Bipyridine Functionalized Polymers Mallory McVannel, Shannon Harris, Conner Graham, M. Lee Pippin, Juan V. A. Requena, Alexander D. Schwab A. R. Smith Department of Chemistry

Abstract We are interested in investigating the preparation of Metal Coordination Polymer Networks (MCPN) by attaching 4’-Methyl-2, 2’-bipyridine-4-carboxylic acid (MCPBY), a ligand for the complexation of metals, to a variety of polymers. MCPBY was reacted with a low molecular weight (Mn: 2,500 g/mol) and a high molecular weight (Mn: 27,000 g/mol) bis-(3-aminopropyl) terminated poly (dimethylsiloxane) (PDMS), a bis (hydroxyalkyl) terminated poly (dimethylsiloxane) (Mn: 5,600 g/mol) and a bis(3-aminopropyl) terminated poly(ethyleneoxide) (Mn: 1,500 g/mol) in order to form the bipyridine terminated polymer product. The resulting products were characterized using 1H NMR and GPC.

Introduction Both thermoplastics and thermosets (e.g. typical rubbers) are composed of polymer molecules Thermoplastics Thermosets (rubbers) Long, unconnected polymer chains, recyclable polymer network, long- chain molecules connected by cross-links, unrecyclable

Metal Coordination Cross-links Our overall goal is to synthesize a rubber that would maintain its desirable physical properties and yet be recyclable. Replace conventional covalent cross-links with non-permanent, metal coordination complexes. New properties are also unlocked with metal coordination cross-links DRAW MOLECULE CROSS LINK PRODUCT (FOUND ON POSTER BOARD)

Our Synthetic Approach Begin with linear polymer molecules Attach metal binding ligands to the ends of the polymer molecules Introduce metal cations for metal coordination to form a polymer network + 2

Polymer Modification Scheme The work presented here deals primarily with the attachment of a metal binding ligand (bipyridine) to various polymer molecules Amine (NH2) terminated polymer 4-methyl-2,2’-bipyridine-4’-carboxylic acid (mcbpy) Bipyridine (bpy) terminated polymer Carbodiimide coupling reagents were also used N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDCI) N,N’-dicyclohexylcarbodiimide (DCC)

Polymer Starting Materials NH2 terminated poly(dimethylsiloxane) (NH2PDMSx, x = 2500 or 27000) Two molecular weights used: 2,500 & 27,000 g/mol NH2 terminated poly(ethyleneoxide) (NH2PEO1500) 1500 g/mol OH terminated PDMS (OHPDMS5600) 5600 g/mol

bpyPDMS2500 1H NMR Results NH2PDMS2500 was reacted with mcbpy in methylene chloride with EDCI for 48 hours bpyPDMS NH2PDMS

bpyPDMS 2500 GPC Results GPC separates molecules based on their size ELSD detects all polymer UV/vis measures light absorbance at 295 nm Sensitive to bipyridine Relative peak positions indicate successful bipyridine attachment

bpyPDMS27000 1H NMR Results NH2PDMS was reacted with mcbpy in methylene chloride with EDCI for 48 hours NH2PDMS bpyPDMS

bpyPDMS27000 GPC Results Fewer endgroups relative to PDMS2500 makes 1H NMR and GPC analysis more challenging. NH2PDMS27000 appears to have a significant low MW component UV-vis indicates bpy attached to PDMS

Fractionated NH2PDMS27000 To eliminate low MW component, fractionation with toluene/methanol was attempted Relative amount of low MW component is reduced by fractionation Further investigation necessary

bpyPEO1500 NH2PEO1500 was reacted with mcbpy and DCC in N,N- dimethylformamide for 48 hours NH2PEO bpyPEO

bpyPDMS5600 OHPDMS5600 was reacted with mcbpy and EDCI in methylene chloride for 48 hours 1H NMR analysis indicated that bpy attachment was unsuccessful Carbodiimide coupling reagents can produce esters, though an acid catalyst is often required In future attempts small quantities of an organic acid will be included.

Future Work Fractionation of the NH2PDMS27000 starting material will be improved NH2PEO1500 synthesis will be further refined to increase yield and reduce impurities Carbodiimide use in ester formation will be further investigated Bpy terminated polymers will be mixed with ruthenium(II) complexes, cast into films, and studied with UV/vis, DSC, and oscillating shear rheometry Solvent annealing might be necessary to promote cross-linking

Acknowledgements We thank the following organization for funding: Pfizer, Inc. NC Biotechnology Center The ACS Petroleum Research Fund NSF supported ACREE Program ASU Office of Student Research ASU Other undergraduates contributing to this project M. Ryan Kincer, Ben Deming, Ben Gray, Sarah Miller, Scott Meadows, Kurtis Price

References McCafferty, D. G.; Bishop, B. M.; Wall, C. G.; Hughes, S. G.; Mecklenbert, S. L.; Meyer, T. J.; Erickson, B. W. Tetrahedron 1995, 51, 1093-1106. Mcbpy synthesis Montalbetti, C. A. G. N.; Falque, V., Tetrahedron 2005, 61, 10827-10852 Carbodiimide coupling reagents for amide and ester bond formation Canard, G.; Piguet, C. Inorganic Chemistry 2007, 46, 3511-3522. Ruthenium(II) precursor complexes for cross-linking Smith, A. P. Fraser, C. L. Macromolecules 2003, 36, 5520-5525 Ruthenium(II) bpy complex syntheses for cross-linking