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 [Langmuir 2007, 23, 175].

• In the case of hollow capsules with ultrathin wall derived from hydrogen-bonded multilayers, we found that such capsules show reversible ~600-fold softening (with stiffness reaching values as low as 1 mN m-1) in response to pH increase as a result of increased polyacid ionization [Soft Matter 2006, 2, 966].

• We have found that hollow capsules flatten upon interacting with a solid surface, and that such flattening is controlled by the capsule mechanical properties, as well as by charge of the surface and the capsule wall [Macromolecules 2006, 39, 6191].

• 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 (Manuscript in preparation). The results are important for design of polymer materials with controlled release properties.

Responsive Films Derived from Weak Polyelectrolyte Multilayers Svetlana Sukhishvili, Stevens Institute of Technology, DMR 0513197

pH-controlled dyes or protein absorption and release within/from surface-attached polyacid hydrogels (atop) and capsules (below).

7 μm

CLSM images of (PMAA)7 capsules adsorbed on bare glass (A) and on

a polycation-coated glass (B) surfaces at pH 10. The scale bar is 5 μm.

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H+

CH3CH3

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Loading Release

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LbL-derived

hydrogels

loading entrapment

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Education:Funding provided by the NSF supported three Ph.D. students: Veronika Kozlovskaya (5th year, partial support), Irem Erel-Unal (3d year, partial support), and Eugenia Kharlampieva (postdoctoral training, 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. Preet Maroke, to participate into Spring 2007 research program. Finally, one high school student, Elia D. Claros, sponsored through the ACS project SEED, is participating this summer in the NSF-supported research in our group. Another high school student, Diana C. Leon, is voluntarily gaining research experience in our group this summer.

Outreach:Undergraduate and graduate students participate in the summer high school student research programs, sponsored by the ACS project SEED project. The picture below shows Elia Claros (in the center) and Diana Leon (to the right) with Sukhishvili’s group members.

NSF-supported project has been presented to a broad community of New York City and NJ businessmen. Results were also presented in four invited talks given by the PI at the College of Staten Island of CUNY, NY, at the Indiana University, IN, at the Optics East SPIE Symposium in Boston, MA, and at the IUMACRO 2007 Conference at Brooklyn Polytechnic University in NY during the period of August 2006/July 2007.

Responsive Films Derived from Weak Polyelectrolyte Multilayers Svetlana Sukhishvili, Stevens Institute of Technology, DMR 0513197