TECHNICAL EXPLANATION The objective of the project is to explore principles and develop strategies for transforming polyelectrolyte multilayers (PEMs) into highly functional pH-, ionic strength- and/or temperature-responsive coatings which reversibly trap or release synthetic macromolecules and proteins. New knowledge generated in this project about physical and chemical ways to stabilize polymer films at surfaces will be a significant contribution to materials and polymer science. Specifically, the project will provide a wealth of information on issues pertaining to molecular design of building block for responsive polymer self-assembly, derivatization of PEMs into active surface coatings and potential capabilities in PEM-based regulation of surface adhesion and absorption properties. Our approach will be based on a combination of molecular engineering and synthesis of polymeric 'building blocks' of PEMs with the chemical composition necessary for further transformation of PEMs into an absorbing film. We will explore several routes of producing surface-attached active absorbing films using electrostatic or hydrogen-bonded polymer multilayers as a starting material. The first route will be based on the dissociation of components of electrostatically assembled multilayers at high concentrations of small ions combined with selective 'salting-out' of one of the film components. In another scenario, we will explore chemical crosslinking of hydrogen-bonding multilayers as a means to produce surface-attached hydrogels. One-component hydrogels of polycarboxylic acids will be produced by selective crosslinking of self-assembled polycarboxylic acids and further release of hydrogen-bonded polymers from the crosslinked polyacid matrix. Two-component hydrogels will be obtained by reacting end-functionalized hydrogen-bonding polymers with carboxylic groups of selfassembled polyacid. In the latter type of absorbing films, response and absorbing properties will be modulated through intermolecular adhesion between hydrogen-bonded polymer chains. Selective monitoring of film composition, ionization of functional groups and quantification of charge balance will be done using in situ ATR-FTIR. The data will be correlated with the results of film swelling as measured with in situ ellipsometry and in situ AFM. The question of how interpolymer interactions respond to environmental stimuli, and how they are translated into changes in film density and absorption properties will be addressed. NON-TECHNICAL EXPLANATION The use of produced films as re-loadable matrices that could reversibly and controllably absorb and desorb macromolecules and proteins from response to environmental stimuli, specifically valuable for separation, concentration, and controlled release of chemicals and proteins in environments with dominating effects of surfaces such as in a microfluidic channel. Results of proposed research will be made available to a broad scientific audience through conference presentations, invited talks given by the PI of this project, poster and oral presentations of graduate students, and archival literature. The educational impact includes building a stronger interdisciplinary polymer program at Stevens that will provide better training for students. The results of the proposed research will be included into recently developed advanced polymer courses, such as Polymers at Solid-Liquid Interfaces, and other core laboratory courses at both graduate and undergraduate levels. Participation of women in advanced research will be enhanced also through support of two female graduate students. Finally, economically disadvantaged high school students will be given an opportunity to be exposed to this research due to activities our group sustains in the ACS SEED program.
