Search results for "soft"

Pattern-recognising Polymer Adsorption on Structured Surfaces: Gaussian Polymers vs. Freely Jointed Chains

2014

Abstract Selective adsorption of homopolymers is exploited as a model for pattern recognition. To this end the strong adsorption regime of Gaussian polymers adsorbed on a regularly structured surface is investigated for square and triangular lattices within a discrete Edwards model. The equilibrium behaviour of the specific heat, the gyration tensor and the (nematic) bond order tensor are analysed and compared to the properties for adsorbed freely jointed polymer chains.

A fast Monte Carlo algorithm for studying bottle-brush polymers

2011

Obtaining reliable estimates of the statistical properties of complex macromolecules by computer simulation is a task that requires high computational effort as well as the development of highly efficient simulation algorithms. We present here an algorithm combining local moves, the pivot algorithm, and an adjustable simulation lattice box for simulating dilute systems of bottle-brush polymers with a flexible backbone and flexible side chains under good solvent conditions. Applying this algorithm to the bond fluctuation model, very precise estimates of the mean square end-to-end distances and gyration radii of the backbone and side chains are obtained, and the conformational properties of s…

Stochastic dynamics of polymer brushes under shear deformation

1998

The dynamical properties of polymer brushes under shear deformation have been studied by computer simulation. Both the local and the global dynamic properties at various shear rates have been calculated. The distribution of orientational and translational mobilities of the different monomers along the chain have been obtained. It was shown that the local mobility of the brushes changes very slowly with increasing of shear rates up to the largest rates. Increase in grafting density leads to an increasingly step like dependence of the correlation times as a function of shear rate.

Polymer-Polymer Interaction: Consistent Modeling in Terms of Chain Connectivity and Conformational Response

2006

An approach developed for the modeling of polymer solutions is extended to polymer blends. It accounts explicitly for the fact that the segments of a given macromolecule cannot spread out over the entire volume of the system (chain connectivity) and that the space a polymer molecule occupies may change after contact formation between the components of a mixture (conformational response ζ). The validity of the equation obtained for the Flory-Huggins interaction parameter between polymers is tested by means of critical data published for the system PVME/PS. The measured phase diagrams can be modeled equally well by two limiting assumptions concerning the temperature dependence of the conforma…

Polymer droplets on substrates with striped surface domains: molecular dynamics simulations of equilibrium structure and liquid bridge rupture

2005

The structure of a polymer nanodroplet adsorbed on a flat lyophobic substrate chemically decorated with a lyophilic stripe of width 2RD is studied by molecular dynamics simulation of a coarse-grained bead–spring model of short macromolecules (containing N = 20 effective monomers). Varying the stripe width, the strength of the monomer–wall attraction and the temperature, the equilibrium morphology of the resulting droplets is studied and discussed in terms of current phenomenological theories. In the second part, the behaviour of a liquid bridge connecting two such lyophilic stripes a distance L apart is analysed. It is shown that for large enough L such free-standing films are unstable and …

On the thermodynamic treatment of poly(vinylidene fluoride)/polystyrene blend under liquid—liquid phase separation conditions

1995

Abstract This paper deals with experimental and theoretical investigations on the compatibility of binary of polymer blends in solution. The experimental phase boundary of a crystalline polymer such as poly(vinylidene fluoride) with polystyrene (an amorphous polymer) in dimethylformamide as solvent has been determined by size-exclusion chromatography at 25°C. The composition of the coexisting phases has been used to calculate interaction parameters by means of the Flory—Huggins-type function for the free energy of mixing, including composition dependence of the polymer-polymer interaction parameter and a first correction term denoted as ternary interaction parameter. The calculation of thes…

Simulation of Copolymer Bottle-Brushes

2007

The structure of bottle-brush polymers with a rigid backbone and flexible side chains is studied in three dimensions, varying the grafting density, the side chain length, and the solvent quality. Some preliminary results of theoretical scaling considerations for one-component bottle-brush polymers in a good solvent are compared with Monte Carlo simulations of a simple lattice model. For the simulations a variant of the pruned-enriched Rosenbluth method (PERM) allowing for simultaneous growth of all side chains in the Monte Carlo sampling is employed. For a symmetrical binary (A,B) bottle-brush polymer, where two types (A,B) of flexible side chains are grafted with one chain end to the backb…

Simulations of phase transitions in macromolecular systems

2002

Abstract The study of phase transitions in concentrated solutions and melts of flexible or stiff polymers is a computational challenge for computer simulations, since already a single polymer coil exhibits nontrivial structure from the scale of a chemical bond (1 A) to the coil radius (100 A), and for the simulation of collective phenomena huge simulation boxes containing many polymers are required. A strategy to deal with this problem is the use of highly coarse-grained models on a lattice, such as the bond fluctuation model. Several studies employing such models will be briefly reviewed, e.g.: temperature-driven isotropic-nematic phase transition in concentrated solutions of semiflexible …

1986

Covalently crosslinked liquid crystalline networks with elastic properties were prepared in isotropic solution from linear liquid crystalline polymers. As linear precursors for the networks were used: (i) polymers with the mesogenic groups in the side groups (polyacrylates and polymethacrylates), (ii) polymers with the mesogenic groups in the main chain (polymalonates) and (iii) polymers with the mesogenic groups in main chain and side groups (“combined liquid crystalline polymers”). In all crosslinked polymers the liquid crystalline phases of the linear polymers are retained. For low degrees of crosslinking (≤2 mol-%) the phase transition temperatures remain nearly unchanged. These elastom…

Phase transitions of single polymer chains and of polymer solutions: insights from Monte Carlo simulations

2008

The statistical mechanics of flexible and semiflexible macromolecules is distinct from that of small molecule systems, since the thermodynamic limit can also be approached when the number of (effective) monomers of a single chain (realizable by a polymer solution in the dilute limit) is approaching infinity. One can introduce effective attractive interactions into a simulation model for a single chain such that a swollen coil contracts when the temperature is reduced, until excluded volume interactions are effectively canceled by attractive forces, and the chain conformation becomes almost Gaussian at the theta point. This state corresponds to a tricritical point, as the renormalization gro…