Modeling Swelling Behavior of Thermoresponsive Polymer Brush with Lattice Density Functional Theory

Abstract

A key problem in designing thermoresponsive polymer brushes on a solid surface is to find a relation between the targeted thermoresponsive properties and controllable conditions. Usually, a temperature-thickness curve showing the heating-induced swelling behavior of polymer brushes is chosen as the relation by either experimental or theoretical investigation. In this work, a lattice density functional theory (LDFT) developed previously is employed to investigate the temperature-thickness curves for five different types of polymer brushes, where the density profiles of polymer brushes calculated by LDFT are compared directly with simulation. It is found that the thermoresponsive behavior of a polymer brush can be characterized by the bulk phase behaviors of its corresponding polymer solution, including UCST, LCST, both UCST and LCST, closed LOOP and hourglass-shaped, which implies that the bulk phase diagram of polymer solutions can help us to find an appropriate polymer brush for a targeted thermoresponsive behavior. As an example, we show that the swelling behavior of a thermoresponsive polymer brush found in the experiment could be predicted by our LDFT results with the bulk phase diagram of real polymer solution only.

Time-dependent density functional theory for the charging kinetics of electric double layer containing room-temperature ionic liquids

“…14 Time-dependent density functional theory (TDDFT) is an extension of the classical density functional theory (DFT) to describe dynamic or time-dependent processes based on the assumption of local thermodynamic equilibrium. [45][46][47][48][49][50][51][52][53] For ion diffusion in an electrolyte solution near electrodes, TDDFT asserts that the time evolution for the local density profiles of ionic species, ρ i (r, t), follows the generalized diffusion equation…”

Modeling micelle formation and interfacial properties with iSAFT classical density functional theory

“…Recently, models based on statistical mechanics such as classical density functional theory (DFT) have been developed to model the meso-scale structure of complex fluids. DFT has shown its strength in modeling inhomogeneous and complex fluids and excellent agreement with molecular simulations and experiments for a variety of systems, including the phase behavior of associating fluids under confinement, 65,66 the behavior of polymer brushes, [17][18][19][20][21] the phase behavior and structure of block copolymers, [22][23][24] the interfacial properties of oil/water systems, 25,26 and the impact of surfactant architecture on interfacial properties. 27 The theory can be computationally more efficient than molecular simulations since density fields rather than trajectories of individual molecules are calculated, and the method takes advantage of system symmetry.…”

“…The interfacial tension γ is the excess grand potential, γ = Ω−Ω bulk A , where Ω bulk and Ω are the grand potentials of the bulk phase and of the system, respectively, which are obtained from Eq. (17).…”

Photoelectrochemical cell for simultaneous electricity generation and heavy metals recovery from wastewater

“…6a, Cu 2+ was completely removed within 30 min in the first cycle. However, only about 70% of copper metal ion was removed at the end of the 9 th cycle, indicating that some inactivation at the photoanode or cathode occurred [37,38]. The inactivation of the photoanode may be associated with the depletion of P123, which served as hole scavenger under continuous UV irradiation [21].…”