EXPERIMENT 17
NYLON BY INTERFACIAL CONDENSATION POLYMERIZATION
Macromolecules or polymers are formed from the union of smaller
molecules, called monomers. This process is called polymerization. When this
process is accompanied by the elimination of small molecules such as water or
ammonia, it is called CONDENSATION polymerization. When this process
occurs by simple addition of unsaturated or cyclic molecules, it is called
ADDITION polymerization.
The specific reaction studied in this experiment is the formation of nylon 6-10
by the process of CONDENSATION. This form of nylon was one of the first
synthetic polymers. It is formed by the nucleophilic acyl substitution between an
acid chloride R-CO-Cl and an amine R’-NH2. The amine attacks the carbonyl
carbon pushing out Cl- to form a protonated amide. After the transfer of H+, the
neutral amide, R-CO-NHR’ and HCl are produced. HCl is then reacts with NaOH
in the solution to form water and NaCl. The amide linkage is relatively stable. In
order to achieve polymerization, this reaction must link both ends of the
molecules together. Thus, effective polymerization occurs when the acid chloride
and the amine are DIFUNCTIONAL.
The specific compounds require to prepare nylon 6-10 are sebacoyl chloride
and 1, 6-Diaminohexane. Sebacoyl chloride has the structure indicated below:
O
O
‫׀׀‬
‫׀׀‬
Cl-C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-C-Cl
Notice that there are TEN carbon atoms in the sebacoyl chloride. Each end of
this large molecule is capable of undergoing nucleophilic acyl substitution to form
the amide linkage.
The 1, 6-diaminohexane has the structure shown below. Notice that it
contains six carbons, hence the polymer is called nylon 6-10.
NH2-CH2-CH2-CH2-CH2-CH2-CH2-NH2
The reaction between these two compounds results in the formation of a
linear polyamide and HCl:
O
nCl
O
C (CH 2)8-C-Cl
O
+ n H2N (CH2)6-NH 2
[HN(H2C) 6HN
O
C (CH 2)8-C
] + 2n HCl
n
This reaction is carried out by interfacial condensation polymerization. This
involves the careful layering of two immiscible liquids. One liquid, cylcohexane,
serves to dissolve the sebacoyl chloride. Sebacoyl chloride does not dissolve in
water, but is soluble in the cyclohexane because it’s high carbon content. A
solution of these two compounds forms the top layer of the two immiscible
liquids.
The other reactant, 1, 6-diaminohexane, is dissolved in aqueous NaOH to form
the upper layer. The diamine is soluble in water because it is capable of
hydrogen bonding and contains a relatively small number of carbon atoms per
amine group. It is also soluble in the cyclohexane. Once the two solutions are
carefully layered, reaction occurs at the interface. If the product polymer is drawn
out, fresh solution is exposed for further reaction. Thus a continuous strand of
nylon may be obtained.
Nylon 6/10
At interfacial
------------
← Sebacoyl chloride in cyclohexane)
← 1,6diaminonexane inNaOH
Procedure
1. To a 250 mL beaker, add 2 ml of 20% NaOH solution and 10 mL of 1,6Hexanediamine solution(5% aqueous solution).
2. With a dropper pipet, slowly in a circular motion, add 2-3 mL of 5% Sebacoyl
Chloride solution. A thin film will appear between the two solutions.
3. Use a tweezers to pick up the polymer film at the interface. Wrap the
resulting nylon string around a glass rod. Continue to curl the resulting string
of nylon around the end of the glass rod until no more of the polymer will form.
4. Remove the nylon from the glass rod. Dip the nylon into a beaker containing
about 15-20mL of 5% Hydrochloric Acid for 2 minutes (Hydrochloric acid is
used to neutralize the NaOH from the reaction solution.). Wash it thoroughly
in water and press dry with a paper towel.
5. Determine the weight of nylon polymer. Describe its appearance.
EXPERIMENT 17
NYLON BY INTERFACIAL POLYMERIZATION
Student Name: _____________________
Day: ____________
Total mass of polymer:
Appearance of polymer film:
Characteristics:
QUESTIONS
1. What is the equation for the reaction between sebacoyl chloride and
hexane-1, 6-diamine?
2. What type of polymer is NYLON 6.10 (condensation or addition)?
3. The two solvents used in this polymerization are water and
dichloromethane.
(a) What is the solubility of sebecoyl chloride in each?
(b) What is the solubility of the diamine in each?
4. Why is NaOH dissolved in the water layer?
5. Why is the polymer washed in dilute acid?