Mesoscopic phase separation dynamics of compressible copolymer melts

Abstract

In this paper we extend the dynamic mean-field density functional method, derived from the generalized time-dependent Ginzburg-Landau theory, to the mesoscopic dynamics of compressible polymer liquids. We discuss and compare different classes of compressibility models: exactly incompressible, the Helfand's harmonic penalty model, and a cell model. We present numerical results and show that the penalty model is a very practical and easy to use solution. In the current nVT ensemble dynamics algorithms application of the cell model leads to a variation of the pressure and, depending on conditions, the system develops liquid-gas transitions. We show that the morphology of a phase separated diblock copolymer melt around a gas bubble has intruiging structures, with lamellar phases oriented towards the gas-liquid interface.

Simulation of the Phase Behavior of the (EO)13(PO)30(EO)13(Pluronic L64)/Water/p-Xylene System Using MesoDyn

“…The noise-scaling parameter used here was 100, and the compressibility parameter was fixed at 10.0. 25,26 The solvent-polymer interaction parameters were estimated as where δ s and δ p are Scatchard-Hildebrand solubility parameters of the solvent and of the polymer, respectively, 27 and V s is the molar volume of the solvent. The interaction parameters of p-xylene, H 2 O, and PEO-PPO are not suitable to be estimated by the above equation, and consequently, wx used here was estimated to be 5.0 because p-xylene is nearly insoluble in water; AB was estimated by group contribution methods.…”

Asymmetric block copolymers confined in a thin film

“…͑2͒ takes into account the excluded volume interactions, by imposing a free energy penalty when the total density deviates at a certain position from its average value. 39,43 The parameter H is the Helfand compressibility parameter.…”

“…͑3͒ it follows that the range of the bead-bead interactions is comparable to the size of the chain fragments represented by the beads. The parameter IJ 0 is related to the widely used Flory-Huggins parameter, 39 IJ…”

“…35,36,38,39 In the DDFT model a box with periodic boundaries is filled with fixed amounts of beads of different types, ͕N I ͖. A polymer is represented as a string of beads.…”

Comparison of aggregation behaviors between branched and linear block polyethers: MesoDyn simulation study

“…The aggregation behaviors of block polyethers have been studied extensively by various methods, for example, micro-calorimetry [10][11][12], small-angle neutron or X-rays scattering [13][14][15], static and dynamic light scattering [16][17][18], and rheometry [19][20][21][22]. Besides, computer simulation methods, such as dissipative particle dynamics [23][24][25] and mesoscopic dynamics (MesoDyn) [26][27][28] have been used in the study on the aggregation behavior of polyether. These mesoscopic models build a bridge between fast molecular kinetics and slow thermodynamic relaxation of macro-scale properties [29].…”