A Monte Carlo Study of Weak Polyampholytes:  Stiffness and Primary Structure Influences on Titration Curves and Chain Conformations†

2007 ◽  
Vol 111 (29) ◽  
pp. 8459-8467 ◽  
Author(s):  
Serge Ulrich ◽  
Marianne Seijo ◽  
Serge Stoll
Keyword(s):  
Monte Carlo ◽  
Primary Structure ◽  
Monte Carlo Study ◽  
Titration Curves ◽  
Chain Conformations

A Monte Carlo Study of Flexible Polymer Chain Conformations in Restricted Volumes. I. A Model for Insoluble Blocks Conformations in Swollen Cores of Multimolecular Spherical Block Copolymer Micelles

1993 ◽  
Vol 58 (10) ◽  
pp. 2290-2304 ◽  
Author(s):  
Zuzana Limpouchová ◽  
Karel Procházka
Keyword(s):  
Monte Carlo ◽  
Block Copolymer ◽  
Monte Carlo Study ◽  
Volume Effect ◽  
Micellar Systems ◽  
Flexible Polymer ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles ◽  
Chain Conformations ◽  
Chain Lengths

Monte Carlo simulations of chain conformations in a restricted spherical volume at relatively high densities of segments were performed for various numbers of chains, N, and chain lengths (number of segments), L, on a tetrahedral lattice. All chains are randomly end-tethered to the surface of the sphere. A relatively uniform surface density of the tethered ends is guaranteed in our simulations. A simultaneous self-avoiding walk of all chains creates starting conformations for a subsequent equilibration. A modified algorithm similar to that of Siepmann and Frenkel is used for the equilibration of the chain conformations. In this paper, only a geometrical excluded volume effect of segments is considered. Various structural and conformational characteristics, e.g. segment densities gS(r), free end densities gF(r) as functions of the position in the sphere (a distance from the center), distributions of the tethered-to-free end distances, ρTF(rTF), etc. are calculated and their physical meaning is discussed. The model is suitable for studies of chain conformations is swollen cores of multimolecular block copolymer micelles and for interpretation of non-radiative excitation energy migration in polymeric micellar systems.

A Monte Carlo Study of Copolymer Chain Conformations in Dilute Solutions in Good and Selective Solvents

1995 ◽  
Vol 60 (5) ◽  
pp. 736-750
Author(s):  
Tereza Vrbová ◽  
Zuzana Limpouchová ◽  
Karel Procházka
Keyword(s):  
Monte Carlo ◽  
Diblock Copolymers ◽  
Structural Characteristics ◽  
Monte Carlo Study ◽  
Dilute Solutions ◽  
Copolymer Chain ◽  
Selective Solvents ◽  
Nearest Neighbours ◽  
Lattice Distance ◽  
Chain Conformations

Conformations of symmetric diblock copolymers AB in dilute solutions in good and selective solvents were studied by Monte Carlo simulations on a simple cubic lattice. Individual chain conformations were created by the self-avoiding walk algorithm. A modified thermal equilibration of the system based on the Metropolis acceptance criteria for energies of the system and the Rosenbluth weights of chain conformations was applied. Interactions of the nearest neighbours (r = l), where l is the lattice distance, and interactions for r = sqrt(2l) and r = sqrt(3l) were considered. Various structural characteristics of the whole copolymer chain and individual blocks A, B were obtained in the course of computer simulations. It was found that a moderate contraction of the worse soluble block B and a certain segregation of blocks occurs in dilute solutions in selective solvents for the block A, however neither that contraction, nor the segregation of blocks are extensive.

scholarly journals Influence of Explicit Ions on Titration Curves and Conformations of Flexible Polyelectrolytes: A Monte Carlo Study

2010 ◽  
Vol 43 (5) ◽  
pp. 2544-2553 ◽  
Author(s):  
Fabrice Carnal ◽  
Serge Ulrich ◽  
Serge Stoll
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Study ◽  
Titration Curves

Tethered Chains in Concave Volumes. A Monte Carlo Study

1994 ◽  
Vol 59 (10) ◽  
pp. 2166-2189 ◽  
Author(s):  
Karel Procházka ◽  
Zuzana Limpouchová
Keyword(s):  
Monte Carlo ◽  
Spherical Cavity ◽  
Monte Carlo Study ◽  
Volume Effect ◽  
Distribution Functions ◽  
Spherical Cavities ◽  
Chain Conformations ◽  
Tethered Chains ◽  
Self Avoiding Walk ◽  
Tethered Chain

Monte Carlo study of tethered chain conformations in spherical cavities was performed in a relatively broad range of average segment densities (i.e. numbers of tethered chains with increasing length in the sphere). Simulations were performed on a tetrahedral lattice using (i) an equilibrated self-avoiding walk for systems containing a single tethered chain with increasing length, and (ii) a simultaneous self-avoiding walk of many tethered chains in the spherical cavity together with equilibration of the system which was performed by a modified algorithm similar to that of Siepmann and Frenkel. Only a geometric excluded volume effect of segments was considered (i.e. the prohibition principle of a double occupancy of one lattice site by two different segments). Various distribution functions (e.g. distribution of the end-to-end and the end-to-gravity center distances and their orientations with respect either to the radial direction, or to the direction of the first-to-second segment connection, etc.) were calculated and the effect of increasing average segment density in the sphere on conformational characteristics of individual chains was studied. It was found that conformational and orientational properties of relatively short tethered chains are only little affected by increasing segment density (i.e. by the number of chains in the spherical cavity), whereas arrangements of long tethered chains are significantly influenced by the density of the system.

Analyzing Observed Composite Differences Across Groups

Methodology ◽  
2013 ◽  
Vol 9 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Holger Steinmetz
Keyword(s):  
Monte Carlo ◽  
Structural Equation Modeling ◽  
Measurement Invariance ◽  
Structural Equation ◽  
Monte Carlo Study ◽  
Equation Modeling ◽  
Factor Loadings ◽  
Latent Mean Differences ◽  
Partial Invariance ◽  
Mean Differences

Although the use of structural equation modeling has increased during the last decades, the typical procedure to investigate mean differences across groups is still to create an observed composite score from several indicators and to compare the composite’s mean across the groups. Whereas the structural equation modeling literature has emphasized that a comparison of latent means presupposes equal factor loadings and indicator intercepts for most of the indicators (i.e., partial invariance), it is still unknown if partial invariance is sufficient when relying on observed composites. This Monte-Carlo study investigated whether one or two unequal factor loadings and indicator intercepts in a composite can lead to wrong conclusions regarding latent mean differences. Results show that unequal indicator intercepts substantially affect the composite mean difference and the probability of a significant composite difference. In contrast, unequal factor loadings demonstrate only small effects. It is concluded that analyses of composite differences are only warranted in conditions of full measurement invariance, and the author recommends the analyses of latent mean differences with structural equation modeling instead.

Sign in / Sign up

Export Citation Format

Share Document