A polymer is a large molecule constructed from many smaller, repeating chemical units linked together in a chain-like structure. This arrangement allows polymers to exhibit unique properties like flexibility, elasticity, and strength. Understanding how to construct these molecular chains opens the door to creating materials ranging from plastics and textiles to biological structures like DNA. This article provides accessible methods for synthesizing two distinct types of polymers using common household materials, demonstrating the fundamental chemistry of polymer creation.
Understanding the Basics of Polymer Creation
The creation of a polymer relies on two fundamental components: the small, individual building blocks called monomers, and the chemical reaction that connects them, known as polymerization. Think of the monomer as a single bead and the polymer as the long necklace formed by stringing many beads together. The resulting polymer chain can contain hundreds of thousands of these repeating units, leading to a very large molecular mass.
There are two primary ways these chains form. The first is addition polymerization, where monomers simply link together without losing any atoms, like linking hands to form a chain. The second method is condensation polymerization, which involves the linking of monomers while simultaneously releasing a small byproduct molecule, often water. This release occurs as two functional groups on the monomers react to form the new, longer polymer bond.
Simple Experiment: Creating Slime Through Cross-Linking
The popular experiment of making slime uses polyvinyl acetate (PVA) glue as the liquid polymer and a borax solution as the activator. When the borax solution is introduced, it provides borate ions that act as molecular bridges between the existing PVA polymer chains.
To begin, create the borax solution by dissolving one-quarter teaspoon of borax powder into one-half cup of warm water, stirring until fully dissolved. In a separate bowl, mix one-half cup of PVA glue with one-half cup of water to create a uniform glue mixture.
Slowly pour the borax solution into the glue mixture, adding a small amount at a time while stirring continuously. The mixture will immediately begin to thicken and pull away from the sides of the bowl as the borate ions link the PVA chains. This linking process, called cross-linking, transforms the liquid polymer chains into a single, large, three-dimensional network. Knead the material vigorously until it becomes less sticky, allowing the cross-links to fully form and distribute evenly.
Simple Experiment: Making Edible Bioplastics
Creating a bioplastic film using gelatin demonstrates a different type of polymerization that relies on natural protein chains. Gelatin, a protein derived from collagen, serves as the building block for this material. The process involves heating the ingredients, which causes the gelatin’s protein chains to denature and then re-form into a new solid structure upon cooling.
To make the mixture, combine 12 grams of powdered gelatin, 3 grams of glycerol, and 60 milliliters of hot water in a small saucepan. Glycerol (glycerin) is added as a plasticizer, a small molecule that wedges itself between the polymer chains to increase the material’s flexibility. Heat the mixture gently over a low setting while stirring constantly until the gelatin is completely dissolved and the liquid becomes clear and slightly thick.
Pour the warm liquid onto a flat, non-stick surface, such as parchment paper or a glass plate, and allow it to cool and dry undisturbed for 24 to 48 hours. As the water evaporates, the protein chains in the gelatin link together, forming a solid, flexible bioplastic film. The resulting film’s final thickness and texture will depend on the initial water content and the amount of glycerol used.
Essential Safety and Cleanup Procedures
Always ensure an adult is present to supervise the activity, and wear protective equipment like safety goggles and gloves. The materials used, particularly the borax solution, should never be ingested. Hands must be washed thoroughly after the experiment is complete.
For cleanup, the resulting polymer materials, such as slime and bioplastic, should be disposed of in the regular household trash rather than poured down the drain. Any leftover liquid chemicals should be handled according to local disposal guidelines. Small amounts of the mild solutions used here can generally be diluted with water and washed away. Ensure the workspace is completely wiped down to remove any residues.