1. 化工学院第七届国际交流月系列讲座 邀请人：王文俊 化学工程与生物工程学院 化学工程联合国家重点实验室（浙江大学）
Prof. Nicholas L. Abbott
Department of Chemical and Biological Engineering
University of Wisconsin-Madison
Dr. Nicholas L. Abbott is Professor and Director of Wisconsin Materials Research and Engineering Center at University of Wisconsin-Madison. He received his Ph.D. degree from Massachusetts Institute of Technology in He works in the fields of interfacial phenomena, colloid science, soft materials, biomolecular interfaces, polymers, liquid crystals and surfactant and hydrophobic effect. He has received numerous awards, including Byron Bird Award in 2015 and ACS Award in Colloid and Surface Chemistry in He was elected as a Member of National Academy of Engineering in 2014 and a Fellow of American Institute for Medical and Biological Engineering in 2016.
Lecture 1: May 23rd, :00 am - 12:00 pm Room Building 7
Topological Defects in Liquid Crystals as Templates for Molecular Self-assembly
Topological defects in liquid crystals (LCs) have been widely used to organize colloidal dispersions and template polymerizations, leading to a range of elastomers and gels with complex mechanical and optical properties. However, little is understood about molecular-level assembly processes within defects. This presentation will describe an experimental study that reveals that nanoscopic environments defined by LC topological defects can selectively trigger processes of molecular self-assembly. By using fluorescence microscopy, cryogenic transmission electron microscopy and super-resolution optical microscopy, key signatures of molecular self-assembly of amphiphilic molecules in topological defects are observed - including cooperativity, reversibility, and controlled growth of the molecular assemblies. By using polymerizable amphiphiles, we also demonstrate preservation of molecular assemblies templated by defects, including nanoscopic “o-rings” synthesized from “Saturn-ring” disclinations. Our results reveal that topological defects in LCs are a versatile class of three-dimensional, dynamic and reconfigurable templates that can direct processes of molecular self-assembly in a manner that is strongly analogous to other classes of macromolecular templates (e.g., polymer—surfactant complexes). Opportunities for the design of exquisitely responsive soft materials will be discussed using bacterial endotoxin as an example.
Lecture 2: May 24th, :00 am - 12:00 pm Room Building 7
Modulation of the Strength of Hydrophobic Interactions at Heterogeneous Interfaces
The structuring of water near non-polar molecular fragments or surfaces mediates cohesive interactions (so-called hydrophobic interactions) that underlie a broad range of interfacial, colloidal and biophysical phenomena. Substantial progress has been made during the past decade towards understanding hydrophobic interactions in simple model systems, but in most biological and technological contexts, non-polar domains are found in close proximity to polar and charged functional groups. Theories and simulations hint that the effects of nanometer-scale chemical heterogeneity on hydrophobic interactions may be important, but these ideas have not been tested experimentally. In this presentation, I will show that ions immobilized adjacent to non-polar domains can substantially increase or decrease the strength of hydrophobic interactions, with the effect strongly dependent on the specific ion type. By using chemical force microscopy and surfaces presenting alkyl and amine/ammonium (Am) units, we have found that protonation of amines can double the strength of hydrophobic interactions. In contrast, guanidine/guanidinium (Gdm) groups, when co-immobilized with alkyl groups, are found to eliminate measurable hydrophobic interactions. These divergent effects of proximally immobilized cations were confirmed by single-molecule measurements with a biologically-inspired system comprised of conformationally-stable -amino acid oligomers (-peptides) that generate precise nanopatterns of non-polar and either Am- or Gdm-bearing subunits (3-homolysine and 3-homoarginine residues, respectively). These results demonstrate that the “hydrophobicity” of non-polar domains is not a property of the species that constitute the domain but rather is strongly modulated by functional groups located as far away as 1 nm.This understanding provides a fresh starting point for optimizing molecular recognition processes as well as the self-assembly of synthetic amphiphiles, colloids, or macromolecules by judiciously placing charged groups near non-polar domains to tune hydrophobic driving forces.
邀请人：王文俊
化学工程与生物工程学院
化学工程联合国家重点实验室（浙江大学）