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Engineering Materials Essay on Polypyrrole Essay

1.0 Introduction to Polypyrrole

The reason of this report is to determine the effects of temperature on the thermal, physical and mechanical properties of Polypyrrole. And then conclude the possible applications of this polymer according to its properties. Known as the conducting polymer, it is a black insoluble material according to Richard Doyle (2011), usually in the form of a thin film. It was the first polyacetylene-derivative to show high conductivity. Over the years it has become one of the most studied and extensively applied conducting polymer due to the reason being that it can be easily prepared, has high conductivity and has relatively greater stability amongst other heteroatom containing polymers.

It is made up of monomers that are amines attached to aromatic rings. Some of the physical properties of Polypyrrole, as mentioned on WolframAlpha (2011), it has a Melting Point temperature of 573.15K and as identified by T.F. Otero, J.J Lopez Cascales and G Vazquez Arenas. (2005), Young’s Modulus was found to be of 310 MPa. The Glass Transition State, as indicated by P. Syed Abthagir and R. Saraswathi (2004), in their report Thermal stability of polypyrrole prepared from a ternary eutectic melt, was found to be 545k.

2.0 Methodology of the simulation tests

In order to determine the effect of Temperature on Polypyrrole, simulations were carried out using the simulation software called Materials Studio.

2.1 Model Generations

1) The monomer of polypyrrole known as pyrrole was imported from software library and shown. To make presentable the display style was chosen to be “Ball and Stick” by right clicking the model. 2) Then to make the polymer the “Build Polymer” was selected from “Build” tab and chosen Current Project from library menu. Chain Length was re-arranged to 5 monomers to fit on screen for simulation purposes. 3) Click “Window” tab from Title Bar and chose “Tile Vertically” as Display Style. Then Click on any of the two pictures and right click and select “Display Style”, navigate to Legends tab and uncheck Show axis indicator.

Then go to background and change it to White to comply with report’s page background. Follow the same instructions for the other picture also. 4) Then right click on any of the two pictures and chose “Label”, change the font to 16 and change text colour to Black, then chose “Element Symbol” from Properties and press close. Repeat this step for the other picture as well. 5) Select 3D viewer from the buttons above to fit to screen for both pictures and then from “File” click Export, change the format to “.bmp” and save to simulations folder.

2.2 Thermal, Physical and Mechanical Properties

1) Now from the generated model choose the Polymer and go to “Modules” tab and choose second last option known as “Synthia”. From the setup adjust the temperature to 200-800 and steps to 60. 2) Then go to properties, Select all the properties with “CTRL A” and uncheck them and then only select Density from Thermo-physical Filter and Brittle Fracture Stress from Mechanical Filter. Then Calculate. Export the results as MS Excel file and save to simulations folder to be used later.

3.0 Results and Discussions

All the results and there conclusions are mentioned here on. The results of simulation include effects of temperature on Glass Transition Temperature, Brittle Fracture Stress and Density. 3.1 Model Generation

The model for simulation was generated with the following monomer (Pyrrole) having this structure (Figure 1.0):

Figure 1.0 Structure of Pyrrole

The monomer is made up of an aromatic ring which is an amine due to its bonding with NH group. The basic formula is C4H4NH. There is a delocalised pair of electrons on Nitrogen. At position 2, 3, 4 and 5 each carbon atom is bonded to one hydrogen atom. Positions 2-3 and 4-5 have double bonds between the carbon atoms. Although pyrrole belongs to an amine group but it has relatively low basicity because of the lone pair of electrons of Nitrogen in the aromatic ring.

The monomers synthesis to form the polymer, Polypyrrole:

Figure 1.1 Structure of Polypyrrole

The polymer is synthesised in two manners, electrically and chemically. In Figure 1.1, a chain of 5 repeat units is used. The preferred bond formation in the aromatic ring occurs at position 2 and 5. In support to the Wan Der Walls forces, there is also hydrogen bonding of side chains between Nitrogen and Hydrogen thus forming a Branched structure of the polymer. Since the structure consists of Benzene ring so it gives the polymer a very rigid form.

3.2 Thermal, Physical and Mechanical Properties

3.2.1 Study on thermal property (Glass transition temperature, Tg) According to Notes by Mr Lim SC (2012), “Glass Transition Temperature (Tg) is the specific temperature at which a non-crystalline material changes it state from being Glassy/Brittle to being Ductile or rubbery.” With the help of Simulation, the following Results table was devised for Pyrrole.


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