Modeling of thermosensitive stereoregular polymers within the coarse-grained force field: Poly(N-isopropylacrylamide) as a benchmark case

Abstract

In this article, we introduce the Martini model of a widely used thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPA). Importantly, our model takes into account polymer's stereoregularity (i.e., tacticity) by defining different intramolecular potentials for meso- and racemic diads of the polymer. We highlight the effect of changing the polarity of coarse-grained particles comprising the polymer on its ability to exhibit a temperature-dependent coil-to-globule transition. Our approach allows to study the behavior of thermoresponsive polymers at large time and length scales, which is important since atomistic simulations are unable to capture a reverse globule-to-coil transition of PNIPA that is observed experimentally with decreasing temperature. Our model differs from those previously introduced as it is fully compatible with the most widespread coarse-grained force field.