Phenogel column

The number-average molecular weight (M_n) and dispersity (Đ). of each polymer were characterized by both matrix-assisted laser desorption ionization (MALDI) mass spectroscopy (AB SCIEX TOF/TOF 5800) and size exclusion chromatography (SEC) (Phenogel columns, Phenomenex) with a multiangle laser light scattering detector (Wyatt DAWN). Polymer compositions (w_PEO) were determined on the basis of the mole fraction obtained by ¹H NMR spectroscopy (Bruker AV-500). MALDI samples were prepared by mixing a polymer solution (1 mg/mL in THF, 0.1 mL) with a matrix solution of CHCA (20 mg/mL in THF, 0.2 mL) and a salt solution of AgTFA (1 mg/mL in THF, 5 μL). Sample solutions of 10 mg/mL polymers in THF were prepared for SEC measurements, using THF as the mobile phase at a flow rate of 1 mL/min. The refractive index increment (dn/dc) for each polymer was estimated from the weight average of PPO (dn/dc = 0.087 mL/g) and PEO (dn/dc = 0.068 mL/g).^{56 ,57 1}H NMR samples were prepared as 10 mg/mL polymers in CDCl₃. Table 1 summarizes the number-average molecular weight M_n, dispersity Đ, weight fraction of PEO w_PEO, and the corresponding average number of repeat units of PO (N_PO) and EO (N_EO). These data were also reported in our previous study.^{25 (link)}

Polymer molecular weight (M_w and M_n) and polydispersity (Đ) were measured by GPC using an Agilent 1260 Infinity II. Polymer samples were eluted through a Phenomenex 5.0 μm guard column (50 × 7.5 mm) preceded by two Phenomenex Phenogel columns (10⁴ and 10³ Å). GPC calibration was completed with Agilent PMMA standards. Polymers were prepared at 50:1 eluent/polymer ratio in DMF and filtered with a 0.45 μm PTFE filter. Polymer conversion was calculated by obtaining ¹H NMR spectra using a Varian VNMRS 500 MHz spectrometer with mesitylene as an internal standard and processed using Mestrenova 11.0.4.

SEC was carried out with dimethylformamide (DMF) with LiBr as the eluent. A Phenomenex 5.0 μm guard column (50 × 7.5 mm) preceded two Phenomenex Phenogel columns (10⁴ and 10³ Å). In series with the columns were the Agilent 1200 Series differential refractive index (RI) detector, Agilent UV detector, and a Wyatt Technology miniDAWN TREOS MALS detector. Calibration of the SEC and normalization of the MALS detector was completed with Agilent PEO standards without correction. Polymers were prepared at 2 mg/mL in DMF and filtered with a 0.45 μm PTFE filter.