Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) is a way of forming carbon-carbon bonds in a controlled piece-by-piece fashion using a transition metal catalyst. ATRP is used to make polystyrene, poly(methyl methacrylate) and polyacrylamide.

The ATRP process relies on paired reduction-oxidation (redox) reactions between two species of copper:

• the activator, Cu⁺
  
• the deactivator, Cu²⁺
  

where the two catalysts exchange electrons back and forth.
Occasionally, one of the exchanges will spontaneously stop, called a radical termination, resulting in the accumulation of Cu²⁺. To keep the polymerization going, chemists must re-balance the system by compensating for the excess Cu²⁺. Simply adding more Cu⁺ to the system produces materials with high, sometimes toxic, levels of copper, up to 5,000 ppm. Such levels of copper are hard to remove using current industrial equipment. It has been found that reducing agents like sugars or vitamin C are highly effective in reducing the amount of copper catalyst used in ATRP reactions.

In a new study, Carnegie Mellon University chemists have found that they can use electricity from a battery to drive these ATRP reactions. Adding electricity capitalized on the redox reaction by moderating the transfer of electrons. This allowed them to compensate for the radical terminations and reduce the amount of copper needed to run ATRP. As a result the amount of copper in the system was reduced to 50 ppm, a 100-fold decrease.

Reference
Andrew J. D. Magenau, . Nicholas C. Strandwitz, . Armando Gennaro and Krzysztof Matyjaszewski. Electrochemically Mediated Atom Transfer Radical Polymerization. Science, 1 April 2011: Vol. 332 no. 6025 pp. 81-84 DOI: 10.1126/science.1202357

Further Reading:
Parts per Million (ppm)
Polymers and Polymerization
Oxidation and Reduction
Le Chatelier's Principle

Study Questions:

1. If 1kg of polystyrene contained 5000 ppm copper, what mass of copper would be present?
2. If 1kg of polyacrylamide contained 50 ppm copper, what mass of copper would be present?
   
3. Name the monomer that is used to produce each of the following polymers:
   
   • polystyrene
   • poly(methyl methacrylate)
   • polyacrylamide
4. Provide the structural formula for each of the monomers in question 1.
5. Draw the structure for each of the polymers listed in question 1.
6. In the reaction:
   Cu⁺ Cu²⁺ + e
   which species is
   • being oxidized?
   • being reduced?
   • the oxidant?
   • the reductant?
7. What is meant by each of the following terms:
   • oxidation
   • reduction
   • redox
     
   
   
8. Explain the statement "Adding electricity capitalized on the redox reaction by moderating the transfer of electrons. "
9. In the article, it is suggested that adding Cu⁺ or using electricity can moderate the transfer of electrons. Suggest another way that this might be accomplished.
   
   

Fukushima Radiochemistry

On the 11^th March 2011 at 14:46 Japan Standard Time, a category 9 earthquake was recorded off the northeast coast of Japan. The epicenter was approximately 72 kilometers east of the Oshika Peninsula of Tohoku. The earthquake moved Honshu 2.4 m east and shifted the Earth on its axis by almost 10 cm. The earthquake was recorded as an upper 6 at the prefecture of Fukushima.

6 separate boiling water nuclear reactors make up the Fukushima I power plant. Nuclear reactors numbers 4, 5 and 6 had already been shut down prior to the earthquake for routine maintenance. Nuclear reactors 1, 2 and 3 were shut down after the earthquake but the subsequent tsunami flooded the plant and incapacitated the emergency generators which ran the pumps to cool the reactors. Reactors 1, 2 and 3 suffered partial nuclear meltdowns (melting of the core of the nuclear reactor), hydrogen explosions destroyed parts of the buildings housing reactors 1 and 3, an explosion damaged reactor 2's containment which is designed to prevent the release of radioactivity into the environment, and several fires broke out in reactor 4. As the water levels in spent fuel pools dropped, the spent fuel rods began to overheat.
On 25th March, Japan's nuclear regulator announced a likely breach of Number 3's containment vessel. World wide measurements of wind-born radioactive iodine and caesium vented from reactors suggested a massive increase in these substances which led to bans on the sale of food grown within a 100km radius of the Fukushima I plant

Cesium-137 is a radioactive isotope of cesium that is formed during the nuclear fission of uranium. It has a half-life of 30.17 years and decays by beta emission to metastable barium-137. Cesium-137 is soluble in water, and its behaviour in living things is similar to that of potassium. The biological half-life of cesium is about 70 days. Experiments with dogs have shown that a dose of 44μg/kg of cesium-137 is lethal within 3 weeks. Prussian blue, Fe₇(CN)₁₈.14H₂O, chemically binds cesium-137 and speeds up its expulsion from the body, so it can be used to treat ingestion of cesium-137.

