One-pot Synthesis of Dumbbell Polymers through Chain Walking Polymerization Zhibin Guan, University of California - Irvine DMR Figure 1. AFM images of dumbbell-shaped polymer. The right picture is an expansion of the left image (images collected by Prof. Sergei Sheiko at UNC-CH). Current preparation of organic/polymer based nanomaterials usually requires tedious multi-step synthesis. Highly efficient synthetic methodology for nanostructured polymers should benefit many nanotechno- logy applications. In our effort on design of new polymer topologies through chain walking polymerization, we recently explored the use of multi-site chain walking catalysts for one-pot synthesis of nanostruc- tured polymers. For concept demonstration, we first synthesized a dual-site catalyst in which two chain walking catalytic sites are linked onto one spacer. Upon exposure to ethylene at low pressure, polymerization occurs independently at each catalytic site and chain walking at both ends leads to the formation of dumbbell-shaped nanostruc- tures. These unusual polymers are potentially useful as oil and polyolefin additives and can be used as building blocks for nanotechnology applications.

Robust Living Olefin Polymerization by a Cyclophane Nickel Catalyst Zhibin Guan, University of California – Irvine DMR Figure 2. Living polymerization of olefins at elevated temperatures A major breakthrough in our olefin polymerization studies is the development of a new family of cyclophane-based catalysts that show very high activity and high thermal stability for olefin polymerization. The Ni(II)-cyclophane catalyst has a productivity of 42,000 kg PE/(mol Ni·h) and is thermally stable at 90 °C, the temperature suitable for industrial gas phase olefin polymerization processes. Our recent results show that the cyclophane-Ni system catalyzes living polymerizations for a-olefins at high temperatures. These unique features make them promising candidates for further development of transition metal catalyzed ethylene-polar monomer copolymer synthesis. Macromolecules 2005, 38, Angew. Chem., Int. Ed. 2004, 43, 1821.

Design of New Polymer Topologies through Chain Walking Polymerization Zhibin Guan, University of California - Irvine DMR Education: Under the support of this grant, currently one graduate student is finishing his Ph.D. degree: Guanghui Chen (5 th year, accepted a job offer from DuPont) and another graduate student is in 3 rd year: Chris Popeney; with partial support of this grant, two post-doctoral scientists have been involved in this research program: Dr. Drexel Camacho (accepted a job offer from DuPont Central Research Laboratory) and Dr. Jingsong You (now Professor at Sichuan University in China); a number of undergraduate students have also been trained through doing undergraduate research on this project: Lacey Matthews, Justin Lanz and Mr. Alex Nguyen. Outreach: For each summer in the past two years, I have participated in the California State Summer School for Mathematics and Science (COSMOS) program. The mission of COSMOS is to motivate the most creative minds of the new generation of prospective scientists, engineers, and mathematicians who will become leaders for California, the nation, and the world. I discussed about polymer science, nanomaterials and biomaterials topics with a class of very bright high school students. I was also involved with the local activities of the Osher Lifelong Learning Institute (OLLI). I presented a talk this spring with a title of “Better Things for Better Living: Through Polymers”.