Coil–Globule Transition Thermodynamics of Poly(N-isopropylacrylamide)

• DOI: 10.1021/acs.jpcb.9b06125
• Publication Date: 2019-09-23T15:48:44Z
• Authors: Maren Podewitz; Yin Wang; Patrick K. Quoika; Johannes R. Loeffler; Michael Schauperl; Klaus R. Liedl
• Keywords: Poly(N-isopropylacrylamide); Metadynamics; Random coil

Thermosensitive polymers such as poly(N-isopropylacrylamide) (PNIPAM) undergo a phase transition in aqueous solution from random-coil structural ensemble to globule at the lower critical temperature (LCST). Above this temperature, PNIPAM agglomerates and becomes insoluble, whereas it is soluble below temperature. Thus, thermosensitive represent essential targets for several applications, e.g., drug delivery. Although their ability change structure response alteration highly relevant industrial processes, thermodynamic properties are mostly qualitatively understood, quantitative picture still elusive. In study, we used combined atomistic molecular dynamics well-tempered metadynamics simulation approach estimate coil–globule thermodynamics. An isotactic 30-mer of was investigated over broad range between 200 360 K. The observed with metadynamics. For first time, free energy surface estimated shown that results line experimentally behavior. Below LCST, represents global minimum thermodynamically favored by 21 ± 9 kJ/mol compared ensemble; both separated barrier 49 14 kJ/mol. contrast, above 8 ensemble. 17 10