jxren at uchicago.edu
Previous work in the Nealey group has demonstrated that the self-assembly of block copolymers can be precisely controlled with chemically patterned surfaces by tuning the interactions at the interface between a BCP film and the substrate on which it is deposited. This works involved relatively simple morphologies like lamella and cylinders oriented normal to the supporting substrate. Other block copolymer systems can self-assemble into more complex 3D lattice structures like those found in crystals. Through careful engineering of their self-assembled morphologies, thick films of these novel materials have promising applications in membrane separation as well as energy generation and storage.
Jiaxing is investigating strategies to direct the assembly of block copolymers by using 2D chemical patterns that match the projection of the desired 3D morphologies. As a first step, he studied the directed self-assembly of sphere-forming poly(styrene-b-methyl methacrylate) (PS-b-PMMA), achieving perfect assembly of PMMA spheres in a body-centered cubic (BCC) lattice on chemical patterns with square arrays of spots that mirror the (100) plane of the BCC lattice. He has been able to induce perfect orderings in thicker films up to 240nm, which contain five layers of BCC unit cells.
Through extensive collaborations with researchers at Argonne National Laboratory, Jiaxing is also developing methods to back etch the silicon substrate after polymer assembly. Through this approach, the detailed 3D structures within the polymer films can be studied in situ by transmission X-ray and TEM without distorting or damaging the films.
Jiaxing Ren did his undergraduate study in chemical engineering at Tsingshua University in Beijing, where he got his first research experience investigating the dispersion of carbon nanotubes. During his senior year, Jiaxing was chosen to join an industry-sponsored exchange program and went to University of Illinois at Urbana-Champaign to pursue a master’s degree in chemical engineering. While at Illinois, he joined Prof. Charles Zukoski’s (now Provost of the University at Buffalo) laboratory and studied the crosslinking of hydrogels with stearic acid. As part of the exchange program, he also interned at the PepsiCo R&D center and established formulas and processing conditions for the Quaker Popped Hummus Chips in the pilot plant. He graduated in 2010 with bachelor’s degree from Tsinghua University and master’s degree from University of Illinois.
Jiaxing joined Prof. Paul Nealey’s group at the University of Wisconsin–Madison in 2011 and started working on the directed self-assembly of block copolymers. There he developed methods to precisely control the 3D lattice structures of block copolymers using 2D chemical patterns. In 2013, Jiaxing obtained a master’s degree from the University of Wisconsin and relocated with the Nealey group to the University of Chicago to continue his doctoral study at the newly established Institute for Molecular Engineering. At Chicago, he collaborated extensively with the Center for Nanoscale Materials at Argonne National Laboratory and developed membrane fabrication techniques that enabled TEM tomography and X-ray characterization to investigate the in-film 3D structures in block copolymer self-assembly.
- Controlling Domain Orientation of Liquid Crystalline Block Copolymer in Thin Films Through Tuning Mesogenic Chemical Structures
- Quantitative Three-Dimensional Characterization of Block Copolymer Directed Self-Assembly on Combined Chemical and Topographical Prepatterned Templates
- Interconnected ionic domains enhance conductivity in microphase separated block copolymer electrolytes
- Post-directed-self-assembly membrane fabrication for in situ analysis of block copolymer structures