Pressure-Dependence of Poly(N-isopropyl acrylamide) Mesoglobule Formation in Aqueous Solution

Above their cloud point, aqueous solutions of the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAM) form large mesoglobules. We have carried out very small-angle neutron scattering (VSANS) and Raman spectroscopy experiments on a 3 wt% PNIPAM solution in D₂O at atmospheric and elevated pressures (up to 113 MPa) ¹. Raman spectroscopy reveals that, at high pressure, the polymer is less dehydrated upon crossing the cloud point. VSANS demonstrates that the mesoglobules are significantly larger and contain more D₂O than at atmospheric pressure. We conclude that the size of the mesoglobules and thus their growth process are closely related to the hydration state of PNIPAM.

[1] ACS Macro Lett. 2017, 6, 1180−1185