The crystal structure of polylauryllactam (nylon 12)

Abstract

The crystal structure of nylon I2 was determined from the X-ray diffraction patterns of uniaxially oriented specimens. The unit cell is monoclinic (pseudo-hexagonal) with the following dimensions: a = 4,79 if, b = 31,9 A (fiber axis), c = 9,58 if, B = 120". There are four monomeric units in the unit cell and the space group is P21/c. The structure presents a distortion of the amide group from the planar chain conformation and it is rather similar to y-nylon 6. The hydrogen bond length is about 2 , 8 0 A and the molecular packing is characterized by alternate, "up and down", highly disordered sheets of parallel chains, linked by hydrogen bonds. The agreement between observed and calculated intensities has been improved by introducing a statistical disorder. ZUSAMMENFASSUNG:Die KristaIIstruktur von Nylon-I2 wurde mit Hilfe von Rontgenbeugungsdiagrammen uniaxial orientierter Praparate bestimmt. Die Elementarzelle besitzt eine monokline (pseudo-hexagonale) Symmetrie mit den Parametern a = 4,79 A, b = 31,9 if (Faserachse), c = 9,58 if, = 120'. Die Zelle enthalt 4 monomere Einheiten; die Raumgruppe ist P21/c. Die Amidgriippen sind gegeniiber der Ebene der planaren Zick-zack-Kette verdreht. Fur die Lange der Wasserstoffbindung ergibt sich ein Wert von etwa 2,80if. Die Struktur scheint der y-Form des Nylons-6 ahnlich zu sein. Parallel laufende Molekiile sind durch Wasserstoffbriicken verbunden und bilden sog. Rostebenen; diese sind mit einem hohen Unordnungsgrad antiparallel angeordnet. Die Ubereinstimmung zwischen den beobachteten und den berechneten Intensitaten konnte durch die Annahme einer statistischen Unordnung verbessert werden.

A novel use of the Amplatzer muscular ventricular septal defect occluder

“…As illustrated in Figure 6, the locations of intensity maximums of γ(0 k 0), γ(200), and γ(001) can be related to the crystallographic angles of the monoclinic γ‐unit cell of polyamide 12. The angles (α = γ = 90° and β = 121°) obtained from the relationship numerically confirmed the monoclinic symmetry of polyamide 12 γ crystals that had been previously proposed by many investigators 12–14, 19…”

“…The crystal structure and polymorphism of polyamide 12 have been extensively examined generally using uniaxially oriented filaments and solution‐cast films 12–14, 17, 19. The interplanar spacings and angles of our films showed great similarity to those of Cojazzi et al's13 monoclinic γ crystal with the b axis as a chain axis. Therefore, we may assign the reflections 14.73, 7.73, and 5.28 Å to γ(020), γ(040), and γ(060), respectively.…”

“…A large volume of research has been made on the crystal structure and polymorphism of polyamides 1–22. It is generally accepted that below their Brill transition points,23 the polyamides are composed of hydrogen‐bonded sheets that are formed into a layerlike structure.…”

“…It is generally accepted that below their Brill transition points,23 the polyamides are composed of hydrogen‐bonded sheets that are formed into a layerlike structure. Similar to polyamide 6,1, 4, 5, 9, 10, 16 polyamide 1212–14, 17, 19 may crystallize into α or γ forms depending on the crystallization conditions. Polyamide 12 can establish perfect hydrogen bonding between two adjacent molecules in a layer when they are either antiparallel or parallel to each other.…”

“…The material prefers the γ‐unit cell. Table 1 presents a list of the γ‐unit cells of polyamide 12 that have been proposed by various investigators 12–14, 19. All of the unit cells in Table 1 are monoclinic and contain the shortened chain‐axis repeat distance from that of the fully extended trans chain conformation.…”