Responsive Films Derived from Weak Polyelectrolyte Multilayers

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TECHNICAL EXPLANATION The objective of the project is to explore principles and develop strategiesfor transforming polyelectrolyte multilayers (PEMs) into highly functional pH-, ionicstrength- and/or temperature-responsive coatings which reversibly trap or releasesynthetic macromolecules and proteins. New knowledge generated in this project aboutphysical and chemical ways to stabilize polymer films at surfaces will be a significantcontribution to materials and polymer science. Specifically, the project will provide a wealth ofinformation on issues pertaining to molecular design of building block for responsive polymerself-assembly, derivatization of PEMs into active surface coatings and potential capabilitiesin PEM-based regulation of surface adhesion and absorption properties.Our approach will be based on a combination of molecular engineering and synthesis ofpolymeric 'building blocks' of PEMs with the chemical composition necessary for furthertransformation of PEMs into an absorbing film. We will explore several routes of producingsurface-attached active absorbing films using electrostatic or hydrogen-bonded polymermultilayers as a starting material. The first route will be based on the dissociation of componentsof electrostatically assembled multilayers at high concentrations of small ions combined withselective 'salting-out' of one of the film components. In another scenario, we will explorechemical crosslinking of hydrogen-bonding multilayers as a means to produce surface-attachedhydrogels. One-component hydrogels of polycarboxylic acids will be produced by selectivecrosslinking of self-assembled polycarboxylic acids and further release of hydrogen-bondedpolymers from the crosslinked polyacid matrix. Two-component hydrogels will be obtained byreacting end-functionalized hydrogen-bonding polymers with carboxylic groups of selfassembledpolyacid. In the latter type of absorbing films, response and absorbing properties willbe modulated through intermolecular adhesion between hydrogen-bonded polymer chains.Selective monitoring of film composition, ionization of functional groups and quantification ofcharge balance will be done using in situ ATR-FTIR. The data will be correlated with the resultsof film swelling as measured with in situ ellipsometry and in situ AFM. The question of howinterpolymer interactions respond to environmental stimuli, and how they are translated intochanges in film density and absorption properties will be addressed.NON-TECHNICAL EXPLANATION The use of produced films as re-loadable matrices that could reversibly andcontrollably absorb and desorb macromolecules and proteins from response to environmentalstimuli, specifically valuable for separation, concentration, and controlled release of chemicalsand proteins in environments with dominating effects of surfaces such as in a microfluidicchannel. Results of proposed research will be made available to a broad scientific audiencethrough conference presentations, invited talks given by the PI of this project, poster and oralpresentations of graduate students, and archival literature.The educational impact includes building a stronger interdisciplinary polymer program atStevens that will provide better training for students. The results of the proposed research will beincluded into recently developed advanced polymer courses, such as Polymers at Solid-LiquidInterfaces, and other core laboratory courses at both graduate and undergraduate levels.Participation of women in advanced research will be enhanced also through support of twofemale graduate students. Finally, economically disadvantaged high school students will begiven an opportunity to be exposed to this research due to activities our group sustains in theACS SEED program.