Nylon 18 18 and nylon 18 1,3-adamantanedicarboxylic acid (ADA) have been synthesized via melt polycondensation and characterized by thermal and spectroscopic techniques. Good film forming behavior combined with film toughness and flexibility indicate reasonable molecular weights for both. The higher aliphatic content of nylon 18 18 leads to increased resistance to common organic solvents over commercial nylons. Crystallization of nylon 18 18 combines hydrogen bonding of the amide units with a more significant contribution from van der Waals forces than possible for lower aliphatic content nylons due to the greater aliphatic chain lengths. Solid state 15 N CP/MAS NMR indicates a mostly amorphous polymer, with crystalline regions comprised of the thermodynamically stable a-form generally adopted by even-even nylons. Nylon 18 ADA as-produced is completely amorphous as determined by differential scanning calorimetry. However, solution cast samples of nylon 18 ADA shows some ordered structures that can grow into more stable crystals with annealing. These crystals, once melted, do not recrystallize possibly due to chain rearrangement inhibited by bulky adamantly-groups. V

High-aliphatic-content linear nylons were produced with an 18-carbon diacid with diamines containing both odd and even methylene segments. The resulting polymers were characterized with viscosimetric, thermal, and spectroscopic techniques. Solid-state 15 N NMR was used to determine the nylon crystalline form present. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 936 -945, 2005

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Summary: Linear unsaturated nylons 6 u18 and 18 u18 have been made containing a double bond in the center of the diacid segment with potential for additional functionalization. Solution state NMR showed the presence of a small portion of cis amide units. Solid state NMR verified the presence of the double bond in the bulk, and that the polyamides were present in the α‐crystalline form. Thermal stability was comparable to linear saturated nylons, and the melting and crystallization temperatures of the unsaturated nylons were lower compared to the saturated analogs.

A series of copolyamides of various compositions of nylon 6 and nylon 6,18 were produced. Increased resistance to organic solvents resulted from greater incorporation of nylon 6,18, as shown by decreasing solubility. High-resolution solution NMR indicated there were four amide carbonyls that corresponded to the four possible pairs of comonomer units, allowing detailed composition determination. The melting points of the comonomers decreased as the ratio of hydrogen bonding amide units to methylene groups increased, going from nylon 6 to copolymers with an increasing number of nylon 6,18 repeat units.