Iodine-131, also called radioiodine, makes up about 3% of the products of uranium fission. It undergoes beta decay and has a half-life of about 8.02 days. High doses of iodine-131 can be less dangerous than low doses since high doses tend to kill thyroid tissues which could otherwise become cancerous as a result of the radiation. Ingestion of iodine-131 is treated by taking iodine supplements containing non-radioactive iodine-127 as iodide ions. This raises the total amount of iodine in the body and therefore reduce the uptake and retention of radioactive iodine-131.

Reference:
http://www.newsdaily.com/stories/tre72l501-us-japan-contaminants/

Further Reading:
Isotopes
Nuclear Decay
Half-life

Study Questions:

1. Explain what is meant by the term nuclear fission.
2. Give the atomic number and mass number for each of the following:
   
   • uranium-235
   • uranium-238
   • cesium-137
   • iodine-131
3. How many protons and neutrons are contained within the nucleus of each of these atoms:
   
   • uranium-235
   • uranium-238
   • cesium-137
   • iodine-131
4. Explain what is meant by beta decay.
5. Write balanced chemical equations for the beta decay of each of the following:
   
   • cesium-137
   • iodine-131
6. What does a Chemist mean by the term half-life?
7. If a 20kg dog ingests 880μg of cesium-137, how much cesium-137 will remain after 3 weeks? (The half-life of cesium-137 is about 30.17 years)
8. "The biological half-life of cesium is about 70 days". What do you think this means?
9. If a 20kg dog ingests 880μg of cesium-137, how much cesium-137 will remain in the dog's body after 70 days?
10. Iodine pills were distributed to people living around the Fukushima power plants on 12^th March. A typical emergency dose is 130 milligrams of potassium iodide. What mass of iodine is contained in each dose?
11. The iodine dose contained in the emergency pills is about 700 times larger than the normal nutritional daily need of an adult. What is the approximate mass of iodine is required per adult daily?
    
    

Anti-Fog Coating

Fog forms on a surface when water vapor in the air condenses in fine droplets. The fog that forms on glasses is not a continuous film, rather, it consists of tiny droplets of water that coalesce on the surface and reduce light transmission. A good anti-fog coating should prevent the formation of these droplets. Existing anti-fog coatings can't withstand repeated washings so must be re-applied regularly.

Researchers have used polyvinyl alcohol, a hydrophilic compound that allows water to spread uniformly, in the first reported permanent anti-fogging coating.

Four successive layers of molecules, which formed strong bonds with their adjoining layers, were applied to the surface prior to adding the anti-fog compound over this base. The result was a thin, transparent, multilayered coating that does not alter the optical properties of the surface on which it is overlaid. In addition, the chemical bonds that join the different layers ensure the hardness and durability of the entire coating.

Reference:
Pascale Chevallier, Stéphane Turgeon, Christian Sarra-Bournet, Raphaël Turcotte, Gaétan Laroche. Characterization of Multilayer Anti-Fog Coatings. ACS Applied Materials & Interfaces, 2011; : 110307090243075 DOI: 10.1021/am1010964

Further Reading
Physical and Chemical Changes
Balancing Chemical Equations
Intermolecular Forces
Polymers and Polymerization

Study Questions

1. Write a word equation to describe the production of fog.
2. Write a balanced chemical equation to describe the production of fog.
   
3. Is the production of fog an example of a physical or a chemical change? Explain your answer.
4. If vinyl chloride has the formula CH₂=CHCl and vinyl acetate has the formula CH₃COOCH=CH₂, what do you predict the formula for vinyl alcohol to be?
5. Draw a structure for polyvinyl chloride showing three repeating monomer units.
6. Draw a structure for polyvinyl acetate showing three repeating monomer units.
7. Draw a structure for polyvinyl alcohol showing three repeating monomer units.
8. Using your understanding of intermolecular forces, explain how a coating of polyvinyl alcohol could help water droplets forming on glasses.
   

