Tandem Catalytic Polymerization as Efficient Method to Synthesize Organic Nanoparticles Zhibin Guan, University of California - Irvine DMR Highly efficient synthetic methodology for preparation of organic nanoparticles is important for many nano- and biotechnology. We recently developed a tandem chain walking polymerization (CWP) and ATRP for efficient synthesis of nanoparticles for bioconjugation. Using the chain walking palladium-  -diimine catalyst (catalyst 1), dendritic polymers bearing multiple initiation sites were synthesized and used as macro-initiators for subsequent Cu(I)- mediated ATRP. Both the size and surface active groups can be easily controlled for the synthesis. Conjugation with both small dye molecule and protein yielded nanoparticle conjugates with relatively high conjugation. With the efficient synthesis and good biocompatibility, these nanoparticles may find many potential applications in bioconjugation.. Scheme 1. Concept of tandem chain walking- ATRP polymerization Fig. 1. The living polymerization ensures linear growth of MW for the core- shell nanoparticle, which provides a simple way to control the nanoparticle size. J. Am. Chem. Soc. 2006, 128, 4298.

Discovery of Unexpected Miscibility of Dendritic PE with Linear Polystyrene Zhibin Guan, University of California – Irvine DMR Polyethylene-polystyrene (PE-PS) is a classical example of immiscible polymer blend. However, in a recent collaborative investigation with a group of chemists and engineers, it was discovered that dendritic PE made with our chain walking methodology is fully miscible with linear chain polystyrene as long as the radius of the PE is smaller than the radius of gyration of PS. This finding points to a promising opportunity to prepare many miscible blends of our dendritic polyethylene with various conventional polymers to modify their processibility and physical properties. Science 2006, 311, 1740.

Design of New Polymer Topologies through Chain Walking Polymerization Zhibin Guan, University of California - Irvine DMR Education/Training: Under the support of this grant, Guanghui Chen has finished his Ph.D. and is working at DuPont as a Senior Research Scientist. Chris Popeney is in his forth year of graduate study who will carry out a collaborative research on making new core-shell organic nanoparticles in Germany this fall. Two former post-doctoral scientists being involved in this research program, Dr. Drexel Camacho is working as a senior chemist at Intel; and Dr. Jingsong You is now a full professor at the Sichuan University in China. We continue training undergraduate students by offering research opportunities to them. A sophomore student, Chris Levins, won the SURF-IT research fellowship this year. Outreach: - Participated in the California State Summer School for Mathematics and Science (COSMOS) program. - Participated in our freshman seminar series and discussed polymers and biomaterials. - Shared my industrial experience with undergraduate and graduate students by giving special seminars at OChem and Industrial Chemistry classes.