green chemistry workshop #6: polymers us – thai distance learning program march 17, 2010 professor...
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Green Chemistry Workshop #6:
Polymers
Green Chemistry Workshop #6:
Polymers
US – Thai Distance Learning Program
March 17, 2010
Professor Kenneth M. Doxsee
University of Oregon
The Principles of Green Chemistry
1. Prevention
2. Atom Economy
3. Less Hazardous Synthesis
4. Designing Safer Chemicals
5. Safer Solvents and Auxiliaries
6. Design for Energy Efficiency
7. Renewable Feedstocks
8. Reduce Derivatives
9. Catalysis
10. Design for Degradation
11. Real-time Analysis
12. Inherently Safer Chemistry
Polymer Packing “Peanuts”
Premise• Packing “peanuts,” made up of various
polymers, can be used for simple and safe demonstrations of various chemical properties.
Chemical Concepts • Polymers; carbohydrates;
solubility.
Image: http://www.turtlerescues.com/images/packing%20peanuts%20on%20top%20of%20inside%20box.jpg
Background
• Packing “peanuts,” used to protect fragile items during shipping, are available in a variety of compositions.
• Varying in chemical properties – polarity, solubility, etc. – these different types of packing peanuts can be used to demonstrate these properties in simple and safe ways.
Polystyrene
styrene polystyrene
HC
HCCH
CH
CH
CH C
H
H
Pink: antistaticGreen: recycled content
Polystyrene image: http://i.ehow.com/images/a04/cu/il/packing-peanuts-200X200.jpg
Polyurethanes
R OH R' N C O RO
CN
O
R'
H
+
CH3
N
NCO
C
O
HO
H2C CH2
OH
N
H
CO
O
CH3
N C
H O
O
CH2
H2C
+
toluene diisocyanate a polyurethane
Alcohols react with isocyanates to formurethanes:
Diols react with diisocyanates to form polyurethanes:
Polyurethane image: http://www.redpackaging.com/images/packing_peanuts.jpg
Starch
O
OH
OHO
HO O
OH
OHO
HO O
OH
OHO
HO O
OH
OHO
HO O
OH
OHO
HO O
OH
OHO
HO
Starch image: http://cracklecdn-zoovy-1.simplecdn.net/img/bamtar/W678-H574-Bffffff/packing_peanuts/eco_packing_peanuts_shipping_supplies_zoom.jpg
Materials and Procedure
• Add a polystyrene peanut to water, observe.• Repeat for a biodegradable, starch-based peanut.• Repeat for the two types of peanuts in acetone.
Polystyrene “peanutsBiodegradable “peanuts”Acetone (10 – 25 mL)Water (10 – 15 mL)Containers – beakers or jars
Laboratory Safety
Accident: An unexpected and undesirable event, especially one resulting in damage or harm.
Safety glasses image from: http://facilitysigns.wordpress.com/category/signs-and-labels/
Results
“Like Dissolves Like”
Lotus flower image from: http://tsvetankapetrova.files.wordpress.com/2009/01/1663153-lotus-flower-0.jpgLotus with droplet image from: http://www.smartgarmentpeople.com/images/page_image/
water%20droplet%20on%20lotus%20leaf%20NANOSURFACES.jpgClose-up image from: http://www.ramehart.com/goniometers/newsletters/lotus2.jpg
H3CC
CH3
O
HO
H
Green Relevance
Green Concepts• Consider Green Principles
– #1 (prevent waste)
– #3 (less hazardous reagents)
– #4 (safer chemicals)
– #7 (renewable feedstocks)
– #10 (design for degradation)
Trash image: http://www.sfgate.com/blogs/images/sfgate/green/2008/12/30/styrofoam_trash.JPG
Carbohydrates
Premise• Simple household materials can be used to explore
concepts of polymer chemistry.
Chemical Concepts • Properties of covalent compounds;
carbohydrates; food chemistry;polymers; acid/base; intermolecularinteractions.
Sugar image: http://img.alibaba.com/photo/100383368/Sugar_Thailand_Origin.jpg
Background
• Pectin is the major binding component of the cell walls of plants and fruits. It is chemically a polysaccharide, consisting of a linear chain of linked molecules of galacturonic acid.
• Aqueous solutions of pectin become gelatinous when treated with carbohydrates (e.g., sucrose) under suitable conditions of concentration and pH.
Image: http://www.pickyourown.org/blueberry/pectin_types.jpg
Chemistry
• Gelation is not a chemical reaction.• Enhanced strand-strand interaction caused by high
sugar concentration (reduced water activity).• Moderate acidity also required – too many
carboxylates can prevent chain aggregation.• Ca2+ can induce gelation in ‘low methoxyl’ pectin.
