Poly(N-isoproylacrylamide) (PNIPAM) is a synthetic polymer which has attracted considerable attention in the last years due to its responsive behavior. Indeed, its capability to reversibly respond to external stimuli, such as temperature, makes it a promising candidate to design smart materials with targeted functions.
In addition to temperature, pressure can also promote phase separation of PNIPAM in aqueous solution, but its role has been much less investigated so far. In this talk I will report a comprehensive molecular investigation of PNIPAM phase diagram obtained through extensive all-atom molecular dynamics simulations . By analyzing the solution behavior of an atactic polymer chain at infinite dilution in a wide range of temperatures and pressures, I will show that both temperature and pressure induce a conformational transition of PNIPAM, but through different molecular mechanisms.
Moreover, I will provide a description of the reentrant behavior of the coil-to-globule transition with increasing pressure, showing the presence of two different shrunken states at low and high pressures, in full qualitative agreement with experimental observations [2,3]. Overall, this work highlights the non-trivial interplay between temperature and pressure, which, when combined together, give rise to unexpected behaviors.
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