Dynamics of Bond-Fluctuation Model Chains in Good and Theta Solvents

Simulation of the collective dynamics scattering of diblock copolymers with heterogeneous composition in the semidilute regime

“…The simulation model and algorithm has been described in detail in our previous work [22]. We consider n selfavoiding walk (SAW) chains, each composed of N beads in a cubic lattice of length L, adequately chosen according to the predicted mean chain size, including periodic boundary conditions.…”

“…[22]). The combination of the three quantities into the single parameter 6hS 2 i/Ds 1 should give a nearly constant quantity, if the system friction affects the three properties similarly [27].…”

“…The closer approach to the Gaussian limit is found for the N = 100 systems, that, at a given volume fraction, should exhibit greater chain overlapping and a more effective screening of excluded volume effects. In any case, the present model, with only repulsions between units belonging to different types of blocks, does not show the stronger deviations found for this parameter in systems with an attractive interaction between similar units [22]. (In these latter systems, the mobility is retarded because of their proximity to the macroscopic phase separation.…”

“…Therefore, though the model may be less accurate in the local description of the polymers and does not include hydrodynamic interactions (which are especially important in dilute systems) we consider it is particularly valuable with respect to capturing the essential physical behavior of more concentrated solutions. In previous studies we have usefully employed this model in the investigation of the dynamic scattering of solutions, particularly semidilute solutions of linear homopolymers and diblock copolymers without compositional heterogeneity [22]. Specifically for the latter systems, we have considered symmetric diblock copolymers, where each block consists of N/2 beads of either type A or type B with opposite contrast factors in a non-selective solvent (represented by the lattice voids).…”

“…The initial configurations are taken from previously equilibrated samples. (These equilibration runs were performed with the more efficient 'reptation' moves, where a bead is removed from a randomly chosen end of a chain and a new bead is inserted in a random position at the opposite end [22].) Typical samples consist of 10 6 attempted moves per chain for equilibration, followed by 10 6 time units for the statistical production runs.…”