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Condensed Matter & Materials Physics

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Supramolecular Electronics

This project will explore the physics and technological applications of insulated molecular wires, IMWs, consisting of conjugated polymers threaded into cyclodextrin rings, and capped at the end with bulky steric groups to prevent un-threading, as indicated in the molecular model shown below.

Rotaxane

The energy-minimized structure of a 2-repeat-unit β-CD-PPP rotaxane

This is an essentially new class of materials that are engineered at a supramolecular level to achieve a greater control over the photo-physical and charge-carrying properties of the conjugated cores, and that has become available thanks to an ongoing collaboration with the group of Dr HL Anderson at Oxford (Chemistry).

The aim of the project is to investigate both the nature of the electronic process in the single supramolecular structures, and in large ensembles of them, which will be studied with the help of solid-state optoelectronic applications such as light-emitting diodes, LEDs, light-emitting electrochemical cells (LECs) and photovoltaic diodes, PVDs. The groups of Dr HL Anderson (Oxford University, Chemistry), and Dr D.G Bucknall (Oxford University, Materials), will be working on the synthesis and structural characterisation of different families of these polyrotaxane "insulated molecular wires".

Scanning probe microscope images

Surface morphology of spin-coated polyrotaxanes and un-insulated polymer. Tapping mode SFM images of β-CD-PPP (a) and unthreaded PPP (c) films spin-coated from a water solution on a mica substrate. The average degree of polymerization is N=10 (a and c) and N≈20-30 (b), leading to average contour lengths along the extended rod-like chains of about 17 nm and 30-50 nm. We estimate a corrected rod width of ~1.6 nm and height of 0.4±0.1 nm. The self-assembled monolayers shown in c exhibit holes with constant depths. The vertical scale is 4 nm (a), 3 nm (b),and 10 nm (c) (from reference below).

  1. F. Cacialli, J.S. Wilson, J. J. Michels, C. Daniel, C. Silva, R. H. Friend, N. Severin, P. Samorì, J. P. Rabe, M. J. O'Connell, P. N. Taylor, H. L. Anderson. Cyclodextrin-threaded conjugated polyrotaxanes as electroluminescent insulated molecular wires with reduced interstrand interactions.Nature materials 1, 160-164 (2002).