Other than 6 and 66
The image on top above is of the 3D model of nylon 6,9; below that is nylon 6,10.
Just click on the image to view the model you can rotate and zoom in a new window.
Close it when you are ready to come back here.
For Nylon 6,10 at a glance, click here!
For Nylon 4,6 at a glance, click here!
A Few Examples From Hundreds...
Here is a table with melting points (Tm's) for a variety of AA-BB nylons. It's interesting to compare the decrease in Tm as the methylene content increases or conversely, as the amide concentration along the backbone decreases. And just in case you were wondering, these are all fairly crystalline materials, meaning that crystallinity is around 30-50% for most of these. Why not higher? Ah, excellent question.
The answer is related to entanglement and time-scale of motion. In other words, it's really hard to make these nylons MORE crystalline because of who or what they are: fairly high molecular polymers with strong intermolecular interactions that make it hard and slow for them to untangle from the amorphous domains and get into the crystalline ones. Can they be made more crystalline? Sure, if you try hard and use various tricks, but is it worth it? You lose toughness if you make them too crystalline, so in general, the answer would be "No."
Nylons are also called polyamides, because of the characteristic
amide groups in the backbone chain. Proteins,
such as the silk nylon was made to replace, are also polyamides. These amide groups
are very polar, and can hydrogen bond with each other. Because
of this, and because the nylon backbone is so regular and symmetrical,
nylons
are often crystalline, and make very good fibers.
The nylon in the pictures on this page is called nylon 6,10, because each repeat unit of the polymer chain has two stretches of carbon atoms, one with six carbon atoms and two nitrogens, the other ten carbon atoms long which includes the carbons of the carbonyls. Other nylons can have different numbers of carbon atoms in these stretches.
Nylons can be made from diacid chlorides and diamines. Nylon 6,10 is made from the monomers sebacoyl chloride and hexamethylene diamine in this synthesis. Of course, that's not how it's made industrial. For large scale synthesis of this specialty nylon, the two monomers are combined to form a "strike" which is actually the bis-salt. This purified salt is then thermally polymerized under vacuum to remove the water by-product and drive the reaction to high conversion and therefore, high molecular weight.
Nylon 6,6 can be made the same way in the laboratory. But in a nylon plant, it's usually made by reacting adipic acid with hexamethylene diamine:
The model on the left is an image of the adipic acid model you can view by clicking here or you can just click on the image itself. The second image is of the diamine monomer. Either way, be sure to close the new windows that open up with the 3D model in it when you are ready to come back here.
If you want to know how this condensation polymerization works, click here.
Another kind of nylon is nylon 6. It's a lot like nylon 6,6 except that it only has one kind of carbon chain, which is six atoms long. It's made by a ring opening polymerization from the monomer caprolactam as shown below. Click on the image of nylon 6 on the right to open a new window with a 3D model of the polymer.
The image below is of the caprolactam pdb model you can view by clicking here or on the image.
Click here to find out more about this polymerization. Nylon 6 doesn't behave much differently from nylon 6,6 although its melting point is about 40 C lower. The main reason both were invented is because DuPont patented nylon 6,6 before anyone else could. Other companies had to invent nylon 6 in order to get in on the nylon business. Today, both are commercially made and sold into huge markets worldwide.
A family of very different nylons with much better properties have their own page at aramids. These aromatic versions of nylons have much higher melting points and can be made into super-strong fibers that are used in high performance applications.
Tested Synthetic Procedures
So for a representative synthesis of an AA-BB nylon, we offer you nylon 6-10 in all its glory. If you want to just view the pdf of the synthetic procedure, click here and here to download a copy.Here's an unusual synthesis of an AA-BB nylon that is actually not easy to make nor is it thermodynamically all that stable. Seems the five-membered ring imide competes with linear polyamide formation. So this is method for making nylon 2-4 in all its glory. If you want to just view the pdf of the synthetic procedure, click here and here to download a copy.
Here's a weird example of an AA-BB nylon that also doesn't look to be all that stable, but hey, if someone has actually made it, what can we say? Nylon 10/2 can be made in a straightforward polyamidation, so if you want to just view the pdf of the synthetic procedure, click here and here to download a copy.
Recent advances in amide bond formation allow the simple, straightforward syntheses of semi-aromatic nylons. Here's one involving a diisocyanate reacting with an aliphatic diacid: click here to view the procedure and here to download a copy.
| Other polymers used as plastics include: | Other polymers used as fibers include: |
| Polypropylene | Polypropylene |
| Polyesters | Polyesters |
| Polystyrene | Polyethylene |
| Polycarbonate | Kevlar and Nomex |
| PVC | Polyacrylonitrile |
| Polyethylene | Cellulose< |
| Poly(methyl methacrylate) | Polyurethanes |
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