Back row, left-right: Mohamad,
Bobby, Maroun, JBS, Rana, Amir, Jad
Front row: Marie, Lara, Layal
surfaces, polyelectrolytes, polyelectrolyte structures.
Analytical chemistry of macromolecules.
Electrochemistry of materials.
science offers many opportunities to explore the connections between basic and
applied chemistry. Our laboratory is engaged in multidisciplinary research
centered on the use of novel structures made from polyelectrolytes. These
charged, water-soluble macromolecules, found in products from shampoos to water
treatment chemicals, can be formed into ultrathin films by a very simple
technique: when a substrate is exposed to oppositely-charged polyelectrolytes
in an alternating fashion, a thin, uniform film of polymer is deposited layer
by layer. Potential applications are in several areas, including light-emitting
devices, nonlinear optics, sensors, patterning, separations, enzyme active
films and bioadhesion.
Ongoing research projects are wide-ranging and follow the entire “food chain” from synthesis to functional structures. Here are some examples:
Block and Random Copolymer Modification
We have made copolymers, charged and neutral, designed to stick to surfaces through the metal-thiol interactions. Other new materials include triblock copolymers rendered charged via selective sulfonation or alkylation to produce surface active “polysoaps.”
Polyelectrolyte Multilayer Construction
Polyelectrolytes offer great versatility as building blocks: their conformation is a sensitive function of solution ionic strength, which also regulates interaction between the charges on the backbone. When these and other experimental variables are added to the vast palette of polyelectrolyte architectures available for multilayer synthesis, a large parameter space for experimentation is created. We have built several computer controlled robots that assist us in optimizing the synthesis of multilayers with desired properties. We have designed and built multilayers for patterning, programmed deconstruction, separations, and biomolecule adsorption control.
Polyelectrolyte Multilayers in Separations
Multilayers used for analytical and membrane purification separations are under study. For analytical separations, fused silica capillaries coated with multilayers are particularly effective for the separation of proteins by capillary zone electrophoresis. Permeability experiments using electrodes coated with multilayers show a strong selectivity for ions of low charge. Furthermore, the membrane transport of polyvalent ions is a strong function of salt concentration in the bathing solution.
Most polyelectrolytes multilayers actually have little “structure” in terms of distinct stratification. One of the most important materials parameters, dictating the multilayer performance in many applications, is the mechanism by which charge is balanced and distributed throughout the multilayer. For example, a multilayer containing no salt ions has very low permeability for ion exchange and transport, but high selectivity. We are engaged in fundamental studies determining the population and location of small (“salt”) counterions throughout multilayers. This knowledge is used to produce models for the structure and mechanism for multilayer buildup and propagation.
SEE OUR WEB PAGE ON POLYELECTROLYTE
J.A. Jaber, J.B. Schlenoff, J. Am. Chem. Soc., 128, 2940-2947 (2006) “Mechanical Properties of Reversibly Crosslinked Ultrathin Polyelectrolytes Complexes.”
C. Bucur, J.B. Schlenoff, Analytical Chemistry, 17, 2360-2365 (2006). “Electrogenerated Chemiluminescence in Polyelectrolyte Multilayers: Efficiency and Mechanism”
H.W. Jomaa, J.B. Schlenoff, Langmuir, 21, 8081-8084 (2005). “Accelerated Exchange in Polyelectrolyte Multilayers by "Catalytic" Polyvalent Ion Pairing.”
H.W. Jomaa, J.B. Schlenoff, Macromolecules, 38, 8473-8480 (2005). “Salt Induced Polyelectrolyte Interdiffusion in Multilayered Films: A Neutron Reflectivity Study.”
S.G. Olenych, M.D. Moussallem, D.S. Salloum, J.B. Schlenoff, T.C.S. Keller, Biomacromolecules 6, 3252-2458 (2005). “Fibronectin and Cell Attachment to Cell and Protein Resistant Polyelectrolyte Surfaces.”
R.A. Jisr, H.H. Rmaile, J. B. Schlenoff, Angewandte Chemie Intl Ed., 44, 782-785 (2005). “Hydrophobic and Ultrahydrophobic Thin Films from Perfluorinated Polyelectrolytes.”
D.S. Salloum, S.G. Olenych, T.C.S. Keller, J. B. Schlenoff, Biomacromolecules, 6, 161-167 (2005). “Vascular Smooth Muscle Cells on Polyelectrolyte Multilayers: Hydrophobicity-Directed Adhesion and Growth.”
J.A. Jaber, J.B. Schlenoff, Macromolecules, 38, 1300-1306 (2005). “Polyelectrolyte Multilayers with Reversible Thermal Responsivity”
D.S. Salloum, J.B. Schlenoff; Electrochem. Sol. State. Lett., 7, E45-E47 (2004). “Rectified Ion Currents through Ultrathin Polyelectrolyte Complex: Towards Chemical Transistors.”
