Structure of a Cyclic Trimer as a Model of Nylon 11. Folding at Lamellar Surfaces

Abstract

We have studied by single-crystal X-ray diffraction the structure of a cyclic trimer model of nylon 11 (IUPAC name: 1,13,14,. The crystal is organized in layers of hydrogen-bonded rings similar to nylon lamellar crystals. The rings fold both at the amide and methylene regions. Neighbor layers show van der Waals contacts among similar turns, either methylene/ methylene or amide/amide. A new type of fold has been found, which includes an amide group and a methylene unit. Such folds may coexist in nylon lamellar crystals with conventional turns similar to the -turn found in proteins. The orientation of up and down chains in the crystal is different from the orientation usually assumed for nylon 11, which suggests an alternative unit cell for nylon 11. We also include an analysis of the vertical displacement of hydrogen bonded layers found by different authors in nylon 11, which shows that it may vary between zero and three methylene units. In the trimer crystal we find a displacement of two methylene units.

Bolaamphiphiles

“…60 A corresponding trimer was also obtained as crystalline byproduct in the industrial synthesis of Nylon 11 (Rilsan). 61 In the latter trimer the C-11 spacer between two amide groups allowed a strong intramolecular hydrogen bond between two amide groups as well as intramolecular hydrogen-bond chains ( Figure 14b). 61 In even m,n-Nylons made of diamines and diacids, similar patterns of hydrogen bonds lead to equally stable crystallites.…”

“…61 In the latter trimer the C-11 spacer between two amide groups allowed a strong intramolecular hydrogen bond between two amide groups as well as intramolecular hydrogen-bond chains ( Figure 14b). 61 In even m,n-Nylons made of diamines and diacids, similar patterns of hydrogen bonds lead to equally stable crystallites. Intermolecular hydrogen bonding may occur in progressive intrasheet patterns (p-sheets) with acid and amine regions, which leads to a shear by 13°parallel to the chain axis.…”

Effect of hydrogen bonds on the modulus of bulk polybenzoxazines in the glassy state

“…Hydrogen bonds are perhaps one of the most fascinating topics in polymer science, because their interactions between the hydrogenbonding donors and acceptors greatly affect the aggregation structures and properties, like crystallinity, physical properties and thermal degradation. [1][2][3] Hydrogen bonds also give us constant surprise, they are strong enough to lead to self-assembly in supramolecular systems, while weak enough to be broken by a mere increasing in temperature. 4,5 Hence, a large number of investigations about hydrogen bonds have been performed, nonetheless, lots of puzzles still remain, particularly in thermosets due to their complex architectures, as in the case of phenolic resins.…”

The Three-Dimensional Structure of Monodisperse 5-Amide Nylon 6 Crystals in the λ-Phase

“…Indeed, this structure bears a noticeable resemblance to the nylon 6 6 α-structure ( c -direction intersheet shearing angle ≈ 50°) found in lamellae and fibers and chain tilt in monodisperse cyclic trimers of nylon 11 2 Projections (parallel to a -axis) of the 5-amide nylon 6 structures: (a) the α-structure and (b) the λ-structure.…”

“…4 Progressive c-axis intersheet shear has been discussed in other nylons, for example nylon 4 6, 28 and chain tilt in monodisperse cyclic trimers of nylon 11. 29 To our knowledge, a constant progressive c-axis intersheet shear in even nylons was first reported in 1985 by Cojazzi et al 30 for nylon 10. We shall comment further on the nylon 10 R*-structure and on the relationship between the even nylon R*-and λ-phases in the Discussion section later.…”