Impact of the Environment on the PNIPAM Dynamical Transition Probed by Elastic Neutron Scattering

By means of elastic incoherent neutron scattering, we investigated how the addition of stabilizing cosolvents (glycerol and glucose) affects the dynamics of hydrated PNIPAM chains at the pico- and nanosecond time scale, where a low-temperature dynamical transition is observed. From the elastic intensities, the atomic mean square displacements of the PNIPAM samples were extracted using a global fitting procedure. Both the dynamical transition temperature Td and the amplitude of the displacements are found to be strongly dependent on solvent composition. The close analogies between the dynamical transition of PNIPAM and that of biomolecules reveal PNIPAM as an excellent system for reproducing complex solvent-biopolymer interactions.