The Notes for
Polymer and Coatings Science-
Chapter Three- part one

CONDENSATION POLYMERS

Definition of Condensation Polymer

A condensation polymer can be defined as a polymer in which the structural unit contains fewer atoms than the monomer or monomers from which the polymer is derived. There must be an elimination of a by-product, usually water.

As an example, a polyester may be obtained from the reaction of a diol with a diacid. (Polymer chemists abbreviate "dicarboxylic acid" to "diacid.")

 
                      O          O                              O         O
                      ||         ||                             ||        ||
HO -A-A-A- OH  + HO - C -B-B-B - C - OH --> ... - O -A-A-A- O - C -B-B-B- C - O - ...

Pictures of Condensation Polymer Functionalities

  O
  ||              <---  Polyester
- C - O -


  H   O
  |   ||          <---  Polyamide
- N - C - 


      O   H
      ||  |       <---  Polyurethane
- O - C - N - 


  H   O   H
  |   ||  |       <---  Polyurea
- N - C - N -


  O       O
  ||      ||      <---  Polyanhydride
- C - O - C -


- S -             <---  Polysulfide


  R
  |
- Si - O -        <---  Polysilicone
  |
  R

Applications for various condensation polymers

Polyester- clothing (dacron)

Polyamide- nylons

Polyurethane- foams

Polyurea- foams

Polyacetals- engineering plastics

Silicones- silicones, heat exchange fluids

Polyanhydride- not widely used

Phenolformaldehyde- plastics, coatings

Cellulose polymers- woods, plant fibers, cotton, flax, starches, cotton fibers

Preparation of nylons

Nylon 1

                                O
                NaCN            ||
R - N = C = O   ----->  -[- N - C -]-
                            |
                            R

Nylon 2

    H   O                  H   O       O                         O
    |   ||      COCl2      |   ||      ||     100 deg C          ||
R - C - C - OH ------> R - C - C - O - C - NH   ----->   -[- C - C - N -]- 
    |                                        2   -CO         |       |
    NH                                              2        R       H
      2
                         O
                         ||
COCl2 is phosgene,  Cl - C - Cl, a nerve gas used in World War II.

You can use triphosgene, a solid, which can be weighed out in precise
amounts and used for the same chemical reactions.  This is preferable
to hooking up a gas cylinder of phosgene to a reactor and hoping there
isn't an accident which would release a cloud of phosgene into your
building.

Nylon 3

    H   H   O
    |   |   ||
-[- C - C - C - N -]-
    |   |       |
    H   H       H

Nylon 5 from butadiene

H   H   H   H            C = C                H   H   H   H   O
|   |   |   |     -      |   |                |   |   |   |   ||
C = C - C = C  + C-O --> C   C --> ?? --> -[- C - C - C - C - C - N -]-
|   |   |   |     -       \ /                 |   |   |   |       |
H   H   H   H              C                  H   H   H   H       H
                           ||
                           O

For nylons made from diamines and diacids, the name takes two numbers as in Nylon xy. Example: a hypothetical Nylon 65 would come from a diamine with 6 carbons and a diacid with 5 carbons.

Nylon 6 can be made using a Beckman rearrangement.

Ring size vs. polymerization rate- 8 > 7 > 11 > 5,6

This is taken to mean that the fastest polymerization rate occurs for a polymer with eight carbons in the ring.

Nylon 11 has a good market share, and it is made from a natural source.

Fatty Poly(amides)

Resinoleic acid- fatty acids are usually the source for fatty polyamide nylons.

Fatty polyamides are obtained by the reaction of di- and polyfunctional amines with polybasic acids which in turn were prepared from unsaturated vegetable oil acids.

Mixtures of fatty acids obtained by the saponification of unsaturated vegetable oils such as linseed, soybean and gun (gum?) oil are heated for several hours at 300 deg C.

The resulting mixture is then heated under reduced pressure to remove the more volatile components, which are mainly monobasic acids.

The residue, a dimer acid, is used for the production of fatty polyamides.

Fatty polyamides prepared from dimer acids are of two types: solid and liquid polymers.

Solid- linear products are obtained by reaction of dimer acids and diamines with molecular weights of 2000 to 15000.
Liquid- highly branched products of lower molecular weight which result from the interaction of dimer acids and polyamines contain 3 or more amino groups.

Nylon 66, the largest produced nylon, is prepared using adipic acid. Nylon 6, the second largest produced nylon, is prepared from caprolactam. There is no date listed to correspond to these two facts.

Nylon 66 is synthesized by the reaction of diamine and dibasic acid. It is necessary to have an exact stoichiometric equivolence of the reactants. To achieve this, a "nylon salt" can be prepared, where the dibasic acid donates a proton to the diamine. The nylon salt is purified, and when the salt is converted back to acid and salt, there is one diamine molecule for every dibasic acid molecule, and thus, a perfect stoichiometric balance (assuming perfect purification.)

