Green Chemistry Workshop #6: Polymers

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/

LABORATORY SESSIONBreak for ….

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

Image: http://www.jbei.org/images/feedstocks/pectin_structure.png

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

LABORATORY SESSIONBreak for ….

Results

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/

LABORATORY SESSIONBreak for ….

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

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