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The Science of Self-Assembly of Charged Macromoelcules and Soft Matter
Research Theme 1: Quasi-coacervate gel composites — from physical models to smart materials
Coacervates are dense liquid states composed of oppositely charged macromolecules formed via liquid-liquid phase separation, dominated by physical ionic associations. We propose to controllably introduce additional chemical crosslinks and thermo-sensitive polymers by using neutral-charged-neutral triblock polymers to elicit a variety of tunable elastic, transport, and functional properties, in addition to the usual coacervate properties. These quasi coacervate gels, responding synergistically/antagonistically to salt, temperature and orientation, are expected to exhibit discontinuous transitions in mechanical properties, and enhanced charge/heat transport, leading to designable smart soft materials for sensors, energy preservation, and bioelectronics.
Aim 1: Designing hierarchical building blocks to realize multifunctions
Aim 2: Mechanical Response
Aim 3: Dielectric Response
1.Hierarchically dynamical relaxations in non-equilibrium state
2.New regimes of dielectric properties for energy storage materials
Research Theme 2: Mimicry of cellular organelles and design of bioreactors
Our understanding of the influence of the crowding environment and confinement on the stability and activity of biomacromolecules is still rather poor, due to our inability to artificially mimic intracellular organelle environments. We propose to harness several novel water-rich hierarchical structures to mimic cellular organelles and design bioreactors. My strategy includes three parts: compartmentalization to realize multi-functionalities by precisely tuning the charge density, charge distribution (charge pattern) and crosslinking density (mesh size) of the gel matrix according to the shape, size, and charge sequence of the guest molecules; localization of long DNA/RNA chains to improve the searching and binding efficiency; and immobilization of the proteins to enable enzyme reusability and high reactive efficiency.
Research Theme 3: Volume Phase Transition of Mucus and Its Application in Developing Adhesive Vaccine
We will explore the criterion and nature of the first order volume transition (“Jack-in-the-box explosion”) of the gel upon thermodynamic triggers. We will also model the hierarchical mucin assembly and its stability against ionic strength and Donnan pressure. Finally we will explore the critical conditions for the transportation of macromolecules such as antibodies and nutrients through the mucus barriers.
Research Theme 4: Stable mesoscopic assemblies in charged complex systems and its application in water-based memristor
Charged polymer-colloid coacervates/complexation and adsorption of polyelectrolytes on charged colloidal particles are essential in numerous applications such as water-based memristor and memory device. Yet, these are poorly understood. We aim at designing novel polyanion-b-polycation diblock copolymers with different length ratios in a charged colloid-polyelectrolyte system to explore order-disorder transitions and gelation, and building fundamental understanding of the phase behavior, structure, kinetics and rheology of these materials.
Even a modest strength of an external electric field is expected to be a handle to assemble/disassemble the above gel-like structures. We will study the fundamentals of assembly of such large-scale structures under the various stimuli including ionic strength, dielectric constant, and electrostatics. At later stage we will also study such self-assembly behaviors under alternating electric field.
We will study the phase behavior and λ-transition induced by the interference between the gelation line and the phase separation line due to the competition between short-range and long-range interacitons in a self-assmbled system.
Research Theme 5: Physics of coacervation/complexation of charged macromolecules and its applications in neuron science