Sticking Non-stick Surfaces Together

Polymers made up of non-polar, or only very slightly polar, functional groups are said to have low surface energy and poor adsorption which means that the surfaces are not "sticky".
Teflon (polytetrafluoroethylene or PTFE) is an example of a polymer with a very low surface energy, so low that it is used to provide non-stick coatings to things like pots and pans.
Silicones (polysiloxanes), with the general formula [R₂SiO]_n in which R is an organic group such as a methyl or ethyl group, also tend to have low surface energies. Because most materials do not adhere to, or stick to, silicones, silicones have become widely used to make flexible "rubber" molds.

So, how do you join together materials like these that are not "sticky"?

This is the question that scientists at Kiel University in Germany have been studying, and the solution they have devised is to use nano-scaled crystal linkers as internal staples. These staples are made of zinc oxide in which the crystals are shaped like tetrapods, that is, each staple has 4 legs. Zinc oxide crystals are sprinkled evenly onto a heated layer of teflon. Then a layer of silicone is poured on top. The material is then heated to 100^oC for less than an hour in order to join the materials firmly together.When the zinc oxide crystals are heated, the tetrapods pierce the teflon and silicone materials, sink into them and get anchored.
Peeling the teflon layer off the silicone layer held together by the tetrapod staples is about the same as peeling sticky tape off glass.

Reference:
X. Jin, J. Strueben, L. Heepe, A. Kovalev, Y.K. Mishra, R. Adelung, S.N. Gorb, A. Staubitz. Joining the un-joinable: Adhesion between low surface energy polymers using tetrapodal ZnO linkers. Advances Materials, 2012 DOI: 10.1002/adma201201780

Further Reading
Polymers and Polymerization
Functional Groups
Molecule Polarity

Suggested Study Questions:

1. Define the term polymer
2. Give two examples of polymers that are commonly used in households.
3. Define the term functional group and give three exaples.
4. Explain what is meant by a polar functional group and a non-polar functional group.
5. Give the structural formula for the monomer that can be used to form teflon.
6. Are the bonds in the monomer you have drawn in question 5 polar or non-polar bonds. Explain your answer.
7. Is the molecule that is the monomer in question 5 polar or non-polar. Explain your answer.
8. Given the general formula for silicones provided in the article, write the formula for:
   • polydimethylsiloxane
   • polydiethylsiloxane
9. Give a possible structural formula for the monomer used to produce each of the silicone polymers in question 8.

New Electrochemistry Resources

AUS-e-TUTE has just updated its Faraday's Laws of Electrolysis and added new resources for Q = It and E=QV calculations.

A "draft" of the VCE 2013-16 chemistry syllabus study guide has also been added.

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New Electrochemistry Resources

AUS-e-TUTE has been updating its electrochemistry section.
The latest additions have been tutorials, games, tests, exams and drills on the following topics:

• Strength of Electrolytes
• Galvanic (Voltaic) Cell Diagrams
• Electroplating Concepts

Periodic Table Teaching Resources

AUS-e-TUTE has downloadable resources related to the teaching and learning of Periodic Table concepts.

Visit http://ausetute.com.au/downloads.html to download:

• Interactive Periodic Table (only for Windows)
• Lesson Outlines for teaching Periodic Table concepts (designed to be used with AUS-e-TUTE's interactive Periodic Table)

AUS-e-TUTE Update July 2012

AUS-e-TUTE's electrochemistry resources are currently being updated.

This has resulted in a major revision of most of the resources relating to the concepts of electrochemistry.

Below is a list of the new and updated resources that have recently been added to AUS-e-TUTE.

Links to all of these resources can be found in the Test Centre :

• Oxidation and Reduction Concepts: (tutorial, game, test, drill)
• Oxidation Numbers (States): (tutorial, game, tests, exams)
• Writing Half-equations (simple ions): (tutorial, game, test, drill)
• Writing Half-equations (aqueous solutions): (tutorial, game, test, exam)
• Redox Reaction Concepts: (tutorial, game, test, exams)
• Writing Redox Reaction Equations: (tutorial, game, test, exams)
• Spontaneous and Non-spontaneous Redox Reactions: (tutorial, game, test, exam)
• Displacement Reactions: (tutorial, game, tests, exam)          

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