Revealing sol-gel type main effects by exploring a molecular cluster behavior in model in-plane amphiphilic aggregations

In-plane (bio)matter aggregations of amphiphilic nature are modeled extensively by Monte Carlo simulation in their natural entropic contexts. The modeling starts by designing the aggregations at a molecular level, pointing to its well-known configuration vs conformation character. Then, the conformational behavior is distributed over the aggregations obtained, with the aim of revealing their main sol-gel type (viscoelastic) effects. The passage between the resulting sol and gel phases is not controlled by a scan in the temperature domain, on the contrary, the control parameter is selected to be the hydrophobic-interaction strength while the temperature remains unchanged. The distribution of ordered fringed micelles, and the overall crystalline inclusions of the gel phase, suggested a first-order phase change, reasonably conceivable in terms of Avrami-Kolmogorov formalism for such hydrophobic-force driven and percolation-in-nature systems. A phase transition diagram has been presented as a novel proposition to discern between sol vs gel phases. As specific results, also of high experimental value, a damped-oscillating cluster-involving effect on the resulting hydrophobic-polar matrices has been detected and analysed. Other additional intermolecular-sharing entropy-influenced effects on clustering, as seen in terms of chain-to-chain connectivities, have been addressed as being of sufficient relevance to the gelation mechanism described. The microcrystalline inclusions downgrade to some extent the overall picture of entropy-affected gelation, being all together suitable for experimental check-out.     

Phase separation of symmetrical polymer mixtures in thin-film geometry

Monte Carlo simulations of the bond fluctuation model of symmetrical polymer blends confined between two neutral repulsive walls are presented for chain lengthN _A=N _B=32 and a wide range of film thicknessD (fromD=8 toD=48 in units of the lattice spacing). The critical temperaturesT _c (D) of unmixing are located by finite-size scaling methods, and it is shown that , wherev ₃0.63 is the correlation length exponent of the three-dimensional Ising model universality class. Contrary to this result, it is argued that the critical behavior of the films is ruled by two-dimensional exponents, e.g., the coexistence curve (difference in volume fraction of A-rich and A-poor phases) scales as , where ₂ is the critical exponent of the two-dimensional Ising universality class ( ₂=1/8). Since for largeD this asymptotic critical behavior is confined to an extremely narrow vicinity ofT _c (D), one observes in practice effective exponents which gradually cross over from ₂ to ₃ with increasing film thickness. This anomalous flattening of the coexistence curve should be observable experimentally.     

Model of phase separation and of morphology evolution in two-phase alloy

Elementary theory of mass-transfer in two-phase alloy under electromigration with account of two competing mechanisms of the fluxes equilibration is presented. These two competing mechanisms are Kirkendall effect and backstress. Various versions of Monte Carlo models for simultaneous simulation of structure evolution kinetics and of mass-transfer kinetics under high-density current are presented. Possibility of self-organization with minimization of Joule heating is demonstrated.     

Monte Carlo simulation of many-arm star polymers in two-dimensional good solvents in the bulk and at a surface

A Monte Carlo technique is proposed for the simulation of statistical properties of many-arm star polymers on lattices. In this vectorizing algorithm, the length of each arml is increased by one, step by step, from a starting configuration withl=1 orl=2 which is generated directly. This procedure is carried out for a large sample (e.g., 100,000 configurations). As an application, we have studied self-avoiding stars on the square lattice with arm lengths up tol _max=125 and up tof=20 arms, both in the bulk and in the geometry where the center of the star is adsorbed on a repulsive surface. The total number of configurations, which behaves asNl ^{G–1 fl} , where=2.6386 is the usual effective coordination number for self-avoiding walks on the square lattice, is analyzed, and the resulting exponents G=(f) and _s (f) for the bulk and surface geometries are found to be compatible with predictions of Duplantier and Saleur based on conformai invariance methods. We also obtain distribution functions for the monomer density and the distance of the end of an arm from its center. The results are consistent with a scaling theory developed by us.     

Entropy and equilibrium property of QCD-instanton induced final state in deep-inelastic scattering

The scaling and additivity properties of Rényi entropy in rapidity space of the instanton final state (IFS) and current jet identified by the r-sorting method from the QCDINS Monte Carlo event sample are to saturation with decreasing phase space scale. Furthermore, it is found that the additivity of H2 holds well for the IFS in narrow rapidity windows at different positions. These results indicate that the IFS produced in the instanton-induced process of deep inelastic scattering has reached local equilibrium.