Multivalent Ions Induce Lateral Structural Inhomogeneities in Biomimetic Polyelectrolyte Brushes

2018-08-06 17:26:00
报告题目:Multivalent Ions Induce Lateral Structural Inhomogeneities in Biomimetic Polyelectrolyte Brushes
报告人:ProfYu Jing (俞璟)

Dr. Yu Jing is anassistant professor in the School of Materials Science and Engineering (MSE) atNanyang Technological University (NTU) in Singapore. He obtained his Bachelor’sdegree from Tsinghua University in 2007, and PhD from the University ofCalifornia, Santa Barbara in 2012, both in Chemical Engineering. His PhDresearch under the supervision of Prof. Jacob Israelachvili focused on thenanomechanics of biomaterials and biomimetics. He conducted experimental andtheoretical studies on both mussel and gecko adhesive systems, and developedbio-inspired polymer surfaces and nano-structured materials. Following his PhD,Jing did a postdoc with Prof. James Heath at California Institute ofTechnology, where he worked on engineered T cell immunotherapy. In 2014, heexpanded his research interests towards polyelectrolytes brushes during hispostdoc with Prof. Matthew Tirrell at the University of Chicago.
The overall goalof Dr. Yu Jing’s research is to characterize the dynamic properties of interfaceswith hierarchical structures, and to gain molecular-level control of softinterfaces to enable design of integrated, multifunctional interfaces. He isinterested in non-equilibrium properties of soft interfaces, bioinspiredmaterials and biomimetics, intermolecular interactions, nanomechanics,self-assembly of supramolecular structures, as well as X-ray and neutronscattering.
Understanding the response of polyelectrolytes totheir environment has challenged materials scientists for decades.Polyelectrolyte brushes are of particular interest, as they can regulatetransport of ions and molecules, control wettability and adhesion of surfaces,or convert chemical and biochemical stimuli into optical, electrical, andmechanical signals. We combined neutron-reflectivity (NR), atomic forcemicroscopy (AFM), surface forces apparatus (SFA) measurements, andcoarse-grained molecular dynamics (MD) simulations to study the structure ofplanar biomimetic polyelectrolyte brushes (poly(styrenesulfonate), PSS) in avariety of solvent conditions, especially in the presence of multivalentcounterions. Multivalent-ion induced lateral structural inhomogeneities of thePSS brushes were first indicated by NR measurements. AFM images provide adirect visualization of lateral inhomogeneities on the surface ofpolyelectrolyte brushes collapsed in solutions containing trivalentcounterions. These images are interpreted in the context of a coarse-grainedmolecular model, and are corroborated by accompanying interaction-forcemeasurements with the SFA. Our findings indicate that lateral inhomogeneitiesare absent from PSS brush layers collapsed in a poor solvent withoutmultivalent ions. The inhomogeneous structures of the polyelectrolyte brushesin the presence of multivalent ions can dramatically alter theirfunctionalities in various biomedical applications, such as lubrication,sensors, and DNA-based microarrays.

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