Modeling Impact of Regiodefects on the Electrocaloric Effect in Poly(VDF--TrFE) Copolymers.

Impact of regiodefects in the ferroelectric poly(vinylidene difluoride--trifluoroethylene) copolymer [poly(VDF--TrFE)] on the electrocaloric effect was studied with use of a developed analytical model and molecular dynamics (MD) simulations. It was shown earlier that the electrocaloric effect in these polymers is caused by the first-order phase transition from the ferroelectric β phase to the paraelectric conformationally disordered (condis) phase. MD simulations performed in the current work show that the presence of regiodefects in polymer chains makes this phase transition more gradual, the second order.

Surface tension model for surfactant solutions at the critical micelle concentration.

A model for the limiting surface tension of surfactant solutions (surface tension at and above the critical micelle concentration, cmc) was developed. This model takes advantage of the equilibrium between the surfactant molecules on the liquid/vacuum surface and in micelles in the bulk at the cmc. An approximate analytical equation for the surface tension at the cmc was obtained.