The synthesis of nylon 66 is a batch process. Adipic acid is neutralized by the addition of hexamethylenediamine.

The above picture suggests that the two -COO(-) groups of an acid colombically adhere to the two -NH3(+) groups of a base. Perhaps this is misleading. This should be looked up.

The nylon salt solution is fed into an autoclave together with a small amount of acetic acidto limit molecular weight The reactor is sealed and the temperature raised to 220 deg C and a pressure of 20 atm. After 1 to 2 hours the temperature is increased to 270 to 280 deg C and steam is bled off to maintain the pressure of 20 atm.

The heating is continued for two more hours and the pressure is allowed to fall to atmospheric pressure.

The molten polymer is extruded from the reactor by pumping in nitrogen (to protect the melt from oxygen.)

The extrudate is fed onto a water cooled drum to for a ribbon which is then chopped.

Synthesis of adipic acid- benzene is hydrogenated in the liquid phase at 150 to 200 deg C at 25 (atm ??) using the Raney nickel catalyst to form cyclohexane. The cyclohexane is oxidized with air at 125 to 160 deg C, 4 to 18 atm, using cobalt naphthenate as the catalyst. A mixture of cyclohexanol and cyclohexane of approximately equal amounts is obtained. The second oxidation step, which appears from the notes, to convert cyclohexanol to adipic acid, is carried out by treating the mixture with 50% aqueous nitric acid in the presence of ammonium vanadate-copper catalyst. The adipic acid is crystallized from the reaction mass.

An alternative route is the hydrogenation of phenol to cyclohexanol, and then conversion of cyclohexanol to adipic acid with nitric acid.

Synthesis of hexamethylenediamine- the standard commercial route starts with adipic acid:

     O   H   H   H   H   O                    H   H   H   H
    ||   |   |   |   |   ||      NH3    -     |   |   |   |     - 
HO - C - C - C - C - C - C - OH  ---> N - C - C - C - C - C - C - N
         |   |   |   |                  -     |   |   |   |     -
         H   H   H   H                        H   H   H   H


H     H   H   H   H   H   H   H
 2    |   |   |   |   |   |   |
---> :N - C - C - C - C - C - C - N:
      |   |   |   |   |   |   |
      H   H   H   H   H   H   H

Another route for the preparation of hexamethylenediamine starts with butadiene:

H   H   H   H  Cl        H   H   H   H                H   H   H   H
|   |   |   |    2       |   |   |   |      NaCN      |   |   |   |
C = C - C = C  --->  H - C - C = C - C - H  --->  H - C - C = C - C - H
|   |   |   |            |           |                |           |
H   H   H   H            Cl          Cl               C           C
                                                     |||         |||
                                                      N           N

 H            H   H   H   H           H          H   H   H   H   H   H   H
  2     -     |   |   |   |     -      2         |   |   |   |   |   |   |
---> :N - C - C - C - C - C - C - N:  --->  :N - C - C - C - C - C - C - C -N:
        -     |   |   |   |     -                |   |   |   |   |   |   |
              H   H   H   H                      H   H   H   H   H   H   H

Nylon 66 can be prepared from plant sources, such as the refuse corn cobs discarded by cereal makers such as Kellogg's and General Mills.

Interfacial Polymerization

Interfacial polymerization occurs when an water soluble monomer and an organic soluble monomer are brought together at the interface between water and a water immiscible organic solvent:

\            /
|            |
|  organic   |      for most nonpolar organic solvents that don't mix
|            | with water, the density is less than 1.00, and the organic
| monomer 1  | therefore forms the top phase.  This is not the case, though, 
|            | for carbon tetrachloride, density = 1.589. 
|------------| 
|            |
|   water    |    
|            |   
| monomer II |
|            |
 ------------

Example of interfacial polymerization: Nylon can be prepared from

 H   H   H   H
 |   |   |   |    dissolved in water; there is sodium hydroxide (NaOH) 
:N - C - C - N:   in the water to convert the diamine into a salt, 
 |   |   |   |    which has a higher water solubility. 
 H   H   H   H    

and

     O   H   H   H   H   H   H   H   H   O
     ||  |   |   |   |   |   |   |   |   ||        dissolved in the organic
Cl - C - C - C - C - C - C - C - C - C - C - Cl    solvent.
         |   |   |   |   |   |   |   |
         H   H   H   H   H   H   H   H

A nylon fibre is pulled, and attached to a rotating spool. As the spool turns, and pulls the fibre, more polymerization occurs, generating more fibre, until all the monomer is reacted.

