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
H
H
C
C
HC
H
CH
HC
CH
C
H
styrene
polystyrene
Pink: antistatic
Green: recycled content
Polystyrene image: http://i.ehow.com/images/a04/cu/il/packing-peanuts-200X200.jpg
Polyurethanes
Alcohols react with isocyanates to form
urethanes:
O
R
OH + R'
N
C
O
R
C
O
R'
N
H
Diols react with diisocyanates to form polyurethanes:
HO
O
C
N
CH3 +
H2C
H
CH2
OH
N
N
O
CH3
C
O
O
C
N
H
C
H2C
O
O
toluene diisocyanate
Polyurethane image: http://www.redpackaging.com/images/packing_peanuts.jpg
a polyurethane
CH2
Starch
OH
O
HO O
HO
OH
O
HO O
HO
OH
O
OH
HO O
HO
O
HO O
HO
OH
O
HO O
HO
O
HO O
HO
Starch image: http://cracklecdn-zoovy-1.simplecdn.net/img/bamtar/W678-H574Bffffff/packing_peanuts/eco_packing_peanuts_shipping_supplies_zoom.jpg
OH
Materials and Procedure
Polystyrene “peanuts
Biodegradable “peanuts”
Acetone (10 – 25 mL)
Water (10 – 15 mL)
Containers – beakers or jars
• Add a polystyrene peanut to water, observe.
• Repeat for a biodegradable, starch-based peanut.
• Repeat for the two types of peanuts in acetone.
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/
Break for ….
LABORATORY SESSION
O
Results
C
H3C
O
H
CH3
“Like Dissolves Like”
Lotus flower image from: http://tsvetankapetrova.files.wordpress.com/2009/01/1663153-lotus-flower-0.jpg
Lotus with droplet image from: http://www.smartgarmentpeople.com/images/page_image/
water%20droplet%20on%20lotus%20leaf%20NANOSURFACES.jpg
Close-up image from: http://www.ramehart.com/goniometers/newsletters/lotus2.jpg
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; intermolecular
interactions.
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
Image: http://www.jbei.org/images/feedstocks/pectin_structure.png
OH
CO2H
Chemistry
O
HO
HO
O
HO
HO
HO
O
HO
H
HOH2C
O
CH2OH
CO2H
O
H
OH
HO
HO
H
sucrose
O
pectin
CO2H
O
HO
HO
• 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 Experiments
Macromolecules, 2002, 35 (21), pp 8147–8151
O
CO2H
O
HO
HO
O
pH Adjustment
O
H2
C
HO
C
O
C
C
HO
OH
H
malic acid
fruit juice
(apple or white grape)
malic acid
Apple juice image: http://hotelminishop.com/Dole_apple.jpg
Polymer swelling schematic: http://www.physik.uni-halle.de/im/1221849046_513_00_800.gif
Materials & Procedure
Water Pectin Fruit juice Sucrose
•
•
•
•
•
Test 1 60 mL
7g
18 mL
53 g
Test 2 60 mL
7g
18 mL
26 g
Test 3 60 mL
7g
18 mL
106 g
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
Break for ….
LABORATORY SESSION
Results
Observations
Test 1
Test 2
Test 3
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
Wet
D ry
H2
C
CH
C
O
O- Na+
Sodium ion
Water molecule
• 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.
Procedure
Polypropylene
Composite fiber
Polyacrylate
Polyethylene
• 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
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/
Break for ….
LABORATORY SESSION
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 Relevance
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)
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
ขอบคุณครับ
สวัสดีครับ