Forming Conducting Polymers Utilising Room Temperature Ionic Liquids PhD student: Lavinia Astratine Supervisors: Dr. Anthony Betts & Prof. John Cassidy.

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)

• 1. Concept 1. Concept • 2. Objectives2. Objectives • 3. Lab Work3. Lab Work

• 4.Other polymers: polythiophene 4.Other polymers: polythiophene & Ionic Liquids& Ionic Liquids

• 5.Future work5.Future work

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).

• 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).

2. Objectives2. Objectives

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 potentialelectrode 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

3. Lab Work Method used: Cyclic Voltammetry

• a) Form PPy films using organic solvents as Electrolyte ExperimentalExperimental 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

Results and DiscussionResults and Discussion

→Potential range:

-1V to +0.8V

→ After 3 sweeps a

yellow film was

deposited on the

electrode surface

• 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

• b) Form PPy 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 VRun for 6 sweeps→ Results in a black oxidized

film, which is unstable→ Polypyrrole was overoxidized

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.

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 SolventsGreen 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

• Examples include 1-butyl-3-methylimidazolium

hexafluorophosphate (BMIM PF6) and its borate counterpart (BMIM.BF4)

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

Making polymers in ionic liquids

25cycles

0.1 M Pyrrole &BMIM PF6

WE: FTO glass (3cm x 0.5mm) Monomer Solution:CE: Pt coilRE: 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

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

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.

Aknowledgements

- Dr. Anthony Betts & Prof. John Cassidy (DIT)

- Prof. Edmond Magner (MSSI, Limerick)

- Edmond Magner Research Group (MSSI,Limerick)

Thank youfor your attention!