EXPERIMENT 14

[nylon.lab]

OBJECTIVES:

1. To be able to make models of hydrocarbons with simple functional groups.

2. To learn how functional groups interact with each other.

3. To prepare a polymer and study some of its properties.

DISCUSSION:

The word nylon is used to identify a group of polyamides made by condensation polymerization. It is a copolymer since two different monomers are used. NYLON was originally a trademark name of the DuPont Company and was discovered in 1935. Stockings made of nylon were first sold in 1938. The word nylon has come to be a generic name for linear polymers that have almost no crosslinking. This absence of cross-linking gives nylon more flexibility and the ability to be molded or become fine threads. There are many types of nylon and they are produced by several methods. Our method requires no heat or special apparatus. In this experiment, nylon 6-10 is prepared by the condensation of sebacoyl chloride and 1,6-hexanediamine. The "6-10" designation comes from the fact that polymer chain consists of alternating groups of 6 and 10 consecutive carbon atoms, separated by nitrogen atoms of the amide functional groups. The hydrogen chloride released by the reaction is neutralized by reaction by sodium hydroxide.

O O O O

" " " "

n ClC(CH₂)₈CCl + n H₂N(CH₂)₆NH₂ ==> Cl-[C(CH₂)₈C-NH(CH₂)₆NH]_n-H + n HCl

sebacoyl chloride 1,6-hexanediamine Nylon 6-10 [one unit]

The synthetic procedure uses a two-liquid-phases system in which the reactants separately dissolved in two immiscible solvents. The polymer is formed as a film at the interface of the two liquid layers.

EXPERIMENTAL PROCEDURE: ... Work in pairs.

Part 1. Models:

1. The Instructor will tell you to make a model of sebacoyl chloride ("SEB") OR of 1,6-hexanediamine ("HDA"). Identify the atoms that will be removed from the molecules when the polymer is formed. Remove these atoms and combine your model with that of the pair next to you (who should have a different model).

2. You have made ONE UNIT of the polymer, a MONOMER. Two of these units together would make a DIMER. This dimer would contain 2 molecules of SEB and 2 molecules of HDA. Let's combine the units of the whole class. How many units do we have? How would we write this formula? Is there any limit to the number of units in the polymer? The letter "n" in the formula above tells us the number of units.

Part 2. Experimental: DO NOT TOUCH THE NYLON ... USE GLOVES.

1. Add about 20 mL of Solution A (an aqueous solution containing 1,6-hexanediamine and sodium hydroxide) to a small (100 mL) beaker. Add two or three drops of phenolphthalein indicator; this will help you see the solution mixture better. (Why does the solution become red?)

2. Using a clean dry test tube, obtain about 20 mL of Solution B (a solution of sebacoyl chloride in hexane). Use a glass measuring cylinder, not a plastic one.

3. Transfer the sebacoyl chloride to the beaker by slowly pouring the solution down in the inside wall of the beaker, being careful not to mix the solutions.

4. Allow the reaction mixture stand for about 1 minute. A thin white layer of nylon polymer forms at the liquid interface.

5. Using tongs, reach into the center of the beaker and grasp the nylon film at the interface area. SLOWLY raise the polymer vertically out of the solution and wrap the top of the "thread" around the center of a large test tube. (If this does not work, slowly pass a metal spatula around the interior wall of the beaker to catch the nylon film from the glass, then transfer to the test tube.)

6. Holding the tube at each end, use it as a spool to wind up the nylon. Be sure to continue drawing the polymer from the center at a constant rate. If the thread breaks, use the forceps to get more nylon from the beaker.

7. Wash the nylon threads by rotating the test tube under a gentle stream of tap water. Don't handle the nylon before washing.

8. Slide the nylon from the test tube. You may need to use a metal spatula between the polymer and the test tube.

9. Test the strength of the wet nylon by stretching the thread until it snaps (breaks). How much effort is required?

10. Discard the nylon in a solid waste container. In cleaning the beaker and test tube, you can use the metal scoopula to remove the residual deposits of nylon fiber.

REVIEW QUESTIONS

1. Model okay ? YES - NO

2. What is the formula for the AMINO group?

3. When a polymer is formed, how many UNITs are there?

4. a. How many units would there be in a TRIMER?

b. Write the structural formula of the TRIMER of nylon 6-10, using the abbreiviations SEB and HDA instead of the full formulas.

5. How many units will be formed if 50 molecules of SEB are mixed with 80 molecules of HDA ?