Responsive Films Derived from Weak Polyelectrolyte Multilayers Svetlana Sukhishvili, Stevens Institute of Technology, D

1. Responsive Films Derived from Weak Polyelectrolyte MultilayersSvetlana Sukhishvili, Stevens Institute of Technology, DMR 0513197 Loading LbL-derived hydrogels Release pH, I release entrapment loading pH, I pH 9 pH 11 • The main goal of our project is to explore principles and develop strategies for transforming hydrogen-bonded multilayers into ultrathin highly functional pH-, temperature- and/or ionic strength-responsive coatings and capsules which reversibly trap and release synthetic macromolecules and proteins. The following findings resulted from our studies: • Surface-attached polyacid hydrogels reversibly absorb and release dyes or proteins in response to pH or ionic strength variations. These ultrathin surface hydrogel and can be used as high capacity re-loadable matrices in bioseparation and controlled delivery applications [Langmuir2007, 23, 175-181]. • In the case of hollow capsules with ultrathin wall derived from hydrogen-bonded multilayers, we found that capsules made of a more hydrophobic polycarboxylic acid show minimum of swelling at pH values which are close to physiological [Soft Matter2008, 4,1499-1507]. Possibility of such tuning has implications forthe future application of such capsules for infection control. • We have also constructed novel biocompatible polyvinylpyrroli-done/tannic acid (TA) and polyvinylcaprolactam/TA films via layer-by-layer hydrogen-bonding self-assembly. Distinctively, these films are stable up to high pH values of 9-9.5. However, their disintegration can be tuned to physiological pH~7.5 by incorporating weak polyacids with low pKa values [Macromolecules2008, 41, 3962-3970] • The results are important for design of polymer materials with controlled release properties. pH-controlled dyes or protein absorption and release within/from surface-attached polyacid hydrogels (atop) and capsules (below). 7 μm

2. Responsive Films Derived from Weak Polyelectrolyte MultilayersSvetlana Sukhishvili, Stevens Institute of Technology, DMR 0513197 Outreach: Undergraduate and graduate students participate in the summer high school student research programs. The picture shows a high school ACS SEED student Lessy Pereda (front, center) and an undergraduate student Kate Santullo (front, left) working on the NSF project in summer 2008. NSF-supported project has been presented in four invited talks given by the PI at International Conferences and symposia during the period of August 2007 - July 2008. Education: Funding provided by the NSF supported two graduate students: Veronika Kozlovskaya (5th-6th year, partial support), Svetlana Pavlukhina (2nd year, partial support). Results were incorporated into graduate courses in the Department of Chemistry and Chemical Biology CH “Polymers at Solid-Liquid Interfaces” and CH/NANO 525 “Techniques of Surface and Nanostructure Characterization”. Knowledge accumulated in the group as a result of the NSF support enabled an undergraduate student, Ms. Kate Santullo, to participate into Spring 2008 and summer 2008 research program. Finally, one high school student, Lessy Pereda, sponsored through the ACS project SEED, is participating this summer in the NSF-supported research in our group.