Self-Assembly of Lamellar- and Cylinder-Forming Diblock Copolymers in Planar Slits: Insight from Dissipative Particle Dynamics Simulations

Abstract

We present a dissipative particle dynamics simulation study on nanostructure formation of symmetric and asymmetric diblock copolymers confined between planar surfaces. We consider symmetric and slightly asymmetric diblock copolymers that form lamellar nanostructures in the bulk, and highly asymmetric diblock copolymers that form cylindrical nanostructures in the bulk. The formation of the diblock copolymer nanostructures confined between the planar surfaces is investigated and characterized by varying the separation width and the strength of the interaction between the surfaces and the diblock copolymers. Both the slit width and the surface interaction strongly influence the phase diagram, especially for the asymmetric systems. For the symmetric and slightly asymmetric diblock copolymer systems, the confinement primarily affects the orientation of the lamellar domains and only marginally influences the domain morphologies. These systems form parallel lamellar phases with different number of lamellae, and perpendicular and mixed lamellar phases. In a narrow portion of the phase diagram, these systems exhibit a parallel perforated lamellar phase, where further insight into the appearance of this phase is provided through free-energy calculations. The confined highly asymmetric diblock copolymer system shows, in addition to nanostructures with parallel and perpendicular cylinders, noncylindrical structures such as parallel lamellae and parallel perforated lamellae. The formation of the various confined nanostructures is further analyzed by calculating structural characteristics such as the mean square end-to-end distance of the diblock copolymers and the nematic order parameter.

Scaling behaviour of different polymer models in dissipative particle dynamics of unentangled melts

“…Model 2 differs from Model 1 by employing the FENE potential (12) instead of the harmonic potential. Model 3 corresponds to the mesoscopic model of PE and it employs the coarse-grain beadbead, spring and bending potentials.…”

“…DPD was introduced by Hoogerbrugge and Koelman in 1992 [1,2], and soon after refined for polymers by Groot and Warren [3]. Presently for polymer systems, DPD has been used to simulate a variety of problems such as the static and dynamic properties of polymer melts, [4] polymer solutions, [5,6] self-assembly of block copolymers in bulk, [7 -9] under shear [10] and in confinement, [11,12] self-assembly of nanoparticle mixtures in diblock copolymers, [13 -15] polymer brushes, [16 -18] pressuredriven flow of polymer solutions in nanoconfinement [19] and polymer translocation through a nanopore, [20] as well as many others.…”

Changes in the structure of tethered chain molecules as predicted by density functional approach

“…They can find applications in drug delivery, as chemical sensors and in controlling the nanoparticle transport [4][5][6][7]. Furthermore, applications in nanotechnology include end grafted polymers on nanopatterned surfaces, on nanoparticles, or on carbon nanotubes [8][9][10][11][12].…”

Morphology and molecular bridging in comb- and star-shaped diblock copolymers

“…Among several mesoscale simulations techniques, the Dissipative Particle Dynamics (DPD) technique is suitable and convenient for the analysis of complex fluids at lengthand time-scales necessary to examine the self-assembled morphologies. 17 DPD has been shown to effectively simulate self-assembly for a variety of copolymer architectures including: diblock, 18-20 random, 21 graft, 22 or comb, 23 star, 24,25 homopolymer copolymer blends, 26 copolymers in confined spaces, 27,28 block terpolymers, 29 coil-comb polymers, 30 dendritic diblocks, 31 copolymer nanorod mixtures, 32 diblock nanoparticle mixtures, 33,34 polymer solutions, 35 coil-rod-coil triblocks, 36 and miktoarm block copolymers. 37 It has been shown in experimental investigations 38, 39 and DPD simulations that certain self-assembled diblock copolymers (e.g., comb-and star-shaped) have the ability to interconnect two A-rich phases, effectively behaving as an A-B-A tri-block copolymer.…”

“…An example of the top-down mapping of DPD copolymer systems on real systems using the concept of Kuhn's segments and solubility parameters can be found in Appendix B of Ref. 27.…”