270 dual detector

GPC (Malvern Instruments) was used to determine the molecular weight distribution of the synthesized copolymers. Analysis was performed on each sample using a 100 μL injection into a single Viscotek D6000M column and a 270 Dual Detector with right angle light scattering with DMF as the system solvent. The column and detector temperatures were kept constant at 45 °C. The instrument was calibrated with polystyrene standards (MW of 105000, dn/dc of 0.185 mL/g).

Triple-detection gel permeation chromatography (GPC; Viscotek) with differential refractive index (RI, Viscotek VE 3580), viscosity and light scattering detectors (Viscotek 270 dual detector) was used for the analysis of nanogel molecular weight, polydispersity index (PDI) and average hydrodynamic radius (R_h).
Ellman’s test was employed to determine the concentration of pendant thiol functionality in the nanogels: nanogels in tetrahydrofuran (THF) solution were mixed with Ellman’s reagent solution with N,N-diisopropylethylamine (DIPEA) as catalyst. After stirring for 15 min, ultraviolet–visible spectroscopy (Thermo-Fischer Scientific) was used to obtain the absorption peak at 412 nm, and by comparing with the standard curve, thiol functionality concentration of nanogels can be determined.
A rheometer (TA ARES) was used to measure the viscosity of the bulk liquid nanogels between 20 mm diameter plates from shear rate sweeps. Three replicates were conducted for each nanogel. The solvent swollen particle size of nanogels were determined by dynamic light scattering (DLS) using a Zetasizer NanoZS (ZEN 3600, Malvern). Separate measurements were made in DCM and THF. All measurements were performed three times on 0.5 mg mL⁻¹ of solutions in quartz cuvettes.

PDA-PEG-PNiPMA polymer was synthesized by free radical polymerization as shown in Figure 1A. PDA monomer was prepared following our previously reported method [14 (link)]. Typically, PDA (241.3 mg, 1 mmol), Poly(ethylene glycol)methacrylate (Mn = 360 Da) (360 mg, 1 mmol) and N-isopropylmethacrylamide (NiPMA, 63.6 mg, 0.5 mmol) were dissolved in 10 mL degassed anisole. 2, 2-azobisisobutyronitrile (AIBN, 14 mg, 0.085 mmol) in 1 mL degassed anisole was then added, and the reaction mixture was stirred for 24 hours at 65 °C. The final product was precipitated (3×) in ice cold ether and dried for 48 hours in vacuum. The structure of PDA-PEG-PNiPMA was confirmed by ¹H-NMR (Figure S1A). Gel permeation chromatography (viscotek GPCmax VE 2001 GPC solvent/sample module, Viscotek VE 3580 RI detector and 270 Dual Detector) using THF as mobile phase was empolyed to charactrize the polymer and found PDA-PEG-PNiPMA has an absolute molecular weight of 27,557 Da (Mw) and polydispersity (PDI: 1.35) (Figure S1B). For the quantification of side chain functionality, PDA-PEG-PNiPMA (1.0 mg/mL) was dissolved in DMSO and incubated with dithiothreitol (DTT, 10 mM) for 1 hour at room temperature, and then the amount of 2-pyridinethione released was quantified through UV-Vis spectrophotometer at λ = 375 nm (ε, molar absorption coefficient = 8080 M⁻¹cm⁻¹).