Interface Orientation and Chain Conformation in Simulated Symmetric Diblock Copolymer Lamellar Systems

Abstract

Summary: We describe the results of Monte Carlo simulations, based on the cooperative motion algorithm, of the lamellar structure generated at finite temperature by a symmetric diblock copolymer. The (70 × 70 × 70) simulation box in which the polymer chains were embedded for each simulation was rotated, based on the interface orientation, to bring the interfacial planes of the simulated structure into parallel. We found that the interface thickness, as defined by the distribution of the junction points, became narrower at lower temperature, and that the interface plane was characterized by a waviness with a maximum peak‐to‐valley distance of 20–30 lattice bonds. Compared with the isotropic state (T/N = ∞), chains at lower temperatures were stretched in the direction perpendicular to the interface; but only modestly compressed in the direction parallel to the interface. Individual block chains within the lamellar domains still behave like random coils. The block copolymer molecules exhibit only a modest tendency to orient themselves with their end‐to‐end vector perpendicular to the plane of the lamellar interface. Considered as an ensemble average, the results we obtained are similar to those reported from small angle neutron scattering measurements for the mean conformation of the PSd blocks of symmetrical PSd‐PVP diblock copolymers.2‐D projections onto the X‐Z plane of the end beads for the A‐ and B‐chains (gray) and the junction points J (black) at T/N = 0.2. The interface plane is oriented parallel to the Y‐Z plane by rotating the simulation box. The distribution profiles of junction points and the end beads across the system in the direction of interface normal are shown in the lower part of the figure.image2‐D projections onto the X‐Z plane of the end beads for the A‐ and B‐chains (gray) and the junction points J (black) at T/N = 0.2. The interface plane is oriented parallel to the Y‐Z plane by rotating the simulation box. The distribution profiles of junction points and the end beads across the system in the direction of interface normal are shown in the lower part of the figure.

Heterogeneity of the Segmental Dynamics in Lamellar Phases of Diblock Copolymers

“…There are other types of monomers which also follow the criterium Δ z < 2σ. Such monomers are those close to the block ends , (in the following denoted as end monomers ), as indicated (see Figure ) by the two secondary peaks of p ( i ) in the ranges i ≲ 50 and i ≳ 300. The presence of these secondary peaks is easily understood by inspection of the bottom panel of Figure , which shows that stretched blocks extend from one interface to the next one.…”

Energy Transfer Study of the Cylindrical Interface Formed by Asymmetric Isoprene−Methyl Methacrylate Diblock Copolymers Bearing a Dye at the Junction

“…We have tried in previous studies to address the issue of possible nonrandom dye orientation. Monte Carlo simulations of block copolymer chains , showed that there was no detectable preference for the chain backbone orientation with respect to the plane of the interface. Experiments in which the position of the attachment of the An dye to the chain backbone at the junction between the blocks was varied had no effect, for PI−PMMA lamellae, on the interface width determined in FRET experiments .…”

Theory and Simulation of Multiphase Polymer Systems

“…Later, intense work has been devoted to studying ordered lamellar structures below the ODT in melts of symmetrical diblock copolymers, and analyzing them with respect to their structure, their dynamics, and their fluctuations [320][321][322][323][324][325][326][327][328][329][330][331]. Simulation studies of asymmetric diblock copolymer melts have also reproduced most of the other mesophases -the cylindrical phase, the bcc sphere phase, and even the gyroid phase [204,211,235,[332][333][334][335].…”