Polymer Bead

Introduction

Give students a concrete understanding of polymers and their unique properties by performing this gravity defying, highly visual demonstration.

Concepts

• Polymers
• Monomers

Materials

Safety Precautions

This demonstration is considered relatively nonhazardous. Use extreme care if the demonstration is performed on a stepladder or other elevated area.

Procedure

1. Obtain the polymer bead strand. Show students that each bead represents a monomer and the entire chain of monomers represents a polymer.
2. Place a 500-mL beaker on the floor.
3. Stand over the beaker and load the string of polymer beads into the beaker. Feed the beads into the beaker hand over hand so the beads fall neatly into the beaker in a coiled, clockwise fashion (see Figure 1).
   {13975_Procedure_Figure_1}
4. Leave the end of the polymer strand extended over the edge of the beaker.
5. Pick up the beaker from the floor. Stand in a location visible to all students. A stepladder may be used to ensure student visibility.
6. Give the beads a slight pull upwards out of the beaker. All of the beads will selfsiphon out of the beaker and remain at a constant location roughly 2" to 3" above the rim of the beaker. Point out this gravity defying motion of the beads as they exit the beaker (see Figure 2). 
   {13975_Procedure_Figure_2}
7. Have students observe the pile of beads on the floor. This represents a small polymer molecule with a somewhat random configuration.
8. Repeat steps 1–7 as desired.
9. The beads may be saved and reused for future demonstrations.

Student Worksheet PDF

13975_Student1.pdf

Teacher Tips

• The polymer beads may be uses as many times as desired.
• This is a great demonstration to show before or after performing the Super Duper Polymer Gel Demonstration (Flinn Cat. No. AP4556). The polymer polyethylene oxide used in this activity is a water soluble high molecular weight polymer that has many unique properties. Polyethylene oxide has the ability to thicken in water and form a viscoelastic gel that has the ability to self-siphon itself out of a container.

Answers to Questions

1. What does each bead on the string represent? What does the entire string of beads represent?

   Each bean is a monomer. The entire string of beads represent a polymer.

2. Observe and draw the beads in the beaker before the demonstration.
   {13975_Answers_Figure_4}
3. What is happening to the beads (polymer strand) during the demonstration?

   The beads are defying gravity and self-siphoning themselves out of the beaker.

4. Observe and draw the beads on the floor after the demonstration has been performed. Are they in a crystalline or amporphus structure?
   {13975_Answers_Figure_5}

   The beads are in an amporphous or spaghetti-like pile.

Discussion

A polymer is a substance that is made up of many units. The units, or monomers, are small molecules that usually contain less than ten atoms in a row. Carbon and hydrogen are the most common atoms in monomers, but oxygen, nitrogen, chlorine, silicon, fluorine, silicon and sulfur may also be present. Polymers can be best visualized as numerous beads (monomers) linked together (or polymerized) on a string to make a chain with at least 100 repeating units. Each bead or monomer is polymerized to the next to form thousands of atoms in a row (see the string of beads presented in this activity).

Polymers are found in the human body, plants, animals, minerals and manufactured products. Substances such as DNA, diamonds, home insulation, shampoo and paint all contain polymers. Polymers found in animals and plants are responsible for biochemical reactions, structural support and growth. Cellulose and lignin are polymers that give structure to plants. Cellulose is a starch or polysaccharide macromolecule that is composed of individual sugar molecules that are bonded together to give molecular weights in the millions. Cellulose is the basis for cotton and rayon fibers. Starch in plants stores sugar and largely consist of two forms of polymer—branched and linear. Proteins are polymers that are responsible for the makeup of hair and fibers such as wool and silk. DNA is a polymer that is necessary for life processes in plants and animals. Natural rubber is composed of isoprene monomers which are very elastic. Artificial rubber is made from butadiene and other monomers. Inorganic polymers (those not containing carbon atoms) include glass with its silicon–oxygen framework and other silicates such as those found in granite and agate.

Strands of polymers can be pictured as spaghetti on a plate. An amorphous arrangement (lacking crystalline structure) of a polymer does not have a three-dimensional order in which the polymer chains arrange themselves. Amorphus polymers are also transparent in the absence of additives. Transparency does not guarantee the absence of crystalline structure but it does indicate that there are no structures present that cause the reflection of visible light that would prevent transparency. This is a very important characteristic in items such as Plexiglass^® and contact lenses. Controlling the polymerization process can result in a transparent film from semi-crystalline polymers. Not all polymers are transparent. Many polymers are crystalline in structure and are translucent or opaque. Crystalline structures are arrangements of atoms, ions of molecules in a distinct pattern. The higher degree of crystallinity of a polymer the less light that can pass through. Increased crystallinity of a polymer does not change its melting point, but it does mean that more energy is needed to cause the polymer to separate, melt or flow. Amorphous polymers on the other hand, do not have melting points-they have glass transition temperatures above which flow is permitted.

If a polymer has all of the same monomers it is known as a homopolymer. Examples of homopolymers are polyvinylchloride, polyethylene oxide and cellulose. A block copolymer would appear as two monomers in s set sequence such as A-A-A-A-B-B-BB. Random copolymers, such as rubber, contain a random distribution of polymers such as A-A-B-B-B-A-B-B-B-B-A-A-A.

By changing the factor of which a polymer is produced, engineers continually produce better-suited materials for countless applications. Manufacturers constantly introduce various fillers and additives into polymers to expand product possibilities. Polymers may also have different end units, branches or variations in sequences that lead to various types of materials. Figure 3 shows a few manufactured polymers and the monomers they are built from. The double bond of the monomer is generally broken or water is eliminated in the polymerization process.

References

What is a Polymer? Polymer Ambassadors.