All-atom REMD simulation of poly-N-isopropylacrylamide thermodynamics in water: a model with a distinct 2-state behavior

Understand

Poly-N-isopropylacrylamide (PNIPAM) is a thermoresponsive polymer, an essential building block of a large family of soft smart materials.

• In neat water it undergoes upon heating at $\approx$305K a phase transition from swollen to collapsed state.
• This interesting polymer behavior has been subject to a large number of computer modelling studies, mostly described with original OPLS force field suggested in the first works, where qualitatively correct behavior was observed.
• Nevertheless, employing converged replica exchange molecular dynamics simulations, we have shown on PNIPAM 30mer that this widely used force-field can not describe the phase transition thermodynamics.