Experiments and Simulations Probing Local Domain Bulge and String Assembly of Aligned Nanoplates in a Lamellar Diblock Copolymer

Abstract

Within ordered poly(styrene-b-methyl methacrylate) (PSb-PMMA) block copolymer (BCP) lamellae, oriented nanoplates [gadolinium trifluoride doped with ytterbium and erbium, GdF 3 :Yb/Er (20/2 mol %)] grafted with polyethylene glycol assemble into aligned strings at small interparticle separations. Herein, we investigate the origin of these aligned assemblies using X-ray scattering, electron microscopy, and hybrid particle/self-consistent field theory simulations. From previous reports, the insertion of a nanoplate in a BCP microdomain is expected to perturb the polymer chains and produce a local domain bulge as the PS/PMMA interface distorts to optimize conformational entropy. While experimental techniques are unable to directly resolve this small distortion, the two-dimensional simulations of the equilibrium BCP nanocomposite structure clearly show bulge formation around the nanoplates. As a function of particle separation, the potential of mean force (PMF) calculation reveals a global minimum corresponding to an equilibrium interparticle spacing of 7.0 nm, which agrees well with a mean experimental value of 6.4 nm. Furthermore, the PMF calculation exhibits a small activation barrier due to the high curvature penalty between two nanoplates at a separation distance of 21.7 nm. Ultimately, nanoplate strings form to fulfill the criteria where the energy benefit of decreasing interfacial area and minimizing chain stretching outweighs the energy penalty associated with reducing the translational entropy affiliated with evenly distributing the nanoplates. The simulations also illustrate a narrow tolerance for orientation angles, supporting the high degree of nanoplate alignment observed experimentally. We anticipate that the ability to align and couple anisotropic nanoparticles in BCPs presents opportunities to create functional polymer nanocomposites with orientation-dependent properties.

Effect of Graft Length and Matrix Molecular Weight on String Assembly of Aligned Nanoplates in a Lamellar Diblock Copolymer

“…Likewise, we use two graft lengths in our simulations designed to represent M n = 5 kg/mol and M n = 10 kg/mol (referred to 5kPEG and 10kPEG, respectively), though only M n = 5 kg/mol grafted PEG–PO 3 H 2 was performed experimentally (referred herein as 5kPEG). We note that the 38kBCP with 5kPEG system was originally studied in our previous paper and has been recasted here for easier comparison . Skeletal representations of the polymers used can be found in Figure .…”

Spray-Deposited Anisotropic Ferromagnetic Hybrid Polymer Films of PS-b-PMMA and Strontium Hexaferrite Magnetic Nanoplatelets

“…Apart from these approaches, utilization of the above-mentioned DBC templates was also an efficient way to control the orientation of the nanoplatelets. For example, Krook et al employed a lamellar PS- b -PMMA to template the alignment of the rhombic nanoplatelets, which are gadolinium trifluoride doped with ytterbium and erbium. , …”

“…For example, Krook et al employed a lamellar PS-b-PMMA to template the alignment of the rhombic nanoplatelets, which are gadolinium trifluoride doped with ytterbium and erbium. 26,27 So far, concerning nanoplatelet-DBC hybrid films, less attention has been paid to the use of magnetic nanoplatelets and the study of kinetic processes during film fabrication. Because of the orientation-dependent magnetic properties of the magnetic nanoplatelets, it is of great significance to systematically investigate the kinetic processes during the film preparation process.…”

Enhanced Dynamics of PMMA Brushes Induced by the Chain Ends of a Flexible Polymer Chain

“…Polymer monomers are forbidden to penetrate into the substrate. PMMA and PBMA are modeled as CG linear polymer chains bonded by MMA and BMA units without considering their side groups, which is a common method used in simulations. − We mostly considered diblock copolymer A N A B N B brushes in the simulations, where block A representing PMMA is end-grafted regularly on the substrate, with the anchored monomers arranged in an immobile square lattice pattern during the simulation, and block B representing PBMA is linked above A. In the present work, a high grafting density ω = N p / L x L y = 0.64, similar to our experiment, is considered; here, N p is the chain number of the end-grafted diblock copolymers.…”