Moleküldynamik-Computersimulation des Phasenverhaltens nichtionischer Tenside

The Self-Assembly of an Amphiphilic Block Copolymer: A Dissipative Particle Dynamics Study

The self-assembly of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) blockcopolymer (EO13PO30EO13) in the presence of water was investigated. The phases have been studied with the mesoscopic simulation technique Dissipative Particle Dynamics (DPD). The micellar, hexagonal, lamellar, bicontinuous and inverse micellar phase have been identified with this method and showed remarkable agreement with the experimental phase behavior. This work showed that the Dissipative Particle Dynamics simulations are also suitable for complicated polymer systems such as the EO13PO30EO13 triblock copolymer.

Mesoscale Computer Simulations on the Phase Behavior of the Non-Ionic Surfactant C12E5

Dissipative Particle Dynamics is a mesoscopic simulation method which allows to predict the self-assembly of amphiphilic polymers and surfactants. It was possible to reproduce the phase behavior of the non-ionic surfactant C12E5 in water. The three different phases L1, La and L2 could be characterized with Dissipative Particle Dynamics.

Molecular Modeling Computer Simulations of Organic Polymers: A Novel Computer Simulation Technique to Characterize Nanostructured Materials

The understanding and prediction of complex nanostructured self-assemblies such as colloidal suspensions, micelles, immiscible mixtures, microemulsions, etc., represent a challenge for conventional methods of simulation due to the presence of different time scales in their dynamics.

We have recently successfully applied a novel computer simulations technique, Dissipative Particle Dynamics (DPD), to model the behavior of diblockcopolymers at the water/oil interface. With the use of a simple model we have performed simulations of polymer/water/oil systems at different concentrations.

We present the results of nanoscale “coarse-grained” simulations with DPD. DPD is a mesoscale simulation technique that has been introduced in order to simulate three-dimensional structures of organic polymer aggregates.

In DPD the polymer is modeled using particles which are interacting by conservative, dissipative and random forces. Particles are not regarded as molecules but rather as droplets or nanoclusters of molecules.

We have successfully applied this technique to simulate the three-dimensional structures of microemulsions, e.g. the bicontinuous phase of a surfactant in water and oil, in domains of less than 100 nm. The different structures of the polymer/water/oil system were effectively characterized with DPD and are in remarkable agreement with the experiment.

The DPD method proofed to be a reliable tool to get a better understanding of the nanostructure of self-assemblies and is therefore applicable to support the often complicated experiments or even to obtain experimentally unavai1able data.

Aggregation of Poly(ethylene oxide)−Poly(propylene oxide) Block Copolymers in Aqueous Solution: DPD Simulation Study

The dissipative particle dynamics (DPD) simulation method was applied to simulate the aggregation behavior of three block copolymers, (EO)16(PO)18, (EO)8(PO)18(EO)8, and (PO)9(EO)16(PO)9, in aqueous solutions. The results showed that the size of the micelle increased with increasing concentration. The diblock copolymer (EO)16(PO)18 would form an intercluster micelle at a certain concentration range, besides the traditional aggregates (spherical micelle, cylindrical micelle, and lamellar phase); while the triblock copolymer (EO)8(PO)18(EO)8 would form a spherical micelle, cylindrical micelle, and lamellar phase with increasing concentration, and (PO)9(EO)16(PO)9 would form intercluster aggregates, as well as a spherical micelle and gel. New mechanisms were given to explain the two kinds of intercluster micelle formed by the different copolymers. It is deduced from the end-to-end distance that the morphologies of the diblock copolymer and triblock copolymer with hydrophilic ends were more extendible than the triblock copolymer with hydrophobic ends.

Deformation and bursting of nonspherical polysiloxane microcapsules in a spinning-drop apparatus

We analyze the deformation and bursting process of nonspherical organosiloxane capsules in centrifugal fields. Measurements were performed in a commercial spinning-drop tensiometer at different values of tube rotation. A theoretical analysis of the mechanics of initially ellipsoidal elastic shells subjected to centrifugal forces is developed where the deformation of the capsule is predicted as a function of the initial geometry and membrane elastic properties. For different types of organosiloxane membranes the Poisson number varies between 0 and 0.9. This phenomenon points to a considerable reduction of the membrane thickness at the onset of mechanical stress. Membrane-breaking processes always initiated at one of the pole ends of the capsules. Such rupture processes can be interpreted in terms of the derived theoretical model.