Azobis(isobutyronitrile)

Poly(allyl
glycidyl ether) [poly(AGE)] and poly(allyl glycidyl ether-stat-ethylene oxide)s [poly(AGE-stat-EO)s]
were synthesized by using oxyanionic ring-opening copolymerization
of ethylene oxide (EO) and allyl glycidyl ether (AGE) according to
a previously reported procedure.^{52 (link)} Polymerizations
were initiated with commercial potassium tert-butoxide
solution in tetrahydrofuran (1 M in THF)^{53 (link)} to afford polymers of number-average degree of polymerization (N_n) = 200 ± 10% and containing mole fractions
AGE of 0.10, 0.30, 0.54, 0.72, or 1.0 (f_AGE). Crude polymerization mixtures were precipitated into cold hexanes
(−78 °C); the purified polymers were dried under high
vacuum and stored in a −78 °C freezer. Postpolymerization
modification by thiol–ene click chemistry was performed by
using azobis(isobutyronitrile) (AIBN) (0.7 equiv per mole of alkene)
and either cysteamine hydrochloride (20 equiv per mole of alkene)
or sodium 3-mercapto-1-propanesulfonate (10 equiv per mole of
alkene) in a degassed solution of 5/1 dimethylformamide (DMF)/water
(H₂O) or 3/1 DMF/H₂O, respectively, at 80 °C.
Upon full consumption of alkenes, the (co)PEs were purified by dialysis
in snakeskin tubing (MWCO = 3.5 kg/mol, eight cycles) against 4 L
of Milli-Q water (or Milli-Q water acidified to pH 3–4 for
polycations), concentrated in Amicon-15 tubes [MWCO = 3 or 10 kg/mol,
depending on (co)PE number-average molar mass (M_n)], filtered through 0.22 μm polyethersulfone membranes,
and lyophilized. All neutral polymers were characterized by proton
(¹H) nuclear magnetic resonance (NMR) spectroscopy to establish M_n by end-group analysis, and a size exclusion
chromatograph (SEC) equipped with a refractive index detector was
used to determine neutral (co)polymer dispersity (Đ) by using 0.01 M sodium bromide in DMF as eluent (Figures S1 and S2). Neat (co)PEs were characterized by ¹H and carbon (¹³C) NMR spectroscopy (Figures S3–S6).