Development of a coarse-grained model for thermoresponsive polymer

Some polymers, the so-called hydrogels, show a thermoresponsive behavior, what can be used in different applications, e.g., for drug delivery.1 At low temperatures hydrogels are hydrophilic and tend to expand in water, while at high temperature they are hydrophobic and have collapsed coil structure. Admixture of different salts changes the thermal response of hydrogels.2

In our work we study thermoresponsive behavior of poly(n-isopropylacrylamide) (PNiPAM) by Molecular Dynamics simulations. On atomistic scale we investigate structural characteristics of PNiPAM and reasons, which lead to the thermal response. Furthermore, we study an influence of presence of different salts in aqueous solution on the conformation change of the polymer as well as on the temperature of the transformation.

In order to simulate bigger systems we need to develop a coarse-grained model, which is capable of reproducing the thermoresponsive behavior of PNiPAM. On the basis of atomistic simulations we develop a coarse-grained model using Iterative Boltzmann Inversion method.3 In this approach we take water into account implicitly. A key question for all coarse-grained methods is the degree of transferability. A challenging point in our work is a development of a coarse-grained model of PNiPAM, which would reproduce its thermoresponsive behavior at different conditions.

1. Ghugare, S. V.; Mozetic, P.; Paradossi, G. Biomacromolecules 2009, 10, 1589.

2. Zhang, Y. J.; Furyk, S.; Bergbreiter, D. E.; Cremer, P. S. J. Am. Chem. Soc. 2005, 127, 14505.

3. Reith, D.; Pütz, M.; Müller-Plathe, F. J. Comput. Chem. 2003, 24, 1624.