Thursday, 16 November, 2017
UT Host: Dr. Bin Zhao, Chemistry Professor
Speaker: Dr. Christopher Li, Materials Science & Engineering Professor at Drexel University
Title: “Designed Polymer Crystallization for Functional Nanomaterials”
Abstract: Crystallization is ubiquitous in nature and semicrystalline polymers are of crucial importance in our daily life. Compared with small molecules, polymers crystallize via a more complex pathway because of their long chain nature and various metastable states associated with polymer crystals. In this talk, I will show that this complex conformational change of polymer chains upon crystallization can be employed to design and fabricate functional nanomaterials. Three examples will be discussed. First, ordered hybrid nanomaterials were formed by controlling the interaction between low dimensional nanoparticles and polymer single crystals (PSC) with tailor-designed folds. These ordered hybrids can find applications ranging from polymer nanocomposites to artificial nanomotors. Second, a miniemulsion crystallization method was developed to grow nanosized, PSC capsules. We coined the name “crystalsome” to describe this unique structure because their structure mimics liposomes and polymersomes. Atomic force microscopy measurement demonstrated a two �' three orders of magnitude increase in bending modulus compared with conventional polymersomes. Third, by using end-functionalized crystalline polymers and controlling chain folding during crystallization, super dense and loop polymer brushes with precise chain anchoring points can be synthesized. Novel responsive molecular Velcro was also prepared. We envisage that not only can the designed polymer crystallization help better understand the crystallization mechanisms of long chain polymers, it is also a powerful tool to synthesize novel functional nanomaterials.
Biography: Christopher Li received his B. S. from the University of Science and Technology of China in 1995 and his Ph.D. from the Department of Polymer Science, The University of Akron in December, 1999. After working as a post-doc at the Maurice Morton Institute of Polymer Science, UA for 2 years, he joined Drexel University, the Department of Materials Science and Engineering in January, 2002 as an assistant professor, and was promoted to associate and full professor in 2007, and 2011, respectively. His research interests center on the structure and morphology of ordered polymeric systems and hybrid materials. Christopher Li is a Fellow of American Physical Society and North American Thermal Analysis Society, and is on the Editorial Advisory Board of Macromolecules, ACS macro letters, and Polymer. He has received a number of awards including the NSF Creativity Award, NSF-CAREER Award, the Inaugural Provost Award for Outstanding Mid-Career Scholarly Productivity, Alexander von Humboldt Research Fellowship, ASM Bradley Stoughton Award, DuPont Young Faculty Award, among others. He served as the President of the North American Thermal Analysis Society (NATAS) in 2016.
Web Cast: This seminar is not web cast.