Soft matter is a cross disciplinary research field involving physics, chemistry, biology, and materials science. Dr. Chen uses basic tools such as statistical physics, field theory, neural networks, and computer simulations to study structural formation in polymers and liquid crystals.
Contact information
Office: PHY 367
Phone: 519 888-4567 ext. 45361
Email: jeffchen@uwaterloo.ca
Website: Jeff Chen, University of Waterloo
Soft matter is a cross disciplinary research field involving physics, chemistry, biology, and materials science. It studies physical systems that can be deformed relatively easily in response to external and internal physical and chemical conditions. Examples include colloids, polymers, gels, liquid crystals, and a number of biological systems. These materials compete with and sometimes outperform the traditional solid-state materials. Soft matter theory is a field that has seen vast new developments in the last half century, in both fundamental and applied research.
My research group has built a comprehensive soft-matter-theory research program that covers a number of challenging problems in polymers, membranes, and liquid crystals. The primary thrust is to establish a fundamental understanding of the structures, states, and dynamics of soft matter systems such as semiflexible polymers, as well as liquid crystals and their defect structures. The main research tool is statistical physics, which includes scaling theory, Monte Carlo and molecular dynamics simulations, and field-theory simulations.
Example Problems
Block copolymers are basic building blocks that can be used to design exquisitely tailored materials with unparalleled control over nanoscale-domain geometry, packing symmetry, and chemical composition. Semiflexibility is a factor that plays a crucial role in the conformational properties of wormlike polymer chains. Formulating as well as solving the self-consistent field theory for wormlike copolymers that take semiflexibility into account has long been known as one of the main challenges in polymer physics. We developed a numerical technique to calculate the phase diagram where semiflexibility is one of the additional tuning parameter beyond the classical phase diagram of flexible diblock copolymers. [Y. Jiang and J. Z. Y. Chen, Phys. Rev. Lett. 110, 138305 (2013); J. Z. Y. Chen, Prog. Polym Science 54-55, 3 (2016)]
In recent years, a whole body of knowledge has been generated on defect structures resulting from placing a liquid crystal within a finite geometry that frustrates the director field. The natural tendency of forming a uniform bulk nematic configuration is interrupted by the curvature of the embedded surface or boundary conditions of the confining walls. We studied the extended Onsager model that contains identifiable physical parameters instead of phenomenological parameters used in Landau-de Gennes and Frank elastic models. We theoretically presented a unified phase diagram for the evolution of defect structures from the isotropic-nematic transition to a deep nematic state, over a wide range of parameter space. For the first time, we captured the results observed in recent Monte Carlo simulations and calculated from the Frank model all within one unified physical picture. [W.-Y. Zhang, Y. Jiang and J. Z. Y. Chen, Phys. Rev. Lett. 108, 057801 (2012). Q. Liang, S. Ye, P. Zhang, and J. Z. Y. Chen, J. Chem. Phys. 141, 244901(2014)]
