Fig. 3 gives the phase diagram of four ATP systems with different
phase-formingmaterials including PEG, I-PEG, C-PEG and [Bmim]Br
at pH 7. The dot lines refer to the tie line of ATP systems. It is found
that the phase-separation in I-PEG ATP is easier than that of PEG.
This observation could be attributed to the hydrophobicity of imidazole
ring at neutral pH [30] (exact analogy is N-alkylimidazole,
which has a similar N-substituted group as imidazole-terminal
PEG), which decreases the compatibility of I-PEG with water and
facilitates its phase separation into ATP. On the contrary, the phaseseparation
of C-PEG ATP is postponed due to the hydrophilic nature
of carboxylic acid terminals. The phase separation of [Bmim]Br ATP
is much difficult comparing with other polymer systems due to the
extreme hydrophilic nature of [Bmim]Br [20,26].