Syntactic and Syndiotactic are NOT Synonymous

 

Question 20 from paper 1 of the QCAA chemistry exam 2022 is shown below. Can you answer it?

 

 You can if you make a couple of assumptions first:

1/ The 3D structure isn't given, so you have to assume (given the possible answers) that methyl groups above the chain are in fact coming out of the plane, while methyl groups below the chain are behind the plane.

2/ You have to assume that "syntactic" is a misprint of "syndiotactic" since there was no mention of this being a composite material.

Then you can choose (A) as the answer, and according to the answer sheet you would be correct.

 

However, here is an excerpt from the draft new Queensland Chemistry syllabus (for implementation in 2025 I believe),

      "Describe the structure features of

           -polyethene (LDPE and HDPE), polypropene (syntactic, isotactic and atactic) and                                             polytetrafluorethene."

(Cross my heart, this is what is says, the syllabus writers seem to have difficulties with adjectives as well as chemical nomenclature, where are the round brackets around tetrafluoroethene?)

 

So, it appears that students will study tacticity of polymers but only isotactic and atactic not syndiotactic, then they will look at composite materials in the form of syntactic foams.

Really?

 

Dear Queensland Chemistry syllabus and exam writers, the 3D structure of a polymer results in an isotactic, syndiotactic or atactic polymer.

A syntactic foam refers to a composite material in which hollow spheres are bound together by a polymer.

Vegan Leather

 My local bag shop is now full of bags that proudly state they are made out of "Vegan Leather".

Vegan leather? Surely that is an oxymoron?

    vegan = not consuming/using any animal products

    leather = animal skin that has been tanned or undergone a similar process.

So what is "vegan leather"?

It turns out that the majority or "vegan leather" is just poly(vinyl chloride) (PVC) or poly(urethane) (PU), polymers produced from reagents derived from fossil fuels. Handbags made out of PVC (vinyl bags) have been around for decades, and have been a much, much cheaper option than expensive genuine leather bags.Until now! By re-branding vinyl bags as "Vegan Leather" suppliers can increase the price, capitalizing on the significant consumer trend toward "vegan" products.

I live in a city that is trying to ban the use of single use plastic items including shopping bags and straws etc which end up in landfill and stay there for (not-quite but almost) ever. How do you feel about your new plastic "vegan leather" handbag? When it starts to fall apart (anything from about a month to a year or so depending on use and quality) and you throw it out, do you feel that you have done your bit for the environment?

If you live in a country where there are growing demands to reduce coal-fired power generation, and reduce the use of fossil fuels in cars etc, in order to reduce the community's "carbon footprint",  how do you feel about your fossil fuel based "vegan leather" bag?

It isn't "vegan leather". It is plastic.

vegan leather bag = plastic bag

Slime

One of the most popular school holiday "science projects" is to make slime by adding an aqueous solution of borax to PVA glue. Young children, and adults, can have hours of fun playing with this oozey slime, discovering some of its interesting properties along the way.

But what is slime and why should we be interested in it?

Read this edition of AUS-e-NEWS to find out more.

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Polymerize or Polymerise?

A polymer is produced when lots of monomers bond together. Monomer has Greek roots, mono meaning one and mer meaning parts. Polymer also has Greek roots, poly meaning many and mer meaning parts.

So  we can form a verb that means to produce a molecule of many parts. Because the words monomer and polymer have Greek roots, we should use the "ize" suffix, that is, polymerize. Yet, particularly in Australia,  the Latin "ise" suffix is used to produce the verb polymerise.

The word, polymerise, would have a Greek root (poly, many), a French root (mer, sea), and a latin suffix (ise). This would appear to suggest that to polymerise would be to make many seas. On the other hand, a monomer would be just one sea.

Merde!

Why is polyvinyl chloride an addition polymer?

Question: Why is polyvinyl chloride an addition polymer?

Answer:

1. An addition polymer is produced in an addition polymerization reaction.

2. In an addition polymerization reaction, the double bonds (C=C) in the monomer molecules open up so that one monomer molecule can "add on to" another monomer molecule to make a longer chain resulting in a polymer.

3. When vinyl chloride monomers (chloroethene monomers, CH₂=CHCl) join together in an addition polymerization reaction the polymer product is polyvinyl chloride, -(-CH₂-CHCl-)_n-

Find out more about addition polymerisation at https://www.ausetute.com.au/polymers.html

Find out more about polyvinyl chloride at  https://www.ausetute.com.au/pvc.html

Polypropene

Polypropene is one of the most widely used plastics in the world.
What is it? How do you make it? What properties does it have? What is it used for?

AUS-e-TUTE has just added a new tutorial, game, test, and exam for our members to help them understand polypropene, and apply that knowledge to answering test and exam questions.
AUS-e-TUTE Members should log-in to use these new resources.

