Nylon Rope Trick

Equipment

Ringstand with roller, 4 ounce jar with lid, glass rod with hooked end.

Reagents

Solution "A" (0.5 M hexamethylenediamine ( H₂N(CH₂)₆NH₂, also called 1,6-diaminohexane) and 0.5 M sodium hydroxide in water),
Solution "B" (0.2 M sebacoyl chloride ( ClOC(CH₂)₈COCl ) in hexane).

Presentation

Preparation

1. Make solution "A" by placing a bottle of hexamethylenediamine in warm water to melt it (m.p. 39-40°C). Dispense 6.0 g of the hexamethylenediamine into a bottle. Add 2.0 g of sodium hydroxide and add 100 mL of DI water to the bottle. Cap the bottle tightly and shake to dissolve and mix.
2. Make solution "B" by dispensing 2.0 g (1.6 mL) of sebacoyl chloride into a bottle, add 100 mL of hexane to the bottle. Cap the bottle tightly and shake to mix.

Demonstration

1. Add 25-50 mL of solution "A" to the jar.
2. Place the glass rod in the center of the jar with the hook down.
3. Carefully pour the same volume of solution "B" as solution "A" down the glass rod, so as not to disturb the interface between the two solutions.
4. After solution "B" has been added, pull the glass rod out of the jar. The hook will snag the nylon that has formed at the interface of the two solutions.
5. Wrap the strand of nylon around the roller and wind the nylon strand onto the roller with a steady pace.
6. When you are done winding the nylon, close the jar to minimize the hexane fumes.

Hazards

Sebacoyl chloride is corrosive and reacts with water, so it causes severe burns to every area of contact. It is harmful if swallowed, inhaled or absorbed through skin.
1,6-diaminohexane is corrosive. It causes burnes to any area of contact. It is harmful if swallowed, inhaled or absorbed through skin. 1,6-diaminohexane is extremely destructive to the upper respiratory tract, eyes and skin. It is combustible either as liquid or as vapor.
Solid sodium hydroxide and its concentrated solutions can cause severe burns to eyes, skin, and mucous membranes.
Overexposure to vapors of hexane is irritating to the respiratory tract. Contact with liquid is irritating to skin and to eyes.

Discussion

The word "nylon" is used to represent synthetic polyamides. The various nylons are described by a numbering system that indicates the number of carbon atoms in the monomer chains. Nylons from diamines and dibasic acids are designated by two numbers, the first representing the diamine and the second the dibasic acid [2]. The nylon formed in this demonstration would be 6-10 nylon.

n H2N(CH2)6NH2  +  n ClCO(CH2)8COCl  ®  [-NH(CH2)6NH-CO(CH2)8CO-]n  +  2n HCl

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References

1. B. Z. Shakhashiri, Chemical Demonstrations, A Handbook for Teachers of Chemistry, Wisconsin, 1983, Vol.1, p.213-215.
2. A. Ravve, Organic Chemistry of Macromolecules, Marcel Dekker: New York, 1967, ch. 15.