Nanoscale Self-Assembly of Well-Defined Binary Mixed PowerPoint Presentation, PPT - DocSlides

Nanoscale Self-Assembly of Well-Defined Binary Mixed Homopolymer Brushes Grafted on Inorganic ParticlesLei Zhu, Case Western Reserve University, DMR 1007918

The focus of this Materials World Network project is the

self-assembled phase

morphology of binary mixed polymer brushes alternately immobilized via covalent bonds on inorganic silica nanoparticles. We seek to achieve fundamental understanding of effects of molecular weight, surface free energy, grafting density, substrate geometry, and environmental conditions on the phase behavior of two surface-tethered homopolymers in a confined geometry. In this year, we utilized electron tomography (3D TEM) to study the hierarchical self-assembly of mixed poly(tert-butyl acrylate) (PtBA)/ polystyrene (PS) brush-grafted silica nanoparticles. For a dense monolayer film of the particles, isolated cylindrical PS microdomains were formed in the PtBA matrix in the top protruded part of large particles, owing to the low PS volume fraction (37%). In the continuous film, bicontinuous phase morphology was obtained, which was caused by strong brush interactions among densely packed nanoparticles [see Fig. 1 (A)-(E)]. For isolated individual mixed brush-grafted silica particle, clear microphase separation was seen in the bottom portion rather than in the top hemisphere. This is because of the lack of interparticle interactions [see Fig. 1 (F)-(I)].

Fig. 1. (A) Conventional TEM image of a dense monolayer film of mixed PtBA/PS brush-grafted silica particles. The red box is selected for 3D reconstruction. (B) Top-view 3D TEM image of the reconstructed box. (C) and (D) Top and bottom z-scan 3D TEM images of the reconstructed box. (E) Schematic illustration of a dense monolayer of mixed brush-grafted silica particles. (F) Conventional TEM image of an individual mixed PtBA/PS brush-grafted silica particle. (G) and (H) Top-view and bottom z-scan 3D TEM images of the individual particle. (I) Schematic illustration of an individual mixed PtBA/PS brush-grafted silica particle. In all 3D TEM images, PS/SiO2 phases are visible and PtBA phase is invisible.

Education in 2012-2013Graduate Research Ph.D. student: Saide Tang (3rd yr.)High School Student Julie De La PenaInternational Collaborations1. Collaborating with Mr. Ting-Ya Luo and Prof. Rong-Ming Ho in National Tsing Hua University, Taiwan, we performed 3D reconstruction of self-assembled mixed brushes grafted particle monolayer film by electron tomography.2. Prof. Zhu visited Fudan University in the summer of 2013, exchanged experience with Prof. Tang and Qiu and their students, completed a manuscript on computer simulation of microphase separation of mixed brushes grafted on nanorods, and planned future research on mixed brush self-assembly.Publication:1. Tang, S.; Luo T. Y.; Horton, J. M.; Ho, R. M.; Zhao, B.; Tang, P.; Qiu, F.; Zhu, L. Direct visualization of three-dimensional morphology in hierarchically self-assembled mixed poly(tert-butyl acrylate)/polystyrene brush-grafted silica nanoparticles. Macromolecules 2013, doi:10.1021/ma401264m.

Fig. 2

. In the summer of 2012, Prof. Zhu and Saide Tang visited Fudan University and discussed the experimental details of mixed brush self-assembly with Prof. Feng Qiu (right) and Prof. Ping Tang (left).

Fig. 3

.

Graduate student Saide Tang (left) with high school student Julie De La Pena (right) in the TEM lab at CWRU.

Nanoscale Self-Assembly of Well-Defined Binary Mixed

Homopolymer

Brushes Grafted on Inorganic Particles

Lei Zhu, Case Western Reserve University, DMR 1007918