Inhomogeneities in PNIPAM Aqueous Solutions: The Inside View by Spin Probe EPR Spectroscopy.

Ekaterina M Zubanova Sergei V Kostjuk Vladimir I YusupovYury A RochevAlexander I KokorinMikhail Ya MelnikovElena N Golubeva

Published in: Polymers (2021)

Coil to globule transition in poly(N-isopropylacrylamide) aqueous solutions was studied using spin probe continuous-wave electronic paramagnetic resonance (CW EPR) spectroscopy with an amphiphilic TEMPO radical as a guest molecule. Using Cu(II) ions as the "quencher" for fast-moving radicals in the liquid phase allowed obtaining the individual spectra of TEMPO radicals in polymer globule and observing inhomogeneities in solutions before globule collapsing. EPR spectra simulations confirm the formation of molten globules at the first step with further collapsing and water molecules coming out of the globule, making it denser.

Keyphrases

single molecule
density functional theory
living cells
quantum dots
molecular dynamics
high resolution
room temperature
solid state
ionic liquid
energy transfer
transition metal
monte carlo
metal organic framework