Segmental + Dipole moment = q × ℓ ℓ _ Normal (Type-B) || (Type -A) Dynamics of MacromoleculesJovan Mijovic, Polytechnic University, DMR-0101182 For animation: click on the picture Studies of dynamics probe the motions of molecular chains in an applied field, such as electrical or mechanical. Those motions cover a range of time scales (from slow to fast) and are crucial for understanding processing and properties of materials. We utilize dielectric relaxation spectroscopy (DRS) and dynamic mechanical spectroscopy (DMS) to explore dynamics of macromolecules. The aim of our research is to realize macroscopic properties from molecular concepts. Three types of molecular architectures (Figure 1) were investigated: 1) Polymer networks; 2) Multigraft block copolymers; 3) Helical biopolymers (DNA). In Figure 2 we show how the slower motions of entire chains (normal mode) can be distinguished from the faster motions of chain segments (segmental mode). Type 1 Type 3 Figure 1. Three types of molecular architectures investigated. Type 2 ε" log ƒ (Hz) Figure 2. Type A and type B dipoles in polymer chains give rise to normal (slow) and segmental (fast) modes detectable by DRS and DMS. An example of a dielectric spectrum of polypropylene oxide (PPO) is shown in the right.
Dynamics of Macromolecules Jovan Mijovic, Polytechnic University, DMR-0101182 Education: Five Chemical Engineering Ph.D students: Mingyun Sun (4th year), Hua Zhang (4th year), Hyungki Lee (2nd year), Yu Bian (2nd year), Chetan Khamar (1st year) and three undergraduate students in Chemical and Biological Engineering: Ruel McKenzie (Junior), Jelena Culic-Viskota (Sophomore), and Marcin Steckiewicz (Junior) are currently involved in this program. Outreach: Every year our lab accommodates a number of under-represented minority students from New York City high schools under the aegis of the YES (Youth in Engineering and Science) summer program at Polytechnic University. Recent Publications Macromolecules, 2002, 35, 6417; 2003, 36, 4589, 7640. Photo Caption: From left to right: Jelena Culic-Viskota, Marcin Steckiewicz, Mingyun Sun, Hyungki Lee, Ruel McKenzie, Hua Zhang, Chetan Khamar, Professor Mijovic, Yu Bian.