Forming Conducting Polymers Utilising Room Temperature Ionic Liquids

1. Forming Conducting Polymers Utilising Room Temperature Ionic Liquids PhD student: Lavinia Astratine Supervisors: Dr. Anthony Betts & Prof. John Cassidy (DIT) Prof. Edmond Magner (MSSI, Limerick)

2. 1. Concept • 2. Objectives • 3. Lab Work • 4.Other polymers: polythiophene & Ionic Liquids • 5.Future work

3. 1. Concept • The aim of this project is to use conducting polymers (CPs), in conjunction with Room Temperature Ionic Liquids (RTILs), to produce electrochromic films. • Such films, which change colour in response to electrical potential changes, could be used in electronic display devices and in light and energy-control applications (eg. smart windows which control light transmittance).

4. 2. Objectives • Production of improved electrochromic devices, using a more environmentally-friendly “Green Chemistry” approach is a desirable goal. • Conducting polymers (CPs, such as polypyrrole, polythiophene, polyaniline and/or their derivatives) have been studied extensively. A promising CP for electrochromic applications is polypyrrole (PPy).

5. Characteristics of polypyrrole: • Thin films of polypyrrole are yellow in the undoped insulating state and black in the doped conductive state • Electrochemical degradation has been reported in many studies • The electrode potential applied has been found to influence greatly the degradation process (electrode potential limit 0.6 V vs. Ag/AgCl) • Polypyrrole is a quite labile electrode material that undergoes a relatively fast electrochemical degradation, at least in aqueous solutions Electrochimica Acta 52 (2007) 4784–4791

6. 3. Lab Work Method used: Cyclic Voltammetry • a) Form PPy films using organic solvents as Electrolyte Experimental set up Working Electrode (WE): Pt electrode (diameter 2mm) Counter Electrode (CE): Silver Wire Reference Electrode (RE): saturated Ag/AgCl Pyrrole used for synthesis of PPy films was purified by distillation and kept refrigerated in the dark. Monomer solution: 0.1 M Pyrrole and 0.1 M LiClO4 and H2O Electrolyte solution: 0.1 M LiClO4 and H2O

7. Results and Discussion →Potential range: -1V to +0.8V →After 3 sweeps a yellow film was deposited on the electrode surface

8. In order to change the polymer colour the electrode was placed in electrolyte solution • Potential range: -0.4V to +0.5V • CV in electrolyte for 10 cycles • The polymer changed colour to blue

9. b)FormPPy on FTO glass (WE), [0.5cmx3cm] Monomer solution (deoxygenated for 10 minutes): 0.1 M Py, 0.1 M LiClO4, H2O Electrolyte solution: 0.1 M LiClO4, H2O Potential range: -0.9 V to 1.5 V Run for 6 sweeps → Results in a black oxidized film, which is unstable → Polypyrrole was overoxidized

10. Observations: • PPy is oxidizing at ca. 0.6V. From 0.55V on, the current increases with each potential sweep. • No colour change of the polymer was observed on the FTO glass. • Probably 1 or 2 scans are enough in the region where the pyrrole starts to be oxidized (0.95 V). • The results are better with FTO glass when the monomer solution is degassed before starting polymer formation.

11. 4.Other polymers: polythiophene Combines the flexibility, elasticity and malleability of plastics + electrical conductivity + also often exhibit colour (polychromism) as electrochromic materials Ionic Liquids ‘Green Solvents’ • Ionic liquids (ILs) are room temperature molten salts, composed mostly of organic ions that can undergo almost unlimited structural variations • ILs which function at room temperature, the most desirable operational temperature range, are termed “Room Temperature Ionic Liquids”, RTILs

12. Examples include 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM PF6) and its borate counterpart (BMIM.BF4)

13. Making polymers in ionic liquids 25cycles WE: Pt electrode CE: Pt coil Monomer Solution: RE: Pt wire Polymerization range: -1 V to +1 V Colours of the film: yellow→orange→red→Black 0.1 M Pyrrole & BMIM PF6

14. WE: FTO glass (3cm x 0.5mm) Monomer Solution: CE: Pt coil RE: Pt wire Polymerization range: -1 V to +1 V Colours of the film: yellow→light Brown→Brown→Black 0.1 M Pyrrole & BMIM PF6 16 cycles

15. 5. Future work • Combine conducting polymers (pyrrole, thiophene) with other RTILs such as [ChCl][EG], [BMIM][CF3SO3], [Py][CF3SO3] in order to get different colours during electropolymerization on optically transparent FTO and Au-sputtered glass substrates. • Conduct spectroelectrochemical studies of the polymer films, in order to detect colour changes in situ • Gain insight into the mechanisms of electrochromism • Construct simple Proof of Concept Device/Prototype illustrating potential of technology and transfer technology

16. Papers • Electrochimica Acta 52 (2007) 4784–4791, A.Brazier et al. • Polymer Degradation and Stability 75 (2002) 255–258, R. Mazeikiene, A. Malinauskas • Synthetic Metals 157 (2007) 485-491, A. Alumaa et al. • Electrochimica Acta, Vol.42,No.2,pp. 203-210, 1997, Yongfang Li • Journal of Electroanalytical Chemistry 618 (2008) 87–93, by D. Asil et al. • Nature Materials, 8, (2009), 621-629, M. Armand, D.R. MacFarlane, H. Ohno and B. Scrosati • Polymer 45(2004) 1447-1453, J.M. Pringle et al.

17. Aknowledgements - Dr. Anthony Betts & Prof. John Cassidy (DIT) - Prof. Edmond Magner (MSSI, Limerick) - Edmond Magner Research Group (MSSI,Limerick) Thank you for your attention!