Role of Sucrose in Pectin Gelation: Static and Dynamic Light Scattering ExperimentsMacromolecules, 2002, 35 (21), pp 8147–8151
OCO2H
HO
HO
OCO2H
HO
HO
O
OCO2H
HO
HO
O
OCO2H
HO
HOO
O
O
OH
HOHO
HOO CH2OH
HOH2C H
H
HO HOH
sucrose
pectin
pH Adjustment
Apple juice image: http://hotelminishop.com/Dole_apple.jpgPolymer swelling schematic: http://www.physik.uni-halle.de/im/1221849046_513_00_800.gif
fruit juice(apple or white grape)
malic acid
C
H2C
CC
OH
O
HO
HO H
O
malic acid
Materials & Procedure
• Place water, pectin, and juice in 600 mL beaker.
• Stir and heat until just about to boil.
• Add sugar, heat to hard boil with constant stirring.
• After 1 minute, remove from heat.
• Allow to cool, removing any foam with a spoon.
Laboratory Safety
Accident: An unexpected and undesirable event, especially one resulting in damage or harm.
Image from: http://facilitysigns.wordpress.com/category/signs-and-labels/Hot image from: http://www.freesignage.co.uk/pdfthumbs/warning/caution_hot_liquids_warning_sign.png
Other Approaches
• Polystyrene, other polymers - crosslinking.
• Styrene, divinylbenzene.
• Solvent-swollen polymers (e.g., rubber o-ring in THF)
Hazardous reagents. Reagents derived from petroleum -
nonrenewable resource. Disposal of hazardous waste.
Image from: http://www.drugdeliverytech.com/Media/PublicationsArticle/000647.jpg
Green Relevance
Green Concepts
• Consider Green Principles
– #3 (prevent waste)
– #4 (safer chemicals)
– #5 (safer solvents)
– #7 (renewable feedstocks)
– #10 (design for degradation)
Image from: http://hostedmedia.reimanpub.com/TOH/Images/Photos/37/exps24652_TH10525D15.jpg
Analysis of Charge with Polymer Gels
Premise• The “superabsorbent” polymer
used in disposable baby diapers
can be used as an ion exchange resin.
Chemical Concepts • Properties of ionic and covalent compounds; cation
analysis; solubility; polymers.
Disposable diaper image: http://reflectionsofamirror.files.wordpress.com/2008/02/disposable_baby_diaper.jpg
Background
• Disposable baby diapers contain a small amount of a polymer that is able to absorb many times its own weight in water.
Image: http://bp2.blogger.com/_PDb1K6TmuWc/SD8dET_sN6I/AAAAAAAAAKk/sAJoIUkirIk/s1600-h/04.15.08-05.29.08+002.jpg
Chemistry
• More highly-charged cations – e.g., Ca2+ - interact with the carboxyl groups, causing the gel to collapse.
• Cations are attracted to the charged polymer chain, while anions are not.
H2C
CH
CO O- Na+
Dry
Sodium ion Water molecule
Wet
Procedure
• Carefully take apart a clean disposable baby diaper, transferring the cotton (fluffy white) portion to a plastic bag.
• In the bag, tear apart the cotton, shaking to separate the superabsorbent polymer grains.
• Remove as much of the cotton as possible.
Bag image: http://www.supplierlist.com/photo_images/66082/LDPE_Ziplock_Bag_Plastic_Bag_Packaging_Bag_Zip_loc.jpg
Polypropylene
Composite fiber
Polyacrylate
Polyethylene
Procedure
• Hydrate about 0.5 g of polymer.
• In each of six plastic cups, place water and a sample of a dye – e.g., 1 drop of food coloring (red, blue, green), methylene blue, malachite green, crystal violet.
• To each cup add a portion of the polymer gel.
• Let stand for 15 minutes.
• While waiting, use a hot paperclip to melt small holes into the bottoms of six plastic cups.
• Transfer the samples to these plastic cups, allowing liquid to drain out through the holes.
• Rinse with excess water, allowing to drain.
Plastic cups image: https://www.inspire4less.com/productimages/9780784725290.jpg
Laboratory Safety
Accident: An unexpected and undesirable event, especially one resulting in damage or harm.
Safety glasses image from: http://facilitysigns.wordpress.com/category/signs-and-labels/
Results
• Other things that can be explored (see packet):
– Effect of salts on gel.– Effect of acids on gel.– Other dyes or colored ions.– Your students’ ideas.
Green Concepts• Consider Green Principles
– #1 (prevent waste)
– #4 (safer chemicals)
– #5 (safer solvents)
– #10 (design for degradation)
– #11 (real-time analysis)
– #12 (inherently safer chemistry)
Green Relevance
Ion exchange image from: http://www.systemsaver.com/windsor-website/education/how-softeners-work/ion-exchange.jpg
Questions and Discussion
Image from: http://www.legis.state.wi.us/senate/sen11/news/images/questions.jpg