D.S. Salloum, J.B. Schlenoff, Biomacromolecules, 5, 1089-1096 (2004). “Protein Adsorption Modalities on Polyelectrolyte Multilayers.”
Z. Sui, J.B. Schlenoff, Langmuir, 20, 6026-6031, (2004). “Phase Separations in pH-Responsive Multilayers: Charge Extrusion vs. Charge Expulsion.”
J.A. Jaber, P.B. Chase, J.B. Schlenoff, Nano Letters, 3, 1505-1509 (2003). “Actinomyosin-Driven Motility of Patterned Polyelectrolyte Mono- and Multilayers.”
H.H. Rmaile, T.R. Farhat, J.B. Schlenoff, J. Phys. Chem. B. 107, 14401-14406 (2003). “pH-gated Permeability of Variably-Charged Species Through Polyelectrolyte Multilayers.”
Z. Sui, J.B. Schlenoff; Langmuir 19, 7829-7831 (2003). “Controlling Electroosmotic Flow in Microchannels with pH-responsive Polyelectrolyte Multilayers.”
T.R. Farhat, J.B. Schlenoff, J. Am. Chem. Soc., 125, 4627-4636 (2003). “Doping-Controlled Ion Diffusion in Polyelectrolyte Multilayers: Mass Transport in Reluctant Exchangers.”
Book: “Multilayer Thin Films - Sequential Assembly of Nanocomposite Materials” G. Decher, J.B. Schlenoff, Eds., Wiley-VCH, Weinheim, 2003.
Z. Sui, D. Salloum, S.B. Schlenoff; Langmuir, 19, 2491-2495 (2003). “Effect of Molecular Weight on the Construction of Polyelectrolyte Multilayers: Stripping vs. Sticking”
H.H. Rmaile, J.B. Schlenoff; J. Am. Chem. Soc. 125, 6602-6603 (2003). “Optically Active Polyelectrolyte Multilayers as Membranes for Chiral Separations.”
H.H. Rmaile, J.B. Schlenoff; Langmuir, 18, 8263-8265 (2002). “Internal pKa’s in Polyelectrolyte Multilayers: Coupling Protons and Salt”
C.P. Kapnissi, C. Akbay, J.B. Schlenoff, I.M. Warner; Anal. Chem., 74, 2328-2335 (2002). “Analytical Separations Using Molecular Micelles in Open-Tubular Capillary Electrochromatography.”
T.R. Farhat, J.B. Schlenoff; Electrochemical and Solid State Letters, 5, B13 (2002). “Corrosion Control Using Polyelectrolyte Multilayers.”
S.T. Dubas, J.B. Schlenoff; Langmuir, 25, 7725 (2001). “Swelling and Smoothing of Polyelectrolyte Multilayers by Salt.”
J.B. Schlenoff, S.T. Dubas; Macromolecules, 34, 592 (2001). “Mechanism of Polyelectrolyte Multilayer Growth: Charge Overcompensation and Distribution.”
J.B. Schlenoff, T. Farhat; Langmuir, 17, 1184 (2001). “Ion Transport and Equilibria in Polyelectrolyte Multilayers”
S.T. Dubas, J.B. Schlenoff; Macromolecules, 34, 3736 (2001) “Polyelectrolyte Multilayers Containing a Weak Polyacid: Construction and Deconstruction”
S.T. Dubas, T. Farhat, J.B. Schlenoff; J. Am. Chem. Soc., 123, 5368 (2001) "Multiple Membranes from “True” Polyelectrolyte Multilayers.”
J.B. Schlenoff, S.T. Dubas, T. Farhat; Langmuir, 16, 9968 (2000). “Sprayed Polyelectrolyte Multilayers.”
T. Farhat, G. Yassin, S.T. Dubas, J.B. Schlenoff; Langmuir, 15, 6621 (1999), "Water and Ion Pairing in Polyelectrolyte Multilayers."
S.T. Dubas, J.B. Schlenoff; Macromolecules, 32, 8153 (1999), "Factors Controlling the Growth of Polyelectrolyte Multilayers."
T.W. Graul, J.B. Schlenoff; Anal. Chem., 71, 4007 (1999), "Capillaries Modified by Polyelectrolyte Multilayers for Electrophoretic Separations."
J.B. Schlenoff, H. Ly, H. Li; J. Am. Chem. Soc., 120, 7626 (1998), "Charge and Mass Balance in Polyelectrolyte Multilayers."
Prof. Schlenoff is a member of the Center for Materials Research and Technology (MARTECH), and is also a soccer fanatic.