Heleos 2 multi angle laser light scattering detector

Number-average molecular weight (M n) and polydispersity index (M w/M n) of the PLA was determined using gel permeation chromathography with multi-angle light scattering method (GPC-MALS). An instrumental setup included Agilent HPLC 1100 Series instrument with degasser, pump, autosampler, set of two PLgel 5 μm Mixed-C 300 × 7.5 mm columns (Agilent, USA) thermostated to 25 °C and UV-VIS diode array detector in connection with a DAWN HELEOS II multi-angle laser light scattering detector, ViscoStar-II differential viscometer and Optilab T-rEX refractive index detectors (Wyatt Technology, Germany). Both MALS and RI detectors operated at 658 nm. Tetrahydrofurane was used as the mobile phase at a flow rate of 1 mL/min. Sample in THF (concentration 1 mg/mL) was filtered with 0.22 μm filter and injected in the volume of 100 μL. Astra 6.1 software was used for data collection and analysis and Agilent software was used to control the HPLC. The specific refractive increment dn/dc equal to 0.049 for PLA was used for data processing. The specific refractive index values of polylactide were confirmed by a 100% mass recovery.

HPG (1 kDa) was routinely synthesized in our laboratory by using a simple procedure of anionic ring opening multibranching polymerization as described previously.²⁵, ²⁶ The HPG polymer was purified by acetone precipitation and dialysis with deionized water. The chemical structure of the synthesized HPG was characterized by proton nuclear magnetic resonance (NMR) and ¹³C NMR analysis as described previously (Figure S1).²⁰ By using gel permeation chromatography using a Waters 2695 Separations module (Waters Co., Milford, MA) and a DAWN HELEOS II multiangle laser light scattering detector coupled with Optilab T‐rEX refractive index detector (Wyatt Technology, Santa Barbara, CA), the average M_w (g/mol) of the HPG polymer was 820, and polydispersity index (M_w/M_n) was 1.34.²⁵ Also the M_w (M_n = 937) was further confirmed based on the proton NMR integration data from the spectra of a Bruker Avance 300 MHz NMR spectrometer (Bruker Ltd., Milton, ON, Canada).²⁵ The hydrodynamic radius of the HPG was 1.0 nm that was confirmed by using the pulsed‐field gradient NMR.²⁵