Sweeter Natural Gas

Natural gas extracted from the coal beds and methane-rich geologic features must first be purged of hydrogen sulfide before it can be used as fuel in a process called "sweetening".

Thermal Swing Regeneration, a common industry process used for sweetening natural gas, uses chemical sponges called sorbents to remove toxic and flammable gases, such as rotten-egg smelling hydrogen sulfide from natural gas. The gas must first be treated with a solution of chemical sorbents that are dissolved in water. That solution must then be heated up and boiled to remove the hydrogen sulfide, in order to prepare the sorbent for future use. Once the hydrogen sulfide is boiled off, the sorbent is then cooled and ready for use again. The repeated heating and cooling requires a lot of energy and markedly reduces the efficiency of the process.

A new process called Antisolvent Swing Regeneration takes advantage of hydrogen sulfide's ability to dissolve better in some liquids than others at room temperatures. In this process, the hydrogen sulfide "swings" between different liquids during the processing at nearly room temperature, resulting in its removal, in just a few steps, from liquids that can be reused again and again.

First hydrogen sulfide is dissolved in a substance known as a DMEA which is a recyclable binding organic liquid, a substance that can hold onto hydrogen sulfide without the addition of water. DMEA forms a salt with hydrogen sulfide. The salty DMEA is then mixed with hexane (or hexadecane and a small amount of heat) which returns most of the hydrogen sulfide back to the gaseous state which is then bubbled out of the mixture. Separating the hexane from the DMEA allows these substances to be re-used.

Scientists estimate that the Antisolvent Swing Regeneration method could reduce the amount of energy needed to complete the sweetening process by at least 10%.

Reference
Phillip K. Koech, James E. Rainbolt, Mark D. Bearden, Feng Zheng, David J. Heldebrant. Chemically selective gas sweetening without thermal-swing regeneration. Energy & Environmental Science, 2011; DOI: 10.1039/c0ee00839g

Further Reading:
Writing Ionic Formulae
Naming Straight Chain Alkanes
Intermolecular Forces

Study Questions:

1. Write the chemical formula for each of the following:
   
   • methane
   • hydrogen sulfide
   • hexane
2. In a sample of each of the following pure substances, what type of forces would you expect to attract molecules to each other?
   
   • methane
   • hydrogen sulfide
   • hexane
3. Describe what would happen if each of these pure substances was mixed with water.
4. Describe what would happen if each of these substances were mixed with a petroleum-based oil.
5. Use the description of the Thermal Swing Regeneration process to draw a flow chart for this method of sweetening natural gas.
   
6. Use the description of the Antisolvent Swing Regeneration process to draw a flow chart for this method of sweetening natural gas.
   

VMD for Fingerprinting

Forensic experts at the University of Abertay Dundee and the Scottish Police Services Authority (SPSA) are researching vacuum metal deposition (VMD) to recover fingerprint ridge detail and impressions from fabrics.

Vacuum metal deposition, VMD, is a common method of depositing a thin film on a substrate.
The source metal is evaporated in a vacuum which allows the vapor particles to travel directly to the target object, the substrate, where they condense back to the solid state. Evaporated materials deposit non-uniformly if the substrate has a rough surface, and, because the evaporated material attacks the substrate mostly from one direction, protruding features block the evaporated material from some areas which is called "shadowing" or " step coverage".

The Scottish scientists have been using gold and zinc in a VMD process to recover fingerprint marks on fabrics. The fabrics are placed in a vacuum chamber then gold is heated up to evaporate it. The gold particles spread out in a thin film over the fabric. Zinc is then heated up, and the zinc particles attach to the gold particles where there are no fingerprint residues. The fingerprint ridges show up as clear fabric, but where there are no fingerprint ridges the distinctive grey colour of the zinc metal is seen.

While only 20% of the public are classed as "good donors" for leaving fingerprints, the researchers have had great success in revealing the shape of a handprint on a number of fabric types. Handprints could help the police piece together a timeline of events which could be used to provide evidence in cases where someone was pushed, or grabbed, in a particular area of their clothing. For example, an impression of a palm print on the back of someone's shirt might indicate they were pushed off a balcony, rather than jumping.

