Fig. 3: Isothermal titration calorimetry (ITC) measurement for the association between PNIPAm and polymeric membrane.
a Endothermic titration thermograms integrated from titrating PNIAPm into 2.5 mM polymeric vesicle solutions at 25 ˚C, 34 ˚C, and when 10 mM NaNO3 was added into the two groups. b ΔG, ΔH and –TΔS from ITC measurements of the 4 groups. c Binding affinity (Kd) and binding sites (N) from ITC measurements, error bars indicate the errors of integrated heats and estimated Kd. d Illustration for the possible interaction between PEG corona (blue) and PNIPAm (purple), PNIPAm is inserted between PEG chains by hydrophobic effect. e The hydrophobic hydration of the PNIPAm is associated with surface tension and can be modulated by anions; Anions can bind to the amide group of PNIPAm directly; NO3- can destabilize hydrogen bonding between the ester oxygen and water molecules through polarization. f Schematic representation of PNIPAm polymeric membrane interactions with the presence of salt, salt slightly salted out PNIPAm, assisted the hydrophobic association between PNIPAm and polymersomes while increasing temperature (top), addition of organic solvent would also turn PNIPAm to hydrophobic and result in the same hydrophobic association as temperature increasing.
