determined based on the peak intensity ratio of methyl protons in the initiator (CH₃CH₂–, δ = 0.8) to benzyl protons (C₆H₅CH₂–, δ = 7.3) in the proton nuclear magnetic resonance (¹H NMR) spectrum (JNM-ECS 400, JEOL Resonance Inc., Tokyo, Japan) (Figure S1(b)).

Molecular weight and molecular weight distribution were measured using gel permeation chromatography (GPC) system (Shimadzu, Kyoto, Japan). The GPC system consisted of a solvent delivery unit, reflective index detector, and three types of Styragel columns: HT 6E (10 µm, 7.8 mm × 300 mm), HMW 7 column (15–20 µm, 7.8 mm × 300 mm), and HMW 6E column (15–20 µm 7.8 mm × 300 mm). Further, the measured molecular weight was corrected using a polystyrene standard sample (EasiCal PS-1 standard, Agilent Technologies, Santa Clara, CA, USA).

The molecular weight and the molecular weight distribution were measured using a gel permeation chromatography (GPC) system (Shimadzu, Kyoto, Japan). The GPC system consisted of a solvent delivery unit, a refractive index detector, and three types of Styragel columns: HT 6E (10 µm, 7.8 mm × 300 mm), HMW 7 column (15–20 μm, 7.8 mm × 300 mm), and HMW 6E column (15–20 μm, 7.8 mm × 300 mm). The measured molecular weight was corrected using a polystyrene standard sample (Easi Cal PS-1 standard, Agilent Technologies, Santa Clara, CA, USA).