Effect of Graphene and Graphene Oxide on the LCST of PNIPAM

Poly(N-isopropylacrylamide) (PNIPAM) is a thermo-sensitive polymer displaying a coil-to-globule transition above its lower critical solution temperature (LCST) of 305 K.  As its LCST is close to the physiological temperature, PNIPAM is an attractive candidate for in-vivo applications such as drug delivery.  Graphene nanostructures have also shown great potential in the area of biomedicine with applications ranging from drug delivery to tissue engineering.  Additionally, complexes of graphene oxide and various aromatic drugs have yielded vastly improved water solubility allowing for increased efficacy.  In this work, we have conducted all-atom molecular dynamics (MD) simulations of a PNIPAM chain consisting of 30 monomer units along with sheets of either graphene or graphene oxide in the presence of water.  All simulations were carried out at 325 K and 275 K, which are above and below the LCST of PNIPAM, respectively.  The impact of sheet width and its initial angle with respect to PNIPAM on the LCST of PNIPAM is investigated.