Diversity through Supramolecular Processes. Plug and Play Polymers

Intermolecular and intramolecular networks of non-covalent interactions are key aspects of biomolecular function and diversity. Biological systems use specific patterns of complementary functionality to provide exquisite control over biopolymer recognition processes such as protein-protein and protein-polynucleic acid binding. These specific supramolecular interactions play many roles in nature, including information storage and transfer, catalysis, and self-assembly.

In research funded with NSF and industrial funds, we are applying the control and diversity possible via supramolecular chemistry to the creation of polymeric systems. Through the use of specific non-covalent interactions, we have created "plug and play" polymers--materials where molecular properties such as hydrophobicity and electroactivity are controlled via reversible noncovalent modification (Scheme 1). The modular nature of the self-assembly provides a combinatorial array of complex and diverse structures using simple polymer and monomeric building blocks. Additionally, supramolecular complex formation will be thermo- and solvoreversible, allowing thermal processing of the polymeric systems and facilitating both the fabrication and recycling of materials formed via the proposed self-assembly process.

Schematic representation of non-covalent modifications: a) monofunctionalization, b) polyfunctionalization, c) crosslinking.

To provide a suitable scaffold for non-covalent functionalization, we have synthesized triazine-functionalized polystyrene 1.

Triazine-functionalized polymer from:"Control of Polymer Solution Structure via Intra- and Intermolecular Aromatic Stacking" F. Ilhan, M. Gray, K. Blanchette, V. Rotello, Macromolecules, 1999, 32, 6159-6162.

The morphology of this polymer can be controlled by varying the density of triazine functionalization. With high degrees of triazine functionalization (y>0.3 x), the polymer forms insoluble aggregates. At lower substitutions (y=0.25 x), the polymer folds to form micelles.

These micelles can be unfolded through the use of complementary hosts, providing the possibility of chaperone-mediated control of tertiary structure. We are currently exploring transport using these polymers, with the ultimate goals the creation of drug delivery systems and molecular encapsulation of reactive species.

We have also used this triazine-functionalized polymer to encapsulate redox-active guests. This encapsulation mimics the isolation of redox centers provided by enzymatic systems, providing a powerful new route to electroactive materials.

Encapsulation of electroactive guest by polymer 1. From: "Encapsulation of an Electroactive Guest in a Dynamically Self-Assembled Polymer" T. Galow, F. Ilhan, G. Cooke, V. Rotello, J. Am. Chem. Soc., 2000, 122, 3595-3598.

In recent studies, we have explored the interactions of complementary random copolymers. With these systems, we observed the formation of giant vesicles. We rae currently exploring the use of these vesicles as templates for the creation of nano and microstructures.

Vesicle formation using self-assembled polymers. From F. Ilhan, T. Galow, M. Gray, G. Clavier, V. Rotello, J. Am. Chem. Soc., 2000, 122, 5895-5896.

Confocal Micrographs of varying architectures in CHCl3 showing the vesicle nature of these mixed-polymer systems. (a) (x60 mag.) Fused-vesicle morphology; (b) (x60 mag.) Vesicle-in-vesicle structure; (c) (x60 mag.) Regular spherical vesicle morphology; (d) (x120 mag.) Two spherical vesicles and a fused-vesicle.

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Group papers in polymer chemistry

"Photochemical Control of Polymer Folding using Azobenzene Sidechains" G. Clavier, F. Ilhan, V. Rotello, Macromolecules, submitted for publication.

"Control of Polymer Structure: Organization by Non-Covalent Interactions" G. Clavier, F. Ilhan, T. Galow, M. Gray, V. Rotello, Polymer Preprints, 2000, 1322-1323.

"Experimental Study of Release and Uptake in Well-Defined Imprinted Polymer Films" K. Das, D. Duffy, S. Hsu, J. Penelle, V. Rotello, Polymer Preprints, 2000, 1173-1174.

"Polymer-Mediated 'Bricks and Mortar' Self-Assembly of Nanoparticles into Discrete Structured Arrays" Polymer Preprints, 2000, 1348-1349.

"Giant Vesicle Formation through the Self-Assembly of Complementary Random Copolymers" F. Ilhan, T. Galow, M. Gray, G. Clavier, V. Rotello, J. Am. Chem. Soc., 2000, 122, 5895-5896.

"Encapsulation of an Electroactive Guest in a Dynamically Self-Assembled Polymer" T. Galow, F. Ilhan, G. Cooke, V. Rotello, J. Am. Chem. Soc., 2000, 122, 3595-3598.

"Self-Assembly of Nanoparticles into Structured Spherical and Network Aggregates" A. Boal, F. Ilhan, J. DeRouchey, T. Thurn-Albrecht, T. Russell, V. Rotello, Nature, 2000, 404, 746-749.

"Kinetic Trapping of Host-Guest Complexes in a Polymeric Matrix" F. Ilhan, L. Diamondis, L. Gautreau, V. Rotello, J. Chem. Soc., Chem. Comm., 2000, 447-448.

"Molecularly Imprinted Polymer Systems for Selective Recognition via Hydrogen Bonding Interactions" D. Duffy, K. Das, S. Hsu, J. Penelle, V. Rotello, H. Stidham, PMSE Preprints, 2000, 82, 69-70.

"Control of Polymer Solution Structure via Intra- and Intermolecular Aromatic Stacking" F. Ilhan, M. Gray, K. Blanchette, V. Rotello, Macromolecules, 1999, 32, 6159-6162.

"Thermoreversible Polymerization. Formation of Fullerene-Diene Oligomers and Copolymers" F. Ilhan, V. Rotello, J. Org. Chem., 1999, 64, 1455-1458.

"Recognition-Mediated Unfolding of a Polymeric Globule R. Deans, F. Ilhan, V. Rotello, Macromolecules., 1999, 32, 4956-4960.

"Thermoreversible Polymerization. Formation of Fullerene-Diene Oligomers and Copolymers" F. Ilhan, V. Rotello, J. Org. Chem., 1999, 64, 1455-1458.

"Attachment of Fullerenes to Materials: The Importance of Backbone-Fullerene Interactions" B. Nie and V. Rotello, J. Phys. Chem. Solids, 1997, 58, 1897-1899.

"Thermally Controlled Formation of Fullerene-Diene Oligomers and Copolymers" B. Nie, V. Rotello, Macromolecules, 1997, 30, 3949-3951.

"Model Systems for Flavoenzyme Activity. Molecular Recognition of Flavin at the Polymer-Liquid Interface" R. Deans, V. Rotello, J. Org. Chem., 1997, 62, 4528-4259.