Table S1.

Total free-energy cost $\mathrm{\Delta }{\mu }^{bulk}$ (with respect to the bulk solution reference) for inserting single water molecules in the first solvation shell of the PS₂₀ in pure water, 1 M TMAO, and 7 M urea (in kilocalories per mole), and average number of water molecules in the polymer first hydration shell $N_k$

System	$\mathrm{\Delta }{\mu }^{bulk}$	$\langle N_k\rangle$
Pure Water
Collapsed	−0.16(0.01)	167.57
Extended	−0.14(0.01)	230.6
TMAO
Collapsed	−0.09(0.01)	144.0
Extended	−0.08(0.04)	217.0
Urea
Collapsed	−0.14(0.04)	106.2
Extended	−0.10(0.03)	150.0

SDs are given within parentheses.