Reference
Joanna Fraser, Keith Sturrock, Paul Deacon, Stephen Bleay, David H. Bremner. Visualisation of fingermarks and grab impressions on fabrics. Part 1: Gold/zinc vacuum metal deposition. Forensic Science International, 2010; DOI: 10.1016/j.forsciint.2010.11.003

Further Reading
Physical and Chemical Changes

Study Questions

1. What do Chemists mean when they refer to evaporation?
2. What do Chemists mean when they refer to condensation?
3. Are evaporation and condensation examples of chemical or physical changes? Explain your answer.
   
4. Write a chemical equation to represent the evaporation of solid gold as described above in the process of vacuum metal deposition.
5. Do you think the equation you wrote above is an example of an evaporation process? Explain your answer.
6. Write a chemical equation to describe the process of gold vapor condensing on a fabric as described in the process of vacuum metal deposition.
7. Give the name for the change of state being described in each of the following:
   
   • heating solid gold until it forms a liquid
   • heating solid gold in a vacuum so that it forms a vapor
   • cooling gold vapor in a vacuum so that if forms solid gold
   • cooling gold liquid until it forms solid gold
   • heating liquid gold until it forms gold vapor
   • cooling gold vapor until it forms liquid gold
     

Butanol Biofuel

A team of chemical engineers at the University of Arkansas has developed a method for converting common algae into butanol, a renewable fuel that can be used in existing combustion engines.

Butanol has several significant advantages over ethanol, the current primary additive in petrol (gasoline). Butanol releases more energy per unit mass and can be mixed in higher concentrations than ethanol. It is less corrosive than ethanol and can be shipped through existing pipelines. These attributes are in addition to the advantages gleaned from butanol's source. Unlike corn, algae are not in demand by the food industry. Furthermore, it can be grown virtually anywhere and thus does not require large tracts of valuable farmland.

The team grows algae on "raceways," which are long troughs made out of screens or carpet, usually 2 feet wide and ranging from 5-feet to 80-feet long, depending on the scale of the operation. Algae survive on nitrogen, phosphorus, carbon dioxide and natural sunlight, so the researchers grow algae by running nitrogen- and phosphorus-rich creek water over the surface of the troughs. Excess nitrogen and phosphorus in natural waters is sometimes referred to as "dead zones" because these elements in excess can kill fish and plants.
They enhance this algal growth by delivering high concentrations of carbon dioxide through hollow fiber membranes that look like long strands of spaghetti.

The researchers harvest the algae every five to eight days by vacuuming or scraping it off the screens. After waiting for it to dry, they crush and grind the algae into a fine powder as the means to extract carbohydrates from the plant cells. Carbohydrates are made of sugars and starches. They treat the carbohydrates with acid and then heat them to break apart the starches and convert them into simple, natural sugars. They then begin a unique, two-step fermentation process in which organisms turn the sugars into the organic acids butanoic acid( butyric acid), lactic acid and ethanoic acid (acetic acid).

The second stage of the fermentation process focuses on butanoic acid (butyric acid) and its conversion into butanol. The researchers use a unique process called electrodeionization which involves the use of a special membrane that rapidly and efficiently separates the acids during the application of electrical charges.

Reference:
University of Arkansas, Fayetteville (2011, March 2). Algae converted to butanol; Fuel can be used in automobiles. ScienceDaily. Retrieved March 11, 2011, from http://www.sciencedaily.com­ /releases/2011/03/110301200638.htm

Further Reading
Elements and Compounds
Nomenclature
Alkanols (alcohols)
Functional Groups
Carbohydrates
Carbon Cycle


Study Questions

1. Draw a table with the headings elements and compounds. Place each element and compound mentioned in the article above into the table.
2. Give the formula for each of the following:
   
   • butanol
   • ethanol
   • nitrogen gas
   • carbon dioxide gas
   • butanoic acid
3. Describe what is meant when a Chemist uses the term carbohydrate.
4. What is the difference between a sugar and a starch?
   
5. Give 3 examples of compounds that are carbohydrates.
6. Write an equation to represent the process by which algae produce glucose from carbon dioxide and water.
   
7. Write an equation to represent the fermentation of glucose into ethanol.
8. What are the advantages of using butanol as an additive to petrol (gasoline) rather than ethanol?
   

AUS-e-NEWS March 2011

2011 is the International Year of Chemistry and 100 years since Madame Marie Curie was awarded a Nobel Prize for her work with radium.
The March 2011 issue of AUS-e-NEWS takes at look at the elements polonium and radium.

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