Nonequilibrium Behavior of Polymer Systems
Understanding the phase-separation and self-assembling behavior of polymer systems out of thermodynamic equilibrium is of great interest and crucial importance because (a) such systems usually have complex free-energy landscapes that harbor numerous metastable states that trap the system and prevent it from reaching true thermodynamic equilibrium, and (b) the fabrication of certain desired structured materials relies on carefully designed processing pathways and intentional thermodynamic or kinetic trapping. One prominent example is the fabrication of ultrafiltration membranes with finely controlled pore sizes, where an integral, hierarchical, nonequilibrium membrane structure is arrested using solvent-induced self-assembly followed by nonsolvent-induced phase separation, collectively termed SNIPS. Combining theory and particle simulations, we study the nonequilibrium behavior of various polymer systems, particularly the role of processing pathways in determining the final material morphology and characteristic length scales, including in SNIPS-fabricated ultrafiltration membranes.
Selected publications:
1. Xie, J., & Müller, M. (2025). Process-Directed Self-Assembly of Copolymer Blends: I. Micro- and Macrophase Separation. Macromolecules, 58(21), 11523–11538.
2. Xie, J., & Müller, M. (2025). Process-Directed Self-Assembly of Copolymer Blends: II. Continuous Tuning of Structure Size. Macromolecules, 58(21), 11539–11557.
3. Blagojevic, N., Das, S., Xie, J., Dreyer, O., Radjabian, M., Held, M., Abetz, V. and Müller, M. (2024). Toward Predicting the Formation of Integral‐Asymmetric, Isoporous Diblock Copolymer Membranes. Advanced Materials, 36(40), 2404560.
Complex Structural Formation in Polymer Mixtures
Over the past decade, many unconventional, complex structures have been discovered in soft matter. One of the most notable examples is the discovery of Frank-Kasper (FK) phases in self-assemblies from systems containing amphiphilic molecules, ranging from block copolymers to surfactant solutions. In contrast to conventional crystalline structures such as BCC or FCC, the FK phases have more complicated unit cells composed of multiple nonequivalent "mesoatoms". Using polymeric mixtures as a model system, we apply self-consistent field theory (SCFT) to investigate the formation of complex structures, including the FK phases. The results will deepen our understanding of the emergence of complex structures in nature, thus enabling more precise morphological control in fabricating soft materials, which is crucial for applications such as photonic crystals and lithography.
Selected publications:
1. Xie, J., & Shi, A. C. (2021). Formation of complex spherical packing phases in diblock copolymer/homopolymer blends. Giant, 5, 100043.
2. Xie, J., Li, Y., & Shi, A. C. (2021). Binary blends of diblock copolymers: An efficient route to complex spherical packing phases. Macromolecular Theory and Simulations, 30(6), 2100053.
3. Xie, J., & Shi, A. C. (2023). Phase behavior of binary blends of diblock copolymers: Progress and opportunities. Langmuir, 39(33), 11491-11509.
Topological Effects of Block Copolymers
Macromolecules can have a variety of distinct molecular architectures/topologies. Such topological differences can result in significantly different material properties. Block copolymers provide an ideal model system for studying these topological effects. By combining theory, numerical computation, and experiments, we explore the effects of molecular topology on different aspects of the phase behavior of various polymeric systems, including order-disorder transition (ODT), blend miscibility and structural formation. The results will provide valuable insights into molecular design for creating desired materials.
Selected publications:
1. Xie, J., & Shi, A. C. (2024). Phase behavior of triblock copolymer and homopolymer blends: Effect of copolymer topology. Physical Review Materials, 8(1), 015601.
2. Chang, C. Y., Manesi, G. M., Xie, J., et al. (2024). Topology Effect on Order–Disorder Transition of High-χ Block Copolymers. Macromolecules, 57(15), 7087–7097.
3. Li, J., Xie, J., et al. (2024). Effect of Molecular Symmetry on the Self-Assembly Behavior of AB2 Linear–Branched Block Copolymers. Macromolecules, 57(22), 10648-10656.
