Mechanical, Structural, and Transport Properties of Nanostructured Block Copolymer Solutions

Event Date: April 18, 2014
Speaker: Lynn M. Walker
Speaker Affiliation: Professor of Chemical Engineering and Material Science and Engineering (Courtesy), Carnegie Mellon University
Sponsor: Purdue School of Materials Engineering
Type: Spring 2014 Winchell Seminar Series
Time: 3:30pm Coffee, 3:45pm Seminar
Location: ARMS 1010

Self-assembled block copolymer templates are used to control the nanoscale structure of materials that would not otherwise order in solution. In this work, we have developed a technique to use close-packed cubic and cylindrical mesophases of a thermoreversible block copolymer (PEO-PPO-PEO) to impart spatial order on dispersed nanoparticles. The thermoreversible nature of the template allows for the dispersion of particles synthesized outside the template. This feature extends the applicability of this templating method to many particle-polymer systems, including proteins, and also permits a systematic evaluation of the impact of design parameters on the structure and mechanical properties of the nanocomposites. The criteria for forming cocrystals have been characterized using small-angle scatting and the mechanical properties of these soft crystals determined. Numerous crystal structures have been reported for the block copolymer system and we have taken advantage of several to generate soft co-crystals. The result of this templating is spatially ordered nanoparticle arrays embedded within the block copolymer nanostructure. These soft materials can be shear aligned into crystals with long range order and this shear alignment is discussed. Finally, the dynamics of nanoparticles within the nanostructured material are characterized with fluorescence recovery after photobleaching (FRAP). The applications and general behavior of these nanostructured hydrogels are outlined.

Professor Lynn Walker is currently Professor of Chemical Engineering with courtesy appointments in Chemistry and in Materials Science & Engineering. Prof. Walker received her BS Chemical Engineering degree from the University of New Hampshire in 1990 and her PhD from the University of Delaware in 1995, under the supervision of Norman Wagner. After holding a postdoctoral position at Katholieke Universiteit Leuven, Leuven Belgium, Prof. Walker joined Carnegie Mellon's Department of Chemical Engineering in 1997. Prof. Walker was a Visiting Professor during a sabbatical at Polymer IRC, University of Leeds in 2007. The objective of Prof. Walker's research is to quantify the relationship between molecular-level interactions and macroscopic fluid behavior. Her group has developed experimental tools and techniques for systematically controlling molecular-level behavior, characterizing nanoscale and microscale structure in fluid systems and quantifying rheology and flow behavior of complex fluids.