If you are not an AUS-e-TUTE Member you can access a free-to-view tutorial for evaluation purposes at https://www.ausetute.com.au/polypropene.html

polytetrafluoroethene

Polytetrafluoroethene is a very useful polymer. You can can find it encasing electrical wires, being sprayed out of a can of lubricant, and as the non-stick covering on your baking tray. So what is this remarkable polymer? How is it made? What are its properties and uses?
Find out the answers to these and other questions at AUS-e-TUTE.
AUS-e-TUTE members should log-in to view the polytetrafluoroethene tutorial, play the game and take the test and exam.
If you are not a member, you can access a "free-to-view" tutorial at https://www.ausetute.com.au/ptfe.html

Nanocellulose Foam

You have probably held polystyrene cups (styrofoam cups) in your hands. It is a wonderful material for making disposable cups because it is light-weight, holds it shape well, and is an excellent insulator. All this means that you can fill a polystyrene cup with hot tea and drink from it without having it burn your hands. High school chemistry teachers are very fond of using polystyrene cups as "cup calorimeters" in the school laboratory. Unfortunately, polystyrene is not an environmentally friendly polymer, it doesn't break down, it is chemically inert, so persists in the environment.
Plant-based polymers which degrade in time, such as cellulose, could replace polystyrene if we can make a cellulose-based material with same properties as polystyrene.
Cellulose is a polysaccharide. It is composed of many glucose units joined together by ether bonds (glycosidic links). During acid hydrolysis these ether bonds (glycosidic links) are attacked and broken so that the final product of a complete reaction is a lot of glucose molecules. The reaction mechanism for the acid hydrolysis of cellulose is shown below:


If only some of the ether bonds (glycosidic links) within a cellulose polymer chain are attacked, then you could end up with shorter chains of glucose polymer, still enough glucose units in the chain to be considered cellulose. If these chains are only 5-20 nanometres wide (even though they may be several micrometres long) they will be referred to as nanocellulose.
Researchers at Washington State University have added polyvinyl alcohol, shown below:

to nanocellulose. Polyvinyl alcohol binds to the nanocellulose which stabilises the foam that can be  produced. This light-weight material is reported to be a better insulator than polystyrene foam (styrofoam) and "can support up to 200 times its weight without changing shape. It degrades well, and burning it doesn't produce polluting ash."

Suggested Further Reading:
Nanotechnology

Suggested Study Questions:

1. Convert the following measurements to metres (m):
   • 5 nm
   • 20 nm
   • 100 μm
   • 1000 μm
2.  Convert the following measurements to nanometres (nm)
   • 5 × 10^-9 m
   • 2.5 μm
   • 5.2 mm
   • 0.75 cm
3. Draw a section of cellulose polymer containing 6 glucose units. Circle the ether bonds (glycosidic links) in red.
4. Draw the results of acid hydrolysis if all the ether bonds (glycosidic links) in this section of cellulose polymer were broken.
5. Draw the results of acid hydrolysis on the section of cellulose polymer you drew for question 3 if only 2 new "molecules" are produced. Is there only one possible answer? If more than one answer is possible, how many possible answers can you think of?
6. Consider the structure of cellulose and of polyvinyl alcohol. Explain how polyvinyl alcohol can "bind with" cellulose. 
7. Explain why a nanocellulose foam can be stabilised by adding polyvinyl alcohol.
8. Consider the combustion of cellulose. Give the products for
   • complete combustion of cellulose
   • incomplete combustion of cellulose
9. Wood is composed largely of cellulose. When a wood log burns on a camp fire it produces a sooty flame. Explain why.
10. Explain why nanocellulose is unlikely to produce a sooty flame when it burns.

Water-Soluble Plastic

I buy boxes of dishwasher detergent containing plastic bags filled with the detergent. I place these bags straight into the dishwasher. When the dishes are clean and I remove them from the machine there is no trace of either detergent or the plastic bag that held it.

What happened to the plastic bag?

Can plastic dissolve in water?

Find out in the December 2018 edition of AUS-e-NEWS, AUS-e-TUTE's free, quarterly, newsletter for chemistry students and teachers. 

To subscribe to AUS-e-NEWS, go to https://www.ausetute.com.au/ausenews.html

Polylactic Acid

The London Organizing Committee of the Olympic and Paralympic Games (LOCOG) was committed to making 2012 the very first "zero-waste" Olympic and Paralympic Games.

11 million attendees produced 8,500 tons of solid waste, mostly in the form of plastic packaging.

8,000 tons of this plastic waste was transported to a site where it was composted within 9 weeks and subsequently used to fertilize local crops.

That's right!

There are plastics that can be composted, and the plastic used at the London Olympic Games was the most common compostable plastic which is known as polylactic acid or PLA.

And the chemistry of polylactic acid (PLA) is the subject of this edition of AUS-e-NEWS, AUS-e-TUTE's free quarterly newsletter.

You can subscribe to our newsletter by contacting us at http://www.ausetute.com.au/contact.html

Polystyrene

AUS-e-TUTE has just uploaded new resources for the Polystyrene topic.
AUS-e-TUTE members should log-in to view the new tutorial, play the polystyrene game and answer the polystyrene test questions.

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You can find out about membership at
http://www.ausetute.com.au/membership.html 

Polyesters

AUS-e-TUTE has just added new resources for the Polyester topic.
Members can log-in to read the new tutorial, play the new game, take the test or the exam.

http://www.ausetute.com.au

Polymer Banknotes

Australia was the first country to successfully replace paper notes with polymer notes, beginning with the circulation of $10 polymer banknotes back in 1988. Other countries, including Brunei, Canada, Fiji, Israel, Mauritius, New Zealand, Papua New Guinea, Romania, and Vietnam, have now abandoned paper in favour of polymer banknotes. Even the Bank of England will begin circulating polymer banknotes to replace the existing paper banknotes in 2016.

Australia is still the world's leading authority and prints polymer banknotes for more than 20 other countries in the world.

But what is a polymer banknote and why is it better than a paper banknote?

Find out in the March 2014 edition of AUS-e-NEWS, AUS-e-TUTE's free quarterly newsletter.

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