Distinct Viscoelasticity of Hierarchical Nanostructures Self-Assembled from Multiblock Copolymers

Abstract

We employed a nonequilibrium dissipative particle dynamics method to study viscoelastic properties of hierarchical lamellar structures self-assembled from heptablock copolymers. Three ways of shearing with respect to lamellar planes, including parallel, vertical, and transverse shearing, were imposed to study the viscoelasticity of ordered systems. In parallel shear, with the morphology transformation from disorder to general lamellae to parallel lamellae-in-lamella, both the storage and loss moduli of multiblock copolymer melt show a remarkable improvement. In addition to the parallel lamellae-in-lamella, the multiblock copolymers can form perpendicular lamellae-in-lamella with different viscoelastic behaviors. In vertical shear, parallel lamellae-in-lamella shows terminal behavior, while a low-frequency plateau in the storage modulus exists for the perpendicular lamellae-in-lamella. In transverse shear, the storage moduli for both perpendicular and parallel lamellae-in-lamellae with strong separation of small-length-scale structure exhibit a solid-like plateau at low frequency. The physical origin underlying the distinct viscoelasticity of various hierarchical lamellae was revealed by monitoring the motions of polymer blocks at different length scales. The present work could provide information for preparing advanced materials based on packed lamellae.

Effect of Block Number and Weight Fraction on the Structure and Properties of Poly(butylene terephthalate)-block-Poly(tetramethylene oxide) Multiblock Copolymers

“…Among the PTMO-rich and PBT-rich region, a small-length scale light-colored or dark-colored lamellar-like structure can be observed when enlarged. The hierarchical structure is somewhat similar to the double-periodic lamellar-in-lamellar structure reported in mBCPs ,− and close to that observed by Bates’ group in crystalline mBCPs, where they ascribed it as a bicontinuous microemulsion-like disordered phase. ,, …”

Effect of the content and strength of hard segment on the viscoelasticity of the polyurethane elastomer: insights from molecular dynamics simulation

“…Meanwhile, the viscoelasticity of the ordered copolymer systems is studied by performing three shearing ways (parallel, vertical, and transverse shearing), which presents a distinct behavior. 24 The underlying mechanism is attributed to the motions of polymer blocks at different length scales. In addition, the effect of the HS (or SS)-filler interaction on the viscoelasticity of the block copolymer-based nanocomposites is explored, where the network structure is broken down under the shear field.…”

Computational Insight into Phase Separation of a Thiol-Ene Photopolymer with Liquid Crystals for Holography by Dissipative Particle Dynamics Simulation

“…Later, a dissipative particle dynamics (DPD) simulation method coupled with a stochastic reaction model was employed to investigate the dynamic process of polymerization at the water–oil interface and polymerization-induced self-assembly in solution, respectively. These inspiring achievements have provided theoretical guidelines for the facile design of novel polymerization systems. − Besides, the viscoelastic and optical properties of self-assembled multi-block copolymers were also studied by DPD simulations combined with the non-equilibrium and finite difference time domain method, which has offered new insights into the self-assembled hierarchical materials possessing enhanced properties. However, despite these extraordinary advances on the computational simulations of polymer-based systems, the computational insights into the periodic photopolymerization-induced phase separation remain elusive owing to the lack of proper approaches to simulating such a complicated system.…”