Molecular simulation of gas solubilities in crystalline poly(α-alkyl-β-?-aspartate)s

Calculation Methods of Solution Chemical Potential and Application in Emulsion Microencapsulation

Several new biased sampling methods were summarized for solution chemical potential calculation methods in the field of emulsion microencapsulation. The principles, features, and calculation efficiencies of various biased Widom insertion sampling methods were introduced, including volume detection bias, simulation ensemble bias, and particle insertion bias. The proper matches between various types of solution in emulsion and biased Widom methods were suggested, following detailed analyses on the biased insertion techniques. The volume detection bias methods effectively improved the accuracy of the data and the calculation efficiency by inserting detection particles and were suggested to be used for the calculation of solvent chemical potential for the homogeneous aqueous phase of the emulsion. The chemical potential of water, argon, and fluorobenzene (a typical solvent of the oil phase in double emulsion) was calculated by a new, optimized volume detection bias proposed by this work. The recently developed Well-Tempered(WT)-Metadynamics method skillfully constructed low-density regions for particle insertion and dynamically adjusted the system configuration according to the potential energy around the detection point, and hence, could be used for the oil-polymer mixtures of microencapsulation emulsion. For the macromolecule solutes in the oil or aqueous phase of the emulsion, the particle insertion bias could be applied to greatly increase the success rate of Widom insertions. Readers were expected to choose appropriate biased Widom methods to carry out their calculations on chemical potential, fugacity, and solubility of solutions based on the system molecular properties, inspired by this paper.

Aplicaciones de los métodos computacionales al estudio de la estructura y propiedades de polímeros

En este trabajo se revisan las técnicas de simulación molecular más habituales y potentes para la descripción de los polímeros a escala atómica y molecular, las cuales se han clasificado en cuánticas o clásicas dependiendo de cómo se describen las interacciones entre las partículas. Se presentan asimismo diversas aplicaciones de dichas metodologías, realizadas en nuestro laboratorio, en el contexto del estudio de la estructura y propiedades de polímeros. En particular, se muestran aplicaciones de las técnicas clásicas a la determinación de estructuras cristalinas, a estudio del plegamiento lamelar de los nylons, a la estabilidad de las estructuras supramoleculares observadas en algunos complejos tensioactivo·polielectrolito y a la difusión de gases en matrices poliméricas, mientras que el uso de técnicas cuánticas se ha ilustrado presentando estudios dedicados a la predicción de efectos cooperativos, interacciones específicas y parámetros espectroscópicos.

EVEBAT: a fast strategy for the examination of the empty space in polymer matrices

A very efficient strategy to evaluate the "free volume" and the "unoccupied volume" in polymer matrices is proposed. The method, which has been denoted EVEBAT (Empty Volume Evaluation Based on Atom-Types), emerges from the concept of atom type, which is the basis of a force field. Accordingly, the numerical treatment is minimized by analyzing the atom types used to describe the polymer matrix, which are always a few, rather than all the explicit, atoms involved in it. The performance of the new method has been pointed out by a detailed comparison with the classical insertion algorithms.