Analysis of Conducting Polymer:Polypyrrole::Part 2

CH5190: Inroduction to Macromolecules

Summary about the polymer

Polypyrrole (PPy) is a type of organic polymer formed from by polymerization of pyrrole.

PPy is an insulator, but its oxidized derivatives are good electrical conductors. The conductivity of the material depends on the conditions and reagents used in the oxidation. Conductivities range from 2 to 100 S/cm

Important states for discussion-

• Chemically pure doped,redoped and redoped conducting Ppy films doped with different materials.

• Different nanostructures, (mainly nanoscopic tubules )composed of Ppy and relation of conductivity with diameter.

Main applications in –

A. electronic devices ,

B. chemical sensors and also for

C. drug delivery etc.


Molecular arrangements

• Notes on conformation:• With doping by camphor sulphonic acid crystallinity increases.

• ordering of the polymer chains is improved when the pores diameter decreases and is responsible for the enhancement in conductivity.

• State variables which affect the molecular arrangements. :

1. Doping with PP- on chemically pure Ppy films makes it thermally more stable.

2. (pTS-) ion doped film on SS-304 steel has good conductivity.

3. Nanoindentation shows that mechanical properties of polyphosphate and p-toluene sulphonate doped films are better than perchlorate doped films.


Experimental technique/data 1

Chemical synthesis of polypyrrole: structure–properties relationship:Duchet, Roger Legras, ,Demoustier-Champagne:Synthetic MetalsVolume 98, Issue 2, 4 December 1998, Pages 113–122

Example of property being measured

• Nanostructures composed of polypyrrole (PPy) obtained by chemically synthesizing Ppy, measured for conductivity variation with diameter.

Experimental technique that is used for the measurement

• Nanostructures composed of PPy are obtained by synthesizing it within the pores of microporous and nanoporous Particle Track-etched Membranes (PTM)

• A field-effect gun DSM with an accelerating voltage of 1 kV was used to characterize the nanostructures

• Raman Spectra were recorded on spectrophotometer

Structural information obtained from the measurement

• When order of the PPy chains increases, the electron delocalization takes place at longer distance and consequently, the conductivity increases.

• Raman data show that the ordering of the polymer chains is improved when the pores diameter decreases and is responsible for the enhancement in conductivity.


Varrying Conductivity with Ppy Tubule diameter



On the preparation and multiproperties of the polypyrrole films doped with different ionsBy: Cheng Guanggui; Ding Jianning; Zhang Zhongqiang; et al.SURFACE AND INTERFACE ANALYSIS Volume: 44 Issue: 7 Pages: 844-850 Published: JUL 2012


For PPy films doped with different ions(p-toluene sulphonate , perchlorate , polyphosphate)-•Thermal stability•Standard of conductivity•Current-voltage curves•Mechanical properties like hardness and elastic moduli


• Ppy films doped with counterions are electrodeposited on stainless steel(SS-304) and ITO glass electrodes by potentiostatic method.

• Composite films are studied with Fourier transform spectra, integrated thermal analysis & SEM

• 4-probe measurement & in-situ nanotribolab for electrical and mechanical properties.


• Polyphosphate ion doped Ppy film has best thermal stability

• pTS- ion doped Ppy film has good conductivity.• Mechanical properties are not so good in Ppy-perchlorate

films.


Thermal / thermodynamic properties

High Thermal and Environmental StabilityThermal analysis establishes the higher stability of the CSA redoped

PPy film compared to other doped samples.

Polymer CrystalinityInfluences many of the polymer characteristics-mechanical strength,

opacity and thermal properties.

Semi-crystallinity is a desirable property - it combines the strength of crystalline polymers with the flexibility of amorphous ones.

High Electrical ConductivityUse in specific technological applications -super capacitors, conductive

textiles and fabrics, mechanical actuators, electromagnetic interference shielding devices, anti-static coatings.



Thermal stability of electrochemically prepared polythiophene and polypyrrole:F Mohammad,Calvert,Billingham;1995


• Weight loss• Comparative stability with respect to

polyacetylene.


• Preparation of polypyrrole and application of current.• Washing and drying a pumping line.• Thermal gravimetric analysis technique


• Polypyrrole is more stable than polyacetylene• undergo degradation reactions which involve two

steps, viz. loss of dopant and then degradation of polymer backbone.

• Thermogravimetric analysis shows that polypyrrole loses weight in more than one distinct stages in air and nitrogen atmosphere.


TGA Analysis of Polypyrrole



Novel polypyrrole films with excellent crystallinity and goodhermal stability:Pullarkat P. Jeeju,Sreekanth J. Varma,Puthampadath A. Francis XavierAugustine M. SajimoSankaran JayalekshmiMaterials Chemistry and PhysicsVolume 134, Issues 2–3, 15 June 2012, Pages 803–808


• Enhanced crystallinity• Electrical Conductivity• Good thermal stability


• HCl doped Py was prepared by chemical oxidative polymerization of pyrrole using ammonium peroxi disulphate as oxidant.

• Doped PPy was dedoped using ammonia solution and then redoped with camphor sulphonic acid.


• The solution casted films exhibit semi-crystallinity and good thermal stability.

• Percentage crystalinity estimated using XRD and DSC analysis is about 65%.

• Raman studies support the enhancement in crystalinity based on XRD and DSC data.

• The conductivity of the film is 30 times higher than that of HCl doped sample.


Polypyrrole Crystalinity


Polypyrrole crystalinity

Sample Percentage of Crystallinity

HCl doped PPy (bulk)

40

Dedoped PPy (bulk)

20

CSA redoped PPy film

64


Summary1. The sharp peaks in the Raman spectrum of the PPy film

support the increase in crystalinity of the film samples.[1]

2. The conductivity of the polypyrrole film increases with decrease in polypyrrole tubule diameter.[2]

3. Doped films exhibit semi-crystalinity and better crystalline structure.[4]

4. Polyphosphate ion doped Ppy film has best thermal stability[3] and weight loss in Polypyrrole occurs in 3 distinct steps in isothermal condition.

1.Novel polypyrrole films with excellent crystallinity and goodhermal stability:Pullarkat P. Jeeju,Sreekanth J. Varma,Puthampadath A. Francis XavierAugustine M. SajimoSankaran JayalekshmiMaterials Chemistry and PhysicsVolume 134, Issues 2–3, 15 June 2012, Pages 803–80812. On the preparation and multiproperties of the polypyrrole films doped with different ionsBy: Cheng Guanggui; Ding Jianning; Zhang Zhongqiang; et al.SURFACE AND INTERFACE ANALYSIS Volume: 44 Issue: 7 Pages: 844-850 Published: JUL 20123. Chemical synthesis of polypyrrole: structure–properties relationship:Duchet, Roger Legras, ,Demoustier-Champagne:Synthetic MetalsVolume 98, Issue 2, 4 December 1998, Pages 113–1224. Thermal stability of electrochemically prepared polythiophene and polypyrrole:F Mohammad,Calvert,Billingham;1995


Interesting / confusing aspects

In TGA analysis ,methods to calculate comparative stability with respect to polyacetylene.In Raman spectra,methods to develop more percentage of crystalinity.Procedures to reduce Ppy tubule diameter for increase in conductivity.

Reference, author, journal, year

Engineering

Analysis of Conducting Polymer:Polypyrrole::Part 2