Molecular dynamics studies of poly(N-isopropylacrylamide) endgrafted on the surfaces of model slab pores

Single Chain Structure of a Poly(N-isopropylacrylamide) Surfactant in Water

“…41,44,45 Tucker and Stevens, 45 "coiling" of the chain began with N = 30. In addition to single PNIPAM molecules, simulations have been used to study different structural configurations like random copolymers, 46,47 graft copolymers, 43 and end-grafted brushes, 48,49 as well as different aqueous solutions incorporating salt 42 or methanol. 50 In these examples, simulations provided the molecular-level detail necessary to observe specific changes in polymer− polymer and polymer−solvent interactions, 42,44,48,50 hydrogen bonds, 43,44,47,48,50 and solvent mobility.…”

“…Several studies of single chains in water have observed the expected transition behavior, although results vary depending on the force field and water model. − Some of these studies have also found a chain length dependence similar to that noted experimentally. ,, Tucker and Stevens, for instance, observed a transition only in chains of length N = 11 or greater, but “coiling” of the chain began with N = 30. In addition to single PNIPAM molecules, simulations have been used to study different structural configurations like random copolymers, , graft copolymers, and end-grafted brushes, , as well as different aqueous solutions incorporating salt or methanol . In these examples, simulations provided the molecular-level detail necessary to observe specific changes in polymer–polymer and polymer–solvent interactions, ,,, hydrogen bonds, ,,,, and solvent mobility. , In one instance, Deshmukh et al even artificially “turned off” PNIPAM hydrogen bond donors and acceptors to eliminate polymer–polymer and polymer–water hydrogen bonds in the simulation, resulting in globule structures below and above the transition temperature.…”

A new class of nanoengines based on thermoresponsive polymers: Conceptual design and behavior study

“…Due to the geometrical pattern of graphene atoms in a two-dimensional surface, there is a strong attraction between PNIPAM chains and the graphene layer. To decrease this unfavorably strong attraction, which prevents the observation of thermoresponsive behavior of the grafted PNIPAM, the normal nonbonded PNIPAM-graphene interaction is reduced to 10% of the original value [20,21], and hence we use the expression graphene-like for our model system. Of course, many different designs are possible in which the graphene layer can be replaced by other materials or be coated by, e.g., gold [28].…”

“…In this paper, by using molecular dynamics simulations, we investigate the behavior and efficiency of our proposed model system in atomistic detail. In general, the number of polymer chains can of course be much more than four, and the graphene layers can be replaced by any narrow sheet or even a nanoparticle, which exhibits weak interactions with the PNIPAM chains [20,21].…”

Phenol release from pNIPAM hydrogels: scaling molecular dynamics simulations with dynamical density functional theory

“…Simulations are based on an atomistic model, where the OPLS-AA force field is used for the polymer, and water is given by the SPCE model. This force field and its versions are frequently employed for pNIPAM systems [53][54][55][56][57][58][59][60][61][62][63][64] and provide the best results for capturing the coil-to-globule transition when employed with the TIP4P/ice water model. 64 A particular version of the OPLS-AA 65 with the TIP4P/ice can capture the pNIPAM in water behavior at different temperatures and pressures.…”