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Project thoughts / plans

This project overview discusses the development and applications of conducting polymer-based materials, focusing on hyaluronic acid-based materials and glucose-sensing hydrogels. It examines the atomic and molecular structure of conducting polymers, their conductivity enhancement methods (doping, energy transfer), and the challenges they face, such as chemical stability and biodegradability. Proposed research includes functionalization of biodegradable polymers and collaboration with experts in silk proteins and polycaprolactone (PCL) for advanced applications, aiming for sustainable and efficient materials design.

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Project thoughts / plans

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  1. Project thoughts / plans John Hardy February 2011

  2. Overview • Conducting polymer-based materials • Hyaluronic acid-based materials • Glucose sensing hydrogels

  3. Motivation • Conducting polymer-based materials

  4. Overview • Introduction • Why do materials conduct electricity? • State of the art • Conducting polymers • Potential for future research • Non-biodegradable conducting polymers • Biodegradable conducting polymers

  5. Atomic Structure • Electron orbitals • 8th grade

  6. Atomic Structure • Electron orbitals • University • y1

  7. Molecular Structure + s s s-s overlap = s bond + s p s-p overlap = s bond + p p p-p overlap = s bond + p p p-p overlap = p bond

  8. Molecular Structure s* p* p Energy 2p s s* 2s s

  9. Band structures n: 1 2 3 4 ∞ y4 11 y3 Energy y2 y1

  10. Band structures Eg Eg Eg Eg or or

  11. Semiconductors • Improving the conductivity • Approach 1: Transfer energy to the system Eg

  12. Semiconductors • Improving the conductivity • Approach 1: Transfer energy to the system • Approach 2: ‘Doping’ Eg

  13. Semiconductors • Improving the conductivity • Approach 1: Transfer energy to the system • Approach 2: ‘Doping’ Eg

  14. Semiconductors • Improving the conductivity • Approach 1: Transfer energy to the system • Approach 2: ‘Doping’ Eg ‘allegedly’

  15. Semiconductors • Improving the conductivity • Approach 1: Transfer energy to the system • Approach 2: ‘Doping’ Eg Eg Eg • Remove electrons • Insert ‘holes’ • P-type doping • Add electrons • Insert a ‘mid-gap orbital’ • N-type doping

  16. Carbon and Silicon Carbon – 1s2 2s2 2p2 Silicon - 1s2 2s22p6 3s2 3p2 Silicon is a semiconductor • Diamond is an insulator Si Si Si C C C Si Si Si Si Si Si C C C C C C Eg Eg

  17. Doping Silicon P-type doping N-type doping Phosphorous - …3s2 3p3 • Boron - 1s2 2s22p1 Si Si Si Si Si Si . Si Si Si Si Si Si Si Si Si Si B P Eg Eg • Remove electrons • Insert ‘holes’ • P-type doping • Add electrons • Insert a ‘mid-gap orbital’ • N-type doping

  18. Doping conducting polymers • Parapolyphenylene (PPP) P-type doping (oxidation) Polaron Polaron Polaron Further doping Polaron combination

  19. Doping conducting polymers • Polyaniline Oxidation Oxidation Reduction Reduction Leuco-emeraldine base Non-conducting Emeraldine base Non-conducting Base Acid Base Acid Emeraldine salt Conducting form Leuco-emeraldine salt Non-conducting

  20. De-doping conducting polymers • Polypyrrole (PPy) • Conductivity (σ) of film 3to 60 S/cm Literature: Schmidt and co-workers, Biomed. Mater. 2008, 3 (3), 034124-

  21. Self-doped conducting polymers • Polythiophene • Water soluble • Conductivity (σ) of film 10-7 to 10-2 S/cm • Exposure to Br2 vapor – σ ≈ 10 S/cm Oxidation (- M+) Reduction (+ M+) Literature: Wudl and co-workers, JACS. 1987, 109, 1858-

  22. Problems with conductive polymers • Chemical stability • Sensitivity to air / moisture • High crystallinity • Solubility / processability / mechanical properties Polyacetyleneσup to 105S/cm Polyacetyleneσup to 50 S/cm Literature: Grubbs and co-workers, Adv. Mat. 1989, 1 (11), 362-

  23. Problems with conductive polymers • Biodegradability Polythiophene Polyacene Polyfluorene Ester bond Biodegradable polythiophene copolymer Literature: Schmidt and co-workers, Macromol. 2009, 42, 502-

  24. Proposed research • Supramolecular polymers • Functionalization of biodegradable materials with SDCPs • Silk proteins • Polycaprolactone (PCL) • Non-biodegradable SDCPs • Neural electrodes

  25. Supramolecular polymers • Oligothiophene-based • H-bonding, van der Waals interactions & π-π stacking • Oligoaniline-based • Peptide-directed assembly Literature: Schmidt and co-workers, Macromol. 2009, 42, 502- & Yang and co-workers, Tet. Lett. 1996, 37, 731-

  26. Silk-based materials • Silk • Commercially available protein • Processable in solution • Chemically modifiable • ‘Biocompatible’ • Collaborative project: David Kaplan (Tufts)

  27. Silk-based materials • Visit Tufts (03/28-04/11) • Upon my return to Austin Literature: Schmidt and co-workers, Macromol. 2009, 42, 502-

  28. PCL-based materials • PCL • Commercially available biodegradable polymer • Processable in melt/solution • Chemically modifiable • ‘Biocompatible’ • UG project: RushiSukhavasi

  29. PCL-based materials

  30. Neural electrodes • Self-doped polymer films • Non-biodegradable polymers • Simple (2 steps) • Electropolymerization of: • Self-dope by sulfonation with HSO3F • σ up to 72 S/cm • UG project: Tushar Garg Literature: Yildiz and co-workers, J. Solid State Electrochem. 2006, 10, 110-

  31. Hyaluronic acid-based materials • Collaboration with Sarah Mayes • Collaboraiton with Zin Khaing

  32. Collaboration with Sarah • In-situ cross-linking hydrogels • Simple chemistry • UV free • UG project: Phillip Lin

  33. Collaboration with Zin • In-situ cross-linking hydrogels • Complex chemistry • Absolutely bioorthogonal • UG project: Jesus Maldonado Literature: Schmidt/Khaing and co-workers…

  34. Glucose sensing hydrogels • Collaboration with Austin McElroy, Chris Condit, Jordan Dwelle & Tom Milner

  35. Glucose sensing hydrogels • Boronic acid-based hydrogels • Prepare hydrogels that swell/shrink in the presence of glucose High boronic acid content hydrogel Low boronic acid content hydrogel

  36. Conclusion • Prepare further in advance

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