Synthesizing Complex Polymers
from Green Chemistry Colloquy funded by the Burroughs Wellcome Fund

Purpose
To explore how the properties of molecules change when polymers are synthesized

Materials

Each group:

2 graduated cyinders	spoon	stirring sticks
gloves	10 mL gelatin solution	paper towels
polystyrene packing peanuts	starch packing peanuts	beaker

Each table:

4% sodium borate solution (borax)	distilled water	food coloring
ferric nitrate solution	acetone

Procedure

Part I - Polymerizing polyvinyl alcohol

1. Place 10 mL of polyvinyl alcohol (PVA) in a beaker and 2.5 mL of sodium borate in a graduated cylinder. Observe the solutions carefully and record their properties in Table 1

2. Add 1 drop of dye (food coloring) to the PVA. While stirring with a spoon, add the sodium borate. Observe carefully what happens. Do you notice a temperature change? Describe what happens

3. Remove the polymer to a paper towel. Avoid getting your polymer on the table, floor or your clothes.

Questions

How does this polymer compare with PVA?

Observe and describe the following properties

"Stretchiness" (Pull the polymer slowly. Pull the polymer quickly.)

"Bounciness" (See if you can bounce a piece of the polymer off a paper towel)

"Stickiness" (See of a piece of polymer will be flattened or stick to a surface as you press down on it.)

***How might these 3 properties be measured quantitatively? ***

The synthesis of a polymer involves a chemical reaction. What evidence do you have that this occurred.

Part 2 - Creating a natural polymer from gelatin

1. Place 10 mL of gelatin solution in a beaker and find a dropper of ferric nitrate. Observe the solutions carefully and record their properties in Table 1.

2. Stirring constantly, add 5 drops of ferric nitrate to the gelatin solution. Continue to stir until no further change takes place. Describe what happened.

3. Remove the polymer to a paper towel. Avoid getting your polymer on the table, floor or your clothes.

Questions

How does this polymer compare with gelatin?

Observe and describe the following properties

"Stretchiness"

"Bounciness"

"Stickiness"

Part 3: Dissolving polystyrene in acetone

1. Place 10 mL of acetone in a beaker and obtain ~15 packing peanuts (you may need more). Observe the solutions and peanuts carefully and record their properties in Table 1.

2. Stirring continuously, add packing peanuts one at a time to the acetone until no more peanuts will dissolve. Describe what happened.

3. Using gloves, remove the polymer to a paper towel. Avoid getting your polymer on the table, floor or your clothes.

Questions

How does this polymer compare with polystyrene?

Observe and describe the following properties

"Stretchiness" (Pull the polymer slowly. Pull the polymer quickly.)

"Bounciness" (See if you can bounce a piece of the polymer off a paper towel)

"Stickiness" (See of a piece of polymer will be flattened or stick to a surface as you press down on it.)

Data Table 1

Properties of Reactants		Properties of Product
Polyvinyl Alcohol	Sodium Borate	New Polymer
Gelatin Solution	Ferric Nitrate	New Polymer
Polystyrene	Acetone	New Polymer

 

**Extra -

Try dissolving the starch packing peanuts in acetone and in water (10 mL is plenty). What happens? Do you get a polymer? How do you know?

Try dissolving other types of styrofoam (cup, ball...) in acetone. How are they different before you dissolve them? How are they different after?