Physical properties of nylons:

High Impact Strength
Toughness
Flexibility and abrasion resistance
the mechanical properties are considerably affected by the amount of crystallinity
The principle structure difference between different fibres is the length of the aliphatic chain separating the amide groups in the polyamide.
Crystallinity readily occurs and gives materials of high melting point and tensile strength.
Increasing the length of the aliphatic segment reduces the melting point, the tensile strength, the heat distortion temperature, and the water absorption, but increases the impact strength and elongation (to break, I believe.)
Textile fibres are usually prepared from nylon 66 or nylon 6 because these polymers have the highest tensile strengths.
Brushes, sports equipment and surgical sutures are normally nylon 6, nylon 10 or nylon 11, which have greater flexibility and water resistance.
Nylon fibres have satisfactory electrical insulating ability under low frequencies and dry conditions.
Nylon fibres are soluble in acetic acid, formic acid, and phenols.
The oxidation of nylons occurs in air exposure to UV light and or temperature above 70 deg C. This oxidation leads to a distortion in mechanical properties.

Aromatic nylons:

  H
 :O:        H
  |  :      |
  C=O     H-N:              
  |  :      |            :O:    -    :O:  H     -     H
 / \       / \            ||  /   \   ||  |   /   \   |
| O |  +  | O | --->  -[- C -   O   - C - N -   O   - N -]-
 \ /       \ /                \   /       :   \   /   :
  |  :      |                   -               -
  C=O     H-N:
  |  :      |               poly(aramid) is formed and water is the byproduct
 :O:        H
  H

Aromatic nylons are generally prepared from the more reactive acid chlorides
(as opposed to the dicarboxylic acid shown above), and the polymerization
can be carried out either by solution or suspension. 





Polyimides












A dianhydride and a diamine react to for a polyimide.












A dianhydride and a tetraamine react to form a polyimide that is an 
example of a ladder polymer.

A ladder polymer consists of two "main chains" or backbones that bonded
together at regular intervals:

 - - - - - - - - - - - - - - -
   |     |     |     |     |
 - - - - - - - - - - - - - - -








Polyesters




Poly(ethylene terephthalate), the most important polyester, is made from 
ethylene glycol and terephthalic acid.










PET is used for clothing (62%), home furnishings (17%), and textile
cord (10%) (is textile cord, a special kind of rope??)  No year listed
for when this data was taken.








Raw Materials for Polyesters




No construction at this time.




Saturated Polyesters  




Several different materials can be used to make a polyester:

diacid and a diol:

     O        O                                   O        O    
    ||        ||                                 ||        ||           
HO - C - R1 - C - OH + HO - R2 - OH  -->  -[- O - C - R1 - C - O - R2 -]- + H2O


diester and a diol:
     O        O                                   O        O
    ||        ||                                 ||        ||
RO - C - R1 - C - OR + HO - R2 - OH  -->  -[- O - C - R1 - C - O - R2 -]- + ROH


silver salt of dibasic acid and a dihalide:

             O        O                                          O        O
             ||      ||                                          ||      ||
Ag(+) (-)O - C - R1 - C - O(-) (+)Ag + Br-C - C-Br  -->  -[- O - C - R1 - C - O - R2 -]- + AgBr 


transesterification of glycol ester and a diacid:

     O        O                 O        O                       O        O                     O
    ||        ||               ||        ||                     ||        ||                    ||
Cl - C - R1 - C - Cl + R3 - O - C - R2 - C - O - R3  --> -[- O - C - R1 - C - O - R2 -]- + R3 - C - O - H   


diacid chloride and a diol:

     O        O                                   O        O
    ||        ||                                 ||        ||
Cl - C - R1 - C - Cl + HO - R2 - OH  -->  -[- O - C - R1 - C - O - R2 -]- + HCl


transesterification of ethylene carbonate and a diacid:

      O
     //
C - C            O       O                   O       O                       O
     \          ||       ||                 ||       ||                      ||
|     O  +  HO - C - R - C - OH  --> -[- O - C - R - C - O - C - C -]- + H - C - OH 
     /
C - C
     \\
      O


self-condensation of hydroxy acid

          O                           O
          ||                          ||
HO - R1 - C - OH  ---->  -[- O - R1 - C - O -]-


anhydride + diol






diphenol + diacid






diacetate of diphenol + diacid






disodium salt of diphenol + diacid chloride










Factors effecting polyester melt temperature
Factors contributing to high melting points for polyesters:


high interchain forces promote microcrystallinity
molecular inflexibility promotes microcrystallinity
presence of secondary bonding forces
stiffness of internal bonds
symmetry
ability of linear chains to pack closely


Factors contributing to low melting points for polyesters:


structure irregularity
angled chain on the monomer
odd number of carbon atoms in the chain
interchain attraction of dispersed groups (huh? I think this maybe should read "the lack thereof")
flexible bonds between chains
bulkiness of side chains

























Last Update- June 8, 1995- wld

The Notes for Polymer and Coatings Science- Chapter Three- part one

CONDENSATION POLYMERS

The Notes for
Polymer and Coatings Science-
Chapter Three- part one