Materials World Network: US-Russia Collaboration on Responsive Micelles at Surfaces – A Combined Experimental and Theoretical Approach Svetlana A. Sukhishvili, Stevens Institute of Technology, DMR Many potential applications of layer-by-layer (LbL) polymer films, such as actuation and drug delivery from surfaces, depend critically on the capability to impart films with specific environmental response characteristics. We used block copolymer micelles (BCMs) for constructing films responsive to temperature and pH, and explored how the type of copolymer, co-assembled polyelectrolyte (PE) and film assembly conditions determined film response. Using synthesized neutral and ionic diblock copolymers, we have constructed T- and pH-responsive micelles, and deposited them within LbL films. 1 In solutions of micelles with weak PE coronae, we have observed novel pH-induced phase transitions between large, weakly charged and small, strongly charged micelles (Fig. 1) 2. Among micelles with PE cores, we found a new type of micelle with ionomer-like cores 3. Both phenomena were studied theoretically and experimentally. At surfaces, we have constructed novel biocompatible, pH- stable 4,5, and temperature-erasable LbL films 6. We showed that within multilayers, micelles with either pH- or temperature- dissolvable cores were stabilized due to binding with a homopolymer, and provided control over reversible film swelling 7-9 and delivery of incorporated functional molecules (Fig. 2) 7,8. Fig. 1. pH-induced size changes of PDMA-b-PNIPAM micelles 10. Fig. 2. Preserved micellar morphology within PE-covered BCM monolayer (A), and reversible release of pyrene from PNIPAM- core BCM/PMAA multilayer films 11 (B). 45°C 25°C T 0 1  m 20 nm A B

We have established close collaboration with our Russian counterparts. 1 Two US graduate students has visited Russia to present their work at conferences and to discuss results with international collaborators. Irem Erel (Fig. 1, center) has participated in a conference " Molecular Order and Mobility in Polymer Systems", St. Petersburg, Russia in June of Another US graduate student, Alex Zhuk, gave two talks at the 5th conference of young scientists “Modern Problems of Polymer Science” in St. Petersburg (Russia) in October 2009 (Fig.1, right). Results of the project have been incorporated into two graduate courses 2 and presented in ten invited talks at universities and regional or international conferences 3, as well as at the Research and Entrepreneurship Day at Stevens in May 2009 which gathers a broad audience of NY/NJ entrepreneurs, National Lab representatives, and high school teachers. Importantly, the project has further energized the involvement of undergraduate and high school students in our research (Fig. 2). Technological output of our research includes development of environmentally triggered polymer matrices for controlled delivery of active components from surfaces, such as coatings on dental implant surfaces. Fig. 1. US-Russia collaboration. Left: PI Sukhishvili (US, left) and Kramarenko (Russia, right) discuss results of the project in December Center: Ph.D. students Elena Nyrkova (Russia, left) and Irem Erel (US, right) during discussion of their joint paper in June Right: Ph.D. student Alex Zhuk (US, center) receiving an award for his presentation at the international conference in St. Petersburg, Russia in October Fig. 2. Graduate, undergraduate and high-school students participate in the project: undergraduate students Lauren Spagnuolo (2009, in grey) and Rachel Turner (2010, in grey), and high school students Diego Barriga (2009, in white, left; ACS SEED Program), Dipixa Rathod (2009, in white, right; Partners in Science Program), and Iris Sydney (2010, in white, Waldwick High School) Materials World Network: US-Russia Collaboration on Responsive Micelles at Surfaces – A Combined Experimental and Theoretical Approach Svetlana A. Sukhishvili, Stevens Institute of Technology, DMR